Friday, February 29, 2008

Monocyte-Mediated Defense Against Microbial Pathogens

Annu Rev Immunol. 2007 Dec 3 [Epub ahead of print]

Monocyte-Mediated Defense Against Microbial Pathogens

Serbina NV, Jia T, Hohl TM, Pamer EG.

Infectious Diseases Unit, Department of Medicine, Sloan Kettering Cancer Institute, New York, New York 10021; email:

Circulating blood monocytes supply peripheral tissues with macrophage and dendritic cell (DC) precursors and, in the setting of infection, also contribute directly to immune defense against microbial pathogens. In humans and mice, monocytes are divided into two major subsets that either specifically traffic into inflamed tissues or, in the absence of overt inflammation, constitutively maintain tissue macrophage/DC populations. Inflammatory monocytes respond rapidly to microbial stimuli by secreting cytokines and antimicrobial factors, express the CCR2 chemokine receptor, and traffic to sites of microbial infection in response to monocyte chemoattractant protein (MCP)-1 (CCL2) secretion. In murine models, CCR2- mediated monocyte recruitment is essential for defense against Listeria monocytogenes, Mycobacterium tuberculosis, Toxoplasma gondii, and Cryptococcus neoformans infection, implicating inflammatory monocytes in defense against bacterial, protozoal, and fungal pathogens. Recent studies indicate that inflammatory monocyte recruitment to sites of infection is complex, involving CCR2-mediated emigration of monocytes from the bone marrow into the bloodstream, followed by trafficking into infected tissues. The in vivo mechanisms that promote chemokine secretion, monocyte differentiation and trafficking, and finally monocyte-mediated microbial killing remain active and important areas of investigation. Expected final online publication date for the Annual Review of Immunology Volume 26 is March 19, 2008. Please see for revised estimates.

PMID: 18303997 [PubMed - as supplied by publisher]

Transplacental toxoplasmosis in a wild southern sea otter

Vet Parasitol. 2008 Jan 19 [Epub ahead of print]

Transplacental toxoplasmosis in a wild southern sea otter (Enhydra lutris nereis)

Miller M, Conrad P, James ER, Packham A, Toy-Choutka S, Murray MJ, Jessup D, Grigg M.

California Department of Fish and Game-Office of Spill Prevention and Response, Marine Wildlife Veterinary Care and Research Center, 1451 Shaffer Road, Santa Cruz, CA 95060, United States.

In September 2004, a neonatal sea otter pup was found alive on the beach in northern Monterey Bay, CA. Efforts to locate the mother were unsuccessful. Due to a poor prognosis for successful rehabilitation, the pup was euthanized. Postmortem examination revealed emaciation, systemic lymphadenopathy and a malformation of the left cerebral temporal lobe. On histopathology, free tachyzoites and tissue cysts compatible with Toxoplasma gondii were observed in the brain, heart, thymus, liver, lymph nodes and peri-umbilical adipose. The presence of T. gondii within host tissues was associated with lymphoplasmacytic inflammation and tissue necrosis. Immunofluorescent antibody tests using postmortem serum were positive for anti-T. gondii IgM and IgG (at 1:320 and 1:1280 serum dilution, respectively), but were negative for IgG directed against Sarcocystis neurona and Neospora caninum (<1:40 each). Brain immunohistochemistry revealed positive staining for tachyzoites and tissue cysts using antiserum raised to T. gondii, but not S. neurona or N. caninum. T. gondii parasite DNA was obtained from extracts of brain and muscle by PCR amplification using the diagnostic B1 locus. Restriction enzyme digestion followed by gel electrophoresis and DNA sequencing confirmed the presence of Type X T. gondii, the strain identified in the majority of southern sea otter infections.

PMID: 18304737 [PubMed - as supplied by publisher]

Toxoplasma gondii induces prostaglandin E(2) synthesis in macrophages

Parasitol Res. 2008 Feb 28 [Epub ahead of print]

Toxoplasma gondii induces prostaglandin E(2) synthesis in macrophages via signal pathways for calcium-dependent arachidonic acid production and PKC-dependent induction of cyclooxygenase-2

Peng BW, Lin JY, Zhang T

Medical College of Wuhan University, Wuhan, Hubei Province, 430071, People’s Republic of China.

