Monday, December 31, 2012

Toxoplasma gondii: The effect of Fluconazole combined with Sulfadiazine and Pyrimethamine against acute toxoplasmosis in murine model

Exp Parasitol. 2012 Dec 24. pii: S0014-4894(12)00382-7. doi: 10.1016/j.exppara.2012.12.011. [Epub ahead of print]

Toxoplasma gondii: The effect of Fluconazole combined with Sulfadiazine and Pyrimethamine against acute toxoplasmosis in murine model

Martins-Duarte ES, Souza WD, Vommaro RC.

Laboratório de Ultraestrutura Celular Hertha Meyer, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro-UFRJ, Rio de Janeiro, Brazil; Instituto Nacional de Ciência e Tecnologia em Biologia Estrutural e Bioimagens, Rio de Janeiro, Brazil.

Toxoplasma gondii is an important opportunistic pathogen for immunocompromised patients and responsible for toxoplasmic encephalitis, which is often lethal. Treatment for this infection is limited to a restricted therapeutic arsenal. In this work we tested the combination of fluconazole with the current treatment for acute toxoplasmosis on the murine model in vivo. Different experimental groups were treated with combinations of sulfadiazine plus pyrimethamine with fluconazole and pyrimethamine with fluconazole. Fluconazole is an important antifungal triazole used against others CNS related opportunistic pathogens such as Cryptococcus neoformans and Candida spp. The combinations of fluconazole plus sulfadiazine and pyrimethamine or fluconazole plus pyrimethamine were remarkably effective against T. gondii in vivo. The 10-day treatment with 10 mg/kg/day of fluconazole combined with 40/1mg/kg/day sulfadiazine and pyrimethamine resulted in 93% survival of CF1 mice acutely infected with the highly virulent T. gondii RH strain, versus 36% of mice treated with just sulfadiazine and pyrimethamine. Combinations of fluconazole with lower doses of sulfadiazine and pyrimethamine or with just pyrimethamine were also efficient in reducing the mortality of mice compared with the treatment without fluconazole. The results obtained are promising for the treatment of human toxoplasmosis and point to the need to extend these studies to other murine models.

PMID: 23270807 [PubMed - as supplied by publisher]

Introduction of caveolae structural proteins into the protozoan toxoplasma results in the formation of heterologous caveolae but not caveolar endocytosis

PLoS One. 2012;7(12):e51773. doi: 10.1371/journal.pone.0051773. Epub 2012 Dec 14.

Introduction of caveolae structural proteins into the protozoan toxoplasma results in the formation of heterologous caveolae but not caveolar endocytosis

Lige B, Romano JD, Sampels V, Sonda S, Joiner KA, Coppens I.

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

Present on the plasma membrane of most metazoans, caveolae are specialized microdomains implicated in several endocytic and trafficking mechanisms. Caveolins and the more recently discovered cavins are the major protein components of caveolae. Previous studies reported that caveolar invaginations can be induced de novo on the surface of caveolae-negative mammalian cells upon heterologous expression of caveolin-1. However, it remains undocumented whether other components in the transfected cells participate in caveolae formation. To address this issue, we have exploited the protozoan Toxoplasma as a heterologous expression system to provide insights into the minimal requirements for caveogenesis and caveolar endocytosis. Upon expression of caveolin-1, Toxoplasma accumulates prototypical exocytic caveolae 'precursors' in the cytoplasm. Toxoplasma expressing caveolin-1 alone, or in conjunction with cavin-1, neither develops surface-located caveolae nor internalizes caveolar ligands. These data suggest that the formation of functional caveolae at the plasma membrane in Toxoplasma and, by inference in all non-mammalian cells, requires effectors other than caveolin-1 and cavin-1. Interestingly, Toxoplasma co-expressing caveolin-1 and cavin-1 displays an impressive spiraled network of membranes containing the two proteins, in the cytoplasm. This suggests a synergistic activity of caveolin-1 and cavin-1 in the morphogenesis and remodeling of membranes, as illustrated for Toxoplasma.

 PMID: 23272165 [PubMed - in process]

Wednesday, December 26, 2012

Parasite-induced T(H)1 cells and intestinal dysbiosis cooperate in IFN-γ-dependent elimination of Paneth cells

Nat Immunol. 2012 Dec 23. doi: 10.1038/ni.2508. [Epub ahead of print]

Parasite-induced T(H)1 cells and intestinal dysbiosis cooperate in IFN-γ-dependent elimination of Paneth cells

Raetz M, Hwang SH, Wilhelm CL, Kirkland D, Benson A, Sturge CR, Mirpuri J, Vaishnava S, Hou B, Defranco AL, Gilpin CJ, Hooper LV, Yarovinsky F.

