The Toxoplasma Blog

Impaired Chromatin Remodelling at STAT1-Regulated Promoters Leads to Global Unresponsiveness of Toxoplasma gondii-Infected Macrophages to IFN-γ

2012-01-27T06:39:00.001-08:00

PLoS Pathog. 2012 Jan;8(1):e1002483. Epub 2012 Jan 19.

Impaired Chromatin Remodelling at STAT1-Regulated Promoters Leads to Global Unresponsiveness of Toxoplasma gondii-Infected Macrophages to IFN-γ.

Lang C, Hildebrandt A, Brand F, Opitz L, Dihazi H, Lüder CG.

Source
Institute for Medical Microbiology, University Medical Center, Georg-August-University, Göttingen, Germany.

Abstract
Intracellular pathogens including the apicomplexan and opportunistic parasite Toxoplasma gondii profoundly modify their host cells in order to establish infection. We have shown previously that intracellular T. gondii inhibit up-regulation of regulatory and effector functions in murine macrophages (MΦ) stimulated with interferon (IFN)-γ, which is the cytokine crucial for controlling the parasites' replication. Using genome-wide transcriptome analysis we show herein that infection with T. gondii leads to global unresponsiveness of murine macrophages to IFN-γ. More than 61% and 89% of the transcripts, which were induced or repressed by IFN-γ in non-infected MΦ, respectively, were not altered after stimulation of T. gondii-infected cells with IFN-γ. These genes are involved in a variety of biological processes, which are mostly but not exclusively related to immune responses. Analyses of the underlying mechanisms revealed that IFN-γ-triggered nuclear translocation of STAT1 still occurred in Toxoplasma-infected MΦ. However, STAT1 bound aberrantly to oligonucleotides containing the IFN-γ-responsive gamma-activated site (GAS) consensus sequence. Conversely, IFN-γ did not induce formation of active GAS-STAT1 complexes in nuclear extracts from infected MΦ. Mass spectrometry of protein complexes bound to GAS oligonucleotides showed that T. gondii-infected MΦ are unable to recruit non-muscle actin to IFN-γ-responsive DNA sequences, which appeared to be independent of stimulation with IFN-γ and of STAT1 binding. IFN-γ-induced recruitment of BRG-1 and acetylation of core histones at the IFN-γ-regulated CIITA promoter IV, but not β-actin was diminished by >90% in Toxoplasma-infected MΦ as compared to non-infected control cells. Remarkably, treatment with histone deacetylase inhibitors restored the ability of infected macrophages to express the IFN-γ regulated genes H2-A/E and CIITA. Taken together, these results indicate that Toxoplasma-infected MΦ are unable to respond to IFN-γ due to disturbed chromatin remodelling, but can be rescued using histone deacetylase inhibitors.

PMID: 22275866 [PubMed - in process]

Proteomic analysis of fractionated toxoplasma oocysts reveals clues to their environmental resistance

2012-01-27T06:38:00.002-08:00

PLoS One. 2012;7(1):e29955. Epub 2012 Jan 18.

Proteomic analysis of fractionated toxoplasma oocysts reveals clues to their environmental resistance.

Fritz HM, Bowyer PW, Bogyo M, Conrad PA, Boothroyd JC.

Source
Department of Pathology, Microbiology and Immunology, School of Veterinary Medicine, University of California Davis, Davis, California, United States of America.

Abstract
Toxoplasma gondii is an obligate intracellular parasite that is unique in its ability to infect a broad range of birds and mammals, including humans, leading to an extremely high worldwide prevalence and distribution. This work focuses on the environmentally resistant oocyst, which is the product of sexual replication in felids and an important source of human infection. Due to the difficulty in producing and working with oocysts, relatively little is known about how this stage is able to resist extreme environmental stresses and how they initiate a new infection, once ingested. To fill this gap, the proteome of the wall and sporocyst/sporozoite fractions of mature, sporulated oocysts were characterized using one-dimensional gel electrophoresis followed by LC-MS/MS on trypsin-digested peptides. A combined total of 1021 non-redundant T. gondii proteins were identified in the sporocyst/sporozoite fraction and 226 were identified in the oocyst wall fraction. Significantly, 172 of the identified proteins have not previously been identified in Toxoplasma proteomic studies. Among these are several of interest for their likely role in conferring environmental resistance including a family of small, tyrosine-rich proteins present in the oocyst wall fractions and late embryogenesis abundant domain-containing (LEA) proteins in the cytosolic fractions. The latter are known from other systems to be key to enabling survival against desiccation.

PMID: 22279555 [PubMed - in process]

A Novel PAN/Apple Domain-Containing Protein from Toxoplasma gondii: Characterization and Receptor Identification

2012-01-27T06:38:00.001-08:00

PLoS One. 2012;7(1):e30169. Epub 2012 Jan 19.

A Novel PAN/Apple Domain-Containing Protein from Toxoplasma gondii: Characterization and Receptor Identification.

Gong H, Kobayashi K, Sugi T, Takemae H, Kurokawa H, Horimoto T, Akashi H, Kato K.

Source
Department of Veterinary Microbiology, Graduate School of Agricultural and Life Sciences, University of Tokyo, Tokyo, Japan.

Abstract
Toxoplasma gondii is an intracellular parasite that invades nucleated cells, causing toxoplasmosis in humans and animals worldwide. The extremely wide range of hosts susceptible to T. gondii is thought to be the result of interactions between T. gondii ligands and receptors on its target cells. In this study, a host cell-binding protein from T. gondii was characterized, and one of its receptors was identified. P104 (GenBank Access. No. CAJ20677) is 991 amino acids in length, containing a putative 26 amino acid signal peptide and 10 PAN/apple domains, and shows low homology to other identified PAN/apple domain-containing molecules. A 104-kDa host cell-binding protein was detected in the T. gondii lysate. Immunofluorescence assays detected P104 at the apical end of extracellular T. gondii. An Fc-fusion protein of the P104 N-terminus, which contains two PAN/apple domains, showed strong affinity for the mammalian and insect cells evaluated. This binding was not related to protein-protein or protein-lipid interactions, but to a protein-glycosaminoglycan (GAG) interaction. Chondroitin sulfate (CS), a kind of GAG, was shown to be involved in adhesion of the Fc-P104 N-terminus fusion protein to host cells. These results suggest that P104, expressed at the apical end of the extracellular parasite, may function as a ligand in the attachment of T. gondii to CS or other receptors on the host cell, facilitating invasion by the parasite.

PMID: 22276154 [PubMed - in process]

High tissue burden of Toxoplasma gondii is the hallmark of acute virulence in mice

2012-01-25T07:48:00.000-08:00

Vet Parasitol. 2012 Jan 8. [Epub ahead of print]

High tissue burden of Toxoplasma gondii is the hallmark of acute virulence in mice.

Hill RD, Su C.

Source
Department of Microbiology, University of Tennessee, Knoxville, TN 37996, United States.

Abstract
Toxoplasma gondii virulence is commonly determined by mortality rate of infected mice. Limited data showed that virulent T. gondii strains had increased parasite growth in mice compared to that of less virulent strains. To determine if this is a common phenomenon for a variety of strains and to develop an alternative assay to test acute virulence in mice, we measured parasite burdens in experimentally infected outbred CD-1 mice for 19 T. gondii isolates, in which the virulence phenotypes had previously been determined by mortality assay. Our results showed that parasite concentrations in spleen tissues were two orders of magnitude higher in the virulent than the intermediately and non-virulent isolates at day 7 post infection. In competition assays, mice inoculated with mixed tachyzoites of virulent and intermediately virulent strains or virulent and non-virulent strains showed that the former always reached a higher concentration at day 7 post infection. In mixed infection of intermediate and non-virulent strains, both strains were detectable in mice at day 7 post infection. In conclusion, our data showed that the virulence of T. gondii can be predicted by parasite load in the spleen tissue of infected mice at 7 days post infection, providing an alternative method to determine virulence of Toxoplasma.

Copyright © 2012 Elsevier B.V. All rights reserved.

PMID: 22270034 [PubMed - as supplied by publisher]

Significant reduction of Toxoplasma gondii brain cysts after treatment with spiramycin coadministered with metronidazole in a mouse model

2012-01-25T07:40:00.000-08:00

Antimicrob Agents Chemother. 2012 Jan 23. [Epub ahead of print]

Significant reduction of Toxoplasma gondii brain cysts after treatment with spiramycin coadministered with metronidazole in a mouse model of chronic toxoplasmosis.

Chew WK, Segarra I, Ambu S, Mak JW.

Source
Dep. of Human Biology, School of Medicine, International Medical University; No 126 Jalan 19/155B, Bukit Jalil, 57000 Kuala Lumpur; Malaysia.

Abstract
Toxoplasma gondii is a parasite that generates latent cysts in brain which reactivation may lead to fatal toxoplasmic encephalitis for which treatment remains unsuccessful. We assessed spiramycin pharmacokinetics coadministered with metronidazole, the eradication of brain cysts and the in vitro reactivation. Male Balb/c mice were fed 1000 tachyzoites orally to develop chronic toxoplasmosis. Four weeks later infected mice underwent different treatments: infected untreated group (n=9) which received vehicle, spiramycin only group (n=9), 400 mg/kg daily for 7 days, metronidazole only group (n=9) 500 mg/kg daily for 7 days, and combination group (n=9) which received spiramycin (400 mg/kg) and metronidazole (500 mg/kg) daily for 7 days. Uninfected control group (n=10) was administered vehicle only. After treatment, the brain cysts were counted, brain homogenate cultured in confluent Vero cells and cysts and tachyzoites counted after 1 week. Separately, pharmacokinetic profiles (plasma and brain) were assessed after a single dose of spiramycin (400 mg/kg) or metronidazole (500 mg/kg) or both. Metronidazole increased 67% brain spiramycin AUC(0-∞) without affecting its plasma disposition. Metronidazole plasma and brain AUC(0-∞) were reduced 9% and 62% respectively after spiramycin coadministration. Enhanced spiramycin brain exposure after coadministration reduced 15-fold brain cysts (79±23 combination treatment versus 1198±153 untreated control group, p<0.05), and 10-fold versus spiramycin only group (768±125). Metronidazole alone showed no effect (1028±149). Tachyzoites were absent in brain. Spiramycin reduced in vitro reactivation. Metronidazole increased spiramycin brain penetration causing a significant reduction of T. gondii brain cysts with potential clinical translatability for chronic toxoplasmosis treatment.

PMID: 22271863 [PubMed - as supplied by publisher]

Virulence without catalysis: how can a pseudokinase affect host cell signaling?

2012-01-20T06:23:00.000-08:00

Trends Parasitol. 2012 Jan 16. [Epub ahead of print]

Virulence without catalysis: how can a pseudokinase affect host cell signaling?

Reese ML, Boyle JP.

Source
Stanford University, Department of Microbiology and Immunology, 299 Campus Drive, Stanford, CA 94305-5124, USA.

Abstract
A hallmark of the pathogenic lifestyle is the secretion of enzymes and other effectors that dysregulate host signaling. Intriguingly, the most potent virulence locus identified in the intracellular parasite Toxoplasma gondii encodes a family of related catalytically inactive protein kinases, or pseudokinases. Toxoplasma has in its kinome among the highest percentage of pseudokinases among all sequenced organisms, and the majority of these appear to be secreted into the host cell. We posit that the pseudokinase fold represents a particularly well-suited domain for functional diversification, discuss the relevance of gene expansion at these loci, and outline potential mechanisms by which a pseudokinase might affect host signaling.

Copyright © 2012. Published by Elsevier Ltd.

PMID: 22257555 [PubMed - as supplied by publisher]

A DOC2 protein identified by mutational profiling is essential for apicomplexan parasite exocytosis

2012-01-18T08:06:00.001-08:00

Science. 2012 Jan 13;335(6065):218-21.

A DOC2 protein identified by mutational profiling is essential for apicomplexan parasite exocytosis.

Farrell A, Thirugnanam S, Lorestani A, Dvorin JD, Eidell KP, Ferguson DJ, Anderson-White BR, Duraisingh MT, Marth GT, Gubbels MJ.

Source
Department of Biology, Boston College, Chestnut Hill, MA 02467, USA.

Abstract
Exocytosis is essential to the lytic cycle of apicomplexan parasites and required for the pathogenesis of toxoplasmosis and malaria. DOC2 proteins recruit the membrane fusion machinery required for exocytosis in a Ca(2+)-dependent fashion. Here, the phenotype of a Toxoplasma gondii conditional mutant impaired in host cell invasion and egress was pinpointed to a defect in secretion of the micronemes, an apicomplexan-specific organelle that contains adhesion proteins. Whole-genome sequencing identified the etiological point mutation in TgDOC2.1. A conditional allele of the orthologous gene engineered into Plasmodium falciparum was also defective in microneme secretion. However, the major effect was on invasion, suggesting that microneme secretion is dispensable for Plasmodium egress.

PMID: 22246776 [PubMed - in process]

Toxoplasma gondii: Protective immunity against toxoplasmosis with recombinant actin depolymerizing factor protein in BALB/c mice

2012-01-18T08:02:00.000-08:00

Exp Parasitol. 2012 Jan 10. [Epub ahead of print]

Toxoplasma gondii: Protective immunity against toxoplasmosis with recombinant actin depolymerizing factor protein in BALB/c mice.

Huang X, Li J, Zhang G, Gong P, Yang J, Zhang X.

Source
College of Animal Science and Veterinary Medicine, Jilin University, 5333 Xi'an Road, Changchun 130062, China.

Abstract
Toxoplasmosis is one of the most world-wide spread zoonosis representing a very serious clinical and veterinary problem. There is still need for vaccines for toxoplasmosis. In the present study, we evaluated the protective efficacy of a recombinant actin depolymerizing factor (ADF) subunit vaccine against Toxoplasma gondii infection in BALB/c mice. The recombinant T. gondii ADF protein (rADF) was expressed in Escherichia coli and used as antigens for BALB/c mice immunization. The results indicated that specific antibody and the increased percentage of CD4(+) T lymphocyte were found in vaccinated BALB/c mice with rADF, when compared with adjuvant or PBS groups. After challenged with T. gondii (RH strain) tachyzoites, the survival time of the mice in rADF group was longer than those in the control group. The numbers of brain cysts of the mice in rADF group reduced significantly when compared with those in control groups (P<0.05), and the rate of reduction could reach to around 30%. These results suggest that rADF can generate protective immunity against T. gondii infection in BALB/c mice.

Copyright © 2012. Published by Elsevier Inc.

PMID: 22248986 [PubMed - as supplied by publisher]

Sex-specific changes in gene expression and behavior induced by chronic Toxoplasma infection in mice

2012-01-14T12:24:00.001-08:00

Neuroscience. 2012 Jan 3. [Epub ahead of print]

Sex-specific changes in gene expression and behavior induced by chronic Toxoplasma infection in mice.

Xiao J, Kannan G, Jones-Brando L, Brannock C, Krasnova IN, Cadet JL, Pletnikov M, Yolken RH.

Source
Stanley Division of Developmental Neurovirology, Department of Pediatrics, Johns Hopkins School of Medicine, Baltimore, MD 21287, USA.

Abstract
There is growing evidence that Toxoplasma gondii modifies the behavior of its intermediate hosts. We investigated the molecular basis of these infection-induced behavioral changes, followed by five related behavioral tests to assess the extent of biological relevance. Gene expression signatures were generated in the frontal cortex of male and female mice during the latent stage of infection. We found marked sex-dependent expression differences in mice. In female mice, Toxoplasma infection altered the expression of genes involved in the development of the forebrain, neurogenesis, and sensory and motor coordination (i.e. downregulation of fatty acid-binding protein 7 and eyes absent homolog 1, upregulation of semaphorin 7A). In male mice, infection led mainly to modulation of genes associated with olfactory function (i.e. downregulation of a number of olfactory receptors and dopamine receptor D4, upregulation of slit homolog 1). Although infection appears to affect the olfactory function in male mice, it is the female but not male mice that exhibited attraction to cat odor. In contrast, infected male mice showed a deficit in social transmission of food preference. In contrast to males, infected females displayed locomotor hyperactivity in open field. General olfaction and sensorimotor gating were normal in both male and female infection. Our results indicate that the sex of the host plays a major role in determining variable brain and behavior changes following Toxoplasma infection. These observations are consistent with heterogeneity of neuropsychiatric outcomes of the infection in humans.

Copyright © 2012. Published by Elsevier Ltd.

PMID: 22240252 [PubMed - as supplied by publisher]

Behavioral changes in mice caused by Toxoplasma gondii invasion of brain

2012-01-09T19:23:00.000-08:00

Parasitol Res. 2012 Jan 6. [Epub ahead of print]

Behavioral changes in mice caused by Toxoplasma gondii invasion of brain.

Gatkowska J, Wieczorek M, Dziadek B, Dzitko K, Dlugonska H.

Source
Department of Immunoparasitology, University of Lodz, Banacha 12/16, 90-237, Lodz, Poland, gatjus@biol.uni.lodz.pl.

Abstract
Toxoplasma gondii, a protozoan parasite, is capable of infecting a broad range of intermediate warm-blooded hosts including humans. The parasite undergoes sexual reproduction resulting in genetic variability only in the intestine of the definitive host (a member of the cat family). The parasite seems to be capable of altering the natural behavior of the host to favor its transmission in the environment. The aim of this study was to evaluate the number of parasite cysts formed in the hippocampus and amygdala of experimentally infected mice as these regions are involved in defense behaviors control and emotion processing, and to assess the influence of the infection on mice behavior. The obtained results revealed the presence of parasite cysts both in the hippocampus and the amygdala of infected mice; however, no clear region-dependent distribution was observed. Furthermore, infected mice showed significantly diminished exploratory activity described by climbing and rearing, smaller preference for the central, more exposed part of the OF arena and engaged in less grooming behavior compared to uninfected controls.

PMID: 22223035 [PubMed - as supplied by publisher]

A Single Chromosome Unexpectedly Links Highly Divergent Isolates of Toxoplasma gondii

2012-01-05T06:03:00.002-08:00

MBio. 2012 Jan 3;3(1). pii: e00284-11. doi: 10.1128/mBio.00284-11. Print 2012.

A Single Chromosome Unexpectedly Links Highly Divergent Isolates of Toxoplasma gondii.

Walzer KA, Boyle JP.

Source
Department of Biological Sciences, Kenneth P. Dietrich School of Arts and Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.

Abstract
ABSTRACT Toxoplasma gondii is an obligate intracellular parasite that can cause disease in all warm-blooded animals studied to date, including humans. Over a billion people have been infected with this parasite worldwide. In Europe and North America, Toxoplasma has a clonal population structure, where only three lineages are highly dominant (strain types I, II, and III). Khan et al. [mBio 2(6): e00228-11, 2011] have carried out phylogenetic analyses on a large number of diverse strains from outside of these lineages and found evidence for a significant split between the clonal North American/European lineages and those in South America. In contrast to most of the genome, nearly all North American/European strains sampled, and the majority of South American strains sampled, harbored at least portions of a monomorphic chromosome Ia (Ia*). In contrast to previous models, these data suggest that the monomorphic haplotype originated in South America and migrated to the North. These authors propose that South American haplotype 12 was a precursor to modern-day type II, while South American haplotypes 6 and 9 crossed with haplotype 12 to give rise to the type I and III lineages, respectively. However, the findings reported by Khan et al. complicate the origin of chromosome Ia, since there are members of haplotypes 9 and 12 with nearly complete versions of Ia* and members of haplotypes 6 and 12 with over 50% of Ia*. This unexpected finding raises exciting new questions about how an entire common chromosome can be found within strains that are highly divergent at most other genomic loci.

PMID: 22215568 [PubMed - in process]

1-(Fluoroalkylidene)-1,1-bisphosphonic acids are potent and selective inhibitors of Toxoplasma farnesyl pyrophosphate synthase

2012-01-05T06:03:00.001-08:00

Org Biomol Chem. 2012 Jan 3. [Epub ahead of print]

1-(Fluoroalkylidene)-1,1-bisphosphonic acids are potent and selective inhibitors of the enzymatic activity of Toxoplasma gondii farnesyl pyrophosphate synthase.

Szajnman SH, Rosso VS, Malayil L, Smith A, Moreno SN, Docampo R, Rodriguez JB.

Source
Departamento de Química Orgánica and UMYMFOR (CONICET-FCEyN), Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Pabellón 2, Ciudad Universitaria, C1428EHA, Buenos Aires, Argentina. jbr@qo.fcen.ar.

Abstract
α-Fluorinated-1,1-bisphosphonic acids derived from fatty acids were designed, synthesized and biologically evaluated against Trypanosoma cruzi, the etiologic agent of Chagas disease, and against Toxoplasma gondii, the agent responsible for toxoplasmosis, and also towards the target parasitic enzymes farnesyl pyrophosphate synthase of T. cruzi (TcFPPS) and T. gondii (TgFPPS). Interestingly, 1-fluorononylidene-1,1-bisphosphonic acid (compound 43) proved to be an extremely potent inhibitor of the enzymatic activity of TgFPPS at the low nanomolar range, exhibiting an IC(50) of 30 nM. This compound was two-fold more potent than risedronate (IC(50) = 74 nM) that was taken as a positive control. This enzymatic activity was associated with a strong cell growth inhibition against tachyzoites of T. gondii, with an IC(50) value of 2.7 μM.

PMID: 22215028 [PubMed - as supplied by publisher]

Foxp3(+) Regulatory T cells, Immune Stimulation and Host Defense against Infection

2012-01-05T06:00:00.002-08:00

Immunology. 2011 Dec 29. doi: 10.1111/j.1365-2567.2011.03551.x. [Epub ahead of print]

Foxp3(+) Regulatory T cells, Immune Stimulation and Host Defense against Infection.

Rowe JH, Ertelt JM, Way SS.

Source
Departments of Pediatrics and Microbiology University of Minnesota School of Medicine Center for Infectious Disease and Microbiology Translational Research.

Abstract
The immune system is intricately regulated allowing potent effectors to expand and become rapidly mobilized after infection, while simultaneously silencing potentially detrimental responses that averts immune-mediated damage to host tissues. This relies in large part on the delicate interplay between immune suppressive regulatory CD4(+) T cells (Tregs) and immune effectors that without active suppression by Tregs cause systemic and organ-specific autoimmunity. Although these beneficial roles have been classically described to be counter-balanced by impaired host defense against infection, newfound protective roles for Tregs against specific viral pathogens (e.g. Herpes simplex-2, Lymphocytic choriomeningitis, West Nile virus) have been uncovered using transgenic mice that allow in vivo Treg-ablation based on Foxp3-expression. In turn, Foxp3(+) Tregs also provide protection against some parasitic (Plasmodium sp., Toxoplasma gondii) and fungal (Candida albicans) pathogens. By contrast for bacterial and mycobacterial infections (e.g. Listeria monocytogenes, Salmonella enterica, Mycobacterium tuberculosis), experimental manipulation of Foxp3(+) cells continue to indicate detrimental roles for Tregs in host defense. This discordance is likely related to functional plasticity in Treg suppression that shifts discordantly following infection with different types of pathogens. Furthermore, the efficiency whereby Tregs silence immune activation coupled with the plasticity in Foxp3(+) cell activity suggest overriding Treg-mediated suppression represents a prerequisite "signal zero" that together with other stimulation signals (T cell receptor [signal 1], co-stimulation [signal 2], inflammatory cytokines [signal 3]) are essential for T cell activation in vivo. Herein, the importance of Foxp3(+) Tregs in host defense against infection, and the significance of infection-induced shifts Treg suppression are summarized.

