The Synaptic Leap

Infect Disord Drug Targets. 2010 Aug 1;10(4):240-1.

Comparative Analysis of Stage Specific Gene Regulation of Apicomplexan Parasites: Plasmodium falciparum and Toxoplasma gondii

López-Estraño C.

Department of Biology, The University of Memphis, Memphis, TN 38152, USA. cestrano@memphis.edu.

PMID: 20687894 [PubMed - in process]

PLoS Pathog. 2010 Jul 29;6(7):e1001029.

Biogenesis of the Inner Membrane Complex Is Dependent on Vesicular Transport by the Alveolate Specific GTPase Rab11B

Agop-Nersesian C, Egarter S, Langsley G, Foth BJ, Ferguson DJ, Meissner M.

Department of Infectiology, Parasitology, University Hospital Heidelberg, Heidelberg, Germany.

Abstract
Apicomplexan parasites belong to a recently recognised group of protozoa referred to as Alveolata. These protists contain membranous sacs (alveoli) beneath the plasma membrane, termed the Inner Membrane Complex (IMC) in the case of Apicomplexa. During parasite replication the IMC is formed de novo within the mother cell in a process described as internal budding. We hypothesized that an alveolate specific factor is involved in the specific transport of vesicles from the Golgi to the IMC and identified the small GTPase Rab11B as an alveolate specific Rab-GTPase that localises to the growing end of the IMC during replication of Toxoplasma gondii. Conditional interference with Rab11B function leads to a profound defect in IMC biogenesis, indicating that Rab11B is required for the transport of Golgi derived vesicles to the nascent IMC of the daughter cell. Curiously, a block in IMC biogenesis did not affect formation of sub-pellicular microtubules, indicating that IMC biogenesis and formation of sub-pellicular microtubules is not mechanistically linked. We propose a model where Rab11B specifically transports vesicles derived from the Golgi to the immature IMC of the growing daughter parasites.

PMID: 20686666 [PubMed - in process]

Theor Popul Biol. 2010 Jun 2. [Epub ahead of print]

Transmission dynamics of Toxoplasma gondii along an urban-rural gradient

Lélu M, Langlais M, Poulle ML, Gilot-Fromont E.

Université de Lyon, F-69000, Lyon; Université Lyon 1; CNRS, UMR5558, Laboratoire de Biométrie et Biologie Evolutive, F-69622, Villeurbanne, France; 2C2A-CERFE, 5 rue de la Héronniére, F-08240 Boult-aux-Bois, France; Université de Reims Champagne-Ardenne, Laboratoire de Parasitologie-Mycologie, EA 3800, UFR de Médecine, IFR 53, 51 rue Cognacq-Jay, F-51096 Reims, France.

Abstract
Recently, several authors proposed that the availability of intermediate hosts (IH) for definitive hosts (DH) may contribute to determine the dynamics and evolutionary ecology of parasites with facultative complex life cycles. The protozoa Toxoplasma gondii may be transmitted to DH either via predation of infected IH through a complex life cycle (CLC) or directly from contaminated environment through a simple life cycle (SLC). This parasite is also present in contrasting host density environments. We tested the hypothesis that the relative contributions of CLC and SLC along an urban-rural gradient depend on the IH supply. We built and analysed a deterministic model of T. gondii transmission cycle. SLC relative contribution is important only in urban-type environments, i.e., with low predation rate on IH. In contrast, the parasite is predominantly transmitted through CLC in suburban and rural environments. The association of the two cycles enables the parasite to spread in situations of low IH availability and low DH population size for which each cycle alone is insufficient. Copyright © 2010. Published by Elsevier Inc.

PMID: 20685358 [PubMed - as supplied by publisher]

Protein Sci. 2010 Aug 3. [Epub ahead of print]

Structure of the micronemal protein 2 (MIC2) A/I domain from Toxoplasma gondii

Tonkin ML, Grujic O, Pearce M, Crawford J, Boulanger MJ.

Biochemistry & Microbiology, University of Victoria, Victoria, British Columbia V8W 3P6.