Department of Immunology, University of Texas Southwestern Medical Center, Dallas, Texas, USA.

Activation of Toll-like receptors (TLRs) by pathogens triggers cytokine production and T cell activation, immune defense mechanisms that are linked to immunopathology. Here we show that IFN-γ production by CD4(+) T(H)1 cells during mucosal responses to the protozoan parasite Toxoplasma gondii resulted in dysbiosis and the elimination of Paneth cells. Paneth cell death led to loss of antimicrobial peptides and occurred in conjunction with uncontrolled expansion of the Enterobacteriaceae family of Gram-negative bacteria. The expanded intestinal bacteria were required for the parasite-induced intestinal pathology. The investigation of cell type-specific factors regulating T(H)1 polarization during T. gondii infection identified the T cell-intrinsic TLR pathway as a major regulator of IFN-γ production in CD4(+) T cells responsible for Paneth cell death, dysbiosis and intestinal immunopathology.

 PMID: 23263554 [PubMed - as supplied by publisher]

Conditional genome engineering in Toxoplasma gondii uncovers alternative invasion mechanisms

Nat Methods. 2012 Dec 23. doi: 10.1038/nmeth.2301. [Epub ahead of print]

Conditional genome engineering in Toxoplasma gondii uncovers alternative invasion mechanisms

Andenmatten N, Egarter S, Jackson AJ, Jullien N, Herman JP, Meissner M.

1] Wellcome Trust Centre for Molecular Parasitology, Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK. [2].

We established a conditional site-specific recombination system based on dimerizable Cre recombinase-mediated recombination in the apicomplexan parasite Toxoplasma gondii. Using a new single-vector strategy that allows ligand-dependent, efficient removal of a gene of interest, we generated three knockouts of apicomplexan genes considered essential for host-cell invasion. Our findings uncovered the existence of an alternative invasion pathway in apicomplexan parasites.

 PMID: 23263690 [PubMed - as supplied by publisher]

Thursday, December 20, 2012

Recognition of Profilin by Toll-like Receptor 12 Is Critical for Host Resistance to Toxoplasma gondii

Immunity. 2012 Dec 12. pii: S1074-7613(12)00515-8. doi: 10.1016/j.immuni.2012.09.016. [Epub ahead of print]

Recognition of Profilin by Toll-like Receptor 12 Is Critical for Host Resistance to Toxoplasma gondii

Koblansky AA, Jankovic D, Oh H, Hieny S, Sungnak W, Mathur R, Hayden MS, Akira S, Sher A, Ghosh S.

Department of Microbiology & Immunology, College of Physicians & Surgeons, Columbia University, New York, NY 10032, USA.

Toll-like receptor 11 (TLR11) recognizes T. gondii profilin (TgPRF) and is required for interleukin-12 production and induction of immune responses that limit cyst burden in Toxoplasma gondii-infected mice. However, TLR11 only modestly affects survival of T. gondii-challenged mice. We report that TLR12, a previously uncharacterized TLR, also recognized TgPRF. TLR12 was sufficient for recognition of TgPRF by plasmacytoid dendritic cells (pDCs), whereas TLR11 and TLR12 were both required in macrophages and conventional DCs. In contrast to TLR11, TLR12-deficient mice succumb rapidly to T. gondii infection. TLR12-dependent induction of IL-12 and IFN-α in pDCs led to production of IFN-γ by NK cells. Consistent with this observation, the partial resistance of Tlr11(-/-) mice is lost upon pDC or NK cell depletion. Thus, TLR12 is critical for the innate immune response to T. gondii, and this TLR may promote host resistance by triggering pDC and NK cell function.

PMID: 23246311 [PubMed - as supplied by publisher]

Sphingolipid synthesis and scavenging in the intracellular apicomplexan parasite, Toxoplasma gondii

Mol Biochem Parasitol. 2012 Dec 13. pii: S0166-6851(12)00283-6. doi: 10.1016/j.molbiopara.2012.11.007. [Epub ahead of print]

Sphingolipid synthesis and scavenging in the intracellular apicomplexan parasite, Toxoplasma gondii

Pratt S, Wansadhipathi-Kannangara NK, Bruce CR, Mina JG, Shams-Eldin H, Casas J, Hanada K, Schwarz RT, Sonda S, Denny PW.

From the Biophysical Sciences Institute, Department of Chemistry and School of Biological Sciences, University Science Laboratories, South Road, Durham, DH1 3LE; School of Medicine and Health, Durham University, Queen's Campus, Stockton-on-Tees, TS17 6BH, UK.

