Wednesday, October 30, 2013

POSTDOCTORAL POSITION available


POSTDOCTORAL POSITION

Biochemistry, Microbiology, Drug development
 
Indiana University School of Medicine

 
POSTDOCTORAL POSITION available to investigate the efficacy and mechanism of experimental drugs to treat infection caused by the protozoan parasite Toxoplasma gondii. Related to the malaria parasite, Toxoplasma causes birth defects and life-threatening infection in immunocompromised AIDS or heart transplant patients. The successful candidate will continue the study of small molecules that interfere with stress responses and differentiation as a means to subvert acute and chronic parasite infection using in vivo and in vitro models (see Konrad et al., Antimicrob Agents Chemother. 2013, 57(4):1815-22). The candidate is also expected to employ state of the art genetic and biochemical approaches to determine the detailed mechanism of action for these compounds.

Position requires a Ph.D., expertise in animal (mouse) handling, biochemistry & cell biology,  and excellent communication skills (speaking and writing English). Submit CV and contact information for three references to Dr. Bill Sullivan (wjsulliv@iu.edu).

Located in downtown Indianapolis, Indiana University School of Medicine (IUSM) is the second largest medical school in the US and boasts an outstanding intellectual atmosphere and core facilities. IUSM was nationally ranked in the Top 30 Best Places to Work for Postdocs. Our lab is part of a larger intracellular parasitism group at IU that fosters innovation and collaboration. IUSM is an equal opportunity employer. Visit www.sullivanlab.com for more information.

Targeting lipid biosynthesis and salvage in apicomplexan parasites for improved chemotherapies

2013 Oct 28. doi: 10.1038/nrmicro3139. [Epub ahead of print]

Targeting lipid biosynthesis and salvage in apicomplexan parasites for improved chemotherapies

Source

Department of Molecular Microbiology and Immunology, Johns Hopkins University Bloomberg School of Public Health, Baltimore, Maryland 21205, USA.

Abstract

Apicomplexa are some of the most widespread and poorly controlled pathogens in the world. The metabolism of lipids in these parasites, which include Plasmodium spp., Toxoplasma gondii and Cryptosporidium spp., is essential for the production of infectious progeny and pathogen persistence in their mammalian hosts. Metabolic maps of apicomplexan lipid syntheses reveal auxotrophies for many lipid species, which force these parasites to meet their high demand for lipids through networks of both synthesis and scavenging. Here, I review the unique lipid biosynthetic enzymes and lipid transporter systems of Apicomplexa, focusing on isoprenoids, sphingolipids and cholesterol, and highlight promising chemotherapeutic targets in the lipid synthetic and salvage pathways.
PMID:
24162026
[PubMed - as supplied by publisher]

Comparative proteomic analysis of different Toxoplasma gondii genotypes

2013 Oct 24. doi: 10.1002/elps.201300044. [Epub ahead of print]

Comparative proteomic analysis of different Toxoplasma gondii genotypes by two-dimensional fluorescence difference gel electrophoresis combined with mass spectrometry

Source

State Key Laboratory of Veterinary Etiological Biology, Key Laboratory of Veterinary Parasitology of Gansu Province, Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Lanzhou, Gansu Province, 730046, China.

Abstract

Toxoplasma gondii is a protozoan parasite infecting almost all warm-blooded animals and humans. There are three infective stages of T. gondii: the tachyzoites, the bradyzoites and the oocysts. The tachyzoite is a rapidly multiplying stage and the main pathogenic factor. In North America and Europe, T. gondii is consisted of four major clonal lineages (namely Types I, II, III and Type 12). In this study, we explored the proteomic profiles of different genotypes (Type I-RH strain, Type II-PRU strain, Type II-TgQHO strain and ToxoDB 9-TgC7 strain) of T. gondii tachyzoites by using two-dimensional fluorescence difference gel electrophoresis (2D DIGE) combined with MALDI-TOF MS. Totally, 110 differentially abundant protein spots were selected. Of these, 98 spots corresponding to 56 proteins from T. gondii were successfully identified. These included surface antigen (SAG1), heat shock protein 70 (Hsp70), disulfide isomerase, coronin, heat shock protein 60 (Hsp60), pyruvate kinase, receptor for activated C kinase 1 and peroxiredoxin. Gene ontology (GO) enrichment analysis revealed that most of the differentially abundant proteins were involved in biological regulation, metabolic process, response to stress, binding, antioxidant activity and transporter activity. According to the Kyoto Encyclopedia of Genes and Genomes (KEGG) metabolic pathway maps of T. gondii, some identified proteins were involved in the glycolytic/gluconeogenesis pathway. The present study identified differentially abundant proteins among different genotypes of T. gondii and these findings have implications for the better understanding of the phenotypic differences among the examined T. gondii genotypes which in turn may contribute to the better control of toxoplasmosis. This article is protected by copyright. All rights reserved.
This article is protected by copyright. All rights reserved.