In this study, the intracellular signaling pathway of PGE(2) synthesis in macrophages (RAW264.7) induced by Toxoplasma gondii was investigated. The T. gondii-induced PGE(2) production in macrophages increased in a time-dependent manner, as PGE(2) induction began at 4 h, peaked at 12 h, and then plateaued at a high level. COX-2 mRNA in macrophages was detectable as early as 4 h after treatment; the maximal expression was observed at 8 h. The earliest induction of COX-2 protein occurred at 4 h and peaked at 16 h; meanwhile, COX-1 mRNA level and protein production remained unchanged throughout. Indomethacin and nimesulide inhibited tachyzoite-induced PGE(2) production and COX-2 mRNA expression in macrophages but they had no significant effect on COX-2 protein expression. EGTA, TFP and BAPTA/AM inhibited both arachidonic acid (AA) and PGE(2) production without effecting COX-2 protein expression, but verapamil inhibited neither AA nor PGE(2) production. H7 was found to inhibit PGE(2) production, and COX-2 mRNA expression and protein expression by tachyzoite or LPS stimulated macrophages in a dose-dependent manner. Our results demonstrate that T. gondii induces PGE(2) biosynthesis in RAW264.7 macrophages by regulating AA production through a calcium-dependent pathway and induction of COX-2 expression by a PKC-dependent pathway.

PMID: 18305957 [PubMed - as supplied by publisher]

Saturday, February 23, 2008

A photosynthetic alveolate closely related to apicomplexan parasites

Nature. 2008 Feb 21;451(7181):959-63

A photosynthetic alveolate closely related to apicomplexan parasites

Moore RB, Oborník M, Janouskovec J, Chrudimský T, Vancová M, Green DH, Wright SW, Davies NW, Bolch CJ, Heimann K, Slapeta J, Hoegh-Guldberg O, Logsdon JM, Carter DA.

School of Molecular and Microbial Biosciences, University of Sydney, Darlington, New South Wales 2006, Australia

Many parasitic Apicomplexa, such as Plasmodium falciparum, contain an unpigmented chloroplast remnant termed the apicoplast, which is a target for malaria treatment. However, no close relative of apicomplexans with a functional photosynthetic plastid has yet been described. Here we describe a newly cultured organism that has ultrastructural features typical for alveolates, is phylogenetically related to apicomplexans, and contains a photosynthetic plastid. The plastid is surrounded by four membranes, is pigmented by chlorophyll a, and uses the codon UGA to encode tryptophan in the psbA gene. This genetic feature has been found only in coccidian apicoplasts and various mitochondria. The UGA-Trp codon and phylogenies of plastid and nuclear ribosomal RNA genes indicate that the organism is the closest known photosynthetic relative to apicomplexan parasites and that its plastid shares an origin with the apicoplasts. The discovery of this organism provides a powerful model with which to study the evolution of parasitism in Apicomplexa.

Publication Types:
Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.

PMID: 18288187 [PubMed - in process]

Thursday, February 21, 2008

Forward Genetic Analysis of the Apicomplexan Cell Division Cycle in Toxo

PLoS Pathog. 2008 Feb 15;4(2):e36 [Epub ahead of print]

Forward Genetic Analysis of the Apicomplexan Cell Division Cycle in Toxoplasma gondii

Gubbels MJ, Lehmann M, Muthalagi M, Jerome ME, Brooks CF, Szatanek T, Flynn J, Parrot B, Radke J, Striepen B, White MW.

Apicomplexa are obligate intracellular pathogens that have fine-tuned their proliferative strategies to match a large variety of host cells. A critical aspect of this adaptation is a flexible cell cycle that remains poorly understood at the mechanistic level. Here we describe a forward genetic dissection of the apicomplexan cell cycle using the Toxoplasma model. By high-throughput screening, we have isolated 165 temperature sensitive parasite growth mutants. Phenotypic analysis of these mutants suggests regulated progression through the parasite cell cycle with defined phases and checkpoints. These analyses also highlight the critical importance of the peculiar intranuclear spindle as the physical hub of cell cycle regulation. To link these phenotypes to parasite genes, we have developed a robust complementation system based on a genomic cosmid library. Using this approach, we have so far complemented 22 temperature sensitive mutants and identified 18 candidate loci, eight of which were independently confirmed using a set of sequenced and arrayed cosmids. For three of these loci we have identified the mutant allele. The genes identified include regulators of spindle formation, nuclear trafficking, and protein degradation. The genetic approach described here should be widely applicable to numerous essential aspects of parasite biology.