Abstract
Toxoplasma gondii is a widespread zoonotic pathogen capable of causing serious disease in humans and animals. As an obligate intracellular parasite, T. gondii relies on the orchestrated secretion of proteins from its apical complex organelles including the multi-modular, transmembrane micronemal protein 2 (MIC2) that couples recognition of the host cell with cytoskeletal reorganization of the parasite to drive invasion. To probe the basis by which the von Willebrand Factor A (vWA) - Integrin like module of TgMIC2 engages the host cell, we solved the crystal structure of a truncated form of TgMIC2A/I (TgMIC2A/Ic) phased by iodide SIRAS and refined to a resolution of 2.05A. The TgMIC2A/Ic core is organized into a central twisted beta sheet flanked by alpha helices consistent with a canonical vWA fold. A restricted basic patch serves as the putative heparin binding site, but no heparin binding was detected in native gel shift assays. Furthermore, no metal was observed in the metal ion dependent adhesion site (MIDAS). Structural overlays with homologous A/I domains reveal a divergent organization of the MIDAS beta4-alpha4 loop in TgMIC2A/Ic, which is stabilized through the burial of Phe195 into a deep pocket formed by Gly185. Intriguingly, Gly185 appears be unique among A/I domains to TgMIC2A/I suggesting that the divergent loop conformation may also be unique to TgMIC2A/I. Though lacking the C-terminal extension, the TgMIC2A/Ic structure reported here is the first of an A/I domain from an apicomplexan parasite and provides valuable insight into defining the molecular recognition of host cells by these widespread pathogens.

PMID: 20684023 [PubMed - as supplied by publisher]

Parasitol Res. 2010 Aug 3. [Epub ahead of print]

Toxoplasma gondii infection inhibits the mitochondrial apoptosis through induction of Bcl-2 and HSP70

Hwang IY, Quan JH, Ahn MH, Hassan Ahmed HA, Cha GH, Shin DW, Lee YH.

Department of Infection Biology, Research Institute for Medical Science, Chungnam National University School of Medicine, 6 Munhwa-dong, Jung-gu, Daejeon, 301-131, South Korea.

Abstract
Heat-shock protein 70 (HSP70) is highly expressed in Toxoplasma gondii-infected cells. However, the role of this protein is not well understood, especially during apoptosis. This study addresses the mechanism behind the antiapoptotic chaperone activity of HSP70 in Toxoplasma-infected host cells using a human macrophage cell line, THP-1 by Western blot, DNA fragmentation assay, immunoprecipitation, and a caspase-3/7 activity assay based on cleavage of the colorimetric substrate DEVD-pNA. Apoptosis induced by arsenic trioxide (As(2)O(3)) was inhibited in T. gondii-infected THP-1 cells, but not in uninfected cells. Without As(2)O(3) induction of apoptosis, T. gondii infection caused increased expression of Bcl-2 and HSP70, but not caspase-3. However, active form caspase-3 levels were lower in As(2)O(3)-treated infected cells as compared with As(2)O(3)-treated uninfected cells. Bcl-2 expression in As(2)O(3)-treated infected cells was similar to that in cells infected with T. gondii. Translocation of apoptosis-inducing factor (AIF) and release of cytochrome c from mitochondria were inhibited in As(2)O(3)-treated infected cells as compared with As(2)O(3)-treated uninfected cells. Increased parasite loads in Toxoplasma-infected macrophages caused higher HSP70 and Bcl-2 expression in whole-cell extracts and fractionated components, respectively. However, expression of AIF and cytochrome c was unaffected. Toxoplasma dose-dependently inhibited caspase-3 activation, thus revealing an anti-apoptotic parasite activity on cytochrome c-mediated caspase activation in subcellular components. In addition, immunoprecipitation analysis suggested that HSP70 is capable of binding to the pro-apoptotic factors AIF and Apaf-1, but not to cytochrome c or procaspase-9. Taken together, these data demonstrate that T. gondii infection inhibits mitochondrial apoptosis through overproduction of anti-apoptotic Bcl-2 as well as HSP70, which are increased parasite loads dependently.

PMID: 20680337 [PubMed - as supplied by publisher]

Cell Microbiol. 2010 Jul 30. [Epub ahead of print]

Toxoplasma gondii Protease TgSUB1 is Required for Cell Surface Processing of Micronemal Adhesive Complexes and Efficient Adhesion of Tachyzoites

Lagal V, Binder EM, Huynh MH, Kafsack BF, Harris PK, Diez R, Chen D, Cole RN, Carruthers VB, Kim K.

