Wednesday, October 28, 2009

Toxoplasma gondii Inhibits Covalent Modification of Histone H3 at the IL-10 Promoter in Infected Macrophages

PLoS One. 2009 Oct 27;4(10):e7589.

Toxoplasma gondii Inhibits Covalent Modification of Histone H3 at the IL-10 Promoter in Infected Macrophages

Leng J, Denkers EY.

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

Infection of macrophages with the protozoan parasite Toxoplasma gondii results in inhibition of a large panel of LPS-responsive cytokines, including TNF-alpha, while leaving others such as IL-10 intact. Recent studies provide evidence that the parasite interferes with chromatin remodeling at the TNF-alpha promoter that is normally associated with LPS stimulation, but that is not required for TLR4 induction of IL-10. Here, we examined the effect of Toxoplasma on IL-10 induced by simultaneous signaling through TLR4 and FcgammaR, a combined stimulus that triggers histone H3 covalent modification at the IL-10 promoter resulting in high level IL-10 cytokine production. We show that the parasite inhibits high level IL-10 production and prevents histone H3 Ser(10) phosphorylation and Lys(9/14) acetylation at the IL-10 promoter. These results provide compelling evidence that T. gondii targets the host cell chromatin remodeling machinery to down-regulate cytokine responses in infected macrophages.

PMID: 19859561 [PubMed - as supplied by publisher]

Simple Duplex RT-PCR Assay for Detecting SAG1 and BAG1 Genes during Stage Conversion in Immunosuppressed Mice

Exp Parasitol. 2009 Oct 22. [Epub ahead of print]

Toxoplasma gondii: Simple Duplex RT-PCR Assay for Detecting SAG1 and BAG1 Genes during Stage Conversion in Immunosuppressed Mice

Mahittikorn A, Wickert H, Sukthana Y.

Department of Protozoology, Faculty of Tropical Medicine, Mahidol University, 10400, Bangkok, Thailand.

Toxoplasmic encephalitis (TE) is caused by reactivation of dormant bradyzoites into rapidly dividing tachyzoites of the apicomplexan parasite Toxoplasma gondii in immune-compromised hosts. Diagnosis of this life-threatening disease is complicated, since it is difficult to distinguish between these two stages. It is, therefore, mainly based on a test positive for T. gondii antibodies, and specific clinical symptoms. We developed a duplex RT-PCR to detect the expression of bradyzoite (BAG1) and tachyzoite (SAG1) specific genes simultaneously during tachyzoite/bradyzoite stage conversion. The conversion reaction was observed in many organs of experimental mice, indicated by tachyzoites in the cerebrum, cerebellum, heart and lung, beginning in week 1 after the suppression period, and continuing until the end. Bradyzoites were also detected in nearly all organs throughout the study, suggesting that during the reactivation period, bradyzoites not only escape from cysts and reinvade neighboring cells as tachyzoites, but are also driven into developing new bradyzoites. The results of our study show that duplex RT-PCR is an easy, rapid, sensitive, and reproducible method, which is particularly valuable when numerous samples must be analyzed. This technique may usefully serve as an alternate tool for diagnosing TE in severely immunocompromised patients.

PMID: 19854173 [PubMed - as supplied by publisher]

Friday, October 23, 2009

Externally Triggered Egress Is the Major Fate of Toxoplasma gondii during Acute Infection

J Immunol. 2009 Oct 21. [Epub ahead of print]

Externally Triggered Egress Is the Major Fate of Toxoplasma gondii during Acute Infection

Tomita T, Yamada T, Weiss LM, Orlofsky A.

Departments of *Pathology and.

The apicomplexan parasite Toxoplasma gondii expands during acute infection via a cycle of invasion, intracellular replication, and lytic egress. Physiological regulation has not yet been demonstrated for either invasion or egress. We now report that, in contrast to cell culture systems, in which egress occurs only after five or more parasite divisions (2-3 days), intracellular residence is strikingly abbreviated in inflammatory cells in vivo, and early egress (after zero to two divisions) is the dominant parasite fate in acutely infected mice. Adoptive transfer experiments demonstrate rapid, reciprocal, kinetically uniform parasite transfer between donor and recipient compartments, with a t(1/2) of approximately 3 h. Inflammatory macrophages are major participants in this cycle of lytic egress and reinfection, which drives rapid macrophage turnover. Inflammatory triggering cells, principally macrophages, elicit egress in infected target macrophages, a process we term externally triggered egress (ETE). The mechanism of ETE does not require reactive oxygen or nitrogen species, the mitochondrial permeability transition pore, or a variety of signal transduction mediators, but is dependent on intracellular calcium and is highly sensitive to SB203580, an inhibitor of p38 MAPK as well as a related parasite-encoded kinase. SB203580 both inhibited the initiation of ETE and altered the progression of egress. Parasites recently completing a cycle of egress and reinfection were preferentially restricted in vivo, supporting a model in which ETE may favor host defense by a process of haven disruption. ETE represents a novel example of interaction between a parasite infectious cycle and host microenvironment.