KEYWORDS:

2D DIGE, Mass spectrometry, Proteome, Tachyzoites, Toxoplasma gondii
PMID:
24166805
[PubMed - as supplied by publisher]

Wednesday, October 23, 2013

The Role of Clathrin in Post-Golgi Trafficking in Toxoplasma gondii


 2013 Oct 11;8(10):e77620. doi: 10.1371/journal.pone.0077620.

The Role of Clathrin in Post-Golgi Trafficking in Toxoplasma gondii

Source

Wellcome Trust Centre for Molecular Parasitology, Institute of Infection, Immunity & Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom.

Abstract

Apicomplexan parasites are single eukaryotic cells with a highly polarised secretory system that contains unique secretory organelles (micronemes and rhoptries) that are required for host cell invasion. In contrast, the role of the endosomal system is poorly understood in these parasites. With many typical endocytic factors missing, we speculated that endocytosis depends exclusively on a clathrin-mediated mechanism. Intriguingly, in Toxoplasma gondii we were only able to observe the endogenous clathrin heavy chain 1 (CHC1) at the Golgi, but not at the parasite surface. For the functional characterisation of Toxoplasma gondii CHC1 we generated parasite mutants conditionally expressing the dominant negative clathrin Hub fragment and demonstrate that CHC1 is essential for vesicle formation at the trans-Golgi network. Consequently, the functional ablation of CHC1 results in Golgi aberrations, a block in the biogenesis of the unique secretory microneme and rhoptry organelles, and of the pellicle. However, we found no morphological evidence for clathrin mediating endocytosis in these parasites and speculate that they remodelled their vesicular trafficking system to adapt to an intracellular lifestyle.
PMID:
 
24147036
 
[PubMed - in process] 

Mast cells modulate acute toxoplasmosis in murine models


 2013 Oct 16;8(10):e77327. doi: 10.1371/journal.pone.0077327.

Mast cells modulate acute toxoplasmosis in murine models

Source

Department of Parasitology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, Guangdong, China ; Key Laboratory of Tropical Disease Control (Sun Yat-sen University), Ministry of Education, Guangzhou, Guangdong, China.

Abstract

The role of mast cells (MCs) in Toxoplasma gondii infection is poorly known. Kunming outbred mice were infected intraperitoneally with RH strain T. gondii, either treated with compound 48/80 (C48/80, MC activator) or disodium cromoglycate (DSCG, MC inhibitor). Compared with infected controls, infected mice treated with C48/80 exhibited significantly increased inflammation in the liver (P < 0.01), spleen (P < 0.05), and mesentery (P < 0.05) tissues, higher parasite burden in the peritoneal lavage fluids (P < 0.01), and increased levels of mRNA transcripts of T. gondii tachyzoite surface antigen 1 (SAG1) gene in the spleen and liver tissues (P < 0.01), accompanied with significantly increased Th1 cytokine (IFN-γ, IL-12p40, and TNF-α) (P < 0.01) and decreased IL-10 (P < 0.01) mRNA expressions in the liver, and increased IFN-γ (P < 0.01) and IL-12p40 (P < 0.01) but decreased TNF-α (P < 0.01) and IL-4 (P < 0.01) in the spleens of infected mice treated with C48/80 at day 9-10 p.i. Whereas mice treated with DSCG had significantly decreased tissue lesions (P < 0.01), lower parasite burden in the peritoneal lavage fluids (P < 0.01) and decreased SAG1 expressions in the spleen and liver tissues (P < 0.01), accompanied with significantly increased IFN-γ (P < 0.01) and IL-12p40 (P < 0.05) in the liver, and decreased IFN-γ (P < 0.05) and TNF-α (P < 0.01) in the spleens; IL-4 and IL-10 expressions in both the spleen and liver were significantly increased (P < 0.01) in the infected mice treated with DSCG. These findings suggest that mediators associated with the MC activation may play an important role in modulating acute inflammatory pathogenesis and parasite clearance during T. gondii infection in this strain of mice. Thus, MC activation/inhibition mechanisms are potential novel targets for the prevention and control of T. gondii infection.
PMID:
 
24146978
 
[PubMed - in process] 

Toxoplasma gondii Relies on Both Host and Parasite Isoprenoids and Can Be Rendered Sensitive to Atorvastatin


 2013 Oct;9(10):e1003665. doi: 10.1371/journal.ppat.1003665. Epub 2013 Oct 17.

Toxoplasma gondii Relies on Both Host and Parasite Isoprenoids and Can Be Rendered Sensitive to Atorvastatin

Source

Center for Tropical and Emerging Global Diseases and Department of Cellular Biology, University of Georgia, Athens, Georgia, United States of America.