Sphingolipids are essential components of eukaryotic cell membranes, particularly the plasma membrane, and are involved in a diverse array of signal transduction pathways. Mammals produce sphingomyelin (SM) as the primary complex sphingolipid via the well characterised SM synthase. In contrast yeast, plants and some protozoa utilise an evolutionarily related inositol phosphorylceramide (IPC) synthase to synthesize IPC. This activity has no mammalian equivalent and IPC synthase has been proposed as a target for anti-fungals and anti-protozoals. However, detailed knowledge of the sphingolipid biosynthetic pathway of the apicomplexan protozoan parasites was lacking. In this study bioinformatic analyses indicated a single copy orthologue of the putative SM synthase from the apicomplexan Plasmodium falciparum (the causative agent of malaria) was a bona fide sphingolipid synthase in the related model parasite, Toxoplasma gondii (TgSLS). Subsequently, TgSLS was indicated, by complementation of a mutant cell line, to be a functional orthologue of the yeast IPC synthase (AUR1p), demonstrating resistance to the well characterised AUR1p inhibitor aureobasidin A. In vitro, recombinant TgSLS exhibited IPC synthase activity and, for the first time, the presence of IPC was demonstrated in T. gondii lipid extracts by mass spectrometry. Furthermore, host sphingolipid biosynthesis was indicated to influence, but be non-essential for, T. gondii proliferation, suggesting that whilst scavenging does take place de novo sphingolipid synthesis may be important for parasitism.

PMID: 23246819 [PubMed - as supplied by publisher]

Murine Guanylate Binding Protein 2 (mGBP2) controls Toxoplasma gondii replication

Proc Natl Acad Sci U S A. 2012 Dec 17. [Epub ahead of print]

Murine Guanylate Binding Protein 2 (mGBP2) controls Toxoplasma gondii replication

Degrandi D, Kravets E, Konermann C, Beuter-Gunia C, Klümpers V, Lahme S, Wischmann E, Mausberg AK, Beer-Hammer S, Pfeffer K.

Institute of Medical Microbiology and Hospital Hygiene, Heinrich-Heine-University Duesseldorf, Duesseldorf 40225, Germany.

IFN-γ orchestrates the host response against intracellular pathogens. Members of the guanylate binding proteins (GBP) comprise the most abundant IFN-γ-induced transcriptional response. mGBPs are GTPases that are specifically up-regulated by IFN-γ, other proinflammatory cytokines, toll-like receptor agonists, as well as in response to Listeria monocytogenes and Toxoplasma gondii infection. mGBP2 localizes at the parasitophorous vacuole (PV) of T. gondii; however, the molecular function of mGBP2 and its domains in T. gondii infection is not known. Here, we show that mGBP2 is highly expressed in several cell types, including T and B cells after stimulation. We provide evidence that the C-terminal domain is sufficient and essential for recruitment to the T. gondii PV. Functionally, mGBP2 reduces T. gondii proliferation because mGBP2-deficient cells display defects in the replication control of T. gondii. Ultimately, mGBP2-deficient mice reveal a marked immune susceptibility to T. gondii. Taken together, mGBP2 is an essential immune effector molecule mediating antiparasitic resistance.

PMID: 23248289 [PubMed - as supplied by publisher]

Non-canonical maturation of two papain-family proteases in Toxoplasma gondii

J Biol Chem. 2012 Dec 18. [Epub ahead of print]

Non-canonical maturation of two papain-family proteases in Toxoplasma gondii

Dou Z, Coppens I, Carruthers VB.

University of Michigan, United States

Proteases regulate key events during infection by the pervasive intracellular parasite Toxoplasma gondii. Understanding how parasite proteases mature from an inactive zymogen to an active enzyme is expected to inform new strategies for blocking their actions. Herein, we show that T. gondii cathepsin B protease (TgCPB) does not undergo self-maturation, but instead requires the expression of a second papain-family cathepsin protease, TgCPL. Using recombinant enzymes we also show that TgCPL is capable of partially maturing TgCPB in vitro. Consistent with this interrelationship, antibodies with validated specificity detected TgCPB in the lysosome-like vacuolar compartment along with TgCPL. Our findings also establish that TgCPB does not localize to the rhoptries as previously reported. Accordingly, rhoptry morphology and rhoptry protein maturation are normal in TgCPB knockout parasites. Finally, we show that while maturation of TgCPL is independent of TgCPB, it may involve an additional protease(s) in conjunction with self-maturation.

PMID: 23250753 [PubMed - as supplied by publisher]

Neutrophils cast extracellular traps in response to protozoan parasites

Front Immunol. 2012;3:382. doi: 10.3389/fimmu.2012.00382. Epub 2012 Dec 14.