PMID: 19846885 [PubMed - as supplied by publisher]

Wednesday, October 21, 2009

Detection of Toxoplasma gondii oocysts and surrogate microspheres in water using ultrafiltration and capsule filtration

Water Res. 2009 Oct 1. [Epub ahead of print]

Detection of Toxoplasma gondii oocysts and surrogate microspheres in water using ultrafiltration and capsule filtration

Shapiro K, Mazet JA, Schriewer A, Wuertz S, Fritz H, Miller WA, Largier J, Conrad PA.

Department of Pathology, Microbiology and Immunology, School of Veterinary Medicine, University of California, Davis, CA 95616, USA.

While reports on waterborne infections with Toxoplasma gondii are emerging worldwide, detection of this zoonotic parasite in water remains challenging. Lack of standardized and quantitative methods for detection of T. gondii oocysts in water also limits research on the transport and fate of this pathogen through aquatic habitats. Here, we compare the ability of hollow-fiber ultrafiltration and capsule filtration to concentrate oocysts in spiked tap water, fresh surface water, and seawater samples. Detection of T. gondii oocysts in concentrated samples was achieved using molecular methods, as well as visually via epifluorescent microscopy. In addition to oocysts, water samples were spiked with T. gondii surrogate microspheres, and detection of microspheres was performed using flow cytometry and epifluorescent microscopy. Results demonstrate that both water concentration methods followed by microscopy allowed for quantitative detection of T. gondii oocysts and surrogate microspheres. For T. gondii oocysts, microscopy was more sensitive than TaqMan and conventional PCR, and allowed for detection of oocysts in all water samples tested. Compared with flow cytometry, microscopy was also a more cost-efficient and precise method for detection of fluorescent surrogate microspheres in tap, fresh and seawater samples. This study describes a novel approach for quantitative detection of T. gondii oocysts in drinking and environmental water samples. The techniques described for concentrating and detecting surrogate microspheres have broad application for evaluating the transport and fate of oocysts, as well as the efficiency of water treatment methods for removal of T. gondii from water supplies.

PMID: 19836820 [PubMed - as supplied by publisher]

Friday, October 16, 2009

Critical role for the immunoproteasome subunit LMP7 in the resistance of mice to Toxoplasma

Eur J Immunol. 2009 Oct 14. [Epub ahead of print]

Critical role for the immunoproteasome subunit LMP7 in the resistance of mice to Toxoplasma gondii infection

Tu L, Moriya C, Imai T, Ishida H, Tetsutani K, Duan X, Murata S, Tanaka K, Shimokawa C, Hisaeda H, Himeno K.

Department of Parasitology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.

Proteasome-mediated proteolysis is responsible for the generation of immunogenic epitopes presented by MHC class I molecules, which activate antigen-specific CD8(+) T cells. Immunoproteasomes, defined by the presence of the three catalytic subunits LMP2, MECL-1, and LMP7, have been hypothesized to optimize MHC class I antigen processing. In this study, we demonstrate that the infection of mice with a protozoan parasite, Toxoplasma gondii, induced the expression of LMP7 mRNA in APC and increased the capacity of APC to induce the production of IFN-gamma by antigen-specific CD8(+) T cells. In vitro infection of a DC cell line with T. gondii also induced the expression of LMP7 and resulted in enhanced proteasome proteolytic activity. Finally, mice lacking LMP7 were highly susceptible to infection with T. gondii and showed a reduced number of functional CD8(+) T cells. These results demonstrate that proteasomes containing LMP7 play an indispensable role in the survival of mice infected with T. gondii, presumably due to the efficient generation of CTL epitopes required for the functional development of CD8(+) T cells.