Departments of Medicine and Microbiology & Immunology, Albert Einstein College of Medicine, Bronx, NY 10461 USA.

Abstract
Abstract Host cell invasion by Toxoplasma gondii is critically dependent upon adhesive proteins secreted from the micronemes. Proteolytic trimming of microneme contents occurs rapidly after their secretion onto the parasite surface and is proposed to regulate adhesive complex activation to enhance binding to host cell receptors. However, the proteases responsible and their exact function are still unknown. In this report, we show that T. gondii tachyzoites lacking the microneme subtilisin protease TgSUB1 have a profound defect in surface processing of secreted microneme proteins. Notably parasites lack protease activity responsible for proteolytic trimming of MIC2, MIC4 and M2AP after release onto the parasite surface. Although complementation with full-length TgSUB1 restores processing, complementation of Deltasub1 parasites with TgSUB1 lacking the GPI anchor (Deltasub1::DeltaGPISUB1) only partially restores microneme protein processing. Loss of TgSUB1 decreases cell attachment and in vitro gliding efficiency leading to lower initial rates of invasion. Deltasub1 andDeltasub1::DeltaGPISUB1 parasites are also less virulent in mice. Thus TgSUB1 is involved in micronemal protein processing and regulation of adhesive properties of macromolecular adhesive complexes involved in host cell invasion.

PMID: 20678172 [PubMed - as supplied by publisher]

Bioorg Med Chem Lett. 2010 Jul 8. [Epub ahead of print]

Synthesis and evaluation of oryzalin analogs against Toxoplasma gondii

Endeshaw MM, Li C, Leon JD, Yao N, Latibeaudiere K, Premalatha K, Morrissette N, Werbovetz KA.

Division of Medicinal Chemistry and Pharmacognosy, College of Pharmacy, The Ohio State University, 500 West 12th Avenue, Columbus, OH 43210-1291, USA.

Abstract
The synthesis and evaluation of 20 dinitroanilines and related compounds against the obligate intracellular parasite Toxoplasmagondii is reported. Using in vitro cultures of parasites in human fibroblasts, we determined that most of these compounds selectively disrupted Toxoplasma microtubules, and several displayed sub-micromolar potency against the parasite. The most potent compound was N(1),N(1)-dipropyl-2,6-dinitro-4-(trifluoromethyl)-1,3-benzenediamine (18b), which displayed an IC(50) value of 36nM against intracellular T. gondii. Based on these data and another recent report [Ma, C.; Tran, J.; Gu, F.; Ochoa, R.; Li, C.; Sept, D.; Werbovetz, K.; Morrissette, N. Antimicrob. AgentsChemother. 2010, 54, 1453], an antimitotic structure-activity relationship for dinitroanilines versus Toxoplasma is presented. Copyright © 2010 Elsevier Ltd. All rights reserved.

PMID: 20675138 [PubMed - as supplied by publisher]

Amino Acids. 2010 Jul 27. [Epub ahead of print]

Direct evidence of O-GlcNAcylation in the apicomplexan Toxoplasma gondii: a biochemical and bioinformatic study

Perez-Cervera Y, Harichaux G, Schmidt J, Debierre-Grockiego F, Dehennaut V, Bieker U, Meurice E, Lefebvre T, T Schwarz R.

Unit of Structural and Functional Glycobiology, CNRS-UMR 8576, IFR 147, Université de Lille 1, Cité Scientifique, 59655, Villeneuve d'Ascq, France.