Journal compilation © 2011 Blackwell Publishing Ltd.

PMID: 22211994 [PubMed - as supplied by publisher]

Autophagy is a cell death mechanism in Toxoplasma gondii

2012-01-05T06:00:00.001-08:00

Cell Microbiol. 2011 Dec 30. doi: 10.1111/j.1462-5822.2011.01745.x. [Epub ahead of print]

Autophagy is a cell death mechanism in Toxoplasma gondii.

Ghosh D, Walton JL, Roepe PD, Sinai AP.

Source

Department of Microbiology, Immunology and Molecular Genetics; University of Kentucky College of Medicine, Lexington KY 40536, USA. Departments of Chemistry, Biochemistry and Cellular and Molecular Biology, Georgetown University, Washington DC. 20057, USA.

Abstract
Nutrient sensing and the capacity to respond to starvation is tightly regulated as a means of cell survival. Among the features of the starvation response are induction of both translational repression and autophagy. Despite the fact that intracellular parasite like Toxoplasma gondii within a host cell predicted to be nutrient rich, they encode genes involved both in translational repression and autophagy. We therefore examined the consequence of starvation, a classic trigger of autophagy, on intracellular parasites. As expected, starvation results in the activation of the translational repression system as evidenced by elevation of phosphorylated TgIF2α (TgIF2α-P). Surprisingly, we also observe a rapid and selective fragmentation of the single parasite mitochondrion that leads irreversibly to parasite death. This profound effect was dependent primarily on the limitation of amino acids and involved signaling by the parasite TOR homolog. Notably, the effective blockade of mitochondrial fragmentation by the autophagy inhibitor 3-methyl adenine (3-MA) suggests an autophagic mechanism. In the absence of a documented apoptotic cascade in T. gondii, the data suggest that autophagy is the primary mechanism of programmed cell death in T. gondii and potentially other related parasites.

© 2011 Blackwell Publishing Ltd.

PMID: 22212386 [PubMed - as supplied by publisher]

Molecular characterization of Toxoplasma gondii formin 3, an actin nucleator dispensable for tachyzoite growth and motility

2012-01-04T06:17:00.002-08:00

Eukaryot Cell. 2011 Dec 30. [Epub ahead of print]

Molecular characterization of Toxoplasma gondii formin 3, an actin nucleator dispensable for tachyzoite growth and motility.

Daher W, Klages N, Carlier MF, Soldati-Favre D.

Source
Department of Microbiology and Molecular Medicine, CMU, University of Geneva, 1 rue Michel-Servet, 1211 Geneva 4, Switzerland.

Abstract
Toxoplasma gondii belongs to the phylum of Apicomplexa, a group of obligate intracellular parasites that relies on gliding motility to enter host cells. Drugs interfering with the actin cytoskeleton block parasite motility, host cell invasion and egress from infected cells. Myosin A, profilin, formin 1, formin 2 and actin depolymerizing factor have all been implicated in parasite motility, yet little is known regarding the importance of actin polymerization and other myosins for the remaining steps of the parasite lytic cycle. Here we establish that T. gondii formin 3 (TgFRM3), a newly described Formin Homology 2 domain (FH2) containing protein, binds to Toxoplasma actin and nucleates rabbit actin assembly in vitro. TgFRM3 expressed as a transgene exhibits a patchy localization at several distinct structures within the parasite. Disruption of the TgFRM3 gene by double homologous recombination in ku80-ko strain reveals no vital function for tachyzoite propagation in vitro, which is consistent with its weak level of expression in this life stage. Conditional stabilization of truncated forms of TgFRM3 suggests that different regions of the molecule contribute to distinct localizations. Moreover, expression of TgFRM3 lacking the C-terminal domain severely impacts on parasite growth and replication. This work provides a first insight into how this specialized formin, restricted to the group of Coccidia, completes its actin nucleating activity.

PMID: 22210829 [PubMed - as supplied by publisher]

Toxoplasma gondii Sis1-like J-domain protein is a cytosolic chaperone associated to HSP90/HSP70 complex

2012-01-04T06:17:00.001-08:00

Int J Biol Macromol. 2011 Dec 23. [Epub ahead of print]

Toxoplasma gondii Sis1-like J-domain protein is a cytosolic chaperone associated to HSP90/HSP70 complex.

Figueras MJ, Martin OA, Echeverria PC, de Miguel N, Naguleswaran A, Sullivan WJ Jr, Corvi MM, Angel SO.

Source
Laboratorio de Parasitología Molecular, IIB-INTECH, CONICET-UNSAM, Av. Intendente Marino Km. 8.2, C.C 164 (B7130IIWA), Chascomús, Prov. Buenos Aires, Argentina.

Abstract
Toxoplasma gondii is an obligate intracellular protozoan parasite in which 36 predicted Hsp40 family members were identified by searching the T. gondii genome. The predicted protein sequence from the gene ID TGME49_065310 showed an amino acid sequence and domain structure similar to Saccharomyces cerevisiae Sis1. TgSis1 did not show differences in its expression profile during alkaline stress by microarray analysis. Furthermore, TgSis1 showed to be a cytosolic Hsp40 which co-immunoprecipitated with T. gondii Hsp70 and Hsp90. Structural modeling of the TgSis1 peptide binding fragment revealed structural and electrostatic properties different from the experimental model of human Sis1-like protein (Hdj1). Based on these differences; we propose that TgSis1 may be a potentially attractive drug target for developing a novel anti-T. gondii therapy.

Copyright © 2011. Published by Elsevier B.V.

PMID: 22209934 [PubMed - as supplied by publisher]

Toxoplasma gondii infection causes morphological changes in caecal myenteric neurons

2012-01-04T06:16:00.000-08:00

Exp Parasitol. 2011 Dec 22. [Epub ahead of print]

Toxoplasma gondii infection causes morphological changes in caecal myenteric neurons.

Zaniolo LM, da Silva AV, Sant'ana DD, Araújo EJ.

Source
Mestrado em Ciência Animal, Universidade Paranaense (UNIPAR), Umuarama, Paraná, Brazil.

Abstract
The aim of this study was to evaluate the effects of chronic infection of Toxoplasma gondii (with genotype I and genotype III strains) on the population density and morphometry of caecum myenteric neurons in rats. Fifteen, 60-day-old, male Wistar rats (Rattus norvegicus) were used. The animals were assigned into three groups: Control Group (CG), Experimental Group 1 (EG1) and Experimental Group 2 (EG2). EG1 animals received 10(5) tachyzoites of the genotype I (BTU IV) T. gondii strain orally, and the EG2 animals received 10(5) tachyzoites of the genotype III (BTU II) strain orally. Thirty days after inoculation, caecal whole-mount preparations were stained by Giemsa technique. The caecal preparations were then analysed by assessing the population density and morphometry of myenteric neurons in specific regions of the caecum: mesenteric apical (MA), antimesenteric apical (AA), antimesenteric basal (AB) and next to caecal ampulla (NA). Myenteric neurons from the AA region were more clustered in EG1 animals (P<0.05). The EG1 animals presented a 16.8% reduction in the area of the nucleus, whereas the EG2 animals showed 18.4% increase (P<0.05). There was a more marked reduction in the cytoplasm of the animals in EG1 (↓23.2%) compared to EG2 (↓6.2%). There was 35.8% neuronal atrophy in the AB region and 16.8% in the region NA of the EG1 animals (P<0.05). In conclusion, different strains of T. gondii cause morphometric changes in caecal myenteric neurons of rats. Only the genotype I strain was able to cause neuronal density changes.

Copyright © 2011. Published by Elsevier Inc.

PMID: 22210156 [PubMed - as supplied by publisher]

Roles of Apicomplexan protein kinases at each life cycle stage

2012-01-04T06:13:00.000-08:00

Parasitol Int. 2011 Dec 24. [Epub ahead of print]

Roles of Apicomplexan protein kinases at each life cycle stage.

Kato K, Sugi T, Iwanaga T.

Abstract
Inhibitors of cellular protein kinases have been reported to inhibit the development of Apicomplexan parasites, suggesting that the functions of protozoan protein kinases are critical for their life cycle. However, the specific roles of these protein kinases cannot be determined using only these inhibitors without molecular analysis, including gene disruption. In this report, we describe the functions of Apicomplexan protein kinases in each parasite life stage and the potential of pre-existing protein kinase inhibitors as Apicomplexan drugs against, mainly, Plasmodium and Toxoplasma.

Copyright © 2011. Published by Elsevier Ireland Ltd.

PMID: 22209882 [PubMed - as supplied by publisher]

Targeted Disruption of Toxoplasma gondii Serine Protease Inhibitor 1 Increases Bradyzoite Cyst Formation In Vitro and Parasite Tissue Burden in Mice

2011-12-29T06:16:00.000-08:00

Infect Immun. 2011 Dec 27. [Epub ahead of print]

Targeted Disruption of Toxoplasma gondii Serine Protease Inhibitor 1 Increases Bradyzoite Cyst Formation In Vitro and Parasite Tissue Burden in Mice.

Pszenny V, Davis PH, Zhou XW, Hunter CA, Carruthers VB, Roos DS.

Source
Departments of Biology.

Abstract
As an intracellular protozoan parasite, Toxoplasma gondii is likely to exploit proteases for host cell invasion, acquisition of nutrients, avoidance of host protective responses, escape from the parasitophorous vacuole, differentiation, and other activities. The serine protease inhibitor TgPI1 is the most abundantly expressed protease inhibitor in parasite tachyzoites. We show here that alternative splicing produces two TgPI1 isoforms, both of which are secreted via dense granules into the parasitophorous vacuole shortly after invasion, become progressively more abundant over the course of the infectious cycle, and can be detected in the infected host cell cytoplasm. To investigate TgPI1 function, the endogenous genomic locus was disrupted in the RH strain background. ΔTgPI1 parasites replicate normally as tachyzoites, but exhibit increased bradyzoite gene transcription and labeling of vacuoles with Dolichos biflorous lectin and under conditions promoting in vitro differentiation; both phenotypes can be partially complemented by either TgPI1 isoform. Mice infected with the ΔTgPI1 mutant display ∼3-fold increased parasite burden in the spleen and liver, and this in vivo phenotype is also complemented by either TgPI1 isoform. These results demonstrate that TgPI1 influences both parasite virulence and bradyzoite differentiation, presumably by inhibiting parasite and/or host serine proteases.

PMID: 22202120 [PubMed - as supplied by publisher]

The Distribution of Toxoplasma gondii Cysts in the Brain of a Mouse with Latent Toxoplasmosis: Implications for the Behavioral Manipulation Hypothesis

2011-12-25T10:00:00.004-08:00

PLoS One. 2011;6(12):e28925. Epub 2011 Dec 14.

The Distribution of Toxoplasma gondii Cysts in the Brain of a Mouse with Latent Toxoplasmosis: Implications for the Behavioral Manipulation Hypothesis.

Berenreiterová M, Flegr J, Kuběna AA, Němec P.

Source
Biology Section, Faculty of Science, Charles University in Prague, Praha, Czech Republic.

Abstract
BACKGROUND:
The highly prevalent parasite Toxoplasma gondii reportedly manipulates rodent behavior to enhance the likelihood of transmission to its definitive cat host. The proximate mechanisms underlying this adaptive manipulation remain largely unclear, though a growing body of evidence suggests that the parasite-entrained dysregulation of dopamine metabolism plays a central role. Paradoxically, the distribution of the parasite in the brain has received only scant attention.

METHODOLOGY/PRINCIPAL FINDINGS:

The distributions of T. gondii cysts and histopathological lesions in the brains of CD1 mice with latent toxoplasmosis were analyzed using standard histological techniques. Mice were infected per orally with 10 tissue cysts of the avirulent HIF strain of T. gondii at six months of age and examined 18 weeks later. The cysts were distributed throughout the brain and selective tropism of the parasite toward a particular functional system was not observed. Importantly, the cysts were not preferentially associated with the dopaminergic system and absent from the hypothalamic defensive system. The striking interindividual differences in the total parasite load and cyst distribution indicate a probabilistic nature of brain infestation. Still, some brain regions were consistently more infected than others. These included the olfactory bulb, the entorhinal, somatosensory, motor and orbital, frontal association and visual cortices, and, importantly, the hippocampus and the amygdala. By contrast, a consistently low incidence of tissue cysts was recorded in the cerebellum, the pontine nuclei, the caudate putamen and virtually all compact masses of myelinated axons. Numerous perivascular and leptomeningeal infiltrations of inflammatory cells were observed, but they were not associated with intracellular cysts.

CONCLUSION/SIGNIFICANCE:

The observed pattern of T. gondii distribution stems from uneven brain colonization during acute infection and explains numerous behavioral abnormalities observed in the chronically infected rodents. Thus, the parasite can effectively change behavioral phenotype of infected hosts despite the absence of well targeted tropism.

PMID: 22194951 [PubMed - in process]

Iron-saturated lactoferrin and pathogenic protozoa: could this protein be an iron source for their parasitic style of life?

2011-12-25T10:00:00.003-08:00

Future Microbiol. 2012 Jan;7:149-64.

Iron-saturated lactoferrin and pathogenic protozoa: could this protein be an iron source for their parasitic style of life?

Ortíz-Estrada G, Luna-Castro S, Piña-Vázquez C, Samaniego-Barrón L, León-Sicairos N, Serrano-Luna J, de la Garza M.

Source

Departamento de Biología Celular, Centro de Investigación y de Estudios Avanzados del IPN, Apdo. 14-740, México DF 07000, México.

Abstract

Iron is an essential nutrient for the survival of pathogens inside a host. As a general strategy against microbes, mammals have evolved complex iron-withholding systems for efficiently decreasing the iron accessible to invaders. Pathogens that inhabit the respiratory, intestinal and genitourinary tracts encounter an iron-deficient environment on the mucosal surface, where ferric iron is chelated by lactoferrin, an extracellular glycoprotein of the innate immune system. However, parasitic protozoa have developed several mechanisms to obtain iron from host holo-lactoferrin. Tritrichomonas fetus, Trichomonas vaginalis, Toxoplasma gondii and Entamoeba histolytica express lactoferrin-binding proteins and use holo-lactoferrin as an iron source for growth in vitro; in some species, these binding proteins are immunogenic and, therefore, may serve as potential vaccine targets. Another mechanism to acquire lactoferrin iron has been reported in Leishmania spp. promastigotes, which use a surface reductase to recognize and reduce ferric iron to the accessible ferrous form. Cysteine proteases that cleave lactoferrin have been reported in E. histolytica. This review summarizes the available information on how parasites uptake and use the iron from lactoferrin to survive in hostile host environments.

PMID: 22191452 [PubMed - in process]

IL-6 signaling SOCS critical for IL-12 host response to Toxoplasma gondii

2011-12-25T10:00:00.001-08:00

Future Microbiol. 2012 Jan;7:13-6.

IL-6 signaling SOCS critical for IL-12 host response to Toxoplasma gondii.

Mirpuri J, Yarovinsky F.

Source

Department of Immunology, University of Texas Southwestern Medical Center at Dallas, 5323 Harry Hines Boulevard, Dallas, TX 75390-9093, USA. felix.yarovinsky@utsouthwestern.edu.

Abstract

Evaluation of: Whitmarsh RJ, Gray CM, Gregg B et al. A critical role for SOCS3 in innate resistance to Toxoplasma gondii. Cell Host Microbe 10(3), 224-236 (2011). SOCS are a family of proteins that play an important role in the negative regulation of the cytokine-JAK-STAT pathway. Socs3 deletion results in prolonged IL-6 signaling measured by STAT3 phosphorylation. A role for STAT3 and SOCS3 in the context of Toxoplasma gondii infection is of particular importance, because STAT3 appears to be a key target of T. gondii virulence factors. By utilizing LysM-cre Socs3(fl/fl) mice, the Hunter laboratory recently established that macrophage-specific SOCS3 knockout mice have enhanced susceptibility to infection with T. gondii. The authors demonstrated that lack of SOCS3-mediated control of IL-6 signaling results in acute susceptibility to T. gondii due to impaired IL-12 production by inflammatory monocytes, macrophages and neutrophils. This article further explores these findings and their implications in the field of host resistance to microbial pathogens.

PMID: 22191442 [PubMed - in process]

The apicoplast and endoplasmic reticulum cooperate in fatty acid biosynthesis in the apicomplexan parasite Toxoplasma gondii

2011-12-20T05:23:00.000-08:00

J Biol Chem. 2011 Dec 16. [Epub ahead of print]

The apicoplast and endoplasmic reticulum cooperate in fatty acid biosynthesis in the apicomplexan parasite Toxoplasma gondii.

Ramakrishnan S, Docampo MD, Macrae JI, Pujol FM, Brooks CF, van Dooren GG, Hiltunen JK, Kastaniotis AJ, McConville MJ, Striepen B.

Source
University of Georgia, United States;

Abstract
Apicomplexan parasites are responsible for high impact human diseases such as malaria, toxoplasmosis and cryptosporidiosis. These obligate intracellular pathogens are dependent on both de novo lipid biosynthesis as well as the uptake of host lipids for biogenesis of parasite membranes. Genome annotations and biochemical studies indicate that apicomplexan parasites can synthesize fatty acids via a number of different biosynthetic pathways that are differentially compartmentalized. However, the relative contribution of each of these biosynthetic pathways to total fatty acid composition of intracellular parasite stages remains poorly defined. Here we use a combination of genetic, biochemical and metabolomic approaches to delineate the contribution of fatty acid biosynthetic pathways in Toxoplasma gondii. Metabolic labeling studies with (13)Parasite fatty acid synthesis is an attractive drug target but complex and poorly understood.C-glucose showed that intracellular tachyzoites synthesized a range of long and very long chain fatty acids (C14:0-26:1). Genetic disruption of the apicoplast localized type II fatty acid synthase (FASII) resulted in greatly reduced synthesis of saturated fatty acids up to eighteen carbons long. Ablation of FASII activity resulted in reduced intracellular growth that was partially restored by addition of long chain fatty acids. In contrast, synthesis of very long chain fatty acids was primarily dependent on a fatty acid elongation system comprising three elongases, two reductases and a dehydratase that were localized to the endoplasmic reticulum. The function of these enzymes was confirmed by heterologous expression in yeast. This elongase pathway appears to have a unique role in generating very long unsaturated fatty acids (C26:1) that cannot be salvaged from the host.

PMID: 22179608 [PubMed - as supplied by publisher]

Independent Roles of Apical Membrane Antigen 1 and Rhoptry Neck Proteins during Host Cell Invasion by Apicomplexa

2011-12-20T05:22:00.000-08:00

Cell Host Microbe. 2011 Dec 15;10(6):591-602.

Independent Roles of Apical Membrane Antigen 1 and Rhoptry Neck Proteins during Host Cell Invasion by Apicomplexa.

Giovannini D, Späth S, Lacroix C, Perazzi A, Bargieri D, Lagal V, Lebugle C, Combe A, Thiberge S, Baldacci P, Tardieux I, Ménard R.

Source
Institut Pasteur, Unité de Biologie et Génétique du Paludisme, 75724 Paris, France.

Abstract
During invasion, apicomplexan parasites form an intimate circumferential contact with the host cell, the tight junction (TJ), through which they actively glide. The TJ, which links the parasite motor to the host cell cytoskeleton, is thought to be composed of interacting apical membrane antigen 1 (AMA1) and rhoptry neck (RON) proteins. Here we find that, in Plasmodium berghei, while both AMA1 and RON4 are important for merozoite invasion of erythrocytes, only RON4 is required for sporozoite invasion of hepatocytes, indicating that RON4 acts independently of AMA1 in the sporozoite. Further, in the Toxoplasma gondii tachyzoite, AMA1 is dispensable for normal RON4 ring and functional TJ assembly but enhances tachyzoite apposition to the cell and internalization frequency. We propose that while the RON proteins act at the TJ, AMA1 mainly functions on the zoite surface to permit correct attachment to the cell, which may facilitate invasion depending on the zoite-cell combination.

Copyright © 2011 Elsevier Inc. All rights reserved.

PMID: 22177563 [PubMed - in process]

Secretion of multi-protein migratory complex induced by Toxoplasma gondii infection in macrophages involves the uPA/uPAR activation system

2011-12-20T05:21:00.000-08:00

Vet Parasitol. 2011 Nov 20. [Epub ahead of print]

Secretion of multi-protein migratory complex induced by Toxoplasma gondii infection in macrophages involves the uPA/uPAR activation system.

Schuindt SH, Oliveira BC, Pimentel PM, Resende TL, Retamal CA, Damatta RA, Seipel D, Arnholdt AC.

Source
Laboratório de Biologia do Reconhecer, Centro de Biociências e Biotecnologia, Universidade Estadual do Norte Fluminense, Campos dos Goytacazes, Rio de Janeiro, Brazil.

Abstract
Toxoplasmosis is a world wide spread zoonosis caused by Toxoplasma gondii, an obligate intracellular parasite that is able to disseminate into deep tissues and cross biological barriers, reaching immunoprivileged sites such as the brain and retina. The parasite is able to infect macrophages and dendritic cells for dispersal throughout the body. However, the molecular mechanisms or outcomes of the subversion of the host cell are largely unknown. Recently our group established that metalloproteinases are involved in migration of infected macrophages. Herein, we evaluated the recruitment of host invasive machinery components in T. gondii infected murine macrophages. We showed by immunoprecipitation assays that MMP-9, CD44 TIMP-1 and uPAR were secreted as a multi-protein complex by infected macrophages. Zymographic analysis revealed that MMP-9 was present in its pro- and active form. Moreover, inhibition of uPA/uPAR pathway by PAI-1 decreased secretion of MMP-9 active forms, as well those associated to uPAR and TIMP-1, but not to CD44. Data presented here suggest that MMP-9 is secreted as a multiprotein complex by T. gondii infected macrophages, similar to that observed in metastatic cells. We further speculate that uPA/uPAR system is involved in the expression/secretion of complexes containing active MMP-9 forms.

Copyright © 2011 Elsevier B.V. All rights reserved.