Abstract

Intracellular pathogens have complex metabolic interactions with their host cells to ensure a steady supply of energy and anabolic building blocks for rapid growth. Here we use the obligate intracellular parasite Toxoplasma gondii to probe this interaction for isoprenoids, abundant lipidic compounds essential to many cellular processes including signaling, trafficking, energy metabolism, and protein translation. Synthesis of precursors for isoprenoids in Apicomplexa occurs in the apicoplast and is essential. To synthesize longer isoprenoids from these precursors, T. gondii expresses a bifunctional farnesyl diphosphate/geranylgeranyl diphosphate synthase (TgFPPS). In this work we construct and characterize T. gondii null mutants for this enzyme. Surprisingly, these mutants have only a mild growth phenotype and an isoprenoid composition similar to wild type parasites. However, when extracellular, the loss of the enzyme becomes phenotypically apparent. This strongly suggests that intracellular parasite salvage FPP and/or geranylgeranyl diphosphate (GGPP) from the host. We test this hypothesis using inhibitors of host cell isoprenoid synthesis. Mammals use the mevalonate pathway, which is susceptible to statins. We document strong synergy between statin treatment and pharmacological or genetic interference with the parasite isoprenoid pathway. Mice can be cured with atorvastatin (Lipitor) from a lethal infection with the TgFPPs mutant. We propose a double-hit strategy combining inhibitors of host and parasite pathways as a novel therapeutic approach against Apicomplexan parasites.
PMID:
 
24146616
 
[PubMed - in process] 

Tuesday, October 22, 2013

Species or local environment, what determines the infection of rodents by Toxoplasma gondii?

2013 Oct 18:1-10. [Epub ahead of print]

Species or local environment, what determines the infection of rodents by Toxoplasma gondii?

Source

Université de Reims Champagne-Ardenne, Laboratoire de Parasitologie-Mycologie, EA 3800, UFR de Médecine, SFR Cap Santé FED 4231, 51 rue Cognacq-Jay, F-51096 Reims, France.

Abstract

SUMMARY Toxoplasmosis is largely present in rural areas but its spatial distribution in this environment remains poorly known. In particular, it is unclear if areas of high density of cats, the only hosts excreting Toxoplasma gondii, constitute foci of high prevalence. To improve our understanding of the spatial distribution of T. gondii in rural areas, we performed a serological survey in rodents from two villages in France. We trapped 710 rodents including commensal rats and meadow or forest voles and mice. The presence of T. gondii was examined using PCR, mice inoculation and modified agglutination test for antibodies (MAT). We conducted multivariate and discriminant analyses to identify biological, ecological or spatial variables that could explain T. gondii serology in rodents. We then used a logistic regression to assess the relative influence of each explanatory variable. Overall seroprevalence was 4·1%. Commensal-rats were more infected (12·5%) than non-commensal species (3·7%). However, the major determinant of the risk of infection was the distance to the nearest farm (OR = 0·75 for 100 m), which explained the risk in all species or non-commensal species only. We contrast the role of species characteristics and that of the local environment, and discuss the risk of environmental contamination for humans.
PMID:
24135380
[PubMed - as supplied by publisher]

Friday, October 18, 2013

Epidemiology, Pathophysiology, and the Future of Ocular Toxoplasmosis

2013 Oct 16. [Epub ahead of print]

Epidemiology, Pathophysiology, and the Future of Ocular Toxoplasmosis

Source

Livestock Research, Wageningen University and Research Centre, Lelystad, The Netherlands; and University Eye Clinic Maastricht, Maastricht , The Netherlands, Maastricht , The Netherlands and.

Abstract

Abstract Despite large advances in the field of ocular toxoplasmosis, large gaps still exist in our knowledge concerning the epidemiology and pathophysiology of this potentially blinding infectious disease. Although ocular toxoplasmosis is considered to have a high health burden, still little is known about its exact prevalence and how it affects the quality of life. The epidemiology of toxoplasmosis depends on local habits throughout the globe, and changes are likely in view of increased meat consumption in developing countries and demands for higher animal welfare in the Western world. Water is increasingly seen as an important risk factor and more studies are needed to quantitate and control the role of water exposure (drinking, swimming). Tools are now becoming available to study both the human host as well as parasite genetic factors in the development of ocular toxoplasmosis. Further research on the role of Toxoplasma strains as well as basic studies on parasite virulence is needed to explain why Toxoplasma associated eye disease is so severe in some countries, such as Brazil. Although genetic analysis of the parasite represents the gold standard, further developments in serotyping using peptide arrays may offer practical solutions to study the role of parasite strains in the pathogenesis of Toxoplasma retinochoroiditis. More research is needed concerning the pathways whereby the parasite can infect the retina. Once in the retina further tissue damage may be due to parasite virulence factors or could be caused by an aberrant host immune response. Local intraocular immune responses are nowadays used for diagnostic procedures. Future developments may include the use of Raman technology or the direct visualization of a Toxoplasma cyst by optical coherence tomography (OCT). With the availability of ocular fluid specimens obtained for diagnostic purposes and the development of advanced proteomic techniques, a biomarker fingerprint that is unique for an eye with toxoplasmosis may become available. It is hoped that such a biomarker analysis may also be able to distinguish between acquired versus congenital disease. Recently developed mouse models of congenital ocular toxoplasmosis are extremely promising with regard to disease pathogenesis, diagnosis, and treatment.
PMID:
24131274
[PubMed - as supplied by publisher]