Abstract
Toxoplasma gondii and Plasmodium falciparum are apicomplexan parasites responsible for serious diseases in humans. Many studies have focused on the post-translational modifications (PTMs) found in the two protists including phosphorylation, acetylation or SUMOylation but only a few of these are concerned with the nuclear and cytosolic-specific glycosylation O-GlcNAcylation. O-GlcNAcylation is a highly dynamic PTM-regulated by the ON and OFF enzymes: O-GlcNAc transferase and O-GlcNAcase-that can compete with phosphorylation but its function remains unclear. In this work, we directly prove the O-GlcNAcylation in T. gondii using antibodies specifically directed against the modification and we strongly suggest its occurrence in P. falciparum. We found that the inducible 70 kDa-Heat Shock Protein is O-GlcNAcylated, or associated with an O-GlcNAc-partner, in T. gondii. Using anti-OGT antibodies we were able to detect the expression of the glycosyltransferase in T. gondii cultured both in human foreskin fibroblast and in Vero cells and report its putative sequence. For the first time the presence of O-GlcNAcylation is unequivocally shown in T. gondii and suspected in P. falciparum. Since the O-GlcNAcylation is implicated in many biological fundamental processes this study opens a new research track in the knowledge of apicomplexans' life cycle and pathogenic potential.

PMID: 20661758 [PubMed - as supplied by publisher]

PLoS One. 2010 Jul 22;5(7):e11733.

HIV-1 Inhibits Autophagy in Bystander Macrophage/Monocytic Cells through Src-Akt and STAT3

Van Grol J, Subauste C, Andrade RM, Fujinaga K, Nelson J, Subauste CS.

Department of Pathology, Case Western Reserve University School of Medicine, Cleveland, Ohio, United States of America.

Abstract
Autophagy is a homeostatic mechanism of lysosomal degradation. Defective autophagy has been linked to various disorders such as impaired control of pathogens and neurodegeneration. Autophagy is regulated by a complex array of signaling pathways that act upstream of autophagy proteins. Little is known about the role of altered regulatory signaling in disorders associated with defective autophagy. In particular, it is not known if pathogens inhibit autophagy by modulation of upstream regulatory pathways. Cells infected with HIV-1 blocked rapamycin-induced autophagy and CD40-induced autophagic killing of Toxoplasma gondii in bystander (non-HIV-1 infected) macrophage/monocytic cells. Blockade of autophagy was dependent on Src-Akt and STAT3 triggered by HIV-1 Tat and IL-10. Neutralization of the upstream receptors VEGFR, beta-integrin or CXCR4, as well as of HIV-1 Tat or IL-10 restored autophagy in macrophage/monocytic cells exposed to HIV-1-infected cells. Defective autophagic killing of T. gondii was detected in monocyte-derived macrophages from a subset of HIV-1(+) patients. This defect was also reverted by neutralization of Tat or IL-10. These studies revealed that a pathogen can impair autophagy in non-infected cells by activating counter-regulatory pathways. The fact that pharmacologic manipulation of cell signaling restored autophagy in cells exposed to HIV-1-infected cells raises the possibility of therapeutic manipulation of cell signaling to restore autophagy in HIV-1 infection.

PMID: 20661303 [PubMed - in process]

J Clin Microbiol. 2010 Jul 21. [Epub ahead of print]

Specific, Sensitive and Rapid Detection of Active Toxoplasmosis in Patients by Loop-Mediated Isothermal Amplification (LAMP) Method in Blood Samples

Lau YL, Meganathan P, Sonaimuthu P, Thiruvengadam G, Nissapatorn V, Chen Y.

Department of Parasitology, Faculty of Medicine, University of Malaya, 50603 Kuala Lumpur, Malaysia; School of Science, Monash University Sunway Campus, Bandar Sunway, 46150 Selangor, Malaysia; Institute for Research in Molecular Medicine (INFORMM), Universiti Sains Malaysia, 11800 Penang, Malaysia.

Abstract
Loop-mediated isothermal amplification (LAMP), a rapid nucleic acid amplification method was developed for the clinical detection of toxoplasmosis. Three LAMP assays were developed based on SAG1, SAG2 and B1 genes of Toxoplasma gondii. The sensitivity and specificity of the LAMP assays were evaluated in comparison with conventional nested PCR. The LAMP assays were highly sensitive with a detection limit of 0.1 tachyzoites and no cross-reactivity was observed with DNA of other parasites. Blood was collected from 105 individuals to test the LAMP assays: 40 patients with active toxoplasmosis, 40 negative controls and 25 patients with other parasitic infections. SAG2-LAMP had a greater sensitivity (87.5%) compared to SAG1-LAMP (80%), B1-LAMP (80%) and nested PCR (62.5%). All the LAMP assays and nested PCR were 100% specific. This is the first report which applies the LAMP method to diagnose toxoplasmosis from human blood samples. Due to its simplicity, sensitivity, and specificity, LAMP is suggested as an appropriate diagnostic method for routine diagnosis of active toxoplasmosis in humans.