PMID: 22177333 [PubMed - as supplied by publisher]

New insights into parasite rhomboid proteases

2011-12-19T06:16:00.001-08:00

Mol Biochem Parasitol. 2011 Dec 7. [Epub ahead of print]

New insights into parasite rhomboid proteases.

Santos JM, Graindorge A, Soldati-Favre D.

Source
Department of Microbiology, Faculty of Medicine, University of Geneva, 1 Rue-Michel Servet, 1211 Geneva 4, Switzerland.

Abstract
The rhomboid-like proteins constitute a large family of intramembrane serine proteases that are present in all branches of life. First studied in Drosophila, these enzymes catalyse the release of the active forms of proteins from the membrane and hence trigger signalling events. In protozoan parasites, a limited number of rhomboid-like proteases have been investigated and some of them are associated to pathogenesis. In Apicomplexans, rhomboid-like protease activity is involved in shedding adhesins from the surface of the zoites during motility and host cell entry. Recently, a Toxoplasma gondii rhomboid was also implicated in an intracellular signalling mechanism leading to parasite proliferation. In Entamoeba histolytica, the capacity to adhere to host cells and to phagocytose cells is potentiated by a rhomboid-like protease. Survey of a small number of protozoan parasite genomes has uncovered species-specific rhomboid-like protease genes, many of which are predicted to encode inactive enzymes. Functional investigation of the rhomboid-like proteases in other protozoan parasites will likely uncover novel and unexpected implications for this family of proteases.

Copyright © 2011. Published by Elsevier B.V.

PMID: 22173057 [PubMed - as supplied by publisher]

Deficiency of a Niemann-Pick, Type C1-related Protein in Toxoplasma Is Associated with Multiple Lipidoses and Increased Pathogenicity

2011-12-19T06:15:00.000-08:00

PLoS Pathog. 2011 Dec;7(12):e1002410. Epub 2011 Dec 8.

Deficiency of a Niemann-Pick, Type C1-related Protein in Toxoplasma Is Associated with Multiple Lipidoses and Increased Pathogenicity.

Lige B, Romano JD, Bandaru VV, Ehrenman K, Levitskaya J, Sampels V, Haughey NJ, Coppens I.

Source
Department of Molecular Microbiology and Immunology, Johns Hopkins University Bloomberg School of Public Health, Baltimore, Maryland, United States of America.

Abstract
Several proteins that play key roles in cholesterol synthesis, regulation, trafficking and signaling are united by sharing the phylogenetically conserved 'sterol-sensing domain' (SSD). The intracellular parasite Toxoplasma possesses at least one gene coding for a protein containing the canonical SSD. We investigated the role of this protein to provide information on lipid regulatory mechanisms in the parasite. The protein sequence predicts an uncharacterized Niemann-Pick, type C1-related protein (NPC1) with significant identity to human NPC1, and it contains many residues implicated in human NPC disease. We named this NPC1-related protein, TgNCR1. Mammalian NPC1 localizes to endo-lysosomes and promotes the movement of sterols and sphingolipids across the membranes of these organelles. Miscoding patient mutations in NPC1 cause overloading of these lipids in endo-lysosomes. TgNCR1, however, lacks endosomal targeting signals, and localizes to flattened vesicles beneath the plasma membrane of Toxoplasma. When expressed in mammalian NPC1 mutant cells and properly addressed to endo-lysosomes, TgNCR1 restores cholesterol and GM1 clearance from these organelles. To clarify the role of TgNCR1 in the parasite, we genetically disrupted NCR1; mutant parasites were viable. Quantitative lipidomic analyses on the ΔNCR1 strain reveal normal cholesterol levels but an overaccumulation of several species of cholesteryl esters, sphingomyelins and ceramides. ΔNCR1 parasites are also characterized by abundant storage lipid bodies and long membranous tubules derived from their parasitophorous vacuoles. Interestingly, these mutants can generate multiple daughters per single mother cell at high frequencies, allowing fast replication in vitro, and they are slightly more virulent in mice than the parental strain. These data suggest that the ΔNCR1 strain has lost the ability to control the intracellular levels of several lipids, which subsequently results in the stimulation of lipid storage, membrane biosynthesis and parasite division. Based on these observations, we ascribe a role for TgNCR1 in lipid homeostasis in Toxoplasma.

PMID: 22174676 [PubMed - in process]

Dynamics and 3D organization of secretory organelles of Toxoplasma gondii

2011-12-15T05:57:00.000-08:00

J Struct Biol. 2011 Dec 4. [Epub ahead of print]

Dynamics and 3D organization of secretory organelles of Toxoplasma gondii.

Paredes-Santos TC, de Souza W, Attias M.

SourceInstituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Brazil; Instituto Nacional de Ciência e Tecnologia em Biologia Estrutural e Bioimagem, Brazil.

Abstract
Micronemes, rhoptries and dense granules are secretory organelles of Toxoplasma gondii crucial for host cell invasion and formation of the parasitophorous vacuole (PV). We examined whether their relative volumes change during the intracellular cycle. Stereological analysis of random ultrathin sections taken at 5min of interaction, 7 and 24h post-infection demonstrated that the relative volume of each type of organelle decreases just after the respective peak of secretion. Micronemes are radially arranged below the polar ring, while rhoptries converge to but only a few reach the inside of the conoid. In contrast to the apical and polarized organelles, dense granules were found scattered throughout the cytoplasm, with no preferential location in the parasite cell body. Extensive observation of random sections indicated that each organelle probably secretes in a different region. Micronemes secrete just below the posterior ring and probably require that the conoid is extruded. The rhoptries passing through the conoid secrete at a porosome-like point at the most apical region. Dense granules secrete laterally, probably at fenestrations in the inner membrane complex. Immunocytochemistry showed that there are no subpopulations of rhoptries or dense granules, as a single organelle can contain more than one kind of its specific proteins. The vacuolar-like profiles observed at the apical portion of parasites just after invasion were confirmed to be empty rhoptries, as they were positively labeled for rhoptry proteins. These findings contribute for a better understanding of the essential behavior of secretory organelles.

Copyright © 2011. Published by Elsevier Inc.

PMID:22155668[PubMed - as supplied by publisher]

Toxoplasma and Plasmodium protein kinases: Roles in invasion and host cell remodelling

2011-12-15T05:54:00.000-08:00

Int J Parasitol. 2011 Dec 4. [Epub ahead of print]

Toxoplasma and Plasmodium protein kinases: Roles in invasion and host cell remodelling.

Lim DC, Cooke BM, Doerig C, Saeij JP.

SourceDavid H. Koch Institute for Integrative Cancer Research, Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.

Abstract
Some apicomplexan parasites have evolved distinct protein kinase families to modulate host cell structure and function. Toxoplasma gondii rhoptry protein kinases and pseudokinases (ROPKs) are involved in virulence and modulation of host cell signalling. The proteome of Plasmodium falciparum contains a family of putative kinases called FIKKs, some of which are exported to the host red blood cell and might play a role in erythrocyte remodelling. In this review we will discuss kinases known to be critical for host cell invasion, intracellular growth and egress, focusing on (i) calcium-dependent protein kinases (CDPKs) and (ii) the secreted kinases that are unique to Toxoplasma (ROPKs) and Plasmodium (FIKKs).

Copyright © 2011. Published by Elsevier Ltd.

PMID:22154850[PubMed - as supplied by publisher]

A systematic screen to discover and analyze apicoplast proteins identifies a conserved and essential protein import factor

2011-12-08T11:01:00.000-08:00

PLoS Pathog. 2011 Dec;7(12):e1002392. Epub 2011 Dec 1.

A systematic screen to discover and analyze apicoplast proteins identifies a conserved and essential protein import factor.

Sheiner L, Demerly JL, Poulsen N, Beatty WL, Lucas O, Behnke MS, White MW, Striepen B.
SourceCenter for Tropical and Emerging Global Diseases, University of Georgia, Athens, Georgia, United States of America.

Abstract
Parasites of the phylum Apicomplexa cause diseases that impact global health and economy. These unicellular eukaryotes possess a relict plastid, the apicoplast, which is an essential organelle and a validated drug target. However, much of its biology remains poorly understood, in particular its elaborate compartmentalization: four membranes defining four different spaces. Only a small number of organellar proteins have been identified in particular few proteins are known for non-luminal apicoplast compartments. We hypothesized that enlarging the catalogue of apicoplast proteins will contribute toward identifying new organellar functions and expand the realm of targets beyond a limited set of characterized pathways. We developed a bioinformatic screen based on mRNA abundance over the cell cycle and on phyletic distribution. We experimentally assessed 57 genes, and of 30 successful epitope tagged candidates eleven novel apicoplast proteins were identified. Of those, seven appear to target to the lumen of the organelle, and four localize to peripheral compartments. To address their function we then developed a robust system for the construction of conditional mutants via a promoter replacement strategy. We confirm the feasibility of this system by establishing conditional mutants for two selected genes - a luminal and a peripheral apicoplast protein. The latter is particularly intriguing as it encodes a hypothetical protein that is conserved in and unique to Apicomplexan parasites and other related organisms that maintain a red algal endosymbiont. Our studies suggest that this peripheral plastid protein, PPP1, is likely localized to the periplastid compartment. Conditional disruption of PPP1 demonstrated that it is essential for parasite survival. Phenotypic analysis of this mutant is consistent with a role of the PPP1 protein in apicoplast biogenesis, specifically in import of nuclear-encoded proteins into the organelle.

PMID:22144892[PubMed - in process]

Autophagy Protein Atg3 is Essential for Maintaining Mitochondrial Integrity and for Normal Intracellular Development of Toxoplasma gondii Tachyzoites

2011-12-08T09:16:00.001-08:00

PLoS Pathog. 2011 Dec;7(12):e1002416. Epub 2011 Dec 1.

Autophagy Protein Atg3 is Essential for Maintaining Mitochondrial Integrity and for Normal Intracellular Development of Toxoplasma gondii Tachyzoites.

Besteiro S, Brooks CF, Striepen B, Dubremetz JF.

SourceUMR 5235 CNRS, Universités de Montpellier 2 et 1, Dynamique des Interactions Membranaires Normales et Pathologiques, Montpellier, France.

Abstract
Autophagy is a cellular process that is highly conserved among eukaryotes and permits the degradation of cellular material. Autophagy is involved in multiple survival-promoting processes. It not only facilitates the maintenance of cell homeostasis by degrading long-lived proteins and damaged organelles, but it also plays a role in cell differentiation and cell development. Equally important is its function for survival in stress-related conditions such as recycling of proteins and organelles during nutrient starvation. Protozoan parasites have complex life cycles and face dramatically changing environmental conditions; whether autophagy represents a critical coping mechanism throughout these changes remains poorly documented. To investigate this in Toxoplasma gondii, we have used TgAtg8 as an autophagosome marker and showed that autophagy and the associated cellular machinery are present and functional in the parasite. In extracellular T. gondii tachyzoites, autophagosomes were induced in response to amino acid starvation, but they could also be observed in culture during the normal intracellular development of the parasites. Moreover, we generated a conditional T. gondii mutant lacking the orthologue of Atg3, a key autophagy protein. TgAtg3-depleted parasites were unable to regulate the conjugation of TgAtg8 to the autophagosomal membrane. The mutant parasites also exhibited a pronounced fragmentation of their mitochondrion and a drastic growth phenotype. Overall, our results show that TgAtg3-dependent autophagy might be regulating mitochondrial homeostasis during cell division and is essential for the normal development of T. gondii tachyzoites.

PMID:22144900[PubMed - in process]

An atypical strain associated with congenital toxoplasmosis in Tunisia

2011-12-08T09:15:00.002-08:00

New Microbiol. 2011 Oct;34(4):413-6. Epub 2011 Oct 31.

An atypical strain associated with congenital toxoplasmosis in Tunisia.

Boughattas S, Abdallah RB, Siala E, Aoun K, Bouratbine A.

SourceLaboratoire de Recherche 05SP03, Laboratoire de Parasitologie, Institut Pasteur de Tunis, Tunis Belvedère, Tunisia.

Abstract
We report the identification and typing of a congenital toxoplasmosis case in a diabetic pregnant young woman living in Tunis. The Toxoplasma DNA extracted from amniotic fluid was detected by Real Time PCR and subjected to a multilocus genetic characterisation of the strain at markers: 3'SAG2, 5'SAG2, New SAG2, SAG3, GRA6, BTUB, APICO, PK1, KT850 and UPRT1. An atypical genotype of T.gondii with unusual genetic composition was revealed. It is the first time that an atypical strain has been associated with congenital toxoplasmosis in Africa. Atypical strains are associated with severe clinical manifestations so systematic genotyping should be investigated with the amniocentesis.

PMID:22143816[PubMed - in process]

Microbial Infection-Induced Expansion of Effector T Cells Overcomes the Suppressive Effects of Regulatory T Cells via an IL-2 Deprivation Mechanism

2011-12-08T09:15:00.001-08:00

J Immunol. 2011 Dec 5. [Epub ahead of print]

Microbial Infection-Induced Expansion of Effector T Cells Overcomes the Suppressive Effects of Regulatory T Cells via an IL-2 Deprivation Mechanism.

Benson A, Murray S, Divakar P, Burnaevskiy N, Pifer R, Forman J, Yarovinsky F.

SourceDepartment of Immunology, University of Texas Southwestern Medical Center, Dallas, TX 75390.

Abstract
Regulatory Foxp3(+) T cells are a critical cell population that suppresses T cell activation in response to microbial and viral pathogens. We identify a cell-intrinsic mechanism by which effector CD4(+) T cells overcome the suppressive effects of regulatory T (Treg) cells in the context of three distinct infections: Toxoplasma gondii, Listeria monocytogenes, and vaccinia virus. The acute responses to the parasitic, bacterial, and viral pathogens resulted in a transient reduction in frequency and absolute number of Treg cells. The infection-induced partial loss of Treg cells was essential for the initiation of potent Th1 responses and host protection against the pathogens. The observed disappearance of Treg cells was a result of insufficiency in IL-2 caused by the expansion of pathogen-specific CD4(+) T cells with a limited capacity of IL-2 production. Exogenous IL-2 treatment during the parasitic, bacterial, and viral infections completely prevented the loss of Treg cells, but restoration of Treg cells resulted in a greatly enhanced susceptibility to the pathogens. These results demonstrate that the transient reduction in Treg cells induced by pathogens via IL-2 deprivation is essential for optimal T cell responses and host resistance to microbial and viral pathogens.

PMID:22147768[PubMed - as supplied by publisher]

Differential Gene Expression in Mice Infected with Distinct Toxoplasma Strains

2011-12-08T08:55:00.000-08:00

Infect Immun. 2011 Dec 5. [Epub ahead of print]

Differential Gene Expression in Mice Infected with Distinct Toxoplasma Strains.

Hill RD, Gouffon JS, Saxton AM, Su C.

SourceDepartment of Microbiology.

Abstract
Toxoplasma gondii is the causative agent of toxoplasmosis in human and animals. In mouse model, T. gondii strains can be divided into three groups, including the virulent, intermediately virulent and non-virulent. The clonal Type I, II and III T. gondii strains belong to these three groups respectively. To better understand the basis of virulence phenotypes, we investigated mouse gene expression responses to the infection of different T. gondii strains at day 5 post intraperitoneal inoculation with 500 tachyzoites. The transcriptomes of mouse peritoneal cells showed that 1927, 1573, and 1009 transcripts were altered more than 2 fold by Type I, II and III infections, respectively, and majority of altered transcripts were shared. Overall transcription patterns were similar in Type I and Type II infections and both had greater changes than that of Type III. Quantification of parasite burden in mouse spleens showed that Type I was 1000 times higher than Type II, and Type II was 20 times higher than Type III. Fluorescence activated cell sorting revealed that Type I and II infections had comparable macrophage populations and both were higher than Type III infection. In addition, Type I infection had higher percentage of neutrophils than that of Type II and III. Taken together, these results suggested that there is a common gene expression response to T. gondii infection in mice. This response is further modified by parasite strain specific factors that determine their distinct virulence phenotypes.

PMID:22144491[PubMed - as supplied by publisher]

Structural insight into the activation mechanism of Toxoplasma gondii nucleoside triphosphate diphosphohydrolases by disulfide reduction

2011-12-03T16:13:00.001-08:00

J Biol Chem. 2011 Nov 30. [Epub ahead of print]

Structural insight into the activation mechanism of Toxoplasma gondii nucleoside triphosphate diphosphohydrolases by disulfide reduction.

Krug U, Zebisch M, Krauss M, Sträter N.

SourceUniversity of Leipzig, Germany;

Abstract
The intracellular parasite Toxoplasma gondii produces two nucleoside triphosphate diphosphohydrolases (NTPDase1 and -3). These tetrameric, cysteine-rich enzymes require activation by reductive cleavage of a hitherto unknown disulfide bond. Despite a 97% sequence identity both isozymes differ largely in their ability to hydrolyze ATP and ADP. Here, we present crystal structures of inactive NTPDase3 as apo form and in complex with the product AMP to resolutions of 2.0 Ang. and 2.2 Ang., respectively. We find that the enzyme is present in an open conformation that precludes productive substrate binding and catalysis. The cysteine bridge 258-268 is identified to be responsible for locking of activity. Crystal structures of constitutively active variants of NTPDase1 and -3 generated by mutation of C258-C268 show that opening of the regulatory cysteine bridge induces a pronounced contraction of the whole tetramer. This is accompanied by a 12 deg domain closure motion resulting in the correct arrangement of all active site residues. A complex structure of activated NTPDase3 with a non-hydrolyzable ATP analog and the cofactor Mg2+ to a resolution of 2.85 Ang. indicates that catalytic differences between the NTPDases are primarily dictated by differences in positioning of the adenine base caused by substitution of R492 and E493 in NTPDase1 by glycines in NTPDase3.

PMID:22130673[PubMed - as supplied by publisher]

An Inside Job: Hacking Into JAK/STAT Signaling Cascades by the Intracellular Protozoan Toxoplasma gondii

2011-11-24T08:41:00.002-08:00

Infect Immun. 2011 Nov 21. [Epub ahead of print]

An Inside Job: Hacking Into JAK/STAT Signaling Cascades by the Intracellular Protozoan Toxoplasma gondii.

Denkers EY, Bzik DJ, Fox BA, Butcher BA.

SourceDepartment of Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca NY.

Abstract
The intracellular protozoan Toxoplasma gondii is well known for its skill at invading and living within host cells. New discoveries are now also revealing the astounding ability of the parasite to inject effector proteins into the cytoplasm to seize control of the host cell. This Review summarizes recent advances in our understanding of one such secretory protein called ROP16. This molecule is released from rhoptries into the host cell during invasion. The ROP16 molecule acts as a kinase, directly activating both STAT3 and STAT6 signaling pathways. In macrophages, an important and preferential target cell of parasite infection, the injection of ROP16 has multiple consequences, including down-regulation of proinflammatory cytokine signaling and macrophage deviation to an alternatively activated phenotype.

PMID:22104110[PubMed - as supplied by publisher]

Toxoplasma gondii Triggers Release of Human and Mouse Neutrophil Extracellular Traps

2011-11-24T08:41:00.001-08:00

Infect Immun. 2011 Nov 21. [Epub ahead of print]

Toxoplasma gondii Triggers Release of Human and Mouse Neutrophil Extracellular Traps.

Abi Abdallah DS, Lin C, Ball CJ, King MR, Duhamel GE, Denkers EY.

SourceDepartment of Microbiology and Immunology.

Abstract
Neutrophils have recently been shown to release DNA-based extracellular traps that contribute to microbicidal killing and have also been implicated in autoimmunity. The role of neutrophil extracellular trap (NET) formation in the host response to nonbacterial pathogens has received much less attention. Here, we show that the protozoan pathogen Toxoplasma gondii elicits production of NETs from human and mouse neutrophils. Tachyzoites of each of the three major parasite strain types were efficiently entrapped within NETs, resulting in decreased parasite viability. We also show that Toxoplasma activates a MEK-ERK pathway in neutrophils and that inhibition of this pathway leads to decreased NET formation. To determine if Toxoplasma induced NET formation in vivo we employed a mouse intranasal infection model. We found that administration of tachyzoites by this route induced rapid tissue recruitment of neutrophils with evidence of extracellular DNA release. Taken together, these data indicate a role for NETs in the host innate response to protozoan infection. We propose that NET formation limits infection by direct microbicidal effects on Toxoplasma as well as by interfering with the ability of the parasite to invade target host cells.

PMID:22104111[PubMed - as supplied by publisher]

Infectious agents associated with schizophrenia: A meta-analysis

2011-11-24T08:40:00.000-08:00

Schizophr Res. 2011 Nov 18. [Epub ahead of print]

Infectious agents associated with schizophrenia: A meta-analysis.

Arias I, Sorlozano A, Villegas E, Luna JD, McKenney K, Cervilla J, Gutierrez B, Gutierrez J.

SourceCAP El Clot, Institut Català de la Salut, Barcelona, Spain.

Abstract
Schizophrenia is a highly disabling and limiting disorder for patients and the possibility that infections by some microorganisms may be associated to its development may allow prevention and recovery. In the current study we have done a meta-analysis of studies that have assessed the possible association between detection of different infectious agents and schizophrenia. We report results that support the idea that there is a statistically significant association between schizophrenia and infection by Human Herpesvirus 2 (OR=1.34; CI 95%: 1.09-1.70; p=0.05), Borna Disease Virus (OR=2.03; CI 95%: 1.35-3.06; p<0.01), Human Endogenous Retrovirus W (OR=19.31; CI 95%: 6.74-55.29; p<0.001), Chlamydophila pneumoniae (OR=6.34; CI 95%: 2.83-14.19; p<0.001), Chlamydophila psittaci (OR=29.05; CI 95%: 8.91-94.70; p<0.001) and Toxoplasma gondii (OR=2.70; CI 95%: 1.34-4.42; p=0.005). The implications of these findings are discussed and further research options are also explicated.

Copyright © 2011 Elsevier B.V. All rights reserved.

PMID:22104141[PubMed - as supplied by publisher]

Impaired reproductive function of male rats infected with Toxoplasma gondii

2011-11-22T07:29:00.001-08:00

Andrologia. 2011 Nov 18. doi: 10.1111/j.1439-0272.2011.01249.x. [Epub ahead of print]

Impaired reproductive function of male rats infected with Toxoplasma gondii.

Abdoli A, Dalimi A, Movahedin M

Source Department of Parasitology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran Department of Anatomy, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran.