CXCR3-Dependent CD4+ T Cells Are Required to Activate Inflammatory Monocytes for Defense against Intestinal Infection

2013 Oct;9(10):e1003706. Epub 2013 Oct 10.

CXCR3-Dependent CD4+ T Cells Are Required to Activate Inflammatory Monocytes for Defense against Intestinal Infection

Source

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

Abstract

Chemokines and their receptors play a critical role in orchestrating immunity to microbial pathogens, including the orally acquired Th1-inducing protozoan parasite Toxoplasma gondii. Chemokine receptor CXCR3 is associated with Th1 responses, and here we use bicistronic CXCR3-eGFP knock-in reporter mice to demonstrate upregulation of this chemokine receptor on CD4+ and CD8+ T lymphocytes during Toxoplasma infection. We show a critical role for CXCR3 in resistance to the parasite in the intestinal mucosa. Absence of the receptor in Cxcr3-/- mice resulted in selective loss of ability to control T. gondii specifically in the lamina propria compartment. CD4+ T cells were impaired both in their recruitment to the intestinal lamina propria and in their ability to secrete IFN-γ upon stimulation. Local recruitment of CD11b+Ly6C/G+ inflammatory monocytes, recently reported to be major anti-Toxoplasma effectors in the intestine, was not impacted by loss of CXCR3. However, inflammatory monocyte activation status, as measured by dual production of TNF-α and IL-12, was severely impaired in Cxcr3-/- mice. Strikingly, adoptive transfer of wild-type but not Ifnγ-/- CD4+ T lymphocytes into Cxcr3-/- animals prior to infection corrected the defect in inflammatory macrophage activation, simultaneously reversing the susceptibility phenotype of the knockout animals. Our results establish a central role for CXCR3 in coordinating innate and adaptive immunity, ensuring generation of Th1 effectors and their trafficking to the frontline of infection to program microbial killing by inflammatory monocytes.
PMID:
24130498
[PubMed - as supplied by publisher]

Structure of the Toxoplasma gondii ROP18 kinase domain reveals a second ligand binding pocket required for acute virulence


2013 Oct 15. [Epub ahead of print]

Structure of the Toxoplasma gondii ROP18 kinase domain reveals a second ligand binding pocket required for acute virulence

Source

Massachusetts Institute of Technology, United States.

Abstract

At least a third of the human population is infected with the intracellular parasite Toxoplasma gondii, which contributes significantly to the disease burden in immunocompromised and neutropenic hosts and causes serious congenital complications when vertically transmitted to the fetus. Genetic analyses have identified the Toxoplasma ROP18 Ser/Thr protein kinase as a major factor mediating acute virulence in mice. ROP18 is secreted into the host cell during the invasion process, and its catalytic activity is required for the acute virulence phenotype. However, its precise molecular function and regulation are not fully understood. We have determined the crystal structure of the ROP18 kinase domain, which is inconsistent with a previously proposed auto-inhibitory mechanism of regulation. Furthermore, a sucrose molecule bound to our structure identifies an additional ligand-binding pocket outside of the active site cleft. Mutational analysis confirms an important role for this pocket in virulence.

KEYWORDS:

Crystal structure, Protein kinases, Protein phosphorylation, Protozoan, Signal transduction, Toxoplasma gondii, rhoptry protein
PMID:
24129568
[PubMed - as supplied by publisher]

Wednesday, October 16, 2013

GCN2-like eIF2α kinase manages the amino acid starvation response in Toxoplasma gondii

2013 Oct 11. pii: S0020-7519(13)00244-0. doi: 10.1016/j.ijpara.2013.08.005. [Epub ahead of print]

GCN2-like eIF2α kinase manages the amino acid starvation response in Toxoplasma gondii

Source

Department of Biochemistry & Molecular Biology, Indiana University School of Medicine, Indianapolis, IN 46202, USA; Department of Pharmacology & Toxicology, Indiana University School of Medicine, Indianapolis, IN 46202, USA.