PMID: 20660217 [PubMed - as supplied by publisher]

Clin Vaccine Immunol. 2010 Jul 21. [Epub ahead of print]

Toxoplasma gondii cyclophilin 18 regulates the proliferation and migration of murine macrophages and spleen cells

Ibrahim HM, Xuan X, Nishikawa Y.

National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, Inada-cho, Obihiro, Hokkaido 080-8555, Japan; Zoology Department, Faculty of Science, Minufiya University, Shibin El Kom, Egypt.

Abstract
Toxoplasma gondii is an intracellular parasite showing a unique capacity to infect a variety of cell types in warm-blooded animals. It can invade and survive well inside immune cells, such as macrophages, that disseminate the parasite around the body because of their migratory properties. The aim of the present study was to evaluate the role of T. gondii cyclophilin 18 (TgCyp18) on the proliferation, and migration of macrophages and spleen cells (mainly T lymphocytes) in order to understand the effects of TgCyp18 on the dynamics of the infection. The high dose of TgCyp18 enhanced the proliferation of macrophages and spleen cells in a cysteine-cysteine chemokine receptor 5 (CCR5)-independent way. In contrast, TgCyp18 controlled the migration of macrophages and spleen cells in dose and CCR5-dependent manners. Our data suggest that TgCyp18 recruits cells and enhances the growth of host cells at the site of infection for maintenance of the interaction between the parasite and host.

PMID: 20660134 [PubMed - as supplied by publisher]

Cytoskeleton (Hoboken). 2010 Jul 23. [Epub ahead of print]

RNG1 is a late marker of the apical polar ring in Toxoplasma gondii

Tran JQ, de Leon JC, Li C, Huynh MH, Beatty W, Morrissette NS.

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

Abstract
The asexually proliferating stages of apicomplexan parasites cause acute symptoms of diseases such as malaria, cryptosporidiosis and toxoplasmosis. These stages are characterized by the presence of two independent microtubule organizing centers (MTOCs). Centrioles are found at the poles of the intranuclear spindle. The apical polar ring (APR), a MTOC unique to apicomplexans, organizes subpellicular microtubules which impose cell shape and apical polarity on these protozoa. Here we describe the characteristics of a novel protein that localizes to the APR of Toxoplasma gondii which we have named ring-1 (RNG1). There are related RNG1 proteins in Neospora caninum and Sarcocystis neurona but no obvious homologs in Plasmodium spp., Cryptosporidium spp. or Babesia spp. RNG1 is a small, low-complexity, detergent-insoluble protein that assembles at the APR very late in the process of daughter parasite replication. We were unable to knock-out the RNG1 gene, suggesting that its gene product is essential. Tagged RNG1 lines have also allowed us to visualize the APR during growth of Toxoplasma in the microtubule-disrupting drug oryzalin. Oryzalin inhibits nuclear division and cytokinesis although Toxoplasma growth continues, and similar to earlier observations of unchecked centriole duplication in oryzalin-treated parasites, the APR continues to duplicate during aberrant parasite growth. (c) 2010 Wiley-Liss, Inc.

PMID: 20658557 [PubMed - as supplied by publisher]

PLoS Comput Biol. 2010 Jul 15;6(7):e1000852.

The construction and use of log-odds substitution scores for multiple sequence alignment

Altschul SF, Wootton JC, Zaslavsky E, Yu YK.

National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, Maryland, United States of America.