Abstract
Toxoplasmosis is one of the classical conditions known to have an adverse effect on female reproductive functions, but a few investigations into male reproductive parameters have been performed. This work was carried out to study the effects of Toxoplasma gondii on reproductive function in male rats. Male rats were infected with the RH strain of T. gondii tachyzoites, and following every 10 days from 10 to 70 postinfection (PI), the percentage of body weight to testis weight ratio as well as epididymal sperm parameters (number, motility, viability, and morphology rates), serum testosterone (ST), intratesticular testosterone (ITT), serum lactate dehydrogenase (SLDH), intratesticular lactate dehydrogenase and fructose in seminal vesicles and coagulating glands were measured. The results of the study showed sperm motility, viability and concentration rates were significantly decreased temporary after infection up to 70 days. Sperm abnormality was also increased during these days. In addition, temporary alteration in ST, ITT, SLDH, intratesticular LDH and fructose in seminal vesicle and coagulating gland was observed PI. These findings suggest that toxoplasmosis can cause impermanent impairment on the reproductive parameters of male rats.

© 2011 Blackwell Verlag GmbH.

PMID:22098674[PubMed - as supplied by publisher]

Mechanisms of Toxoplasma gondii persistence and latency

2011-11-21T06:35:00.001-08:00

FEMS Microbiol Rev. 2011 Sep 12. doi: 10.1111/j.1574-6976.2011.00305.x. [Epub ahead of print]

Mechanisms of Toxoplasma gondii persistence and latency.

Sullivan WJ Jr, Jeffers V

SourceDepartment of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, IN, USA; Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, IN, USA.

Abstract
Toxoplasma gondii is an obligate intracellular protozoan parasite that causes opportunistic disease, particularly in immunocompromised individuals. Central to its transmission and pathogenesis is the ability of the proliferative stage (tachyzoite) to convert into latent tissue cysts (bradyzoites). Encystment allows Toxoplasma to persist in the host and affords the parasite a unique opportunity to spread to new hosts without proceeding through its sexual stage, which is restricted to felids. Bradyzoite tissue cysts can cause reactivated toxoplasmosis if host immunity becomes impaired. A greater understanding of the molecular mechanisms orchestrating bradyzoite development is needed to better manage the disease. Here, we will review key studies that have contributed to our knowledge about this persistent form of the parasite and how to study it, with a focus on how cellular stress can signal for the reprogramming of gene expression needed during bradyzoite development.

© 2011 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.

PMID:22091606[PubMed - as supplied by publisher]

Fatal Attraction Phenomenon in Humans - Cat Odour Attractiveness Increased for Toxoplasma-Infected Men While Decreased for Infected Women

2011-11-17T08:03:00.001-08:00

PLoS Negl Trop Dis. 2011 Nov;5(11):e1389. Epub 2011 Nov 8.

Fatal Attraction Phenomenon in Humans - Cat Odour Attractiveness Increased for Toxoplasma-Infected Men While Decreased for Infected Women.

Flegr J, Lenochová P, Hodný Z, Vondrová M.

SourceDepartment of Biology, Faculty of Science, Charles University, Prague, Czech Republic.

Abstract
BACKGROUND: Latent toxoplasmosis, a lifelong infection with the protozoan Toxoplasma gondii, has cumulative effects on the behaviour of hosts, including humans. The most impressive effect of toxoplasmosis is the "fatal attraction phenomenon," the conversion of innate fear of cat odour into attraction to cat odour in infected rodents. While most behavioural effects of toxoplasmosis were confirmed also in humans, neither the fatal attraction phenomenon nor any toxoplasmosis-associated changes in olfactory functions have been searched for in them.

PRINCIPAL FINDINGS: Thirty-four Toxoplasma-infected and 134 noninfected students rated the odour of urine samples from cat, horse, tiger, brown hyena and dog for intensity and pleasantness. The raters were blind to their infection status and identity of the samples. No signs of changed sensitivity of olfaction were observed. However, we found a strong, gender dependent effect of toxoplasmosis on the pleasantness attributed to cat urine odour (p = 0.0025). Infected men rated this odour as more pleasant than did the noninfected men, while infected women rated the same odour as less pleasant than did noninfected women. Toxoplasmosis did not affect how subjects rated the pleasantness of any other animal species' urine odour; however, a non-significant trend in the same directions was observed for hyena urine.

CONCLUSIONS: The absence of the effects of toxoplasmosis on the odour pleasantness score attributed to large cats would suggest that the amino acid felinine could be responsible for the fatal attraction phenomenon. Our results also raise the possibility that the odour-specific threshold deficits observed in schizophrenia patients could be caused by increased prevalence of Toxoplasma-infected subjects in this population rather than by schizophrenia itself. The trend observed with the hyena urine sample suggests that this carnivore, and other representatives of the Feliformia suborder, should be studied for their possible role as definitive hosts in the life cycle of Toxoplasma.

PMID:22087345[PubMed - as supplied by publisher]

Congenital parasitic infections: A review

2011-11-17T08:02:00.004-08:00

Acta Trop. 2011 Nov 7. [Epub ahead of print]

Congenital parasitic infections: A review.

Carlier Y, Truyens C, Deloron P, Peyron F.

SourceLaboratoire de Parasitologie, Faculté de Médecine, Université Libre de Bruxelles (ULB), CP 616, Route de Lennik 808, 1070 Brussels, Belgium; Department of Tropical Medicine, School of Public Health and Tropical Medicine, Tulane University, Suite 2210, 1440 Canal Street, New Orleans, LA 70112-2797, USA.

Abstract
This review defines the concepts of maternal-fetal (congenital) and vertical transmissions (mother-to-child) of pathogens and specifies the human parasites susceptible to be congenitally transferred. It highlights the epidemiological features of this transmission mode for the three main congenital parasitic infections due to Toxoplasma gondii, Trypanosoma cruzi and Plasmodium sp. Information on the possible maternal-fetal routes of transmission, the placental responses to infection and timing of parasite transmission are synthesized and compared. The factors susceptible to be involved in parasite transmission and development of congenital parasitic diseases, such as the parasite genotypes, the maternal co-infections and parasitic load, the immunological features of pregnant women and the capacity of some fetuses/neonates to overcome their immunological immaturity to mount an immune response against the transmitted parasites are also discussed and compared. Analysis of clinical data indicates that parasitic congenital infections are often asymptomatic, whereas symptomatic newborns generally display non-specific symptoms. The long-term consequences of congenital infections are also mentioned, such as the imprinting of neonatal immune system and the possible trans-generational transmission. The detection of infection in pregnant women is mainly based on standard serological or parasitological investigations. Amniocentesis and cordocentesis can be used for the detection of some fetal infections. The neonatal infection can be assessed using parasitological, molecular or immunological methods; the place of PCR in such neonatal diagnosis is discussed. When such laboratory diagnosis is not possible at birth or in the first weeks of life, standard serological investigations can also be performed 8-10 months after birth, to avoid detection of maternal transmitted antibodies. The specific aspects of treatment of T. gondii, T. cruzi and Plasmodium congenital infections are mentioned. The possibilities of primary and secondary prophylaxes, as well as the available WHO corresponding recommendations are also presented.

Copyright © 2011. Published by Elsevier B.V.

PMID:22085916[PubMed - as supplied by publisher]

Neonatal antibodies to infectious agents and risk of bipolar disorder: a population-based case-control study

2011-11-17T08:02:00.003-08:00

Bipolar Disord. 2011 Nov;13(7-8):624-629. doi: 10.1111/j.1399-5618.2011.00962.x.

Neonatal antibodies to infectious agents and risk of bipolar disorder: a population-based case-control study.

Mortensen PB, Pedersen CB, McGrath JJ, Hougaard DM, Nørgaard-Petersen B, Mors O, Børglum AD, Yolken RH.

SourceNational Centre for Register-based Research, Faculty of Social Sciences, University of Aarhus, Aarhus, Denmark Queensland Brain Institute, University of Queensland, St. Lucia, Qld, Australia State Serum Institute, København, Denmark Centre for Psychiatric Research, University Hospital in Aarhus, Psychiatric Hospital, Risskov, Denmark Institute of Human Genetics, University of Aarhus, Aarhus, Denmark Stanley Neurovirology Laboratory, Johns Hopkins University, School of Medicine, Baltimore, MD, USA.

Abstract
Mortensen PB, Pedersen CB, McGrath JJ, Hougaard DM, Nørgaard-Petersen B, Mors O, Børglum AD, Yolken RH. Neonatal antibodies to infectious agents and risk of bipolar disorder: a population-based case-control study. Bipolar Disord 2011: 13: 624-629. © 2011 The Authors. Journal compilation © 2011 John Wiley & Sons A/S. Objective: There is a substantial evidence base linking prenatal exposure to infectious agents and an increased risk of schizophrenia. However, there has been less research examining the potential for these exposures to also contribute to risk for bipolar disorder. The aim of this study was to examine the association between neonatal markers of selected prenatal infections and risk for bipolar disorder. Methods: Using population-based Danish registers, we examined 127 individuals with a diagnosis of bipolar disorder, and 127 sex and day-of-birth individually matched controls. Based on neonatal dried blood spots, we measured antibodies to herpes simplex virus type 1 (HSV-1) and 2 (HSV-2), cytomegalovirus (CMV), and Toxoplasma gondii. Relative risks were calculated for the matched pairs when examined for optical density units for antibodies to each of the infectious agents. Results: There was no association between any of the neonatal markers of prenatal infection and risk of bipolar disorder. Conclusions: In contrast with studies of schizophrenia, our analysis does not support maternal infection with HSV-1, HSV-2, CMV, or Toxoplasma gondii as risk factors for bipolar disorder. However, larger study samples are needed, and data on, for example, specific serotypes of Toxoplasma and indicators of the timing of maternal infection are still warranted.

© 2011 John Wiley and Sons A/S.

PMID:22085475[PubMed - as supplied by publisher]

rROP2(186?533): A Novel Peptide Antigen for Detection of IgM Antibodies Against Toxoplasma gondii

2011-11-17T08:02:00.001-08:00

Foodborne Pathog Dis. 2011 Nov 15. [Epub ahead of print]

rROP2(186?533): A Novel Peptide Antigen for Detection of IgM Antibodies Against Toxoplasma gondii.

Liu L, Liu T, Yu L, Cai Y, Zhang A, Xu X, Luo Q, Hu Y, Song W, Lun Z, Lu F, Wang Y, Shen J.

Source1 Anhui Provincial Key Laboratory of Microbiology and Parasitology, Anhui Medical University , Hefei, China .

Abstract
Abstract Toxoplasma gondii infections are prevalent in a wide range of mammalian hosts including humans. Infection in pregnant women may cause the transmission of parasite to the fetus that makes serious problems. IgM antibodies against Toxoplasma (Toxo-IgM) have been believed to be significant indicators for both recently acquired and congenital toxoplasmosis. So far, however, there has not been any recognized protein of T. gondii that specifically reacts to IgM antibodies. Here, an antigen exclusively for detection of IgM antibodies screened by two-dimensional electrophoresis and mass spectrometry has been reported. The study identified 13 Toxoplasma proteins probed by IgG antibodies and one (rhpotry protein 2 [ROP2]) by IgM antibodies with human sera of Toxo-IgM(?)-IgG(+) and -IgM(+)-IgG(?), respectively, which had been prescreened by Toxo-IgM and -IgG commercial kits from the suspected cases. Following cloning, expression, and purification of the fragment of ROP2(186?533), an enzyme-linked immunosorbent assay with rROP2(186?533) to measure IgM and IgG antibodies was developed. As a result, 100%(48/48) of sera with Toxo-IgM(+)-IgG(?)showed positive Toxo-IgM but none of them (0%) showed positive Toxo-IgG when rROP2(186?533) was used as antigen. Neither Toxo-IgG nor Toxo-IgM antibodies were found when tested with 59 sera of Toxo-IgM(?)-IgG(+). These results indicate that rROP2(186?533) could be used as an antigen that specifically capture Toxo-IgM antibodies and may have a high potential in the serological diagnosis of both acute acquired and congenital toxoplasmosis.

PMID:22085219[PubMed - as supplied by publisher]

Tissue barriers of the human placenta to infection with Toxoplasma gondii

2011-11-16T05:31:00.000-08:00

Infect Immun. 2011 Nov 14. [Epub ahead of print]

Tissue barriers of the human placenta to infection with Toxoplasma gondii.

Robbins JR, Zeldovich VB, Poukchanski A, Boothroyd JC, Bakardjiev AI.

SourceDepartment of Pediatrics, University of California, San Francisco, California, USA.

Abstract
Toxoplasma gondii is a ubiquitous, obligate intracellular parasite capable of crossing the placenta to cause spontaneous abortion, pre-term labor or significant disease in the surviving neonate. Exploration of the cellular and histological components of the placental barrier is in its infancy, and both how and where T. gondii breaches it is unknown. The human placenta presents two anatomical interfaces between maternal cells and fetal cells (trophoblasts): 1) the villous region where maternal blood bathes syncytialized trophoblasts for nutrient exchange; and, 2) the maternal decidua, where mononuclear, extravillous trophoblasts anchor the villous region to the uterus. Using first-trimester human placental explants, we demonstrate that the latter site is significantly more vulnerable to infection, despite presenting a vastly smaller surface. This is consistent with past findings concerning two vertically transmitted viruses and one bacterium. We further explore whether three genetically distinct T. gondii types (I, II and III) are capable of preferential placental infection and survival in this model. We find no difference in these strains' ability to infect placental explants; however, slightly slower growth is evident in Type II (Pru) parasites relative to other cell types although this did not quite achieve statistical significance.

PMID:22083708[PubMed - as supplied by publisher]

Oral oocyst-induced mouse model of toxoplasmosis

2011-11-15T07:24:00.001-08:00

Parasitology. 2011 Nov 14:1-13. [Epub ahead of print]

Oral oocyst-induced mouse model of toxoplasmosis: effect of infection with Toxoplasma gondii strains of different genotypes, dose, and mouse strains (transgenic, out-bred, in-bred) on pathogenesis and mortality.

Dubey JP, Ferreira LR, Martins J, McLeod R.

SourceUnited States Department of Agriculture, Animal Natural Resources Institute, Animal Parasitic Disease Laboratory, BARC-East, Building. 1001, Beltsville, MD 20705-2350, USA.

Abstract
SUMMARYHumans and other hosts acquire Toxoplasma gondii infection by ingesting tissue cysts in undercooked meat, or by food or drink contaminated with oocysts. Currently, there is no vaccine to prevent clinical disease due this parasite in humans, although, various T. gondii vaccine candidates are being developed. Mice are generally used to test the protective efficacy of vaccines because they are susceptible, reagents are available to measure immune parameters in mice, and they are easily managed in the laboratory. In the present study, pathogenesis of toxoplasmosis was studied in mice of different strains, including Human Leukocyte Antigen (HLA) transgenic mice infected with different doses of T. gondii strains of different genotypes derived from several countries. Based on many experiments, the decreasing order of infectivity and pathogenicity of oocysts was: C57BL/6 background interferon gamma gene knock out (KO), HLA-A*1101, HLA-A*0201, HLA-B*0702, Swiss Webster, C57/black, and BALB/c. Mice fed as few as 1 oocyst of Type I and several atypical strains died of acute toxoplasmosis within 21 days p.i. Some Type II, and III strains were less virulent. The model developed herein should prove to be extremely useful for testing vaccines because it is possible to accurately quantitate a challenge inoculum, test the response to different strains of T. gondii using the same preparations of oocysts which are stable for up to a year, and to have highly reproducible responses to the infection.

PMID:22078010[PubMed - as supplied by publisher]

The placenta: a main role in congenital toxoplasmosis

2011-11-15T07:21:00.000-08:00

Trends Parasitol. 2011 Nov 11. [Epub ahead of print]

The placenta: a main role in congenital toxoplasmosis?

Robert-Gangneux F, Murat JB, Fricker-Hidalgo H, Brenier-Pinchart MP, Gangneux JP, Pelloux H.

SourceLaboratoire de Parasitologie-Mycologie, Centre Hospitalier et Universitaire de Rennes, Rennes, France; EA4427-SERAIC, IRSET (Institut de Recherche en Santé Environnement Travail), Université Rennes 1, Rennes, France.

Abstract
Systemic infections, such as toxoplasmosis, acquired during pregnancy can lead to placental infection and have profound effects on the mother-to-child relationship and the success of pregnancy. Placental permeability to Toxoplasma gondii is a main parameter that determines parasite transmission to the foetus, and the use of antibiotics to decrease placental parasite load and prevent congenital toxoplasmosis has been suggested for decades. Although parasitological examination of the placenta at birth is commonly used to diagnose neonatal congenital toxoplasmosis, this approach can be controversial. Here we argue in favour of placental examination for both diagnostic and epidemiological purposes.

Copyright © 2011 Elsevier Ltd. All rights reserved.

PMID:22079164[PubMed - as supplied by publisher]

DNA vaccination with a gene encoding Toxoplasma gondii GRA6 induces partial protection against toxoplasmosis in BALB/c mice

2011-11-13T12:06:00.003-08:00

Parasit Vectors. 2011 Nov 9;4(1):213. [Epub ahead of print]

DNA vaccination with a gene encoding Toxoplasma gondii GRA6 induces partial protection against toxoplasmosis in BALB/c mice.

Sun XM, Zou J, Saeed A A E, Yan WC, Liu XY, Suo X, Wang H, Chen QJ.
Abstract
ABSTRACT:

BACKGROUND: Infection with protozoa Toxoplasma gondii causes serious public health problems and is of great economic importance worldwide. Protection from acute toxoplasmosis is known to be mediated by CD8+ T cells, but the T. gondii antigens and host genes required for eliciting protective immunity have been poorly defined. The T. gondii dense granule protein 6 (GRA6), recently proved to be highly immunogenic, produces fully immune protection in T. gondii infected BALB/c mice with an H-2Ld gene. The CD8+ T cell response of H-2Ld mice infected by the T. gondii strain seemed to target entirely to a single GRA6 peptide HF10-H-2Ld complex.

RESULTS: To determine whether GRA6-based DNA vaccine can elicit protective immune response to T. gondii in BALB/c mice, we constructed a eukaryotic expression vector pcDNA3.1-HisGRA6 and tested its immunogenicity in mouse model. BALB/c mice were vaccinated intramuscularly with three doses of GRA6 DNA and then challenged with a lethal dose of T. gondii RH strain tachyzoites. All immunized mice developed high levels of serum anti-GRA6 IgG antibodies, and in vitro splenocyte proliferation was strongly enhanced in mice adjuvanted with levamisole (LMS). Immunization with pcDNA3.1-HisGRA6 with LMS resulted in 53.3% survival of challenged BALB/c mice as compared to 40% survival of BALB/c without levamisole. Additionally, immunized Kunming mice without an allele of H-2Ld failed to survive.

CONCLUSIONS: Our result supports the concept that the immune response is MHC restricted. This study has a major implication for vaccine designs using a single antigen in a population with diverse MHC class I alleles.

PMID:22070984[PubMed - as supplied by publisher]

Protozoan Parasite Toxoplasma gondii Manipulates Mate Choice in Rats by Enhancing Attractiveness of Males

2011-11-13T12:06:00.001-08:00

PLoS One. 2011;6(11):e27229. Epub 2011 Nov 2.

Protozoan Parasite Toxoplasma gondii Manipulates Mate Choice in Rats by Enhancing Attractiveness of Males.

Dass SA, Vasudevan A, Dutta D, Soh LJ, Sapolsky RM, Vyas A.

SourceSchool of Biological Sciences, Nanyang Technological University, Singapore, Republic of Singapore.

Abstract
Females in various species typically avoid males infected with parasites, while parasite-free males advertise their status through conspicuous phenotypic traits. This process selects for heritable resistance and reduces direct exposure of the female to parasites. Coevolving parasites are likely to attempt to circumvent this obstacle. In this paper, we demonstrate a case of parasitic manipulation of host mate choice. We report that Toxoplasma gondii, a sexually transmitted infection of brown rats, enhances sexual attractiveness of infected males. Thus under some evolutionary niches, parasites can indeed manipulate host sexual signaling to their own advantage.

PMID:22073295[PubMed - in process]

A Monomorphic Haplotype of Chromosome Ia Is Associated with Widespread Success in Clonal and Nonclonal Populations of Toxoplasma gondii

2011-11-13T12:05:00.001-08:00

MBio. 2011 Nov 8;2(6). pii: e00228-11. doi: 10.1128/mBio.00228-11. Print 2011.

A Monomorphic Haplotype of Chromosome Ia Is Associated with Widespread Success in Clonal and Nonclonal Populations of Toxoplasma gondii.

Khan A, Miller N, Roos DS, Dubey JP, Ajzenberg D, Dardé ML, Ajioka JW, Rosenthal B, Sibley LD.

SourceDepartment of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, USA.

Abstract
ABSTRACT Toxoplasma gondii is a common parasite of animals that also causes a zoonotic infection in humans. Previous studies have revealed a strongly clonal population structure that is shared between North America and Europe, while South American strains show greater genetic diversity and evidence of sexual recombination. The common inheritance of a monomorphic version of chromosome Ia (referred to as ChrIa*) among three clonal lineages from North America and Europe suggests that inheritance of this chromosome might underlie their recent clonal expansion. To further examine the diversity and distribution of ChrIa, we have analyzed additional strains with greater geographic diversity. Our findings reveal that the same haplotype of ChrIa* is found in the clonal lineages from North America and Europe and in older lineages in South America, where sexual recombination is more common. Although lineages from all three continents harbor the same conserved ChrIa* haplotype, strains from North America and Europe are genetically separate from those in South America, and these respective geographic regions show limited evidence of recent mixing. Genome-wide, array-based profiling of polymorphisms provided evidence for an ancestral flow from particular older southern lineages that gave rise to the clonal lineages now dominant in the north. Collectively, these data indicate that ChrIa* is widespread among nonclonal strains in South America and has more recently been associated with clonal expansion of specific lineages in North America and Europe. These findings have significant implications for the spread of genetic loci influencing transmission and virulence in pathogen populations. IMPORTANCE Understanding parasite population structure is important for evaluating the potential spread of pathogenicity determinants between different geographic regions. Examining the genetic makeup of different isolates of Toxoplasma gondii from around the world revealed that chromosome Ia is highly homogeneous among lineages that predominate on different continents and within genomes that were otherwise quite divergent. This pattern of recent shared ancestry is highly unusual and suggests that some gene(s) found on this chromosome imparts an unusual fitness advantage that has resulted in its recent spread. Although the basis for the conservation of this particularly homogeneous chromosome is unknown, it may have implications for the transmission of infection and spread of human disease.

PMID:22068979[PubMed - in process]

A Toxoplasma gondii mutant highlights the importance of translational regulation in the apicoplast during animal infection

2011-11-13T12:02:00.002-08:00

Mol Microbiol. 2011 Nov 7. doi: 10.1111/j.1365-2958.2011.07879.x. [Epub ahead of print]

A Toxoplasma gondii mutant highlights the importance of translational regulation in the apicoplast during animal infection.

Payne TM, Payne AJ, Knoll LJ.

SourceDepartment of Medical Microbiology and Immunology, University of Wisconsin-Madison, 1550 Linden Drive, Madison, WI 53706, USA.