PMID: 18282098 [PubMed - as supplied by publisher]

Go there.

A new combined flow-cytometry-based assay reveals excellent activity against Toxo and low toxicity of new bisphosphonates

J Antimicrob Chemother. 2008 Feb 19 [Epub ahead of print]

A new combined flow-cytometry-based assay reveals excellent activity against Toxoplasma gondii and low toxicity of new bisphosphonates in vitro and in vivo

Shubar HM, Mayer JP, Hopfenmüller W, Liesenfeld O

Institut für Mikrobiologie und Hygiene, Charité Universtätsmedizin Berlin, Campus Benjamin Franklin, Hindenburgdamm 27, 12203 Berlin, Germany.

Objectives The aim of this study was to investigate the antiparasitic activity and toxicity of bisphosphonates using a new combined flow cytometry assay. Methods Using Toxoplasma gondii tachyzoites carrying the green-fluorescent protein (GFP), we established a new flow cytometry assay combining testing of in vitro and in vivo activity plus toxicity of newly synthesized bisphosphonates against T. gondii. Toxicity as determined by this assay was compared with toxicity as determined by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) test. Results In vivo, therapeutic efficacy was 100% for bisphosphonates 2F, 3B, 18A, 22A and 30B at 490, 1000, 512, 44.05 and 47.6 microM concentrations, respectively. Toxicity at 100% inhibitory concentrations was 20% for 2F and 3B, 60% for 22A and 30B, and 75% for 18A. In vitro, 6 (91A, 203A, 200C, 210A, 204A and 282A) of 15 newly synthesized bisphosphonates (12 nitrogen-containing and 3 n-alkyl) inhibited parasite replication by >50% at a concentration of 100 microM. Whereas substances 91A and 282A (high efficacy) showed moderate and low toxicity (cell viability between 70% and 100%), respectively, toxicities of 203A, 200C, 210A and 204A were 70%, 65%, 80% and 70%, respectively, as determined by flow cytometry. Compounds 290A, 218A, 214A, 266A and 219A inhibited parasite replication by between 20% and 50% at a concentration of 100 microM. Conclusions Newly synthesized bisphosphonates 2F, 3B, 91A and 282A showed excellent therapeutic activity and low toxicity. These antiparasitic drugs may therefore be promising compounds for use in patients with acute and reactivated toxoplasmosis. The new flow cytometry assay allowed simultaneous determination of therapeutic efficacy and toxicity.

PMID: 18285314 [PubMed - as supplied by publisher]

Monday, February 18, 2008

Toxo beta-hydroxyacyl-acyl carrier protein dehydratase (FABZ)

Parasitol Res. 2008 Feb 15 [Epub ahead of print]

Molecular and biochemical characterization of Toxoplasma gondii beta-hydroxyacyl-acyl carrier protein dehydratase (FABZ)

Dautu G, Ueno A, Munyaka B, Carmen G, Makino S, Kobayashi Y, Igarashi M.

National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, 2-13 Inada-cho, Obihiro, Hokkaido, 080-8555, Japan.

Toxoplasma gondii, unlike its mammalian host, utilizes a type II fatty acid biosynthesis pathway in which the steps of fatty acid biosynthesis are catalyzed by independent enzymes. Due to this difference, the enzymes of this pathway are good targets for the development of new therapeutic drugs directed against toxoplasmosis. In this report, we show by using reverse transcription-polymerase chain reaction analysis that beta-Hydroxyacyl-acyl carrier protein dehydratase (TgFABZ) is expressed both in tachyzoites and bradyzoites. Indirect immunofluorescence antibody test further shows the localization of TgFABZ protein in the apicoplast of both tachyzoites and bradyzoites. Enzyme dynamic analysis shows that the purified recombinant TgFABZ protein is soluble and active. The K(m) value of the enzyme for its substrate analog crotonoyl-CoA was estimated to be 82.57 +/- 10 muM.

PMID: 18274777 [PubMed - as supplied by publisher]

Saturday, February 16, 2008

[Molecular cross talk between Toxoplasma gondii and the host immune system]

Med Sci (Paris). 2008 Feb;24(2):191-196.