Abstract

The apicomplexan protozoan Toxoplasma gondii is a significant human and veterinary pathogen. As an obligate intracellular parasite, Toxoplasma depends on nutrients provided by the host cell and needs to adapt to limitations in available resources. In mammalian cells, translational regulation via GCN2 phosphorylation of the alpha subunit of eukaryotic translation initiation factor 2 (eIF2α) is a key mechanism for adapting to nutrient stress. Toxoplasma encodes two GCN2-like protein kinases, TgIF2K-C and TgIF2K-D. We previously showed that TgIF2K-D phosphorylates T. gondii eIF2α (TgIF2α) upon egress from the host cell, which enables the parasite to overcome exposure to the extracellular environment. However, the function of TgIF2K-C remained unresolved. To determine the functions of TgIF2K-C in the parasite, we cloned the cDNA encoding TgIF2K-C and generated knockout parasites of this TgIF2α kinase to study its function during the lytic cycle. The TgIF2K-C knockout did not exhibit a fitness defect compared with parental parasites. However, upon infection of human fibroblasts that were subsequently cultured in glutamine-free medium, the intracellular TgIF2K-C knockout parasites were impeded for induced phosphorylation of TgIF2α and showed a 50% reduction in the number of plaques formed compared with parental parasites. Furthermore, we found that this growth defect in glutamine-free media was phenocopied in parasites expressing only a non-phosphorylatable TgIF2α (TgIF2α-S71A), but not in a TgIF2K-D knockout. These studies suggest that Toxoplasma GCN2-like kinases TgIF2K-C and TgIF2K-D evolved to have distinct roles in adapting to changes in the parasite's environment.
Copyright © 2013. Published by Elsevier Ltd.

KEYWORDS:

Apicomplexa, Glutamine, Parasite, Stress, Translational control, eIF2 kinase
PMID:
24126185
[PubMed - as supplied by publisher]

It is not only the cat that did it: How to prevent and treat congenital toxoplasmosis

2013 Oct 9. pii: S0163-4453(13)00290-9. doi: 10.1016/j.jinf.2013.09.023. [Epub ahead of print]

It is not only the cat that did it: How to prevent and treat congenital toxoplasmosis

Source

Laboratory of Parasitology, Centre Hospitalier Universitaire de Rennes, France; INSERM U1085/IRSET (Institut de Recherche en Santé Environnement Travail), Université Rennes 1, France. Electronic address: florence.robert-gangneux@univ-rennes1.fr.

Abstract

The apicomplexan parasite Toxoplasma gondii was discovered a little over one hundred years ago and was soon recognized as a pathogen responsible for congenital infection. But detailed understanding of its epidemiology emerged only after 1970 with the discovery of its life cycle. In the last ten years, high resolution molecular tools have allowed the characterization of various strain types with different virulence patterns, and current studies are exploring the distribution of these different genotypes. In parallel, sophisticated diagnostic tools have been developed and awareness of disease burden has led some European countries with high prevalence rates to implement screening of pregnant women. In this article, the screening options and therapies used to prevent congenital toxoplasmosis are dissected in the light of recent data from cohort studies and other epidemiological data.
Copyright © 2013 The British Infection Association. Published by Elsevier Ltd. All rights reserved.

KEYWORDS:

Congenital toxoplasmosis, Epidemiology, Pregnancy, Prevention, Treatment
PMID:
24119928
[PubMed - as supplied by publisher]

Friday, October 11, 2013

Antibodies to Toxoplasma gondii in individuals with mania

2013 Sep 18. doi: 10.1111/bdi.12123. [Epub ahead of print]

Antibodies to Toxoplasma gondii in individuals with mania

Source

Stanley Research Program, Sheppard Pratt Health System, Baltimore, MD, USA.

Abstract

OBJECTIVES:

Increased rates of infection with Toxoplasma gondii have been found in individuals with schizophrenia as compared to control groups but this issue has not been studied in mania.

METHODS:

We measured immunoglobulin G (IgG) and IgM class antibodies to T. gondii in 57 individuals with mania who were assessed at up to three time-points. We also measured these antibodies in 743 individuals in other psychiatric groups and in 314 non-psychiatric controls. T. gondii antibody levels were compared among groups by multivariate analyses. IgG class and IgM class antibodies to cytomegalovirus were also measured in the same samples. T. gondii antibody levels were also compared over time in the mania group.

RESULTS:

The mania group had a significantly elevated level of IgM antibodies to T. gondii as compared to the control individuals without a psychiatric diagnosis [odds ratio (OR) = 2.33, p < 0.04 at hospital admission; and OR = 2.32, p < 0.02 at study entry during the hospital stay]. Elevated IgM class antibodies to T. gondii were not found in individuals with the other psychiatric diagnoses. We also did not find an increased level of IgG class antibodies to T. gondii or IgG or IgM class antibodies to CMV in the individuals with mania. Within the mania group, there was a significant difference between the prevalences of increased levels of T. gondii IgM at the baseline and the follow-up time-point (t = 2.97, p < 0.003).

CONCLUSIONS:

Infection with T. gondii may confer risk for mania.
© 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

KEYWORDS:

Toxoplasma gondii , bipolar disorder, infection, mania, parasite
PMID:
24102676
[PubMed - as supplied by publisher]

Apical membrane antigen 1 mediates apicomplexan parasite attachment but is dispensable for host cell invasion

2013 Oct 10;4:2552. doi: 10.1038/ncomms3552.

Apical membrane antigen 1 mediates apicomplexan parasite attachment but is dispensable for host cell invasion

Source

1] Institut Pasteur, Malaria Biology and Genetics Unit, Department of Parasitology and Mycology, 28 Rue du Dr Roux, Paris, France [2].