Abstract
Toxoplasma gondii is an obligate intracellular parasite of all warm-blooded animals. We previously described a forward genetic screen to identify T. gondii mutants defective in the establishment of a chronic infection. One of the mutants isolated was disrupted in the 3' untranslated region (3'UTR) of an orthologue of bacterial translation elongation factor G (EFG). The mutant does not have a growth defect in tissue culture. Genetic complementation of this mutant with the genomic locus of TgEFG restores virulence in an acute infection mouse model. Epitope tagged TgEFG localized to the apicoplast, via a non-canonical targeting signal, where it functions as an elongation factor for translation in the apicoplast. Comparisons of TgEFG expression constructs with wild-type or mutant 3'UTRs showed that a wild-type 3'UTR is necessary for translation of TgEFG. In tissue culture, the TgEFG transcript is equally abundant in wild-type and mutant parasites; however, during an animal infection, the TgEFG transcript is increased more than threefold in the mutant. These results highlight that in tissue culture, translation in the apicoplast can be diminished, but during an animal infection, translation in the apicoplast must be fully functional.

© 2011 Blackwell Publishing Ltd.

PMID:22059956[PubMed - as supplied by publisher]

Insights into inflammatory bowel disease using Toxoplasma gondii as an infectious trigger

2011-11-13T12:02:00.001-08:00

Immunol Cell Biol. 2011 Nov 8. doi: 10.1038/icb.2011.93. [Epub ahead of print]

Insights into inflammatory bowel disease using Toxoplasma gondii as an infectious trigger.

Egan CE, Cohen SB, Denkers EY.

SourceDepartment of Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca, NY, USA.

Abstract
Oral infection of certain inbred mouse strains with the protozoan Toxoplasma gondii triggers inflammatory pathology resembling lesions seen during human inflammatory bowel disease, in particular Crohn's disease (CD). Damage triggered by the parasite is largely localized to the distal portion of the small intestine, and as such is one of only a few models for ileal inflammation. This is important because ileal involvement is a characteristic of CD in over two-thirds of patients. The disease induced by Toxoplasma is mediated by Th1 cells and the cytokines tumor necrosis factor-α and interferon-γ. Inflammation is dependent upon IL-23, also identified by genome-wide association studies as a risk factor in CD. Development of lesions is concomitant with emergence of E. coli that display enhanced adhesion to the intestinal epithelium and subepithelial translocation. Furthermore, depletion of gut flora renders mice resistant to Toxoplasma-triggered ileitis. Recent findings suggest complex CCR2-dependent interactions between lamina propria T cells and intraepithelial lymphocytes in fueling proinflammatory pathology in the intestine. The advantage of the Toxoplasma model is that disease develops rapidly (within 7-10 days of infection) and can be induced in immunodeficient mice by adoptive transfer of mucosal T cells from infected donors. We propose that Toxoplasma acts as a trigger setting into motion a series of events culminating in loss of tolerance in the intestine and emergence of pathogenic T cell effectors. The Toxoplasma trigger model is providing new leaps in our understanding of immunity in the intestine.Immunology and Cell Biology advance online publication, 8 November 2011; doi:10.1038/icb.2011.93.

PMID:22064707[PubMed - as supplied by publisher]

Molecular dissection of novel trafficking and processing of the T. gondii rhoptry metalloprotease Toxolysin-1

2011-11-02T06:07:00.002-07:00

Traffic. 2011 Oct 28. doi: 10.1111/j.1600-0854.2011.01308.x. [Epub ahead of print]

Molecular dissection of novel trafficking and processing of the T. gondii rhoptry metalloprotease Toxolysin-1.

Hajagos BE, Turetzky JM, Peng ED, Cheng SJ, Ryan CM, Souda P, Whitelegge JP, Lebrun M, Dubremetz JF, Bradley PJ.

SourceDepartment of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, Los Angeles CA 90095-1489 USA Pasarow Mass Spectrometry Laboratory, NPI-Semel Institute for Neuroscience and Human Behaviour, David Geffen School of Medicine, University of California, Los Angeles, California UMR 5539, Centre National de la Recherche Scientifique, Université de Montpellier 2, Montpellier, France.

Abstract
Toxoplasma gondii utilizes specialized secretory organelles called rhoptries to invade and hijack its host cell. Many rhoptry proteins are proteolytically processed at a highly conserved SΦXE site to remove organellar targeting sequences that may also affect protein activity. We have studied the trafficking and biogenesis of a secreted rhoptry metalloprotease with homology to insulysin that we named Toxolysin-1 (TLN1). Through genetic ablation and molecular dissection of TLN1 we have identified the smallest rhoptry targeting domain yet reported and expanded the consensus sequence of the rhopty pro-domain cleavage site. In addition to removal of its pro-domain, Toxolysin-1 undergoes a C-terminal cleavage event that occurs at a processing site not previously seen in Toxoplasma rhoptry proteins. While pro-domain cleavage occurs in the nascent rhoptries, processing of the C-terminal region precedes commitment to rhoptry targeting, suggesting that it is mediated by a different maturase, and we have identified residues critical for proteolysis. We have additionally shown that both pieces of TLN1 associate in a detergent resistant complex, formation of which is necessary for trafficking of the C-terminal portion to the rhoptries. Together, these studies reveal novel processing and trafficking events that are present in the protein constituents of this unusual secretory organelle.

© 2011 John Wiley & Sons A/S.

PMID:22035499[PubMed - as supplied by publisher]

Methods to produce and safely work with large numbers of Toxoplasma gondii oocysts and bradyzoite cysts

2011-11-02T06:07:00.001-07:00

J Microbiol Methods. 2011 Oct 20. [Epub ahead of print]

Methods to produce and safely work with large numbers of Toxoplasma gondii oocysts and bradyzoite cysts.

Fritz H, Barr B, Packham A, Melli A, Conrad PA.

SourceDepartment of Pathology, Microbiology and Immunology, School of Veterinary Medicine, 1 Shields Avenue, University of California Davis, CA 95616, USA.

Abstract
Two major obstacles to conducting studies with Toxoplasma gondii oocysts are the difficulty in reliably producing large numbers of this life stage and safety concerns because the oocyst is the most environmentally resistant stage of this zoonotic organism. Oocyst production requires oral infection of the definitive feline host with adequate numbers of T. gondii organisms to obtain unsporulated oocysts that are shed in the feces for 3-10days after infection. Since the most successful and common mode of experimental infection of kittens with T. gondii is by ingestion of bradyzoite tissue cysts, the first step in successful oocyst production is to ensure a high bradyzoite tissue cyst burden in the brains of mice that can be used for the oral inoculum. We compared two methods for producing bradyzoite brain cysts in mice, by infecting them either orally or subcutaneously with oocysts. In both cases, oocysts derived from a low passage T. gondii Type II strain (M4) were used to infect eight-ten week-old Swiss Webster mice. First the number of bradyzoite cysts that were purified from infected mouse brains was compared. Then to evaluate the effect of the route of oocyst inoculation on tissue cyst distribution in mice, a second group of mice was infected with oocysts by one of each route and tissues were examined by histology. In separate experiments, brains from infected mice were used to infect kittens for oocyst production. Greater than 1.3 billion oocysts were isolated from the feces of two infected kittens in the first production and greater than 1.8 billion oocysts from three kittens in the second production. Our results demonstrate that oral delivery of oocysts to mice results in both higher cyst loads in the brain and greater cyst burdens in other tissues examined as compared to those of mice that received the same number of oocysts subcutaneously. The ultimate goal in producing large numbers of oocysts in kittens is to generate adequate amounts of starting material for oocyst studies. Given the potential risks of working with live oocysts in the laboratory, we also tested a method of oocyst inactivation by freeze-thaw treatment. This procedure proved to completely inactivate oocysts without evidence of significant alteration of the oocyst molecular integrity.

Copyright © 2011. Published by Elsevier B.V.

PMID:22037023[PubMed - as supplied by publisher]

Movable computer ruler (MCR): A new method for measuring the size of Toxoplasma gondii cysts, tachyzoites and other selected parasites

2011-11-02T05:58:00.000-07:00

Exp Parasitol. 2011 Oct 20. [Epub ahead of print]

Movable computer ruler (MCR): A new method for measuring the size of Toxoplasma gondii cysts, tachyzoites and other selected parasites

Otify YZ

SourceDepartment Parasitology, Faculty of Veterinary Medicine, Alexandria University, Edfina, Behira 22758, Egypt.

Abstract
A new method for measuring the size of parasites and other objects using optical microscopy was developed using a specifically designed movable computer ruler (MCR) derived from digital images of a stage micrometer. Subsequently, MCR can be superimposed on images of parasites to measure their size. MCR derived from the stage micrometer under a particular objective lens can be used to measure the size of an object acquired by the same lens/microscope/camera system. The conditions are fixed for every superimposed image including width, height, pixel number and density. The MCR was tested using selected parasites, and shown to be as accurate as the ocular micrometer disk, screw micrometer eyepiece and image analysis software. The lower technical complexity of the MCR method makes it applicable even in laboratories with limited resources.

Copyright Â© 2011 Elsevier Inc. All rights reserved.

PMID:22041100[PubMed - as supplied by publisher]

Separation and purification of Toxoplasma gondii tachyzoites from in vitro and in vivo culture systems

2011-10-29T15:06:00.003-07:00

Exp Parasitol. 2011 Oct 15. [Epub ahead of print]

Separation and purification of Toxoplasma gondii tachyzoites from in vitro and in vivo culture systems.

Wu L, Chen SX, Jiang XG, Fu XL, Shen YJ, Cao JP.

SourceSchool of Medical Science and Laboratory Medicine, Jiangsu University, 212013 Zhenjiang, People's Republic of China.

Abstract
In this study, we evaluated four methods to separate and purify Toxoplasma gondii tachyzoites from in vivo and in vitro culture systems, including trypsin digestion, purification with a 3-μm filter, CF-11 cellulose purification, and Percoll purification. Our results indicate that both purification with a 3-μm filter and CF11 cellulose purification methods remove leukocytes or HeLa cells, and can therefore be used as candidate methods for the purification of in vivo and in vitro culture products. Trypsin digestion had a high tachyzoite recovery rate, but 22.35% of leukocytes and 69.64% of HeLa cells remained in the purified products. Percoll solution [30% (v/v)] also had a high tachyzoite recovery rate, but 3.44% of leukocytes and 61.61% of HeLa cells remained in the purified products. The 40% Percoll solution was also a candidate method for purifying tachyzoites from in vivo culture products, with a 65.45% tachyzoite recovery rate and without leukocytes.

Copyright © 2011 Elsevier Inc. All rights reserved.

PMID:22033076[PubMed - as supplied by publisher]

Molecular cloning and characterization of Mitogen-activated protein kinase 2 in Toxoplasma gondii

2011-10-29T15:06:00.001-07:00

Cell Cycle. 2011 Oct 31;10(20). [Epub ahead of print]

Molecular cloning and characterization of Mitogen-activated protein kinase 2 in Toxoplasma gondii.

Huang H, Ma YF, Bao Y, Lee H, Lisanti MP, Tanowitz HB, Weiss LM.

SourceDepartment of Pathology; Albert Einstein College of Medicine; Bronx, NY USA.

Abstract
Toxoplasma gondii is an obligate intracellular protozoan that is both a human and animal pathogen. This Apicomplexan causes significant morbidity and mortality in immune competent and immune compromised hosts. In humans, the most common manifestations of T. gondii infections are chorioretinitis in congenital infection and encephalitis in immune compromised patients such as patients with advanced AIDS. Mitogen-activated protein kinase (MAPK) pathways are major signal transduction systems by which eukaryotic cells convert environmental cues to intracellular events such as proliferation and differentiation. We have identified a T. gondii homologue of the MAPK family that we have called TgMAPK2. Sequence analyses demonstrated TgMAPK2 has homology with lower eukaryotic ERK2, but has significant differences from mammalian ERK2. TgMAPK2 has an open reading frame of 2037 bp, 678 amino acids, and its molecular weight is 73.1 kDa. It contains the typical twelve sub-domains of a MAPK and has a TDY motif in the dual phosphorylation and activation subdomains. This suggests that TgMAPK2 may play an important role in stress response. Recombinant TgMAPK2 was catalytically active and was not inhibited by a human ERK2 inhibitor, FR180204. A partial TgMAPK2 lacking the ATP binding motifs, GxGxxGxV, was successfully regulated by a ligand-controlled destabilization domain (ddFKBP) expression vector system in T. gondii. Since TgMAPK2 is significantly different from its mammalian counterpart it may be useful as a drug target. This work establishes a foundation for further study for this unique kinase.

PMID:22030559[PubMed - as supplied by publisher]

Toxoplasma gondii: Determination of the onset of chronic infection in mice and the in vitro reactivation of brain cysts

2011-10-28T04:45:00.001-07:00

Exp Parasitol. 2011 Oct 18. [Epub ahead of print]

Toxoplasma gondii: Determination of the onset of chronic infection in mice and the in vitro reactivation of brain cysts.

Kit CW, Wah MJ, Ambu S, Segarra I.

SourceDepartment of Human Biology, School of Medicine, International Medical University, No. 126 Jalan 19/155B, Bukit Jalil, 57000 Kuala Lumpur, Malaysia.

Abstract
Toxoplasma gondii is an intra-cellular parasite that infects humans through vertical and horizontal transmission. The cysts remain dormant in the brain of infected humans and can reactivate in immunocompromised hosts resulting in acute toxoplasmic encephalitis which may be fatal. We determined the onset and progression of brain cysts generation in a mouse model following acute toxoplasmosis as well as the ability of brain cysts to reactivate in vitro. Male Balb/c mice, (uninfected control group, n=10) were infected orally (study group, n=50) with 1000 tachyzoites of T. gondii (ME49 strain) and euthanized at 1, 2, 4, 8 and 16weeks post infection. Brain tissue was harvested, homogenized, stained and the number of brain cysts counted. Aliquots of brain homogenate with cysts were cultured in vitro with confluent Vero cells and the number of cysts and tachyzoites counted after 1week. Brain cysts but not tachyzoites were detected at week 2 post infection and reached a plateau by week 4. In vitro Vero cells culture showed similar pattern for cysts and tachyzoites and reactivation of cyst in vitro was not influenced by the age of the brain cysts.

Copyright © 2011 Elsevier Inc. All rights reserved.

PMID:22027550[PubMed - as supplied by publisher]

The apicoplast: a red alga in human parasites

2011-10-27T12:24:00.001-07:00

Essays Biochem. 2011 Oct 24;51:111-25.

The apicoplast: a red alga in human parasites.

Striepen B.

SourceCenter for Tropical and Emerging Global Diseases and Department of Cellular Biology, University of Georgia, 500 D.W. Brooks Drive, Athens, GA 30602, U.S.A.

Abstract
Surprisingly, some of the world's most dangerous parasites appear to have had a benign photosynthetic past in the ocean. The phylum Apicomplexa includes the causative agents of malaria and a number of additional human and animal diseases. These diseases threaten the life and health of hundreds of millions each year and pose a tremendous challenge to public health. Recent findings suggest that Apicomplexa share their ancestry with diatoms and kelps, and that a key event in their evolution was the acquisition of a red algal endosymbiont. A remnant of this endosymbiont is still present today, albeit reduced to a small chloroplast-like organelle, the apicoplast. In the present chapter, I introduce the remarkably complex biology of this organelle. The apicoplast is bounded by four membranes, and these membranes trace their ancestry to three different organisms. Intriguingly, this divergent ancestry is still reflected in their molecular makeup and function. We also pursue the raison d'être of the apicoplast. Why did Apicomplexa retain a chloroplast when they abandoned photosynthesis for a life as obligate parasites? The answer to this question appears to lie in the profound metabolic dependence of the parasite on its endosymbiont. This dependence may prove to be a liability to the parasite. As humans lack chloroplasts, the apicoplast has become one of the prime targets for the development of parasite-specific drugs.

PMID:22023445[PubMed - in process]

The Phosphoproteomes of Plasmodium falciparum and Toxoplasma gondii Reveal Unusual Adaptations Within and Beyond the Parasites' Boundaries

2011-10-27T12:07:00.002-07:00

Cell Host Microbe. 2011 Oct 4;10(4):410-9.

The Phosphoproteomes of Plasmodium falciparum and Toxoplasma gondii Reveal Unusual Adaptations Within and Beyond the Parasites' Boundaries.

Treeck M, Sanders JL, Elias JE, Boothroyd JC.

SourceDepartment of Microbiology and Immunology, Stanford University School of Medicine, Stanford, CA 94305, USA.

Abstract
Plasmodium falciparum and Toxoplasma gondii are obligate intracellular apicomplexan parasites that rapidly invade and extensively modify host cells. Protein phosphorylation is one mechanism by which these parasites can control such processes. Here we present a phosphoproteome analysis of peptides enriched from schizont stage P. falciparum and T. gondii tachyzoites that are either "intracellular" or purified away from host material. Using liquid chromatography-tandem mass spectrometry, we identified over 5,000 and 10,000 previously unknown phosphorylation sites in P. falciparum and T. gondii, respectively, revealing that protein phosphorylation is an extensively used regulation mechanism both within and beyond parasite boundaries. Unexpectedly, both parasites have phosphorylated tyrosines, and P. falciparum has unusual phosphorylation motifs that are apparently shaped by its A:T-rich genome. This data set provides important information on the role of phosphorylation in the host-pathogen interaction and clues to the evolutionary forces operating on protein phosphorylation motifs in both parasites.

Copyright © 2011 Elsevier Inc. All rights reserved.

PMID:22018241[PubMed - in process]

Toxoplasmosis: diagnosis, treatment, and prevention in congenitally exposed infants

2011-10-27T12:07:00.001-07:00

J Pediatr Health Care. 2011 Nov;25(6):355-64. Epub 2010 Jun 12.

Toxoplasmosis: diagnosis, treatment, and prevention in congenitally exposed infants.

Kaye A.

Abstract
Toxoplasmosis is a rare disease caused by the obligate intracellular protozoan parasite, Toxoplasma gondii. Most persons with toxoplasmosis in the United States are asymptomatic, but if a woman is infected during pregnancy, the parasite can cross the placenta and cause congenital toxoplasmosis in the fetus. The severity of congenital toxoplasmosis depends on when in the pregnancy the mother is exposed, but it can cause ocular and central nervous system disease as well as lead to growth failure and hearing and vision abnormalities. Congenital toxoplasmosis is treated with a combination of pyrimethamine, sulfadiazine, and leucovorin. It is important for pediatric nurse practitioners to be aware of the clinical presentation and treatment of congenital toxoplasmosis.

Copyright © 2011 National Association of Pediatric Nurse Practitioners. Published by Mosby, Inc. All rights reserved.

PMID:22018426[PubMed - in process]

Toxoplasma gondii: Identification and immune response against a group of proteins involved in cellular invasion

2011-10-27T12:06:00.002-07:00

Exp Parasitol. 2011 Oct 12. [Epub ahead of print]

Toxoplasma gondii: Identification and immune response against a group of proteins involved in cellular invasion.

Azzouz S, Maache M, Osuna A, Lawton P, Pétavy AF.

SourceDepartment of Parasitology and Medical Mycology, Université de Lyon, Université Claude Bernard-Lyon I, ISPB, Faculté de Pharmacie, 8 Avenue Rockefeller, 69373 Lyon Cedex 08, France.

Abstract
Toxoplasma gondii is an ubiquitous intracellular parasite, causative agent of toxoplasmosis, and a worldwide zoonosis for which an effective vaccine is needed. A group of proteins secreted by tachyzoites during host-cell invasion was isolated from the interaction medium. It induced the permeability of the cells as assessed by alpha-sarcin and consequently facilitated the entry of the parasite into the cells. SDS-PAGE of the purified proteins showed a pattern of four proteins of 67, 42, 32 and 27kDa. MRC-5 cells incubated with the total protein and the different electroeluted bands endured a high cellular death in presence of alpha-sarcin. BALb/C mice immunized with the group of proteins had a mixed Th1/Th2 response and were protected upon challenge with the parasites.

Copyright © 2011. Published by Elsevier Inc.

PMID:22019410[PubMed - as supplied by publisher]

Identification of tissue cyst wall components by transcriptome analysis of in vivo and in vitro Toxoplasma bradyzoites

2011-10-27T12:06:00.001-07:00

Eukaryot Cell. 2011 Oct 21. [Epub ahead of print]

Identification of tissue cyst wall components by transcriptome analysis of in vivo and in vitro Toxoplasma bradyzoites.

Buchholz KR, Fritz HM, Chen X, Durbin-Johnson B, Rocke DM, Ferguson DJ, Conrad PA, Boothroyd JC.

SourceDepartment of Microbiology and Immunology, Stanford University School of Medicine, Stanford, California, 94305, USA.

Abstract
The Toxoplasma gondii bradyzoite is essential to establish persistent infection yet little is known about what factors this developmental form secretes to establish the cyst or interact with its host cell. To identify candidate bradyzoite-secreted effectors, the transcriptomes of in vitro tachyzoites 2 days post-infection, in vitro bradyzoites 4 days post-infection, and in vivo bradyzoites 21 days post-infection were interrogated by microarray, and the program SignalP was used to identify signal peptides indicating secretion. One-hundred-and-two putative bradyzoite-secreted effectors were identified with this approach. Two candidates, bradyzoite pseudokinase 1 (BPK1) and microneme adhesive repeat (MAR)-domain containing protein 4 (MCP4), were chosen for further investigation and confirmed to be induced and secreted by bradyzoites in vitro and in vivo. Thus, we report the first analysis of the transcriptomes of in vitro and in vivo bradyzoites and identify two new protein components of the Toxoplasma tissue cyst wall.

PMID:22021236[PubMed - as supplied by publisher]

SPM1 Stabilizes Subpellicular Microtubules in Toxoplasma gondii

2011-10-27T12:05:00.000-07:00

Eukaryot Cell. 2011 Oct 21. [Epub ahead of print]

SPM1 Stabilizes Subpellicular Microtubules in Toxoplasma gondii.

Tran JQ, Li C, Chyan A, Chung L, Morrissette NS.

SourceDepartment of Molecular Biology and Biochemistry, University of California, Irvine, Irvine CA 92697.