[Molecular cross talk between Toxoplasma gondii and the host immune system]

[Article in French]

Buzoni-Gatel D, Dubremetz JF, Werts C

D. Buzoni-Gatel, C. Werts : RPPI, Institut Pasteur-Inra, 28, rue du Docteur Roux, 75724 Paris, France. J.F. Dubremetz : UMR CNRS 5539 Bâtiment 24, CC 10, Université de Montpellier, 2, place Eugène Bataillon, 34095 Montpellier Cedex 05, France.

Toxoplasma gondii is an intracellular parasite that frequently infects a large spectrum of warm-blooded animals. This parasite induces abortion and establishes both chronic and silent infections, particularly in the brain. The chronic infection is therefore a permanent threat for the host in cases of immunosuppression. Parasite penetration into the host activates a strong anti-parasite immune response, but is also used by the parasite to chronically persist. In the present paper, we discuss the data obtained in the laboratory of John Boothroyd that reports the molecular cross talk between the parasite rhoptry proteins and the host cell. During host cell invasion, rhoptries participate to the constitution of the mobile junction that drives the parasite into the host cell, while building the parasitophorus vacuole in which the parasite grows. Some soluble rhoptries, such as ROP16, are shed into the cytoplasm, and then reach the nucleus where they can eventually impact different signaling pathways such as STAT3/6, key molecules in the immune response establishment. double dagger.

PMID: 18272082 [PubMed - as supplied by publisher]

Thursday, February 14, 2008

Secretion of proteins into host cells by Apicomplexan parasites

Traffic. 2008 Feb 11 [Epub ahead of print]

Secretion of proteins into host cells by Apicomplexan parasites

Ravindran S, Boothroyd JC

Department of Microbiology and Immunology Stanford University School of Medicine Stanford, CA 94305-5124, USA.

The phylum Apicomplexa consists of a diverse group of obligate, intracellular parasites. The distinct evolutionary pressures on these protozoans as they have adapted to their respective niches has resulted in a variety of methods that they use to interact with and modify their hosts. One of these is the secretion and trafficking of parasite proteins into the host cell. We review this process for Theileria, Toxoplasma, and Plasmodium. We also present what is known about the mechanisms by which parasite proteins are exported into the host cell, as well as information on their known and putative functions once they have reached their final destination.

PMID: 18266908 [PubMed - as supplied by publisher]

Are some cases of psychosis caused by microbial agents? A review of the evidence

Mol Psychiatry. 2008 Feb 12 [Epub ahead of print]

Are some cases of psychosis caused by microbial agents? A review of the evidence

Yolken RH, Torrey EF

1The Stanley Laboratory of Developmental Neurovirology, Department of Pediatrics, Johns Hopkins University Medical Center, Baltimore, MD, USA.

The infectious theory of psychosis, prominent early in the twentieth century, has recently received renewed scientific support. Evidence has accumulated that schizophrenia and bipolar disorder are complex diseases in which many predisposing genes interact with one or more environmental agents to cause symptoms. The protozoan Toxoplasma gondii and cytomegalovirus are discussed as examples of infectious agents that have been linked to schizophrenia and in which genes and infectious agents interact. Such infections may occur early in life and are thus consistent with neurodevelopmental as well as genetic theories of psychosis. The outstanding questions regarding infectious theories concern timing and causality. Attempts are underway to address the former by examining sera of individuals prior to the onset of illness and to address the latter by using antiinfective medications to treat individuals with psychosis. The identification of infectious agents associated with the etiopathogenesis of schizophrenia might lead to new methods for the diagnosis, treatment and prevention of this disorder.Molecular Psychiatry advance online publication, 12 February 2008; doi:10.1038/mp.2008.5.

PMID: 18268502 [PubMed - as supplied by publisher]

Anti-infectives Targeting the isoprenoid pathway of Toxo

Expert Opin Ther Targets. 2008 Mar;12(3):253-263.