Abstract

Apicomplexan parasites invade host cells by forming a ring-like junction with the cell surface and actively sliding through the junction inside an intracellular vacuole. Apical membrane antigen 1 is conserved in apicomplexans and a long-standing malaria vaccine candidate. It is considered to have multiple important roles during host cell penetration, primarily in structuring the junction by interacting with the rhoptry neck 2 protein and transducing the force generated by the parasite motor during internalization. Here, we generate Plasmodium sporozoites and merozoites and Toxoplasma tachyzoites lacking apical membrane antigen 1, and find that the latter two are impaired in host cell attachment but the three display normal host cell penetration through the junction. Therefore, apical membrane antigen 1, rather than an essential invasin, is a dispensable adhesin of apicomplexan zoites. These genetic data have implications on the use of apical membrane antigen 1 or the apical membrane antigen 1-rhoptry neck 2 interaction as targets of intervention strategies against malaria or other diseases caused by apicomplexans.
PMID:
24108241
[PubMed - as supplied by publisher]

Thursday, October 10, 2013

ApicoAMP: The first computational model for identifying apicoplast-targeted transmembrane proteins in Apicomplexa


 2013 Oct 3. pii: S0167-7012(13)00300-X. doi: 10.1016/j.mimet.2013.09.017. [Epub ahead of print]

ApicoAMP: The first computational model for identifying apicoplast-targeted transmembrane proteins in Apicomplexa

Source

School of Electrical Engineering and Computer Science, Washington State University, Pullman, WA 99164, USA.

Abstract

BACKGROUND:

Computational identification of apicoplast-targeted proteins is important in drug target determination for diseases such as malaria. While there are established methods for identifying proteins with a bipartite signal in multiple species of Apicomplexa, not all apicoplast-targeted proteins possess this bipartite signature. The publication of recent experimental findings of apicoplast membrane proteins, called transmembrane proteins, that do not possess a bipartite signal has made it feasible to devise a machine learning approach for identifying this new class of apicoplast-targeted proteins computationally. Methodology/Principal Findings In this work, we develop a method for predicting apicoplast-targeted transmembrane proteins for multiple species of Apicomplexa, whereby several classifiers trained on different feature sets and based on different algorithms are evaluated and combined in an ensemble classification model to obtain the best expected performance. The feature sets considered are the hydrophobicity and composition characteristics of amino acids over transmembrane domains, the existence of short sequence motifs over cytosolically disposed regions, and Gene Ontology (GO) terms associated with given proteins. Our model, ApicoAMP, is an ensemble classification model that combines decisions of classifiers following the majority vote principle. ApicoAMP is trained on a set of proteins from 11 apicomplexan species and achieves 91% overall expected accuracy. Conclusions/Significance ApicoAMP is the first computational model capable of identifying apicoplast-targeted transmembrane proteins in Apicomplexa. The ApicoAMP prediction software is available at http://code.google.com/p/apicoamp/ and http://bcb.eecs.wsu.edu.
© 2013.

KEYWORDS:

Apicomplexa, apicoplast, apicoplast-targeted membrane proteins, ensemble classification models, gene ontology annotation, machine learning, protein motifs, transmembrane proteins
PMID:
 
24095682
 
[PubMed - as supplied by publisher]

The roles of intramembrane proteases in protozoan parasites


 2013 Dec;1828(12):2908-2915. doi: 10.1016/j.bbamem.2013.04.017.

The roles of intramembrane proteases in protozoan parasites

Source

Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO 63110, USA. Electronic address: sibley@wustl.edu.

Abstract

Intramembrane proteolysis is widely conserved throughout different forms of life, with three major types of proteases being known for their ability to cleave peptide bonds directly within the transmembrane domains of their substrates. Although intramembrane proteases have been extensively studied in humans and model organisms, they have only more recently been investigated in protozoan parasites, where they turn out to play important and sometimes unexpected roles. Signal peptide peptidases are involved in endoplasmic reticulum (ER) quality control and signal peptide degradation from exported proteins. Recent studies suggest that repurposing inhibitors developed for blocking presenilins may be useful for inhibiting the growth of Plasmodium, and possibly other protozoan parasites, by blocking signal peptide peptidases. Rhomboid proteases, originally described in the fly, are also widespread in parasites, and are especially expanded in apicomplexans. Their study in parasites has revealed novel roles that expand our understanding of how these proteases function. Within this diverse group of parasites, rhomboid proteases contribute to processing of adhesins involved in attachment, invasion, intracellular replication, phagocytosis, and immune evasion, placing them at the vertex of host-parasite interactions. This article is part of a Special Issue entitled: Intramembrane Proteases.
Copyright © 2013 Elsevier B.V. All rights reserved.