Abstract
We have identified two novel proteins that co-localize with the subpellicular microtubules in the protozoan parasite Toxoplasma gondii and named these proteins SPM1 and SPM2. These proteins have basic isoelectric points and both have homologs in other apicomplexan parasites. SPM1 contains six tandem copies of a 32 amino acid repeat whereas SPM2 lacks defined protein signatures. Alignment of Toxoplasma SPM2 with apparent Plasmodium SPM2 homologs indicates that the greatest degree of conservation lies in the carboxy-terminal half of the protein. Analysis of Plasmodium homologs of SPM1 indicates that while the central 32 amino acid repeats have expanded to different degrees (seven, eight, nine, twelve or thirteen repeats), the amino and carboxy-terminal regions remain conserved. In contrast, although the Cryptosporidium SPM1 homolog has a conserved carboxy-tail, the five repeats are considerably diverged, and it has a smaller amino-terminal domain. SPM1 is localized along the full length of the subpellicular microtubules but does not associate with the conoid or spindle microtubules. SPM2 has a restricted localization along the middle region of the subpellicular microtubules. Domain deletion analysis indicates that four or more copies of the SPM1 repeat are required for localization to microtubules, and the amino-terminal 63 residues of SPM2 are required for localization to the subpellicular microtubules. Gene deletion studies indicate that neither SPM1 nor SPM2 is essential for tachyzoite viability. However, loss of SPM1 decreases overall parasite fitness and eliminates the stability of subpellicular microtubules to detergent extraction.

PMID:22021240[PubMed - as supplied by publisher]

Unrecognized Ingestion of Toxoplasma gondii Oocysts Leads to Congenital Toxoplasmosis and Causes Epidemics in North America

2011-10-27T12:03:00.000-07:00

Clin Infect Dis. 2011 Oct 21. [Epub ahead of print]

Unrecognized Ingestion of Toxoplasma gondii Oocysts Leads to Congenital Toxoplasmosis and Causes Epidemics in North America.

Boyer K, Hill D, Mui E, Wroblewski K, Karrison T, Dubey JP, Sautter M, Noble AG, Withers S, Swisher C, Heydemann P, Hosten T, Babiarz J, Lee D, Meier P, McLeod R; other members of the Toxoplasmosis Study Group.
SourceDepartment of Pediatrics.

Abstract
Background. Congenital toxoplasmosis presents as severe, life-altering disease in North America. If mothers of infants with congenital toxoplasmosis could be identified by risks, it would provide strong support for educating pregnant women about risks, to eliminate this disease. Conversely, if not all risks are identifiable, undetectable risks are suggested. A new test detecting antibodies to sporozoites demonstrated that oocysts were the predominant source of Toxoplasma gondii infection in 4 North American epidemics and in mothers of children in the National Collaborative Chicago-based Congenital Toxoplasmosis Study (NCCCTS). This novel test offered the opportunity to determine whether risk factors or demographic characteristics could identify mothers infected with oocysts.Methods. Acutely infected mothers and their congenitally infected infants were evaluated, including in-person interviews concerning risks and evaluation of perinatal maternal serum samples.Results. Fifty-nine (78%) of 76 mothers of congenitally infected infants in NCCCTS had primary infection with oocysts. Only 49% of these mothers identified significant risk factors for sporozoite acquisition. Socioeconomic status, hometown size, maternal clinical presentations, and ethnicity were not reliable predictors.Conclusions. Undetected contamination of food and water by oocysts frequently causes human infections in North America. Risks are often unrecognized by those infected. Demographic characteristics did not identify oocyst infections. Thus, although education programs describing hygienic measures may be beneficial, they will not suffice to prevent the suffering and economic consequences associated with congenital toxoplasmosis. Only a vaccine or implementation of systematic serologic testing of pregnant women and newborns, followed by treatment, will prevent most congenital toxoplasmosis in North America.

PMID:22021924[PubMed - as supplied by publisher]

Identification of intracellular and plasma membrane calcium channel homologues in pathogenic parasites

2011-10-27T12:02:00.002-07:00

PLoS One. 2011;6(10):e26218. Epub 2011 Oct 14.

Identification of intracellular and plasma membrane calcium channel homologues in pathogenic parasites.

Prole DL, Taylor CW.

SourceDepartment of Pharmacology, University of Cambridge, Cambridge, United Kingdom.

Abstract
Ca(2+) channels regulate many crucial processes within cells and their abnormal activity can be damaging to cell survival, suggesting that they might represent attractive therapeutic targets in pathogenic organisms. Parasitic diseases such as malaria, leishmaniasis, trypanosomiasis and schistosomiasis are responsible for millions of deaths each year worldwide. The genomes of many pathogenic parasites have recently been sequenced, opening the way for rational design of targeted therapies. We analyzed genomes of pathogenic protozoan parasites as well as the genome of Schistosoma mansoni, and show the existence within them of genes encoding homologues of mammalian intracellular Ca(2+) release channels: inositol 1,4,5-trisphosphate receptors (IP(3)Rs), ryanodine receptors (RyRs), two-pore Ca(2+) channels (TPCs) and intracellular transient receptor potential (Trp) channels. The genomes of Trypanosoma, Leishmania and S. mansoni parasites encode IP(3)R/RyR and Trp channel homologues, and that of S. mansoni additionally encodes a TPC homologue. In contrast, apicomplexan parasites lack genes encoding IP(3)R/RyR homologues and possess only genes encoding TPC and Trp channel homologues (Toxoplasma gondii) or Trp channel homologues alone. The genomes of parasites also encode homologues of mammalian Ca(2+)influx channels, including voltage-gated Ca(2+) channels and plasma membrane Trp channels. The genome of S. mansoni also encodes Orai Ca(2+) channel and STIM Ca(2+) sensor homologues, suggesting that store-operated Ca(2+) entry may occur in this parasite. Many anti-parasitic agents alter parasite Ca(2+) homeostasis and some are known modulators of mammalian Ca(2+) channels, suggesting that parasite Ca(2+) channel homologues might be the targets of some current anti-parasitic drugs. Differences between human and parasite Ca(2+) channels suggest that pathogen-specific targeting of these channels may be an attractive therapeutic prospect.

PMID:22022573[PubMed - in process] PMCID: PMC3194816

Strain-dependent host transcriptional responses to toxoplasma infection are largely conserved in Mammalian and avian hosts

2011-10-27T12:02:00.001-07:00

PLoS One. 2011;6(10):e26369. Epub 2011 Oct 13.

Strain-dependent host transcriptional responses to toxoplasma infection are largely conserved in Mammalian and avian hosts.

Ong YC, Boyle JP, Boothroyd JC.

SourceStanford University, Department of Microbiology and Immunology, Stanford, California, United States of America.

Abstract
Toxoplasma gondii has a remarkable ability to infect an enormous variety of mammalian and avian species. Given this, it is surprising that three strains (Types I/II/III) account for the majority of isolates from Europe/North America. The selective pressures that have driven the emergence of these particular strains, however, remain enigmatic. We hypothesized that strain selection might be partially driven by adaptation of strains for mammalian versus avian hosts. To test this, we examine in vitro, strain-dependent host responses in fibroblasts of a representative avian host, the chicken (Gallus gallus). Using gene expression profiling of infected chicken embryonic fibroblasts and pathway analysis to assess host response, we show here that chicken cells respond with distinct transcriptional profiles upon infection with Type II versus III strains that are reminiscent of profiles observed in mammalian cells. To identify the parasite drivers of these differences, chicken fibroblasts were infected with individual F1 progeny of a Type II x III cross and host gene expression was assessed for each by microarray. QTL mapping of transcriptional differences suggested, and deletion strains confirmed, that, as in mammalian cells, the polymorphic rhoptry kinase ROP16 is the major driver of strain-specific responses. We originally hypothesized that comparing avian versus mammalian host response might reveal an inversion in parasite strain-dependent phenotypes; specifically, for polymorphic effectors like ROP16, we hypothesized that the allele with most activity in mammalian cells might be less active in avian cells. Instead, we found that activity of ROP16 alleles appears to be conserved across host species; moreover, additional parasite loci that were previously mapped for strain-specific effects on mammalian response showed similar strain-specific effects in chicken cells. These results indicate that if different hosts select for different parasite genotypes, the selection operates downstream of the signaling occurring during the beginning of the host's immune response.

PMID:22022607[PubMed - in process] PMCID: PMC3192797

Calcium storage and function in apicomplexan parasites

2011-10-27T12:01:00.002-07:00

Essays Biochem. 2011 Oct 24;51:97-110.

Calcium storage and function in apicomplexan parasites.

Moreno SN, Ayong L, Pace DA.

SourceCenter for Tropical and Emerging Global Diseases and Department of Cellular Biology, University of Georgia, Athens, GA 30602, U.S.A.

Abstract
Calcium is relevant for several vital functions in apicomplexan parasites, including host cell invasion, parasite motility and differentiation. The ER (endoplasmic reticulum) and calcium-rich acidocalcisomes have been identified as major calcium stores. Other potential calcium-storage organelles include the Golgi, the mitochondrion, the apicoplast and the recently described plant-like vacuole in Toxoplasma gondii. Compared with most eukaryotic systems, apicomplexan parasites contain a reduced number of calcium-related genes, a vast majority of which remain uncharacterized. Several Ca2+-ATPases have been described in apicomplexans, several of which are annotated in the different genomes. There is experimental evidence for an IP3 (inositol 1,4,5-trisphosphate)-dependent calcium response in Plasmodium spp. and T. gondii, although no IP3 or ryanodine receptors have been identified. Genes encoding potential calcium channels are present in T. gondi, but not in Plasmodium spp. and Cryptosporidium spp. Effector calcium-binding proteins including calmodulins and CDPK (calcium-dependent protein kinase) genes mainly found in plants have also been described. The characterized CDPKs were found to play important roles in protein secretion, host cell invasion and parasite differentiation. Taken together, the available information on calcium storage and function in apicomplexans, although fragmented, suggest the existence of unique calcium-mediated pathways in these parasites. An in-depth functional characterization of the apicomplexan calcium-related genes could lead to the identification of novel therapeutic targets, and will improve our understanding of the role of calcium in parasite development and virulence.

PMID:22023444[PubMed - in process]

Cell invasion and strain dependent induction of suppressor of cytokine signaling-1 by Toxoplasma gondii

2011-10-27T12:01:00.001-07:00

Immunobiology. 2011 Aug 27. [Epub ahead of print]

Cell invasion and strain dependent induction of suppressor of cytokine signaling-1 by Toxoplasma gondii.

Stutz A, Kessler H, Kaschel ME, Meissner M, Dalpke AH.

SourceDept. of Infectious Diseases - Medical Microbiology and Hygiene, University Heidelberg, 69120 Heidelberg, Germany.

Abstract
Toxoplasma gondii is an intracellular parasite that has to cope with the microbicidal actions of IFNγ. Previously we reported that parasite-mediated induction of suppressor of cytokine signaling protein 1 (SOCS1) contributes to inhibition of IFNγ signaling. However, the signaling requirements remained elusive. We now show that induction of SOCS1 and inhibition of nitric oxide production by IFNγ was independent of stimulation of Toll-like receptors. Instead, infection by T. gondii resulted in induction of egr transcription factors which have been reported to regulate SOCS expression. Indeed, induction of egr2 as well as SOCS1 was dependent on p38 MAP kinase and blockade of egr inhibited SOCS1 expression. Moreover, we found that Mic8, a previously identified invasion factor of T. gondii, was necessary for SOCS1 regulation and escape of IFNγ mediated nitric oxide secretion within macrophages. Surprisingly, when further analyzing Mic8 deficient parasites we noted that inhibition of IFNγ mediated up-regulation of MHC-class II and ICAM1 molecules was independent of cell invasion. Furthermore, these inhibitory effects were equally observed in type I and II strains of T. gondii and were dependent on excreted and secreted antigens. In contrast, only the virulent RH type I strain additionally induced SOCS1 and efficiently inhibited nitric oxide secretion by IFNγ. The results show that T. gondii makes use of two different mechanisms to escape from IFNγ activity with one mode being strain dependent and relying on active cell invasion and SOCS1 induction.

Copyright © 2011 Elsevier GmbH. All rights reserved.

PMID:22015046[PubMed - as supplied by publisher]

Potential immunomodulatory effects of latent toxoplasmosis in humans

2011-10-27T11:57:00.002-07:00

BMC Infect Dis. 2011 Oct 18;11(1):274. [Epub ahead of print]

Potential immunomodulatory effects of latent toxoplasmosis in humans.

Flegr J, Striz I.

ABSTRACT:

BACKGROUND: About 30% of the population worldwide are infected with the protozoan parasite Toxoplasma gondii. Latent toxoplasmosis has many specific behavioral and physiological effects on the human organism. Modified reactivity of the immune system has been suggested to play a key role in many of these effects. For example, the immunosuppression hypothesis explains the higher probability of the birth of male offspring observed in Toxoplasma-positive humans and mice by the protection of the (more immunogenic) male embryos against abortion.

METHODS: Here we searched for indices of immunosuppression in Toxoplasma-positive subjects by comparing clinical records of immunology outpatients.

RESULTS: Our cohort study showed that the male patients with latent toxoplasmosis had decreased and the Toxoplasma-positive women had increased leukocyte, NK-cell and monocyte counts in comparison with controls. The B-cell counts were reduced in both Toxoplasma-positive men and women. The difference between Toxoplasma-positive and Toxoplasma-negative subjects diminished with the decline of the specific Toxoplasma antibody titre (a proxy for the length of infection), which is consistent with the observed decreasing strength of the effect of latent toxoplasmosis on human reproduction. The prevalence of toxoplasmosis in 128 male patients was unusually low (10.9%) which contrasted with normal prevalence in 312 female patients (23.7%) and in general population Prague (20-30%).

CONCLUSIONS: Latent toxoplasmosis has immunomodulatory effects in human and probably protects men against some classes of immunopathological diseases. The main limitation of the present study was the absence of the data on the immunoreactivity of immune cells subpopulations. Therefore further studies are needed to search for indices of immunosuppression in human using more specific markers.

PMID:22008411[PubMed - as supplied by publisher]

Characterization of Toxoplasma gondii 5' UTR with Encyclopedic TSS Information

2011-10-27T11:57:00.001-07:00

J Parasitol. 2011 Oct 19. [Epub ahead of print]

Characterization of Toxoplasma gondii 5' UTR with Encyclopedic TSS Information.

Yamagishi J, Watanabe J, Goo YK, Masatani T, Suzuki Y, Xuan X.

SourceObihiro University of Agriculture and Veterynary Medicine, Professor, National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterynary Medicine.

Abstract
Abstract The 5' UTR is widely involved in gene expression via post-transcriptional regulation. However, the detail profile of the 5' UTR for Toxoplasma gondii has not demonstrated yet. To investigate the issue, we compared the predicted ORFs and transcription start sites (TSSs) of T. gondii obtained by TSS-seq, a method which enables to analyze encyclopedic TSSs with next-generation sequencers. As a result, it was demonstrated that the mode length of the 5' UTR distributes between 120 and 140 nts when a subset of genes with predicted signal peptides was examined. On the contrary, when genes without the signal peptide were examined, the length was extended to around 600 nts (nucleotides). Because additional information on the predicted signal peptide endows increased reliability to the 5' end estimation of each ORF, we believe that the former value was more reliable as a representative 5' UTR length of T. gondii and that the discrepancy indicates that current predictions of the 5' end of the ORF were less accurate and considerably more discordant with the natural status.

PMID:22010783[PubMed - as supplied by publisher]

A new alternative in vitro method for quantification of Toxoplasma gondii infectivity

2011-10-27T11:55:00.000-07:00

J Parasitol. 2011 Oct 19. [Epub ahead of print]

A new alternative in vitro method for quantification of Toxoplasma gondii infectivity.

Useo R, Husson F, De Coninck J, Khaldi S, Gervais P.

Sourcea AgroSup Dijon, Université de Bourgogne, AgroSup Dijon, Université de Bourgogne.

Abstract
Abstract An in vitro method to determine the infectious potency of an unknown suspension of the protozoan parasite Toxoplasma gondii based on kinetics of host cells lysis was developed. Mic1-3KO a mutant strain of Toxoplasma gondii RH tachyzoïtes were inoculated in 25-cm² flasks containing a 90% confluent monolayer of Human Foreskin fibroblast. Lysis kinetics was monitored for infection ratios ranging from 1:10⁶ to 1:10¹ and the threshold value for parasite egress was defined at 10⁶ tachyzoites.ml-¹. Results allowed to build a calibration curve relating the initial infection ratios to the time needed to reach 10⁶ tachyzoites.ml-¹. Finally, the method was validated using of a known mixture of dead and live parasites. This method was found to estimate with accuracy the initial ratio of infection of an unknown parasites suspension. This easy-to-use method is reproducible and application to any Toxoplasma gondii tachyzoïtes RH strain, genetically modified or not. This method is suitable for testing promising candidates for an effective live vaccine.

PMID:22010815[PubMed - as supplied by publisher]

In vitro interactions of Toxoplasma gondii tachyzoites with di-cationic compounds

2011-10-27T11:47:00.000-07:00

Parasitology. 2011 Oct 19:1-13. [Epub ahead of print]

The adaptive potential of a survival artist: characterization of the in vitro interactions of Toxoplasma gondii tachyzoites with di-cationic compounds in human fibroblast cell cultures.

Kropf C, Debache K, Rampa C, Barna F, Schorer M, Stephens CE, Ismail MA, Boykin DW, Hemphill A.

SourceInstitute of Parasitology, Vetsuisse Faculty, University of Berne, Switzerland.

Abstract
SUMMARYThe impact of di-cationic pentamidine-analogues against Toxoplama gondii (Rh- and Me49-background) was investigated. The 72 h-growth assays showed that the arylimidamide DB750 inhibited the proliferation of tachyzoites of T. gondii Rh and T. gondii Me49 with an IC50 of 0·11 and 0·13 μm, respectively. Pre-incubation of fibroblast monolayers with 1 μm DB750 for 12 h and subsequent culture in the absence of the drug also resulted in a pronounced inhibiton of parasite proliferation. However, upon 5-6 days of drug exposure, T. gondii tachyzoites adapted to the compound and resumed proliferation up to a concentration of 1·2 μm. Out of a set of 32 di-cationic compounds screened for in vitro activity against T. gondii, the arylimidamide DB745, exhibiting an IC50 of 0·03 μm and favourable selective toxicity was chosen for further studies. DB745 also inhibited the proliferation of DB750-adapted T. gondii (IC50=0·07 μm). In contrast to DB750, DB745 also had a profound negative impact on extracellular non-adapted T. gondii tachyzoites, but not on DB750-adapted T. gondii. Adaptation of T. gondii to DB745 (up to a concentration of 0·46 μm) was much more difficult to achieve and feasible only over a period of 110 days. In cultures infected with DB750-adapted T. gondii seemingly intact parasites could occasionally be detected by TEM. This illustrates the astonishing capacity of T. gondii tachyzoites to adapt to environmental changes, at least under in vitro conditions, and suggests that DB745 could be an interesting drug candidate for further assessments in appropriate in vivo models.

PMID:22011664[PubMed - as supplied by publisher]

Intrinsic expression of Nod2 in CD4(+) T lymphocytes is not necessary for the development of cell-mediated immunity and host resistance to Toxoplasma

2011-10-27T11:44:00.001-07:00

Eur J Immunol. 2011 Oct 17. doi: 10.1002/eji.201141876. [Epub ahead of print]

Intrinsic expression of Nod2 in CD4(+) T lymphocytes is not necessary for the development of cell-mediated immunity and host resistance to Toxoplasma gondii.

Caetano BC, Biswas A, Lima-Junior DS, Benevides L, Mineo TW, Horta CV, Lee KH, Silva JS, Gazzinelli RT, Zamboni DS, Kobayashi KS.

SourceDepartment of Medicine, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605, USA.

Abstract
Nod2 belongs to the NLR family of proteins and senses bacterial cell wall components to initiate innate immune responses against various pathogens. Recently it has been reported that T cell-intrinsic expression of Nod2 promotes host defense against Toxoplasma gondii infection by inducing type 1 immunity. Here we present results that demonstrate that Nod2 does not play a role in the defense against T. gondii infection. Nod2-deficient mice were fully capable of inducing Th1 immune responses and did not show enhanced susceptibility to infection. Upon T-cell receptor stimulation in vitro, Nod2-deficient CD4(+) T cells showed normal activation, IL-2 production, proliferation and Th1/2 differentiation. Nod2 mRNA and protein were expressed in CD4(+) T and CD8(+) T cells at substantial levels. Therefore Nod2, although expressed in CD4(+) T cells, does not have an intrinsic function in T-cell activation and differentiation.

Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

PMID:22002196[PubMed - as supplied by publisher]

An agent-based model for the transmission dynamics of Toxoplasma gondii

2011-10-27T11:43:00.002-07:00

J Theor Biol. 2011 Oct 12;293C:15-26. [Epub ahead of print]

An agent-based model for the transmission dynamics of Toxoplasma gondii.

Jiang W, Sullivan AM, Su C, Zhao X.

SourceDepartment of Mechanical, Aerospace and Biomedical Engineering, University of Tennessee, Knoxville, TN 37996-2030, United States; School of Civil Engineering and Mechanics, Huazhong University of Science & Technology, Wuhan 430074, China.

Abstract
Toxoplasma gondii (T. gondii) is a unicellular protozoan that infects up to one-third of the world's human population. Numerous studies revealed that a latent infection of T. gondii can cause life-threatening encephalitis in immunocompromised people and also has significant effects on the behavior of healthy people and animals. However, the overall transmission of T. gondii has not been well understood although many factors affecting this process have been found out by different biologists separately. Here we synthesize what is currently known about the natural history of T. gondii by developing a prototype agent-based model to mimic the transmission process of T. gondii in a farm system. The present model takes into account the complete life cycle of T. gondii, which includes the transitions of the parasite from cats to environment through feces, from contaminated environment to mice through oocysts, from mice to cats through tissue cysts, from environment to cats through oocysts as well as the vertical transmission among mice. Although the current model does not explicitly include humans and other end-receivers, the effect of the transition to end-receivers is estimated by a developed infection risk index. The current model can also be extended to include human activities and thus be used to investigate the influences of human management on disease control. Simulation results reveal that most cats are infected through preying on infected mice while mice are infected through vertical transmission more often than through infection with oocysts, which clearly suggests the important role of mice during the transmission of T. gondii. Furthermore, our simulation results show that decreasing the number of mice on a farm can lead to the eradication of the disease and thus can lower the infection risk of other intermediate hosts on the farm. In addition, with the assumption that the relation between virulence and transmission satisfies a normal function, we show that intermediate virulent lineages (type II) can sustain the disease most efficiently, which can qualitatively agree with the fact that the evolution of the parasite favors intermediate virulence. The effects of other related factors on transmission, including the latent period and imprudent behavior of mice, and prevention strategies are also studied based on the present model.

Copyright © 2011 Elsevier Ltd. All rights reserved.

PMID:22004993[PubMed - as supplied by publisher]

Interferon-gamma- and perforin-mediated immune responses for resistance against Toxoplasma gondii in the brain

2011-10-27T11:43:00.001-07:00

Expert Rev Mol Med. 2011 Oct 4;13:e31.

Interferon-gamma- and perforin-mediated immune responses for resistance against Toxoplasma gondii in the brain.