PMID: 19830724 [PubMed - as supplied by publisher]

Thursday, October 15, 2009

Toxoplasma and schizophrenia

Parasite Immunol. 2009 Nov;31(11):706-15

Toxoplasma and schizophrenia

Yolken RH, Dickerson FB, Fuller Torrey E.

Johns Hopkins University School of Medicine, Stanley Division of Developmental Neurovirology, Baltimore, MD, USA.

Research on infectious agents as a possible cause of schizophrenia has become prominent in the past decade. Toxoplasma gondii has emerged as a prime candidate for a variety of reasons; (i) many studies have reported that individuals with schizophrenia, compared to controls, have a higher prevalence of antibodies to T. gondii, (ii) some individuals with adult toxoplasmosis develop psychotic symptoms similar to those of schizophrenia, (iii) epidemiologically, there are many similarities between toxoplasmosis and schizophrenia, (iv) antipsychotic drugs known to be effective in schizophrenia also inhibit some parasites, including T. gondii, (v) Toxoplasma has been shown to induce elevated levels of dopamine in experimentally infected animals (elevated dopamine is commonly seen in individuals with schizophrenia) and (vi) studies have shown that individuals with schizophrenia, compared to controls, have had greater exposure to cats in childhood. A number of questions remain concerning a role for Toxoplasma in the aetiology of schizophrenia, including the roles of strain variation, the timing and source of infection, and the role of host genes in determining disease susceptibility. The establishment of a firm association between Toxoplasma and the aetiology of schizophrenia and related disorders would represent a major breakthrough in the understanding of these disorders and would lead to novel methods for their treatment and prevention.

PMID: 19825110 [PubMed - in process]

TgICMAP1 Is a Novel Microtubule Binding Protein in Toxoplasma gondii

PLoS One. 2009 Oct 12;4(10):e7406

TgICMAP1 Is a Novel Microtubule Binding Protein in Toxoplasma gondii

Heaslip AT, Ems-McClung SC, Hu K.

Department of Biology, Indiana University, Bloomington, Indiana, United States of America.

The microtubule cytoskeleton provides essential structural support for all eukaryotic cells and can be assembled into various higher order structures that perform drastically different functions. Understanding how microtubule-containing assemblies are built in a spatially and temporally controlled manner is therefore fundamental to understanding cell physiology. Toxoplasma gondii, a protozoan parasite, contains at least five distinct tubulin-containing structures, the spindle pole, centrioles, cortical microtubules, the conoid, and the intra-conoid microtubules. How these five structurally and functionally distinct sets of tubulin containing structures are constructed and maintained in the same cell is an intriguing problem. Previously, we performed a proteomic analysis of the T. gondii apical complex, a cytoskeletal complex located at the apical end of the parasite that is composed of the conoid, three ring-like structures, and the two short intra-conoid microtubules. Here we report the characterization of one of the proteins identified in that analysis, TgICMAP1. We show that TgICMAP1 is a novel microtubule binding protein that can directly bind to microtubules in vitro and stabilizes microtubules when ectopically expressed in mammalian cells. Interestingly, in T. gondii, TgICMAP1 preferentially binds to the intra-conoid microtubules, providing us the first molecular tool to investigate the intra-conoid microtubule assembly process during daughter construction.

PMID: 19823689 [PubMed - in process]

12/15-lipoxygenase-dependent myeloid production of interleukin-12 is essential for resistance to chronic toxoplasmosis

Infect Immun. 2009 Oct 12. [Epub ahead of print]

12/15-lipoxygenase-dependent myeloid production of interleukin-12 is essential for resistance to chronic toxoplasmosis

Middleton MK, Zukas AM, Rubinstein T, Kinder M, Wilson EH, Zhu P, Blair IA, Hunter CA, Puré E.

The Wistar Institute, Immunology Graduate Group, School of Veterinary Medicine, Center for Cancer Pharmacology and Institute for Translational Medicine and Therapeutics, and The Ludwig Institute for Cancer Research, University of Pennsylvania, Philadelphia, PA 19104 USA.