Anti-infectives Targeting the isoprenoid pathway of Toxoplasma gondii

Moreno SN, Li ZH

University of Georgia, Department of Cellular Biology and Center for Tropical and Emerging Global Diseases, 500 D. W. Brooks Dr, Athens, Georgia 30602, USA +1 706 542 4736 ; +1 706 542 9493 ;

Background: Isoprenoids are an extensive group of natural products with diverse structures consisting of various numbers of five carbon isopentenyl diphosphate (IPP) units. Objective: We review here what is known about the isoprenoid pathway in T. gondii. Methods: Recent primary literature is reviewed. Results/conclusion: Genomic evidence points toward the presence of a 1-deoxy-D-xylulose 5-phosphate/2-C-methyl-D-erythritol 4-phosphate (DOXP/MEP) pathway, similar to the one found in plants, which will produce isopentenyl diphosphate (IPP). The DOXP/MEP pathway has been validated as a target in the related Apicomplexan parasite Plasmodium. The DOXP/MEP pathway in Toxoplasma has not been characterized. Downstream in the pathway, the enzyme farnesyl diphosphate synthase (FPPS) has a central role in forming important intermediates since farnesyl diphosphate (FPP) is a precursor of critical molecules with fundamental biological function such as dolichols, heme a, cholesterol, farnesylated proteins and others. Strong evidence indicates that this enzyme is a valid target for drugs since bisphosphonates, which are specific FPPS inhibitors, inhibited parasite growth in vitro and in vivo. Our hypothesis is that the isoprenoid pathway constitutes a major novel target for the treatment of toxoplasmosis.

PMID: 18269336 [PubMed - as supplied by publisher]

Friday, February 01, 2008

Biodefense and Emerging Infections Research Resources Repository (BEIR)

Scientists interested in depositing or acquiring biomaterials for Toxoplasma research should consider the Biodefense and Emerging Infections Research Resources Repository (BEIR). BEIR was established by NIAID and is managed by ATCC to provide reagents for Category A, B, and C priority pathogens and emerging infectious disease agents to the scientific community ( A major focus of the Protistology group at BEIR is to expand biological resources for Toxoplasma given its status as a category B priority pathogen by NIAID. This is not restricted to isolates but also antisera, DNA clones, and genetic libraries. Importantly, scientists registered in BEIR may request reagents online and there is no charge for the materials themselves, but recipients are responsible for shipping and handling fees. In addition, secure storage, community access, and distribution is provided while protecting the intellectual property rights of the depositor. For more information please contact:

Robert Molestina, Ph.D.
Collection/Research Scientist
10801 University Boulevard
Manassas, VA 20110
Phone: (703) 365-2700 (ext. 2628)
Facsimile: (703) 365-2701

BeWo trophoblast cell susceptibility to Toxoplasma gondii is increased by interferon-gamma, interleukin-10 and transforming growth factor-beta1

Clin Exp Immunol. 2008 Mar;151(3):536-45.

BeWo trophoblast cell susceptibility to Toxoplasma gondii is increased by interferon-gamma, interleukin-10 and transforming growth factor-beta1

Barbosa BF, Silva DA, Costa IN, Mineo JR, Ferro EA.

Laboratory of Histology and Embryology, Institute of Biomedical Sciences, Federal University of Uberlândia, Uberlândia, MG, Brazil.

The present study aimed to investigate BeWo trophoblast cell susceptibility to Toxoplasma gondii infection under stimulation with anti-inflammatory cytokines in comparison with HeLa cells. Both cell types were submitted to different treatments with recombinant cytokines [interleukin (IL)-10 and transforming growth factor (TGF)-beta1] or the respective antibodies (anti-IL-10 and anti-TGF-beta) before and after T. gondii infection. The effect of interferon (IFN)-gamma was also assessed alone or in combination with anti-inflammatory cytokines or the respective antibodies after the parasite infection. Cells were fixed, stained and parasites quantified under light microscopy to evaluate intracellular replication (mean number of parasites per cell in 100 infected cells) and infection index (percentage of infected cells per 100 examined cells). In contrast with HeLa cells, treatments with IL-10 or TGF-beta1 induced a considerable augmentation in both T. gondii intracellular replication and invasion into BeWo cells. In addition, treatment with IFN-gamma alone or associated with IL-10 or TGF-beta1 increased the same parameters in BeWo cells, whereas the opposite effect was observed in HeLa cells. When endogenous IL-10 or TGF-beta was blocked, both BeWo and HeLa cells were able to control the parasite infection only in the presence of IFN-gamma. Together, these results indicate that the higher susceptibility of BeWo cells to T. gondii may be due to immunomodulation mechanisms, suggesting that the role of trophoblast cells in maintaining a placental microenvironment favourable to pregnancy may facilitate the infection into the placental tissues.

Publication Types:
Research Support, Non-U.S. Gov't

PMID: 18234060 [PubMed - in process]