Abstract
Most pairwise and multiple sequence alignment programs seek alignments with optimal scores. Central to defining such scores is selecting a set of substitution scores for aligned amino acids or nucleotides. For local pairwise alignment, substitution scores are implicitly of log-odds form. We now extend the log-odds formalism to multiple alignments, using Bayesian methods to construct "BILD" ("Bayesian Integral Log-odds") substitution scores from prior distributions describing columns of related letters. This approach has been used previously only to define scores for aligning individual sequences to sequence profiles, but it has much broader applicability. We describe how to calculate BILD scores efficiently, and illustrate their uses in Gibbs sampling optimization procedures, gapped alignment, and the construction of hidden Markov model profiles. BILD scores enable automated selection of optimal motif and domain model widths, and can inform the decision of whether to include a sequence in a multiple alignment, and the selection of insertion and deletion locations. Other applications include the classification of related sequences into subfamilies, and the definition of profile-profile alignment scores. Although a fully realized multiple alignment program must rely upon more than substitution scores, many existing multiple alignment programs can be modified to employ BILD scores. We illustrate how simple BILD score based strategies can enhance the recognition of DNA binding domains, including the Api-AP2 domain in Toxoplasma gondii and Plasmodium falciparum.

PMID: 20657661 [PubMed - in process]

Int J Parasitol. 2010 Jul 14. [Epub ahead of print]

Association of host mitochondria with the parasitophorous vacuole during Toxoplasma infection is not dependent on rhoptry proteins ROP2/8

Pernas L, Boothroyd JC.

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

Abstract
Previous work has proposed rhoptry protein 2 (ROP2) as the physical link that tethers host mitochondria to the parasitophorous vacuole membrane (PVM) surrounding the intracellular parasite, Toxoplasma gondii. A recent analysis of the ROP2 structure, however, raised questions about this model. To determine whether ROP2 is necessary, we created a parasite line that lacks the entire ROP2 locus consisting of the three closely related genes, ROP2a, ROP2b and ROP8. We show that this knockout mutant retains the ability to recruit host mitochondria in a manner that is indistinguishable from the parental strain, re-opening the question of which molecules mediate this association. Copyright © 2010. Published by Elsevier Ltd.

PMID: 20637758 [PubMed - as supplied by publisher]

J Interferon Cytokine Res. 2010 Jul 13. [Epub ahead of print]

Predominant Interferon-gamma-Mediated Expression of CXCL9, CXCL10, and CCL5 Proteins in the Brain During Chronic Infection with Toxoplasma gondii in BALB/c Mice Resistant to Development of Toxoplasmic Encephalitis

Wen X, Kudo T, Payne L, Wang X, Rodgers L, Suzuki Y.

1 Department of Biomedical Sciences and Pathobiology, Center for Molecular Medicine and Infectious Diseases, Virginia-Maryland Regional College of Veterinary Medicine, Virginia Polytechnic Institute and State University , Blacksburg, Virginia.

Abstract
We examined the role of interferon-gamma (IFN-gamma) in expression of chemokine mRNA and proteins in the brain during chronic infection with Toxoplasma gondii using BALB/c and BALB/c-background IFN-gamma knockout (IFN-gamma(-/-)) mice. BALB/c mice are genetically resistant to development of toxoplasmic encephalitis and establish a latent, chronic infection in the brain through IFN-gamma-mediated immune responses. Amounts of mRNA for CXCL9/MIG, CXCL10/IP-10, CXCL11/I-TAC, CCL2/MCP-1, CCL3/MIP-1alpha, and CCL5/RANTES significantly increased in the brains of wild-type mice after infection. CXCL9/MIG, CXCL10/IP-10, and CCL5/RANTES mRNA were most abundant among these chemokines. An increase in amounts of mRNA for CXCL10/IP-10, CCL2/MCP-1, CCL3/MIP-1alpha, and CCL5/RANTES was also observed in the brains of IFN-gamma(-/-) mice after infection, although CXCL10/I-10 and CCL5/RANTES mRNA levels in infected IFN-gamma(-/-) mice were significantly lower than those of infected wild-type animals. Amounts of mRNA for CXCL9/MIG and CXCL11/I-TAC remained at the basal levels in infected IFN-gamma(-/-) mice. When amounts of the chemokine proteins were examined in the brain homogenates of uninfected and infected mice of both strains, large amounts of CXCL9/MIG, CXCL10/IP-10, and CCL5/RANTES were detected only in infected wild-type animals. These results indicate that CXCL9/MIG, CXCL10/IP-10, and CCL5/RANTES are the chemokines predominantly induced in the brains of genetically resistant BALB/c mice during chronic infection with T. gondii, and their expression is dependent on IFN-gamma.