IL-12 is critical for resistance to Toxoplasma gondii during both the acute and chronic stages of infection. However, the cellular and molecular pathways that regulate IL-12 production during chronic toxoplasmosis are incompletely defined. We recently discovered that 12/15-lipoxygenase (12/15-LOX), an enzyme that oxidizes unsaturated lipids in macrophages, is a novel and selective regulator of IL-12 production. We now demonstrate the essential role of this enzyme in the chronic phase of toxoplasmosis. Although 12/15-LOX-deficient mice were resistant to acute T. gondii infection, 80% of 12/15-LOX-deficient mice died during chronic toxoplasmosis, compared to no death in wild-type controls. The morbidity of chronically-infected 12/15-LOX mice was associated with an increase in brain inflammation and parasite burden. These data suggest that the evolution of the immune response to T. gondii is accompanied by an increasing requirement for 12/15-LOX-mediated signaling. Consistent with this conclusion, 12/15-LOX activity was enhanced during chronic, but not acute, toxoplasmosis. Furthermore, the enhanced susceptibility of 12/15-LOX-deficient mice to chronic toxoplasmosis was associated with reduced production of IL-12 and IFN-gamma that was not evident during acute infection. Importantly, ex vivo IFN-gamma production by 12/15-LOX-deficient splenocytes could be rescued by the addition of recombinant IL-12. These data establish that 12/15-LOX is a critical mediator of the chronic type 1 inflammatory response, and that immune mediators can be subject to distinct cellular and or molecular mechanisms of regulation at different stages of inflammation.

PMID: 19822654 [PubMed - as supplied by publisher]

Comparative evaluation of the ARCHITECT Toxo IgG, IgM, and IgG Avidity assays for anti-Toxoplasma antibodies detection in pregnant women sera

Diagn Microbiol Infect Dis. 2009 Nov;65(3):279-87

Comparative evaluation of the ARCHITECT Toxo IgG, IgM, and IgG Avidity assays for anti-Toxoplasma antibodies detection in pregnant women sera

Gay-Andrieu F, Fricker-Hidalgo H, Sickinger E, Espern A, Brenier-Pinchart MP, Braun HB, Pelloux H.

Laboratoire de Parasitologie-Mycologie, Institut de Biologie, CHU de Nantes, 44093 Nantes Cedex 1, France. francoise.gay-andrieu@chu-nantes.fr

We assessed the performance of the ARCHITECT Toxo IgG, IgM, and IgG Avidity assays against corresponding assays on AxSYM and Vidas using 730 sera from pregnant women. The ARCHITECT Toxo IgG and IgM assays showed a relative sensitivity of 97.5% and 89.9% and a relative specificity of 99.1% and 99.8%, respectively. If IgM sensitivity is calculated only for sera drawn less than 4 months after infection, the relative sensitivity rises to 98.1%. Correlation between the ARCHITECT and Vidas Avidity assays was 0.87 (n = 103). Testing 86 IgG-positive specimens from recent infection (<4 months), we never obtained high avidity results, but 2 specimens were in the gray zone, whereas sera from past infections (>4 months) exhibited high avidity results in 72.5% (137/189) of cases. The method can be used reliably to exclude recent infections in sera with concurrently positive results for IgM and IgG (IgG, >3 IU/mL).

PMID: 19822270 [PubMed - in process]

Wednesday, October 14, 2009

Toxoplasma gondii: further studies on the subpellicular network

Mem Inst Oswaldo Cruz. 2009 Aug;104(5):706-9

Toxoplasma gondii: further studies on the subpellicular network

Lemgruber L, Kloetzel JA, Souza W, Vommaro RC.

Laboratório de Ultraestrutura Celular Hertha Meyer, Centro de Ciências da Saúde, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brasil, 21941-902.

The association of the pellicle with cytoskeletal elements in Toxoplasma gondii allows this parasite to maintain its mechanical integrity and makes possible its gliding motility and cell invasion. The inner membrane complex (IMC) resembles the flattened membrane sacs observed in free-living protozoa and these sacs have been found to associate with cytoskeletal proteins such as articulins. We used immunofluorescence microscopy to characterise the presence and distribution of plateins, a sub-family of articulins, in T. gondii tachyzoites. A dispersed labelling of the whole protozoan body was observed. Electron microscopy of detergent-extracted cells revealed the presence of a network of 10 nm filaments distributed throughout the parasite. These filaments were labelled with anti-platein antibodies. Screening the sequenced T. gondii genome, we obtained the sequence of an IMC predicted protein with 25% identity and 42% similarity to the platein isoform alpha 1 present in Euplotes aediculatus, but with 42% identity and 55% similarity to that found in Euglena gracilis, suggesting strong resemblance to articulins.