KEYWORDS:

Adhesion, Apicomplexan parasite, Cell invasion, Rhomboid, Secretory pathway, Signal peptide peptidase
PMID:
 
24099008
 
[PubMed - as supplied by publisher]

Vaccines against Toxoplasma gondii: new developments and perspectives


 2013 Oct 4. [Epub ahead of print]

Vaccines against Toxoplasma gondii: new developments and perspectives

Source

State Key Laboratory of Veterinary Etiological Biology, Key Laboratory of Veterinary Parasitology of Gansu Province, Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Lanzhou, Gansu Province 730046, PR China.

Abstract

Toxoplasmosis caused by the protozoan Toxoplasma gondii is a major public health problem, infecting one-third of the world human beings, and leads to abortion in domestic animals. A vaccine strategy would be an ideal tool for improving disease control. Many efforts have been made to develop vaccines against T. gondii to reduce oocyst shedding in cats and tissue cyst formation in mammals over the last 20 years, but only a live-attenuated vaccine based on the S48 strain has been licensed for veterinary use. Here, the authors review the recent development of T. gondii vaccines in cats, food-producing animals and mice, and present its future perspectives. However, a single or only a few antigen candidates revealed by various experimental studies are limited by only eliciting partial protective immunity against T. gondii. Future studies of T. gondii vaccines should include as many CTL epitopes as the live attenuated vaccines.
PMID:
 
24093877
 
[PubMed - as supplied by publisher]

Toxoplasma gondii: Immune response and protective efficacy induced by ROP16/GRA7 multicomponent DNA vaccine with a genetic adjuvant B7-2


 2013 Oct 4;10(1). [Epub ahead of print]

Toxoplasma gondii: Immune response and protective efficacy induced by ROP16/GRA7 multicomponent DNA vaccine with a genetic adjuvant B7-2

Source

Department of Parasitology; Shandong University School of Medicine; Jinan, Shandong PR China.

Abstract

Toxoplasma gondii infection occurs commonly in humans and other warm-blooded animals. Its serious impact on public health and livestock sectors makes the development of an effective vaccine particularly important. In the current study, we constructed a multiantigenic DNA vaccine expressing ROP16 and GRA7 of T. gondii and evaluated the protective efficacy of these two fragments with or without a plasmid encoding murine costimulatory molecule B7-2. These recombinant eukaryotic expression plasmids were termed pROP16, pGRA7, pROP16-GRA7 and pB7-2, respectively. After intramuscular immunization in Kunming mice, we assessed the immune response using cytokine and antibody determinations, T lymphocyte subsets analysis, and the survival times of mice post acute T. gondii challenge. The results showed that mice immunized with the multiantigenic DNA vaccine pROP16-GRA7 gained higher levels of IgG titers and IgG2a subclass titers, production of IFN-γ, percentage of CD8+ T cells and median survival times against the acute infection of T. gondii compared with those of mice administered with pROP16 or pGRA7 and those in control groups. Moreover, the adjuvant pB7-2 formulated with DNA vaccine boosted these humoral and cellular (Th1, CD8+ T cell) immune responses. Therefore, it might be a promising genetic adjuvant to DNA vaccine against T. gondii for further investigation.

KEYWORDS:

Costimulatory molecule B7-2, DNA vaccine, Dense granule antigen 7, Rhoptry protein 16, Toxoplasma gondii, adjuvant
PMID:
 
24096573
 
[PubMed - as supplied by publisher]

Effects of dextran sulfates on the acute infection and growth stages of Toxoplasma gondii


 2013 Oct 6. [Epub ahead of print]

Effects of dextran sulfates on the acute infection and growth stages of Toxoplasma gondii

Source

National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, Inada-cho, Obihiro, Hokkaido, 080-8555, Japan.

Abstract

Toxoplasma gondii is one of the most prevalent parasites, causing toxoplasmosis in various warm-blooded animals, including humans. Because of the broad range of hosts susceptible to T. gondii, it had been postulated that a universal component of the host cell surface, such as glycosaminoglycans (GAGs), may act as a receptor for T. gondii infection. Carruthers et al. (Infect Immun 68:4005-4011, 2000) showed that soluble GAGs have also been shown to disrupt parasite binding to human fibroblasts. Therefore, we investigated the inhibitory effect of GAGs and their analogue dextran sulfate (DS) on T. gondii infection. For up to 24 h of incubation after inoculation of T. gondii, the inhibitory effect of GAGs on T. gondii infection and growth inside the host cell was weak. In contrast, DS markedly inhibited T. gondii infection. Moreover, low molecular weight DS particularly slowed the growth of T. gondii inside host cells. DS10 (dextran sulfate MW 10 kDa) was the most effective agent in these in vitro experiments and was therefore tested for its inhibitory effects in animal experiments; infection inhibition by DS10 was confirmed under these in vivo conditions. In this report, we showed that DSs, especially DS10, have the potential of a new type of drug for toxoplasmosis.
PMID:
 
24096605
 
[PubMed - as supplied by publisher]

Strategies to discover the structural components of cyst and oocyst walls


 2013 Oct 4. [Epub ahead of print]

Strategies to discover the structural components of cyst and oocyst walls

Source

Department of Molecular and Cell Biology, Boston University Goldman School of Dental Medicine, Boston, Massachusetts, USA.