PMID: 20626297 [PubMed - as supplied by publisher]

Clin Vaccine Immunol. 2010 Jul 14. [Epub ahead of print]

Use of dense granule antigen GRA6 in Immunoglobulin G avidity test to exclude acute Toxoplasma infection during pregnancy

Elyasi H, Babaie J, Fricker-Hidalgo H, Brenier-Pinchart MP, Zare M, Sadeghiani G, Assmar M, Pelloux H, Golkar M.

Molecular Parasitology Laboratory, Parasitology Department, Pasteur Institute of Iran, Tehran, Iran; Parasitology Department, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran; Parasitology and Mycology Laboratory, Grenoble Teaching Hospital A Michallon, BP 217, 38043 Grenoble Cedex 09, France; Laboratoire Adaptation et Pathogénie des Microorganismes, CNRS UMR 5163, Joseph Fourier University (Grenoble I), BP 170, 38042 Grenoble Cedex 09, France.

Abstract
Usefulness of a specific immunoglobulin G (IgG) avidity enzyme-linked immunosorbent assay based on recombinant GRA6 antigen was investigated for distinguishing between acute and chronic Toxoplasma infection. Two sets of sera from pregnant women with acute, chronic or no Toxoplasma infection collected in France and Iran were used. Among French subjects, 19 of 20 (95%) women experiencing seroconversion during the past 4 months before sampling displayed low avidity IgG antibodies against GRA6, while all 17 (100%) women with chronic infection had high avidity antibodies. When Euroimmun IgG avidity ELISA was used, 15 of 19 (78.9%) recently-infected women had low avidity antibodies and 20 of 22 (90.9%) women with chronic infection displayed high avidity antibodies. The results suggested better performance of GRA6 avidity than Euroimmun avidity ELISA for exclusion of a recent infection occurred less than 4 months before. Similarly, all 35 Iranian women with acute Toxoplasma infection had low avidity antibodies against GRA6, whereas all 34 women with chronic infection displayed IgG antibodies of high avidity, indicating value of GRA6 avidity testing for ruling out a recent infection. Avidity tests based on lysed whole-cell T. gondii antigen are currently used to exclude recently acquired infections; however, the use of recombinant antigen(s) might improve diagnostic performance of avidity tests and facilitate development of more standardized assays.

PMID: 20631335 [PubMed - as supplied by publisher]

J Biol Chem. 2010 Jul 12. [Epub ahead of print]

Toxoplasma rhoptry protein 16 (ROP16) subverts host function by direct tyrosine phosphorylation of STAT6

Ong YC, Reese ML, Boothroyd JC.

Stanford University, United States.

Abstract
The obligate intracellular parasite, Toxoplasma gondii, modulates host immunity in a variety of highly specific ways. Previous work revealed a polymorphic, injected parasite factor, ROP16, to be a key virulence determinant and regulator of host cell transcription. These properties were shown to be partially mediated by dysregulation of the host transcription factors STAT3 and STAT6, but the molecular mechanisms underlying this phenotype were unclear. Here, we use a Type I Toxoplasma strain deficient in ROP16 to show that ROP16 induces not only sustained activation but also an extremely rapid (within one minute) initial activation of STAT6. Using recombinant wild-type and kinase-deficient ROP16, we demonstrate in vitro that ROP16 has intrinsic tyrosine kinase activity and is capable of directly phosphorylating the key tyrosine residue for STAT6 activation, Tyr641. Furthermore, ROP16 co-immunoprecipitates with STAT6 from infected cells. Taken together, these data strongly suggest that STAT6 is a direct substrate for ROP16 in vivo.

PMID: 20624917 [PubMed - as supplied by publisher]

Exp Parasitol. 2010 Jul 6. [Epub ahead of print]

Toxoplasma gondii: The effects of infection at different stages of pregnancy on the offspring of mice

Wang T, Liu M, Gao XJ, Zhao ZJ, Chen XG, Lun ZR.

Center for Parasitic OrganismsState Key Laboratory of Biocontrol, School of Life Sciences, and Key Laboratory of Tropical Diseases Control (The Ministry of Education), Zhongshan Medical College, Sun Yat-Sen (Zhongshan) University, Guangzhou 510275, P.R. China.