PMID: 19820829 [PubMed - in process]

Dynamin inhibitor impairs Toxoplasma gondii invasion

FEMS Microbiol Lett. 2009 Sep 21. [Epub ahead of print]

Dynamin inhibitor impairs Toxoplasma gondii invasion

Caldas LA, Attias M, de Souza W.

Laboratório de Ultraestrutura Celular Hertha Meyer, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil.

Abstract The protozoan parasite Toxoplasma gondii infects its host cells through an active mechanism. In this work, we obtained evidence that host cells also play a fundamental role during the infection process. We found that previous incubation of the host cells, but not the parasites, with Dynasore, a small molecule that inhibits dynamin GTPase activity, markedly reduced the penetration of T. gondii tachyzoites into LLC-MK2 cells. In contrast, parasite adhesion to the host cell surface increased, as observed both by light and electron microscopy. Intriguingly, the few parasites internalized by Dynasore-treated cells remained in vacuoles located at the periphery of the cell, in contrast to the perinuclear localization seen in the control.

PMID: 19817867 [PubMed - as supplied by publisher]

First Predictive Study on Proteins of Human Pathogen Parasites

J Proteome Res. 2009 Oct 9. [Epub ahead of print]

Complex Network Spectral Moments for ATCUN Motif DNA Cleavage: First Predictive Study on Proteins of Human Pathogen Parasites

Munteanu CR, Vázquez JM, Dorado J, Sierra AP, Sánchez-González A, Prado-Prado FJ, González-Díaz H.

Department of Information and Communication Technologies, Computer Science Faculty, University of A Coruna, Campus de Elvina, s/n 15071 A Coruna, Spain, Department of Inorganic Chemistry, Faculty of Pharmacy, University of Santiago de Compostela, Praza Seminario de Estudos Galegos, s/n. Campus sur, 15782 Santiago de Compostela, Spain, and Department of Microbiology & Parasitology, Faculty of Pharmacy, University of Santiago de Compostela, Praza Seminario de Estudos Galegos, s/n. Campus sur, 15782 Santiago de Compostela, Spain.

The development of methods that can predict the metal-mediated biological activity based only on the 3D structure of metal-unbound proteins has become a goal of major importance. This work is dedicated to the amino terminal Cu(II)- and Ni(II)-binding (ATCUN) motifs that participate in the DNA cleavage and have antitumor activity. We have calculated herein, for the first time, the 3D electrostatic spectral moments for 415 different proteins, including 133 potential ATCUN antitumor proteins. Using these parameters as input for Linear Discriminant Analysis, we have found a model that discriminates between ATCUN-DNA cleavage proteins and nonactive proteins with 91.32% Accuracy (379 out of 415 of proteins including both training and external validation series). Finally, the model has predicted for the first time the DNA cleavage function of proteins from the pathogen parasites. We have predicted possible ATCUN-like proteins with a probability higher than 99% in nine parasite families such as Trypanosoma, Plasmodium, Leishmania, or Toxoplasma. The distribution by biological function of the ATCUN proteins predicted has been the following: oxidoreductases 70.5%, signaling proteins 62.5%, lyases 58.2%, membrane proteins 45.5%, ligases 44.4%, hydrolases 41.3%, transferases 39.2%, cell adhesion proteins 34.5%, metal binders 33.5%, translation proteins 25.0%, transporters 16.7%, structural proteins 9.1%, and isomerases 8.2%. The model is implemented at http://miaja.tic.udc.es/Bio-AIMS/ATCUNPred.php .

PMID: 19817378 [PubMed - as supplied by publisher]

Thursday, October 08, 2009

Toxoplasma vaccines: appropriate end points and sample size in future human clinical trials

Expert Rev Anti Infect Ther. 2009 Oct;7(8):905-8.

Toxoplasma vaccines: appropriate end points and sample size in future human clinical trials

Silveira C, Gargano N, Kijlstra A, Petersen E.

Publication Types:
Editorial

PMID: 19803697 [PubMed - in process]

Genetic evidence that an endosymbiont-derived ERAD system functions in import of apicoplast proteins

J Biol Chem. 2009 Oct 6. [Epub ahead of print]

Genetic evidence that an endosymbiont-derived ERAD system functions in import of apicoplast proteins

Agrawal S, van Dooren GG, Beatty WL, Striepen B.