Abstract

Cysts of Giardia lamblia and Entamoeba histolytica and oocysts of Toxoplasma gondii and Cryptosporidium parvum are the infectious and sometimes diagnostic forms of these parasites. To discover the structural components of cyst and oocyst walls, we have developed strategies based upon a few simple assumptions. Briefly, the most abundant wall proteins are identified by monoclonal antibodies or mass spectrometry. Structural components include a sugar polysaccharide (chitin for Entamoeba, β-1,3-linked glucose for Toxoplasma, and β-1,3-linked GalNAc for Giardia) and/or acid-fast lipids (Toxoplasma and Cryptosporidium). Because Entamoeba cysts and Toxoplasma oocysts are difficult to obtain, studies of walls of non-human pathogens (E. invadens and Eimeria, respectively) accelerate discovery. Biochemical methods to dissect fungal walls work well for cyst and oocyst walls, although the results are often unexpected. For example, echinocandins, which inhibit glucan synthases and kill fungi, arrest the development of oocyst walls and block their release into the intestinal lumen. Candida walls are coated with mannans, while Entamoeba cysts are coated in a dextran-like glucose polymer. Models for cyst and oocyst walls derive from their structural components and organization within the wall. Cyst walls are composed of chitin fibrils and lectins that bind chitin (Entamoeba) or fibrils of the β-1,3-GalNAc polymer and lectins that bind the polymer (Giardia). Oocyst walls of Toxoplasma have two distinct layers that resemble fungi (β-1,3-glucan in the inner layer) or mycobacteria (acid-fast lipids in the outer layer). Oocyst walls of Cryptosporidium have a rigid bilayer of acid-fast lipids and inner layer of oocyst wall proteins.
PMID:
 
24096907
 
[PubMed - as supplied by publisher]

Friday, October 04, 2013

Co-existence of classical and alternative activation programs in macrophages responding to Toxoplasma gondii

2013 Sep 28. pii: S0020-7519(13)00238-5. doi: 10.1016/j.ijpara.2013.08.003. [Epub ahead of print]

Co-existence of classical and alternative activation programs in macrophages responding to Toxoplasma gondii

Source

Department of Medicine and Center for Immunity and Inflammation, Rutgers-New Jersey Medical School, Newark, NJ 07101, USA.

Abstract

Pro-inflammatory M1 macrophages are critical for defense against intracellular pathogens while alternatively-activated M2 macrophages mediate tissue homeostasis and repair. Whether these distinct activation programs are mutually exclusive or can co-exist within the same cell is unclear. Here, we report the co-existence of these programs in Toxoplasma gondii-elicited inflammatory macrophages. This is independent of parasite expression of the virulence factor ROP16 and host cell expression of signal transducer and activator of transcription 6 (STAT6). Furthermore, this observation was recapitulated by IFN-γ and IL-4 treated bone marrow-derived macrophages in vitro. These results highlight the multi-functionality of macrophages as they respond to diverse microbial and endogenous stimuli.
Copyright © 2013. Published by Elsevier Ltd.

KEYWORDS:

Alternative activation, Classical activation, Macrophage, Toxoplasma gondii, Virulence factor
PMID:
24083945
[PubMed - as supplied by publisher]

Wednesday, October 02, 2013

Cooperation of TLR12 and TLR11 in the IRF8-Dependent IL-12 Response to Toxoplasma gondii Profilin


 2013 Sep 27. [Epub ahead of print]

Cooperation of TLR12 and TLR11 in the IRF8-Dependent IL-12 Response to Toxoplasma gondii Profilin

Source

Department of Immunology, University of Texas Southwestern Medical Center, Dallas, TX 75390;

Abstract

TLRs play a central role in the innate recognition of pathogens and the activation of dendritic cells (DCs). In this study, we establish that, in addition to TLR11, TLR12 recognizes the profilin protein of the protozoan parasite Toxoplasma gondii and regulates IL-12 production by DCs in response to the parasite. Similar to TLR11, TLR12 is an endolysosomal innate immune receptor that colocalizes and interacts with UNC93B1. Biochemical experiments revealed that TLR11 and TLR12 directly bind to T. gondii profilin and are capable of forming a heterodimer complex. We also establish that the transcription factor IFN regulatory factor 8, not NF-κB, plays a central role in the regulation of the TLR11- and TLR12-dependent IL-12 response of DCs. These results suggest a central role for IFN regulatory factor 8-expressing CD8+ DCs in governing the TLR11- and TLR12-mediated host defense against T. gondii.
PMID:
 
24078692
 
[PubMed - as supplied by publisher]