Abstract
Congenital toxoplasmosis can cause fetal damage in humans and domestic animals. This study was focused on the effects of Toxoplasma gondii (Prugniaud strain) infection at different stages of pregnancy on the offspring of mice. Results showed that newborn mice from all infected groups were significantly lower in weight than those from the control group but significant difference was not found among these groups at day 60 after birth. The survival rate of the offspring from the group of mice infected at the earlier stage of pregnancy was significantly lower than those of infected and control groups. The positive offspring (with cysts found in their brain tissues) born from the mice infected at the earlier and intermediate stages of pregnancy showed a shorter latency and greater number of errors in the step-through passive avoidance test than those born from the mice infected at the late stage of pregnancy, the control group and the negative offspring from the infected groups. The number of cysts in the brain tissue was significantly higher in the offspring born from the groups of mice infected at the earlier and intermediate stages of pregnancy than those from the group of mice infected at the late stage of pregnancy. In addition, our results indicated that a high congenital transmission rate (90%) occurred in this NIH mouse model. In conclusion, the earlier and intermediate maternal infection of T. gondii can result in severe congenital toxoplasmosis, exhibiting conditions such as stillbirth or non-viability, and learning or memory capability damage in this mouse model. These results not only provide useful data for better understanding the effects of T. gondii infection on the offspring of mice infected at different stages of pregnancy but also for better consideration of the effect of this infection on other mammalian hosts including humans. Copyright © 2010. Published by Elsevier Inc.

PMID: 20619261 [PubMed - as supplied by publisher]

Folia Parasitol (Praha). 2010 Jun;57(2):88-94.

Manipulation of host behaviour by Toxoplasma gondii: what is the minimum a proposed proximate mechanism should explain?

Vyas A, Sapolsky R.

School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, 637551 Singapore. avyas@ntu.edu.sg

Abstract
The behavioural manipulation hypothesis posits that parasites can change the behaviour of hosts to increase the reproductive fitness of the parasite. The protozoan parasite Toxoplasma gondii fits this description well. Sexual reproduction occurs in the cat intestine, from which highly stable oocysts are excreted in faeces. Grazing animals, including rodents, can then ingest these oocysts. The parasite has evolved the capacity to abolish the innate fear that rodents have of the odours of cats, and to convert that fear into an attraction. This presumably increases the likelihood of the rodent being predated, thereby completing the parasite's life cycle. The behavioural syndrome produced by T. gondii does not have any precedent in neuroscience research. This is not a case where the normal functioning of fear system have been altered. This is not even the case of the altering of fear towards predator odours, while leaving other kinds of fear intact. This is an unprecedented example of one component of the fear being eliminated (and replaced by a novel attraction), while appearing to leave other domains unchanged. An understanding of the neurobiological effects of T. gondii is beginning to emerge. One possibility is T. gondii's preferential localisation to, and effects within the amygdala; this is particularly intriguing, given the role of this brain structure in the normal fear response. Obviously, far more must be understood, and the unique behavioural effects of T. gondii put very demanding constraints on any hypothesis we formulate to explain proximate neurobiological mechanisms.

PMID: 20608470 [PubMed - in process]

Folia Parasitol (Praha). 2010 Jun;57(2):95-104.

Toxoplasma gondii-altered host behaviour: clues as to mechanism of action

Webster JP, McConkey GA.

Department of Infectious Disease Epidemiology, Imperial College, Faculty of Medicine, London, W2 1PG, UK. joanne.webster@imperial.ac.uk

Abstract
A convincing body of evidence now exists, from both human and animal studies, and encompassing epidemiological to experimental, to indicate that the common protozoan Toxoplasma gondii can cause specific behavioural changes in its host. Such behavioural alterations are likely to be the product of strong selective pressures for the parasite to enhance transmission from its intermediate host reservoir, primarily rodent, to its feline definitive host, wherein sexual reproduction can occur and the parasite's life cycle completed. Here we consider what the available data to date may reveal about the potential mechanisms involved, the future research that needs to be performed, and the subsequent implications for animal and human health.

PMID: 20608471 [PubMed - in process]