University of Georgia, United States;

Most apicomplexan parasites harbor a relict chloroplast, the apicoplast, that is critical for their survival. While the apicoplast maintains a small genome, the bulk of its proteins are nuclear-encoded and imported into the organelle. Several models have been proposed to explain how proteins might cross the four membranes that surround the apicoplast, however experimental data discriminating these models is largely missing. Here we present genetic evidence that apicoplast protein import depends on elements derived from the ER associated protein degradation (ERAD) system of the endosymbiont. We identify two sets of ERAD components in Toxoplasma gondii, one associated with the ER and cytoplasm and one localized to the membranes of the apicoplast. We engineer a conditional null mutant in apicoplast Der1, the putative pore of the apicoplast ERAD complex, and find that loss of Der1Ap results in loss of apicoplast protein import and subsequent death of the parasite.

PMID: 19808683 [PubMed - as supplied by publisher]

Tuesday, October 06, 2009

Autophagy in Immunity Against Toxoplasma gondii

Curr Top Microbiol Immunol. 2009;335:251-65

Autophagy in Immunity Against Toxoplasma gondii

Subauste CS.

Department of Ophthalmology and Visual Sciences, Case Western Reserve University School of Medicine, Cleveland, OH, 44106, USA, carlos.subauste@case.edu.

A decisive outcome during host-pathogen interaction is governed by whether pathogen-containing vacuoles fuse with lysosomes. Fusion with lysosomes typically kills microbes. Toxoplasma gondii represents a classical example of an intracellular pathogen that survives within host cells by preventing the endosomal-lysosomal compartments from fusing with the vacuoles that contain the pathogen. Thus, T. gondii provides an excellent model to determine if the immune system can target a pathogen for lysosomal degradation. CD40, a major regulator of cell-mediated immunity, activates macrophages to kill T. gondii through a process that requires recruitment of autophagosomes around the parasitophorous vacuole, leading to lysosomal degradation of the parasite. These studies demonstrate that cell-mediated immunity can activate autophagy to kill a pathogen. CD40-induced autophagy likely contributes to resistance against T. gondii, particularly in neural tissues, the main sites affected by this pathogen.

PMID: 19802569 [PubMed - in process]

Overproduction of the Pro-Apoptotic Molecule, Programmed Cell Death 5, in Toxoplasma gondii Leads to Increased Apoptosis of Host Macrophages

J Vet Med Sci. 2009 Sep;71(9):1183-9

Overproduction of the Pro-Apoptotic Molecule, Programmed Cell Death 5, in Toxoplasma gondii Leads to Increased Apoptosis of Host Macrophages

Bannai H, Nishikawa Y, Ibrahim HM, Yamada K, Kawase O, Watanabe J, Sugimoto C, Xuan X.

National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine.

We established a recombinant strain of Toxoplasma gondii that overexpressed programmed cell death 5 (TgPDCD5), in order to evaluate the role of endogenous TgPDCD5 in macrophage apoptosis during T. gondii infection. Immunofluorescence microscopy revealed that overproduced TgPDCD5 with a hemagglutinin tag was localized in the cytosol, which was consistent with the localization of endogenous TgPDCD5. The induced TgPDCD5-HA was recognized as an additional band by Western blot analysis, indicating successful overexpression of TgPDCD5. Secretion and release of TgPDCD5 by the parasite was also up-regulated in a time-dependent manner, which reflected its overproduction. Apoptosis due to parasite infection and interferon-gamma treatment was significantly up-regulated by the overexpression of TgPDCD5. These results suggest that endogenous TgPDCD5 plays a role in macrophage apoptosis during T. gondii infection.

PMID: 19801898 [PubMed - in process]

Phenotypic and gene expression changes among clonal type I strains of Toxoplasma

Eukaryot Cell. 2009 Oct 2. [Epub ahead of print]

Phenotypic and gene expression changes among clonal type I strains of Toxoplasma gondii

Khan A, Behnke MS, Dunay IR, White MW, Sibley LD.

Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO 63110; Department of Veterinary Molecular Biology, Montana State University, Bozeman, MT 59717, USA; Departments of Molecular Medicine and Global Health, University of South Florida, Tampa, FL 33612.