Suzuki Y, Sa Q, Gehman M, Ochiai E.

SourceDepartment of Microbiology, Immunology and Molecular Genetics, University of Kentucky College of Medicine, Lexington, KY, USA.

Abstract
Toxoplasma gondii is an obligate intracellular protozoan parasite that causes various diseases, including lymphadenitis, congenital infection of fetuses and life-threatening toxoplasmic encephalitis in immunocompromised individuals. Interferon-gamma (IFN-γ)-mediated immune responses are essential for controlling tachyzoite proliferation during both acute acquired infection and reactivation of infection in the brain. Both CD4+ and CD8+ T cells produce this cytokine in response to infection, although the latter has more potent protective activity. IFN-γ can activate microglia, astrocytes and macrophages, and these activated cells control the proliferation of tachyzoites using different molecules, depending on cell type and host species. IFN-γ also has a crucial role in the recruitment of T cells into the brain after infection by inducing expression of the adhesion molecule VCAM-1 on cerebrovascular endothelial cells, and chemokines such as CXCL9, CXCL10 and CCL5. A recent study showed that CD8+ T cells are able to remove T. gondii cysts, which represent the stage of the parasite in chronic infection, from the brain through their perforin-mediated activity. Thus, the resistance to cerebral infection with T. gondii requires a coordinated network using both IFN-γ- and perforin-mediated immune responses. Elucidating how these two protective mechanisms function and collaborate in the brain against T. gondii will be crucial in developing a new method to prevent and eradicate this parasitic infection.

PMID:22005272[PubMed - in process]

A patatin-like protein protects Toxoplasma gondii from degradation in a nitric oxide dependent manner

2011-10-27T10:48:00.000-07:00

Infect Immun. 2011 Oct 17. [Epub ahead of print]

A patatin-like protein protects Toxoplasma gondii from degradation in a nitric oxide dependent manner

Tobin CM, Knoll LJ

SourceDepartment of Medical Microbiology and Immunology, University of Wisconsin-Madison, 1550 Linden Drive, Madison, WI 53706.

Abstract
Toxoplasma gondii is an obligate intracellular parasite that uses immune cells to disseminate throughout its host. T. gondii can persist and even slowly replicate in activated host macrophages by reducing the antimicrobial effects of molecules such as nitric oxide (NO). A T. gondii patatin-like protein called TgPL1 was previously shown to be important for survival in activated macrophages. Here we show that a T. gondii mutant with a deletion of the TgPL1 gene (ΔTgPL1) is degraded in activated macrophages. This degradation phenotype is abolished by the removal of NO by the use of an iNOS inhibitor or iNOS deficient macrophages. Exogenous addition of NO to macrophages results in reduced parasite growth, but not degradation of ΔTgPL1 parasites. These results suggest that NO is necessary but not sufficient for the degradation of ΔTgPL1 parasites in activated macrophages. While some patatin-like proteins have phospolipase A(2) (PLA(2)) activity, recombinant TgPL1 purified from E. coli does not have phospholipase activity. This result was not surprising as TgPL1 contains a G to S change at the predicted catalytic serine residue. An epitope tagged version of TgPL1 partially co-localizing with a dense granule protein in the parasitophorous vacuole space. These results may suggest that TgPL1 moves to the parasitophorous vacuole to protect parasites from nitric oxide by an undetermined mechanism.

PMID:22006568[PubMed - as supplied by publisher]

Evolutionarily divergent, unstable filamentous actin is essential for gliding motility in apicomplexan parasites

2011-10-15T04:25:00.000-07:00

PLoS Pathog. 2011 Oct;7(10):e1002280. Epub 2011 Oct 6

Evolutionarily divergent, unstable filamentous actin is essential for gliding motility in apicomplexan parasites

Skillman KM, Diraviyam K, Khan A, Tang K, Sept D, Sibley LD

SourceDepartment of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri.

Abstract
Apicomplexan parasites rely on a novel form of actin-based motility called gliding, which depends on parasite actin polymerization, to migrate through their hosts and invade cells. However, parasite actins are divergent both in sequence and function and only form short, unstable filaments in contrast to the stability of conventional actin filaments. The molecular basis for parasite actin filament instability and its relationship to gliding motility remain unresolved. We demonstrate that recombinant Toxoplasma (TgACTI) and Plasmodium (PfACTI and PfACTII) actins polymerized into very short filaments in vitro but were induced to form long, stable filaments by addition of equimolar levels of phalloidin. Parasite actins contain a conserved phalloidin-binding site as determined by molecular modeling and computational docking, yet vary in several residues that are predicted to impact filament stability. In particular, two residues were identified that form intermolecular contacts between different protomers in conventional actin filaments and these residues showed non-conservative differences in apicomplexan parasites. Substitution of divergent residues found in TgACTI with those from mammalian actin resulted in formation of longer, more stable filaments in vitro. Expression of these stabilized actins in T. gondii increased sensitivity to the actin-stabilizing compound jasplakinolide and disrupted normal gliding motility in the absence of treatment. These results identify the molecular basis for short, dynamic filaments in apicomplexan parasites and demonstrate that inherent instability of parasite actin filaments is a critical adaptation for gliding motility.

PMID:21998582[PubMed - in process]

Opposing Biological Functions of Tryptophan Catabolizing Enzymes During Intracellular Infection

2011-10-14T08:41:00.001-07:00

J Infect Dis. 2011 Oct 11. [Epub ahead of print]

Opposing Biological Functions of Tryptophan Catabolizing Enzymes During Intracellular Infection

Divanovic S, Sawtell NM, Trompette A, Warning JI, Dias A, Cooper AM, Yap GS, Arditi M, Shimada K, Duhadaway JB, Prendergast GC, Basaraba RJ, Mellor AL, Munn DH, Aliberti J, Karp CL

SourceDivision of Molecular Immunology.

Abstract
Recent studies have underscored physiological and pathophysiological roles for the tryptophan-degrading enzyme indolamine 2,3-dioxygenase (IDO) in immune counterregulation. However, IDO was first recognized as an antimicrobial effector, restricting tryptophan availability to Toxoplasma gondii and other pathogens in vitro. The biological relevance of these findings came under question when infectious phenotypes were not forthcoming in IDO-deficient mice. The recent discovery of an IDO homolog, IDO-2, suggested that the issue deserved reexamination. IDO inhibition during murine toxoplasmosis led to 100% mortality, with increased parasite burdens and no evident effects on the immune response. Similar studies revealed a counterregulatory role for IDO during leishmaniasis (restraining effector immune responses and parasite clearance), and no evident role for IDO in herpes simplex virus type 1 (HSV-1) infection. Thus, IDO plays biologically important roles in the host response to diverse intracellular infections, but the dominant nature of this role-antimicrobial or immunoregulatory-is pathogen-specific.

PMID:21990421[PubMed - as supplied by publisher]

The organization of the wall filaments and characterization of the matrix structures of Toxoplasma gondii cyst form

2011-10-14T08:40:00.000-07:00

Cell Microbiol. 2011 Sep 8. doi: 10.1111/j.1462-5822.2011.01681.x. [Epub ahead of print]

The organization of the wall filaments and characterization of the matrix structures of Toxoplasma gondii cyst form

Lemgruber L, Lupetti P, Martins-Duarte ES, De Souza W, Vommaro RC

SourceLaboratório de Ultraestrutura Celular Hertha Meyer, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil. Instituto Nacional de Ciência e Tecnologia em Biologia Estrutural e Bioimagens, Rio de Janeiro, Brazil. Parasitology - Department of Infectious Diseases, University of Heidelberg Medical School, Heidelberg, Germany. Department of Evolutionary Biology, University of Siena, Siena, Italy. Instituto Nacional de Metrologia e Qualidade Industrial - Inmetro, Rio de Janeiro, Brazil.

Abstract
The encystation process is a key step in Toxoplasma gondii life cycle, allowing the parasite to escape from the host immune system and the transmission among the hosts. A detailed characterization of the formation and structure of the cyst stage is essential for a better knowledge of toxoplasmosis. Here we isolated cysts from mice brains and analysed the cyst wall structure and cyst matrix organization using different electron microscopy techniques. Images obtained showed that the cyst wall presented a filamentous aspect, with circular openings on its surface. The filaments were organized in two layers: a compact one, facing the exterior of the whole cyst and a more loosen one, facing the matrix. Within the cyst wall, we observed tubules and a large number of vesicles. The cyst matrix presented vesicles of different sizes and tubules, which were organized in a network connecting the bradyzoites to each other and to the cyst wall. Large vesicles, with a granular material in their lumen of glycidic nature were observed. Similar vesicles were also found associated with the posterior pole of the bradyzoites and in proximity to the cyst wall.

© 2011 Blackwell Publishing Ltd.

PMID:21899696[PubMed - as supplied by publisher]

Immunological responses induced by a DNA vaccine expressing RON4 and by immunogenic recombinant protein RON4 failed to protect mice against chronic to

2011-10-12T08:24:00.001-07:00

Vaccine. 2011 Oct 4. [Epub ahead of print]

Immunological responses induced by a DNA vaccine expressing RON4 and by immunogenic recombinant protein RON4 failed to protect mice against chronic toxoplasmosis

Rashid I, Hedhli D, Moiré N, Pierre J, Debierre-Grockiego F, Dimier-Poisson I, Mévélec MN

SourceUniversité François Rabelais, INRA, UMR 0483 Université-INRA d'Immunologie Parasitaire, Vaccinologie et Biothérapie anti-infectieuse, IFR136 Agents Transmissibles et Infectiologie, UFR des Sciences Pharmaceutiques, 31 Avenue Monge, 37200 Tours, France.

Abstract
The development of an effective vaccine against Toxoplasma gondii infection is an important issue due to the seriousness of the related public health problems, and the economic importance of this parasitic disease worldwide. Rhoptry neck proteins (RONs) are components of the moving junction macromolecular complex formed during invasion. The aim of this study was to evaluate the vaccine potential of RON4 using two vaccination strategies: DNA vaccination by the intramuscular route, and recombinant protein vaccination by the nasal route. We produced recombinant RON4 protein (RON4S2) using the Schneider insect cells expression system, and validated its antigenicity and immunogenicity. We also constructed optimized plasmids encoding full length RON4 (pRON4), or only the N-terminal (pNRON4), or the C-terminal part (pCRON4) of RON4. CBA/J mice immunized with pRON4, pNRON4 or pCRON4 plus a plasmid encoding the granulocyte-macrophage-colony-stimulating factor showed high IgG titers against rRON4S2. Mice immunized by the nasal route with rRON4S2 plus cholera toxin exhibited low levels of anti-RON4S2 IgG antibodies, and no intestinal IgA antibodies specific to RON4 were detected. Both DNA and protein vaccination generated a mixed Th1/Th2 response polarized towards the IgG1 antibody isotype. Both DNA and protein vaccination primed CD4+ T cells in vivo. In addition to the production of IFN-γ, and IL-2, Il-10 and IL-5 were also produced by the spleen cells of the immunized mice stimulated with RON4S2, suggesting that a mixed Th1/Th2 type immune response occurred in all the immunized groups. No cytokine was detectable in stimulated mesenteric lymph nodes from mice immunized by the nasal route. Immune responses were induced by both DNA and protein vaccination, but failed to protect the mice against a subsequent oral challenge with T. gondii cysts. In conclusion, strategies designed to enhance the immunogenicity and to redirect the cellular response towards a Th1 type response against RON4 could lead to more encouraging results.

Copyright © 2011. Published by Elsevier Ltd.

PMID:21983362[PubMed - as supplied by publisher]

The role of melatonin in parasite biology

2011-10-12T08:23:00.000-07:00

Mol Biochem Parasitol. 2011 Oct 1. [Epub ahead of print]

The role of melatonin in parasite biology

Bagnaresi P, Nakabashi M, Thomas AP, Reiter RJ, Garcia CR

SourceDepartamento de Biofísica, Universidade Federal de São Paulo, São Paulo, Brazil.

Abstract
Regarded as the circadian hormone in mammals, melatonin is a highly conserved molecule, present in nearly all species. In this review, we discuss the role of this indolamine and its precursors in the cell biology of parasites and the role of the molecule in the physiology of the host. In Plasmodium, melatonin can modulate intracellular concentrations of calcium and cAMP, which in turn can regulate kinase activity and cell cycle. In Trypanosoma infections, modulation of the immune system by melatonin is extremely important in controlling the parasite population. Melatonin also contributes to the inflammatory response to Toxoplasma gondii infection. Thus, there are a number of unique adaptations involving intricate connections between melatonin and the biology of the parasite-host relationship.

Copyright © 2011. Published by Elsevier B.V.

PMID:21982826[PubMed - as supplied by publisher]

Quantitative in vivo Analyses Reveal Calcium-dependent Phosphorylation Sites and Identifies a Novel Component of the Toxoplasma Invasion Motor Complex

2011-10-08T06:27:00.000-07:00

PLoS Pathog. 2011 Sep;7(9):e1002222. Epub 2011 Sep 29

Quantitative in vivo Analyses Reveal Calcium-dependent Phosphorylation Sites and Identifies a Novel Component of the Toxoplasma Invasion Motor Complex

Nebl T, Prieto JH, Kapp E, Smith BJ, Williams MJ, Yates JR 3rd, Cowman AF, Tonkin CJ.
SourceThe Walter and Eliza Hall Institute of Medical Research, Melbourne, Australia.

Abstract
Apicomplexan parasites depend on the invasion of host cells for survival and proliferation. Calcium-dependent signaling pathways appear to be essential for micronemal release and gliding motility, yet the target of activated kinases remains largely unknown. We have characterized calcium-dependent phosphorylation events during Toxoplasma host cell invasion. Stimulation of live tachyzoites with Ca(2+)-mobilizing drugs leads to phosphorylation of numerous parasite proteins, as shown by differential 2-DE display of (32)[P]-labeled protein extracts. Multi-dimensional Protein Identification Technology (MudPIT) identified ∼546 phosphorylation sites on over 300 Toxoplasma proteins, including 10 sites on the actomyosin invasion motor. Using a Stable Isotope of Amino Acids in Culture (SILAC)-based quantitative LC-MS/MS analyses we monitored changes in the abundance and phosphorylation of the invasion motor complex and defined Ca(2+)-dependent phosphorylation patterns on three of its components - GAP45, MLC1 and MyoA. Furthermore, calcium-dependent phosphorylation of six residues across GAP45, MLC1 and MyoA is correlated with invasion motor activity. By analyzing proteins that appear to associate more strongly with the invasion motor upon calcium stimulation we have also identified a novel 15-kDa Calmodulin-like protein that likely represents the MyoA Essential Light Chain of the Toxoplasma invasion motor. This suggests that invasion motor activity could be regulated not only by phosphorylation but also by the direct binding of calcium ions to this new component.

PMID:21980283[PubMed - in process]

MIF Participates in Toxoplasma gondii-Induced Pathology Following Oral Infection

2011-10-07T10:30:00.001-07:00

PLoS One. 2011;6(9):e25259. Epub 2011 Sep 22

MIF Participates in Toxoplasma gondii-Induced Pathology Following Oral Infection

Cavalcanti MG, Mesquita JS, Madi K, Feijó DF, Assunção-Miranda I, Souza HS, Bozza MT

SourceDepartamento de Imunologia, Instituto de Microbiologia Professor Paulo de Góes, Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, Brazil.

Abstract
BACKGROUND: Macrophage migration inhibitory factor (MIF) is essential for controlling parasite burden and survival in a model of systemic Toxoplasma gondii infection. Peroral T. gondii infection induces small intestine necrosis and death in susceptible hosts, and in many aspects resembles inflammatory bowel disease (IBD). Considering the critical role of MIF in the pathogenesis of IBD, we hypothesized that MIF participates in the inflammatory response induced by oral infection with T. gondii.

METHODOLOGY/PRINCIPAL FINDINGS: Mif deficient (Mif(-)/(-)) and wild-type mice in the C57Bl/6 background were orally infected with T. gondii strain ME49. Mif(-)/(-) mice had reduced lethality, ileal inflammation and tissue damage despite of an increased intestinal parasite load compared to wt mice. Lack of MIF caused a reduction of TNF-α, IL-12, IFN-γ and IL-23 and an increased expression of IL-22 in ileal mucosa. Moreover, suppressed pro-inflammatory responses at the ileal mucosa observed in Mif(-)/(-) mice was not due to upregulation of IL-4, IL-10 or TGF-β. MIF also affected the expression of matrix metalloproteinase-9 (MMP-9) but not MMP-2 in the intestine of infected mice. Signs of systemic inflammation including the increased concentrations of inflammatory cytokines in the plasma and liver damage were less pronounced in Mif(-)/(-) mice compared to wild-type mice.

CONCLUSION/SIGNIFICANCE: In conclusion, our data suggested that in susceptible hosts MIF controls T. gondii infection with the cost of increasing local and systemic inflammation, tissue damage and death.

PMID:21977228[PubMed - in process]

Review of the series "disease of the year 2011: toxoplasmosis" pathophysiology of toxoplasmosis

2011-10-07T10:29:00.001-07:00

Ocul Immunol Inflamm. 2011 Oct;19(5):297-306

Review of the series "disease of the year 2011: toxoplasmosis" pathophysiology of toxoplasmosis

Subauste CS, Ajzenberg D, Kijlstra A.
SourceDivision of Infectious Diseases and HIV Medicine, Department of Medicine, Case Western Reserve University School of Medicine , Cleveland, Ohio , USA ; Department of Ophthalmology and Visual Sciences, Case Western Reserve University School of Medicine , Cleveland, Ohio , USA ; and Department of Pathology, Case Western Reserve University School of Medicine , Cleveland, Ohio , USA.

Abstract
Toxoplasma gondii is a major cause of chronic parasitic infection in the world. This protozoan can cause retino-choroiditis in newborns and in adults, both immunocompetent and immunodeficient. This disease tends to be recurrent and can lead to severe visual impairment. The authors review current knowledge on the role of parasite genetics in influencing susceptibility to ocular toxoplasmosis and on the immuno-pathogenesis of this disease.

PMID:21970661[PubMed - in process]

Nuclear actin-related protein is required for chromosome segregation in Toxoplasma gondii

2011-10-05T08:26:00.002-07:00

Mol Biochem Parasitol. 2011 Sep 22. [Epub ahead of print]

Nuclear actin-related protein is required for chromosome segregation in Toxoplasma gondii

Suvorova ES, Lehmann MM, Kratzer S, White MW

SourceDepartment of Molecular Medicine, University of South Florida, Tampa, FL 33612, United States; Department of Global Health, University of South Florida, Tampa, FL 33612, United States.

Abstract
Apicomplexa parasites use complex cell cycles to replicate that are not well understood mechanistically. We have established a robust forward genetic strategy to identify the essential components of parasite cell division. Here we describe a novel temperature sensitive Toxoplasma strain, mutant 13-20C2, which growth arrests due to a defect in mitosis. The primary phenotype is the mis-segregation of duplicated chromosomes with chromosome loss during nuclear division. This defect is conditional-lethal with respect to temperature, although relatively mild in regard to the preservation of the major microtubule organizing centers. Despite severe DNA loss many of the physical structures associated with daughter budding and the assembly of invasion structures formed and operated normally at the non-permissive temperature before completely arresting. These results suggest there are coordinating mechanisms that govern the timing of these events in the parasite cell cycle. The defect in mutant 13-20C2 was mapped by genetic complementation to Toxoplasma chromosome III and to a specific mutation in the gene encoding an ortholog of nuclear actin-related protein 4. A change in a conserved isoleucine to threonine in the helical structure of this nuclear actin related protein leads to protein instability and cellular mis-localization at the higher temperature. Given the age of this protist family, the results indicate a key role for nuclear actin-related proteins in chromosome segregation was established very early in the evolution of eukaryotes.

Copyright © 2011 Elsevier B.V. All rights reserved.

PMID:21963440[PubMed - as supplied by publisher]

The Cryptosporidium parvum Kinome

2011-10-05T08:26:00.001-07:00

BMC Genomics. 2011 Sep 30;12(1):478. [Epub ahead of print]

The Cryptosporidium parvum Kinome

Artz JD, Wernimont AK, Allali-Hassani A, Zhao Y, Amani M, Lin YH, Senisterra G, Wasney GA, Fedorov O, King O, Roos A, Lunin VV, Qiu W, Finerty P Jr, Hutchinson A, Chau I, von Delft F, Mackenzie F, Lew J, Kozieradzki I, Vedadi M, Schapira M, Zhang C, Shokat K, Heightman T, Hui R.

ABSTRACT:

BACKGROUND: Hundreds of millions of people are infected with cryptosporidiosis annually, with immunocompromised individuals suffering debilitating symptoms and children in socioeconomically challenged regions at risk of repeated infections. There is currently no effective drug available. In order to facilitate the pursuit of anti-cryptosporidiosis targets and compounds, our study spans the classification of the Cryptosporidium parvum kinome and the structural and biochemical characterization of representatives from the CDPK family and a MAP kinase.

RESULTS: The C. parvum kinome comprises over 70 members, some of which may be promising drug targets. These C. parvum protein kinases include members in the AGC, Atypical, CaMK, CK1, CMGC, and TKL groups; however, almost 35 % could only be classified as OPK (other protein kinases). In addition, about 25 % of the kinases identified did not have any known orthologues outside of Cryptosporidium spp. Comparison of specific kinases with their Plasmodium falciparum and Toxoplasma gondii orthologues revealed some distinct characteristics within the C. parvum kinome, including potential targets and opportunities for drug design. Structural and biochemical analysis of 4 representatives of the CaMK group and a MAP kinase confirms features that may be exploited in inhibitor design. Indeed, screening CpCDPK1 against a library of kinase inhibitors yielded a set of the pyrazolopyrimidine derivatives (PP1-derivatives) with IC50 values of <10 nM. The binding of a PP1-derivative is further described by an inhibitor-bound crystal structure of CpCDPK1. In addition, structural analysis of CpCDPK4 identified an unprecedented Zn-finger within the CDPK kinase domain that may have implications for its regulation.

CONCLUSIONS: Identification and comparison of the C. parvum protein kinases against other parasitic kinases shows how orthologue- and family-based research can be used to facilitate characterization of promising drug targets and the search for new drugs.

PMID:21962082[PubMed - as supplied by publisher] Free full text

The neurotropic parasite toxoplasma gondii increases dopamine metabolism

2011-10-03T05:42:00.001-07:00

PLoS One. 2011;6(9):e23866. Epub 2011 Sep 21

The neurotropic parasite toxoplasma gondii increases dopamine metabolism

Prandovszky E, Gaskell E, Martin H, Dubey JP, Webster JP, McConkey GA.

SourceInstitute of Integrative and Comparative Biology, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom.