Toxoplasma gondii has an unusual population structure consisting of three clonal lineages that predominate in North America and Europe. This simple pattern has encouraged the use of only a few laboratory isolates that are representative of each lineage. Principle among these is the type I RH strain, originally isolated from a child with encephalitis some seventy years ago. Comparison of different passages of the RH strain that have been propagated differently over the intervening time period revealed that the commonly used clonal line called RH-ERP was not representative of natural isolates of the type I lineage. Notably RH-ERP formed much larger plaques than other type 1 strains, including a separate, earlier derived isolate of the RH strain. The RH-ERP variant also showed enhanced extracellular survival, faster growth, and decreased differentiation compared to the prototype type I strain GT-1. Comparison of gene expression differences in the RH-ERP line revealed that several ABC transporters were upregulated, which may provide a growth advantage in vitro. These findings illustrate that dramatic phenotypic changes can arise in laboratory strains, emphasizing the need for comparison with recent clinical isolates.

PMID: 19801420 [PubMed - as supplied by publisher]

The location of invasion-related protein MIC3 of Toxoplasma gondii and protective effect of its DNA vaccine in mice

Vet Parasitol. 2009 Aug 22. [Epub ahead of print]

The location of invasion-related protein MIC3 of Toxoplasma gondii and protective effect of its DNA vaccine in mice

Wu X, Zhang Q, Liu LP, Tan K, Guan JW, Shu HP.

Department of Parasitology of Xiangya School of Medicine, Central Southern University, Changsha, Hunan 410078, China.

The micronemal protein MIC3 of Toxoplasma gondii plays a predominant role in the early phase of the invasion process. In this research, the expression and location of protein MIC3 and fusion protein EGFP-MIC3 were observed in host cells and in T. gondii respectively. Protective experiments of DNA vaccine pcDNA3-MIC3 (pMIC3i) in animals showed that the vaccine could significantly prolong the survival time of the mice challenged by virulent RH strains of T. gondii. All mice vaccinated with plasmid pcDNA3-MIC3 have been elicited specific humoral immunity and cellular immunity. The cellular immune response was associated with the increase of the CD4(+) and CD8(+) T lymphocytes and the decrease of the CD4(+)/CD8(+) T lymphocyte ratio evidently. It indicated that the mic3 DNA vaccine could stimulate the host resisting Toxoplasma mainly by the way of CD8(+)CTL cells. In conclusion, a potent DNA vaccine pcDNA3-MIC3 could elicit a strong specific immune response and induce effective protection against T. gondii challenge in Kunming mice, suggesting that mic3 is a potential vaccine candidate against toxoplasmosis.

PMID: 19800170 [PubMed - as supplied by publisher]

Sunday, October 04, 2009

Long-term immunity to lethal acute or chronic Type II Toxoplasmosis gondii infection

Infect Immun. 2009 Sep 21. [Epub ahead of print]

Long-term immunity to lethal acute or chronic Type II Toxoplasmosis gondii infection is effectively induced in genetically susceptible C57BL/6 mice by immunization with an attenuated Type I vaccine strain

Gigley JP, Fox BA, Bzik DJ.

Department of Microbiology and Immunology, Dartmouth Medical School, 1 Medical Center Drive, Lebanon, NH 03756 USA.

C57BL/6 (B6) mice are genetically highly susceptible to chronic Type II Toxoplasma gondii infections that invariably cause lethal Toxoplasmic encephalitis. We examined the ability of an attenuated Type I vaccine strain to elicit long-term immunity to lethal acute or chronic Type II infections in susceptible B6 mice. Mice immunized with the Type I vaccine strain cps1-1 were not susceptible to a lethal (100 cyst) challenge with the Type II strain ME49. Immunized mice challenged with 10 ME49 cysts exhibited significant reductions in brain cyst and parasite burdens compared to naïve mice, regardless of the route of challenge infection. Remarkably, cps1-1 immunized B6 mice chronically infected with ME49 survived for at least 12 months without succumbing to the chronic infection. Potent immunity to Type II challenge infections persisted for at least 10 months after vaccination. While cps1-1 elicited immunity did not prevent the establishment of a chronic infection or clear established brain cysts, cps1-1 elicited CD8(+) immune T cells significantly inhibited recrudescence of brain cysts during chronic ME49 infection. Additionally, we show that uracil starvation of strain cps1-1 induces early markers of bradyzoite differentiation. Collectively these results suggest that more effective immune control of chronic Type II infection in the genetically susceptible B6 background is established by vaccination with the non replicating Type I uracil auxotroph strain cps1-1.

PMID: 19797073 [PubMed - as supplied by publisher]