Abstract
The highly prevalent parasite Toxoplasma gondii manipulates its host's behavior. In infected rodents, the behavioral changes increase the likelihood that the parasite will be transmitted back to its definitive cat host, an essential step in completion of the parasite's life cycle. The mechanism(s) responsible for behavioral changes in the host is unknown but two lines of published evidence suggest that the parasite alters neurotransmitter signal transduction: the disruption of the parasite-induced behavioral changes with medications used to treat psychiatric disease (specifically dopamine antagonists) and identification of a tyrosine hydroxylase encoded in the parasite genome. In this study, infection of mammalian dopaminergic cells with T. gondii enhanced the levels of K+-induced release of dopamine several-fold, with a direct correlation between the number of infected cells and the quantity of dopamine released. Immunostaining brain sections of infected mice with dopamine antibody showed intense staining of encysted parasites. Based on these analyses, T. gondii orchestrates a significant increase in dopamine metabolism in neural cells. Tyrosine hydroxylase, the rate-limiting enzyme for dopamine synthesis, was also found in intracellular tissue cysts in brain tissue with antibodies specific for the parasite-encoded tyrosine hydroxylase. These observations provide a mechanism for parasite-induced behavioral changes. The observed effects on dopamine metabolism could also be relevant in interpreting reports of psychobehavioral changes in toxoplasmosis-infected humans.

PMID:21957440[PubMed - in process]

Severe Congenital Toxoplasmosis in the United States: Clinical and Serologic Findings in Untreated Infants

2011-10-03T05:40:00.000-07:00

Pediatr Infect Dis J. 2011 Sep 27. [Epub ahead of print]

Severe Congenital Toxoplasmosis in the United States: Clinical and Serologic Findings in Untreated Infants

Olariu TR, Remington JS, McLeod R, Alam A, Montoya JG.

SourceFrom the *Toxoplasma Serology Laboratory, Palo Alto Medical Foundation, Palo Alto, CA; †Division of Infectious Diseases and Geographic Medicine, Department of Medicine, Stanford University School of Medicine, Stanford, CA; ‡Department of Medicine, University of Chicago School of Medicine, Chicago, IL; §Toxoplasmosis Center, University of Chicago Medical Center, Chicago, IL; and ¶Department of Pediatrics, University of Chicago School of Medicine, Chicago, IL.

Abstract
BACKGROUND: Congenital toxoplasmosis can cause significant neurologic manifestations and other untoward sequelae.

METHODS: The Palo Alto Medical Foundation Toxoplasma Serology Laboratory database was searched for data on infants 0 to 180 days old, in whom congenital toxoplasmosis had been confirmed and who had been tested for Toxoplasma gondii-specific immunoglobulin G (IgG), IgM, and IgA antibodies, between 1991 and 2005. Their clinical findings were confirmed at the National Collaborative Chicago-based Congenital Toxoplasmosis Study center. We reviewed available clinical data and laboratory profiles of 164 infants with congenital toxoplasmosis whose mothers had not been treated for the parasite during gestation.

RESULTS: One or more severe clinical manifestations of congenital toxoplasmosis were reported in 84% of the infants and included eye disease (92.2%), brain calcifications (79.6%), and hydrocephalus (67.7%). In 61.6% of the infants, eye disease, brain calcifications, and hydrocephalus were present concurrently. T. gondii-specific IgM, IgA, and IgE antibodies were demonstrable in 86.6%, 77.4%, and 40.2% of the infants, respectively. Testing for IgM and IgA antibodies increased the sensitivity of making the diagnosis of congenital toxoplasmosis to 93% compared with testing for IgM or IgA individually. IgM and IgA antibodies were still present in 43.9% of infants diagnosed between 1 and 6 months of life.

CONCLUSIONS: Our study reveals that severe clinical signs of congenital toxoplasmosis including hydrocephalus, eye disease, or intracranial calcifications occurred in 85% infants whose sera were referred to our reference Toxoplasma Serology Laboratory during a period of 15 years. Laboratory tests, including serologic and polymerase chain reaction tests, were critical for diagnosis in the infants. Our results contrast remarkably with those of European investigators who rarely observe severe clinical signs in infants with congenital toxoplasmosis.

PMID:21956696[PubMed - as supplied by publisher]

Two internal type II NADH dehydrogenases of Toxoplasma gondii are both required for optimal tachyzoite growth

2011-09-30T06:42:00.002-07:00

Mol Microbiol. 2011 Oct;82(1):209-21. doi: 10.1111/j.1365-2958.2011.07807.x. Epub 2011 Sep 2.

Two internal type II NADH dehydrogenases of Toxoplasma gondii are both required for optimal tachyzoite growth

Lin SS, Gross U, Bohne W

SourceInstitute of Medical Microbiology, University Medical Center Göttingen, Kreuzbergring 57, Göttingen D-37075, Germany.

Abstract
In many apicomplexan parasites the entry of electrons from NADH into the electron transport chain is governed by type II NADH dehydrogenases (NDH2s) instead of a canonical complex I. Toxoplasma gondii expresses two NDH2 isoforms, TgNDH2-I and TgNDH2-II with no indication for stage-specific regulation. We dissected the orientation of both isoforms by using a split GFP assay and a protease protection assay after selective membrane permeabilization. The two approaches revealed that both TgNDH2 isoforms are internal enzymes facing with their active sites to the mitochondrial matrix. Single knockout mutants displayed a decreased replication rate and a reduced mitochondrial membrane potential, which were both more severe in the Tgndh2-II-deleted than in the Tgndh2-I-deleted mutant. Complementation with a myc-tagged, ectopic copy of the deleted gene restored the growth rate and the mitochondrial membrane potential. However, an overexpression of the remaining intact isoform could not restore the phenotype, suggesting that the two TgNDH2 isoforms are non-redundant and possess functional differences. Together, our studies indicate that although TgNDH2-I and TgNDH2-II are individually non-essential, the expression of both internal isoforms is required to maintain the mitochondrial physiology in T. gondii tachyzoites.

© 2011 Blackwell Publishing Ltd.

PMID:21854467[PubMed - in process]

Population genetics of Toxoplasma gondii: New perspectives from parasite genotypes in wildlife

2011-09-30T06:42:00.001-07:00

Vet Parasitol. 2011 Nov 24;182(1):96-111. Epub 2011 Jul 20

Population genetics of Toxoplasma gondii: New perspectives from parasite genotypes in wildlife
Wendte JM, Gibson AK, Grigg ME

SourceMolecular Parasitology Unit, Laboratory of Parasitic Diseases, National Institutes of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892-0425, USA; Department of Veterinary Pathobiology, Oklahoma State University Center for Veterinary Health Sciences, Stillwater, OK 74074, USA.

Abstract
Toxoplasma gondii, a zoonotic protozoal parasite, is well-known for its global distribution and its ability to infect virtually all warm-blooded vertebrates. Nonetheless, attempts to describe the population structure of T. gondii have been primarily limited to samples isolated from humans and domesticated animals. More recent studies, however, have made efforts to characterize T. gondii isolates from a wider range of host species and geographic locales. These findings have dramatically changed our perception of the extent of genetic diversity in T. gondii and the relative roles of sexual recombination and clonal propagation in the parasite's lifecycle. In particular, identification of novel, disease-causing T. gondii strains in wildlife has raised concerns from both a conservation and public health perspective as to whether distinct domestic and sylvatic parasite gene pools exist. If so, overlap of these cycles may represent regions of high probability of disease emergence. Here, we attempt to answer these key questions by reviewing recent studies of T. gondii infections in wildlife, highlighting those which have advanced our understanding of the genetic diversity and population biology of this important zoonotic pathogen.

Published by Elsevier B.V.

PMID:21824730[PubMed - in process]

A Purification Method for Enrichment of the Toxoplasma gondii Cyst Wall

2011-09-30T06:16:00.000-07:00

J Neuroparasitology. 2010 Dec;1. pii: N101001

A Purification Method for Enrichment of the Toxoplasma gondii Cyst Wall

Zhang YW, Halonen SK, Ma YF, Tanowtiz HB, Weiss LM.

SourceDepartment of Pathology, Division of Parasitology, Albert Einstein College of Medicine, Bronx, NY 10461, USA.

Abstract
The tissue cyst wall of Toxoplasma gondii is a stage-specific structure that is produced by modification of the bradyzoite-containing parasitophorous vacuole. It is a limiting membrane structure and is critically important for cyst survival and transmission of infection. Studies on the structure and function of the cyst wall should provide new therapeutic strategies for the elimination or prevention of latency during T. gondii infection. The membrane proteins of the T. gondii cyst are an important target for studies of the biochemical and immunological function(s) of the cyst. However, the components of the cyst membrane have been poorly characterized due to the difficulty of purification of these membrane proteins. We developed a lectin DBA (Dolichos biflorus) coated magnetic bead isolation method to isolate T. gondii cyst wall proteins. Our data suggests that this method can isolate cyst wall proteins from both in vitro cell culture or in vivo mouse brain derived tissue cysts. Antibodies to these isolated protein preparations were shown to localize to the cyst wall.

PMID:21687827[PubMed]

A novel benzodioxole-containing inhibitor of Toxoplasma gondii growth alters the parasite cell cycle

2011-09-29T09:12:00.002-07:00

Antimicrob Agents Chemother. 2011 Sep 26. [Epub ahead of print]

A novel benzodioxole-containing inhibitor of Toxoplasma gondii growth alters the parasite cell cycle

Kamau E, Meehan T, Lavine MD, Arrizabalaga G, Mustata G, Boyle J.

SourceDepartment of Biological Sciences, University of Pittsburgh, Pittsburgh, PA. 15260.

Abstract
Toxoplasma gondii is an obligate intracellular parasite that can cause disease in the developing fetus and in immunocompromised humans. Infections can last for the life of the individual, and to date there are no drugs that eliminate chronic cyst stages characteristic of this parasite. In an effort to identify new chemical scaffolds that could form the basis for new therapeutics, we carried out a chemoinformatic screen for compounds that had the potential to interact with members of a superfamily of parasite-secreted kinases, and assayed them for growth inhibition in vitro. Out of 17 candidate compounds we identified one with potent anti-parasitic activity. The compound has an IC50 of ∼2 nM, and structure-function analyses implicate the benzodioxole moiety in its action. The compound does not appear to be cytotoxic to host cells. Using microarray analyses of both parasites and host cells treated with the compound, we found that the levels of very few host cell transcripts are altered by the compound while a large number of parasite transcripts are of different abundance after compound treatment. Gene ontology analyses of parasite transcripts with different abundance revealed an enrichment of cell cycle-related genes, suggesting that the compound alters progression of the parasite through the cell cycle. Assaying nuclear content of treated parasites demonstrated that compound treatment significantly increased the percentage of parasites in the S/M phase of the cell cycle compared to controls. This compound and its analogs represent a novel scaffold with anti-parasitic activity.

PMID:21947387[PubMed - as supplied by publisher]

The first detection of Toxoplasma gondii DNA in environmental fruits and vegetables samples

2011-09-29T09:12:00.001-07:00

Eur J Clin Microbiol Infect Dis. 2011 Sep 25. [Epub ahead of print]

The first detection of Toxoplasma gondii DNA in environmental fruits and vegetables samples

Lass A, Pietkiewicz H, Szostakowska B, Myjak P.

SourceDepartment of Tropical Parasitology, Interfaculty Institute of Maritime and Tropical Medicine in Gdynia, Medical University of Gdansk, Gdansk, Poland, anna.ls1@gumed.edu.pl.

Abstract
Toxoplasma gondii infections are prevalent in humans and animals all over the world. The aim of the study was to estimate the occurrence of T. gondii oocysts in fruits and vegetables and determine the genotype of the parasites. A total number of 216 fruits and vegetables samples were taken from shops and home gardens located in the area of northern Poland. Oocysts were recovered with the flocculation method. Then, real-time polymerase chain reaction (PCR) targeting the B1 gene was used for specific T. gondii detection and quantification. Toxoplasma DNA was found in 21 samples. Genotyping at the SAG2 locus showed SAG2 type I and SAG2 type II. This is the first investigation describing T. gondii DNA identification in a large number of fruits and vegetables samples with rapid molecular detection methods. The results showed that fruits and vegetables contaminated with T. gondii may play a role in the prevalence of toxoplasmosis in Poland.

PMID:21948336[PubMed - as supplied by publisher]

ROP16 Activates STAT3 and STAT6 Resulting in Cytokine Inhibition and Arginase-1-Dependent Growth Control

2011-09-22T06:48:00.003-07:00

PLoS Pathog. 2011 Sep;7(9):e1002236. Epub 2011 Sep 8

Toxoplasma gondii Rhoptry Kinase ROP16 Activates STAT3 and STAT6 Resulting in Cytokine Inhibition and Arginase-1-Dependent Growth Control

Butcher BA, Fox BA, Rommereim LM, Kim SG, Maurer KJ, Yarovinsky F, Herbert DR, Bzik DJ, Denkers EY

SourceDepartment of Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca, New York, United States of America.

Abstract
The ROP16 kinase of Toxoplasma gondii is injected into the host cell cytosol where it activates signal transducer and activator of transcription (STAT)-3 and STAT6. Here, we generated a ROP16 deletion mutant on a Type I parasite strain background, as well as a control complementation mutant with restored ROP16 expression. We investigated the biological role of the ROP16 molecule during T. gondii infection. Infection of mouse bone marrow-derived macrophages with rop16-deleted (ΔROP16) parasites resulted in increased amounts of IL-12p40 production relative to the ROP16-positive RH parental strain. High level IL-12p40 production in ΔROP16 infection was dependent on the host cell adaptor molecule MyD88, but surprisingly was independent of any previously recognized T. gondii triggered pathway linking to MyD88 (TLR2, TLR4, TLR9, TLR11, IL-1ß and IL-18). In addition, ROP16 was found to mediate the suppressive effects of Toxoplasma on LPS-induced cytokine synthesis in macrophages and on IFN-γ-induced nitric oxide production by astrocytes and microglial cells. Furthermore, ROP16 triggered synthesis of host cell arginase-1 in a STAT6-dependent manner. In fibroblasts and macrophages, failure to induce arginase-1 by ΔROP16 tachyzoites resulted in resistance to starvation conditions of limiting arginine, an essential amino acid for replication and virulence of this parasite. ΔROP16 tachyzoites that failed to induce host cell arginase-1 displayed increased replication and dissemination during in vivo infection. We conclude that encounter between Toxoplasma ROP16 and the host cell STAT signaling cascade has pleiotropic downstream effects that act in multiple and complex ways to direct the course of infection.

PMID:21931552[PubMed - in process]

Determinants of GBP Recruitment to Toxoplasma gondii Vacuoles and the Parasitic Factors That Control It

2011-09-22T06:48:00.001-07:00

PLoS One. 2011;6(9):e24434. Epub 2011 Sep 8

Determinants of GBP Recruitment to Toxoplasma gondii Vacuoles and the Parasitic Factors That Control It

Virreira Winter S, Niedelman W, Jensen KD, Rosowski EE, Julien L, Spooner E, Caradonna K, Burleigh BA, Saeij JP, Ploegh HL, Frickel EM

SourceWhitehead Institute for Biomedical Research, Cambridge, Massachusetts, United States of America.

Abstract
IFN-γ is a major cytokine that mediates resistance against the intracellular parasite Toxoplasma gondii. The p65 guanylate-binding proteins (GBPs) are strongly induced by IFN-γ. We studied the behavior of murine GBP1 (mGBP1) upon infection with T. gondii in vitro and confirmed that IFN-γ-dependent re-localization of mGBP1 to the parasitophorous vacuole (PV) correlates with the virulence type of the parasite. We identified three parasitic factors, ROP16, ROP18, and GRA15 that determine strain-specific accumulation of mGBP1 on the PV. These highly polymorphic proteins are held responsible for a large part of the strain-specific differences in virulence. Therefore, our data suggest that virulence of T. gondii in animals may rely in part on recognition by GBPs. However, phagosomes or vacuoles containing Trypanosoma cruzi did not recruit mGBP1. Co-immunoprecipitation revealed mGBP2, mGBP4, and mGBP5 as binding partners of mGBP1. Indeed, mGBP2 and mGBP5 co-localize with mGBP1 in T. gondii-infected cells. T. gondii thus elicits a cell-autonomous immune response in mice with GBPs involved. Three parasitic virulence factors and unknown IFN-γ-dependent host factors regulate this complex process. Depending on the virulence of the strains involved, numerous GBPs are brought to the PV as part of a large, multimeric structure to combat T. gondii.

PMID:21931713[PubMed - in process]

Genetic approaches for understanding virulence in Toxoplasma gondii

2011-09-22T06:47:00.001-07:00

Brief Funct Genomics. 2011 Sep 19. [Epub ahead of print]

Genetic approaches for understanding virulence in Toxoplasma gondii

Weilhammer DR, Rasley A

Abstract
Virulence of the protozoan parasite Toxoplasma gondii is highly variable and dependent upon the genotype of the parasite. The application of forward and reverse genetic approaches for understanding the genetic basis of virulence has resulted in the identification of several members of the ROP family as key mediators of virulence. More recently, modern genomic techniques have been used to address strain differences in virulence and have also identified additional members of the ROP family as likely mediators. The development of forward and reverse genetic, as well as modern genomic techniques, and the path to the discovery of the ROP genes as virulence factors is reviewed here.

PMID:21930659[PubMed - as supplied by publisher]

A Critical Role for SOCS3 in Innate Resistance to Toxoplasma gondii

2011-09-20T09:18:00.003-07:00

Cell Host Microbe. 2011 Sep 15;10(3):224-36

A Critical Role for SOCS3 in Innate Resistance to Toxoplasma gondii

Whitmarsh RJ, Gray CM, Gregg B, Christian DA, May MJ, Murray PJ, Hunter CA

SourceDepartment of Pathobiology, School of Veterinary Medicine, University of Pennsylvania, 380 South University Avenue, Philadelphia, PA 19104, USA.

Abstract
The innate and adaptive immune responses that confer resistance to the intracellular pathogen Toxoplasma gondii critically depend on IL-12 production, which drives interferon-γ (IFN-γ) expression. Certain cytokines can activate STAT3 and limit IL-12 production to prevent infection-associated immune pathology, but T. gondii also directly activates STAT3 to evade host immunity. We show that suppressor of cytokine signaling molecule 3 (SOCS3), a target of STAT3 that limits signaling by the pleiotropic cytokine IL-6, is upregulated in response to infection but is dispensable for the immune-inhibitory effects of T. gondii. Unexpectedly, mice with targeted deletion of SOCS3 in macrophages and neutrophils have reduced IL-12 responses and succumb to toxoplasmosis. Anti-IL-6 administration or IL-12 treatment blocked disease susceptibility, suggesting that in the absence of SOCS3, macrophages are hypersensitive to the anti-inflammatory properties of IL-6. Thus, SOCS3 has a critical role in suppressing IL-6 signals and promoting immune responses to control T. gondii infection.

Copyright © 2011 Elsevier Inc. All rights reserved.

PMID:21925110[PubMed - in process]

Glycosylphosphatidylinositols of Toxoplasma gondii induce matrix metalloproteinase-9 production and degradation of galectin-3

2011-09-20T09:18:00.001-07:00

Immunobiology. 2011 Aug 12. [Epub ahead of print]

Glycosylphosphatidylinositols of Toxoplasma gondii induce matrix metalloproteinase-9 production and degradation of galectin-3

Niehus S, Elass E, Coddeville B, Guérardel Y, Schwarz RT, Debierre-Grockiego F

SourceInstitut für Virologie, AG Parasitologie, Philipps-Universität, Marburg, Germany; UPR9022 du CNRS, Institut de Biologie Moléculaire et Cellulaire, 15 rue René Descartes, 67084 Strasbourg, France.

Abstract
Toxoplasma gondii glycosylphosphatidylinositols (GPIs) bind to galectin-3 to induce TNF-α production in macrophages via Toll-like receptors 2 and 4. Here we show that T. gondii GPIs stimulate human macrophages to synthesize matrix metalloproteinase-9 in a TNF-α-dependent pathway and degrade extracellular galectin-3.

Copyright © 2011 Elsevier GmbH. All rights reserved.

PMID:21924517[PubMed - as supplied by publisher]

The Treg/Th17 Imbalance in Toxoplasma gondii-Infected Pregnant Mice

2011-09-20T09:17:00.003-07:00

Am J Reprod Immunol. 2011 Sep 19. doi: 10.1111/j.1600-0897.2011.01065.x. [Epub ahead of print]

The Treg/Th17 Imbalance in Toxoplasma gondii-Infected Pregnant Mice

Zhang H, Hu X, Liu X, Zhang R, Fu Q, Xu X

SourceDepartment of Immunology, Binzhou Medical College, Yantai, China.

Abstract
Citation Zhang H, Hu X, Liu X, Zhang R, Fu Q, Xu X. The Treg/Th17 Imbalance in Toxoplasma gondii-Infected Pregnant Mice. Am J Reprod Immunol 2011 Aim To evaluate whether impaired Treg/Th17 balance exists in the pregnant mice infected with Toxoplasma gondii. Method of Study Regulatory T (Treg) and T-helper type 17 (Th17) cells were measured in both placenta and spleens of the pregnant mice infected with and without T. gondii by flow cytometry. The mRNA and protein expression levels of transforming growth factor-β (TGF-β) and interleukin-17A (IL-17A) were analyzed using real-time PCR and enzyme-linked immunosorbent assay (ELISA). The mRNA expression levels of forkhead box P3 (Foxp3), retinoic acid-related orphan receptor γt (RORγt), and IL-6 were also analyzed using real-time PCR. The correlations of the ratio of Treg/Th17 to the mRNA or protein expression level of those factors were analyzed by Spearman's correlation analysis. Data were analyzed by unpaired t-test and paired t-test. Results The proportion of Tregs or Th17 cells in the placenta and spleens of the T. gondii-infected pregnant mice was significantly lower or higher than in those of non-infected mice, respectively. Upregulation of TGF-β and downregulation of IL-17A were found in the placenta of T. gondii-infected pregnant mice. The ratio of Treg to Th17 was significantly lower in the infected mice than that in the non-infected mice (P < 0.01).The ratio of Treg to Th17 positively or negatively correlated with the protein expression level of TGF-β (r = 0.6204, P < 0.05) or IL-17A (r = -0.6296, P < 0.05), respectively. The ratio also positively correlated with the mRNA expression level of Foxp3 (r = 0.7985, P < 0.01), but negatively correlated with the mRNA expression level of RORγt (r = -0.6153, P < 0.05), and IL-6 (r = -0.7492, P < 0.01). Conclusion TheTreg/Th17 imbalance exists in the pregnant mice infected with T. gondii, which is associated with the expression of related cytokine and key transcription factors. This result suggests that the embryo loss caused by this parasite may be associated with a reduced ratio of Treg to Th17 cell number.

© 2011 John Wiley & Sons A/S.

PMID:21923716[PubMed - as supplied by publisher]