Neutrophils cast extracellular traps in response to protozoan parasites

Abi Abdallah DS, Denkers EY.

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

Release of extracellular traps by neutrophils is a now well-established phenomenon that contributes to the innate response to extracellular bacterial and fungal pathogens. The importance of NETs during protozoan infection has been less explored, but recent findings suggest an emerging role for release of neutrophil-derived extracellular DNA in response to this class of microbial pathogens. The present review summarizes findings to date regarding elicitation of NETs by Toxoplasma gondii, Plasmodium falciparum, Eimeria bovis, and Leishmania spp.

PMID: 23248631 [PubMed]

A tetracycline-repressible transactivator system to study essential genes in malaria parasites

Cell Host Microbe. 2012 Dec 13;12(6):824-34. doi: 10.1016/j.chom.2012.10.016.

A tetracycline-repressible transactivator system to study essential genes in malaria parasites

Pino P, Sebastian S, Kim EA, Bush E, Brochet M, Volkmann K, Kozlowski E, Llinás M, Billker O, Soldati-Favre D.

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

A major obstacle in analyzing gene function in apicomplexan parasites is the absence of a practical regulatable expression system. Here, we identified functional transcriptional activation domains within Apicomplexan AP2 (ApiAP2) family transcription factors. These ApiAP2 transactivation domains were validated in blood-, liver-, and mosquito-stage parasites and used to create a robust conditional expression system for stage-specific, tetracycline-dependent gene regulation in Toxoplasma gondii, Plasmodium berghei, and Plasmodium falciparum. To demonstrate the utility of this system, we created conditional knockdowns of two essential P. berghei genes: profilin (PRF), a protein implicated in parasite invasion, and N-myristoyltransferase (NMT), which catalyzes protein acylation. Tetracycline-induced repression of PRF and NMT expression resulted in a dramatic reduction in parasite viability. This efficient regulatable system will allow for the functional characterization of essential proteins that are found in these important parasites.

PMID: 23245327 [PubMed - in process]

Tuesday, December 18, 2012

Translational Control in Plasmodium and Toxoplasma Parasites

Eukaryot Cell. 2012 Dec 14. [Epub ahead of print]

Translational Control in Plasmodium and Toxoplasma Parasites

Zhang M, Joyce BR, Sullivan WJ Jr, Nussenzweig V.

Department of Pathology, New York University School of Medicine, New York, NY 10016

The life cycles of apicomplexan parasites such as Plasmodium spp. and Toxoplasma gondii are complex, consisting of proliferative and latent stages within multiple hosts. Dramatic transformations take place during the cycles and they demand precise control of gene expression at all levels, including translation. This review focuses on the mechanisms that regulate translational control in Plasmodium and Toxoplasma, with a particular emphasis on the phosphorylation of the eukaryotic translation initiation factor 2-alpha (eIF2α) subunit. Phosphorylation of eIF2α (eIF2α∼P) is a conserved mechanism that eukaryotic cells use to repress global protein synthesis while enhancing gene-specific translation of a subset of mRNAs. Elevated levels of eIF2α∼P have been observed during latent stages in both Toxoplasma and Plasmodium, indicating that translational control plays a role in maintaining dormancy. Parasite-specific eIF2α kinases and phosphatases are also required for proper developmental transitions and adaptation to cellular stresses encountered during the life cycle. Identification of small molecule inhibitors of apicomplexan eIF2α kinases may selectively interfere with parasite translational control and lead to the development of new therapies to treat malaria and toxoplasmosis.

 PMID: 23243065 [PubMed - as supplied by publisher]

The Toxoplasma nuclear factor TgAP2XI-4 controls bradyzoite gene expression and cyst formation

Mol Microbiol. 2012 Dec 14. doi: 10.1111/mmi.12121. [Epub ahead of print]

The Toxoplasma nuclear factor TgAP2XI-4 controls bradyzoite gene expression and cyst formation

Walker R, Gissot M, Croken MM, Huot L, Hot D, Kim K, Tomavo S.

Center for Infection and Immunity of Lille, UMR CNRS 8204, INSERM U 1019, Institut Pasteur de Lille, Université Lille Nord de France, Lille, France

Toxoplasma gondii undergoes many phenotypic changes during its life cycle. The recent identification of AP2 transcription factors in T. gondii has provided a platform for studying the mechanisms controlling gene expression. In the present study, we report that a recombinant protein encompassing the TgAP2XI-4 AP2 domain was able to specifically bind to a DNA motif using gel retardation assays. TgAP2XI-4 protein is localised in the parasite nucleus throughout the tachyzoite life-cycle in vitro, with peak expression occurring after cytokinesis. We found that the TgAP2XI-4 transcript level was higher in bradyzoite cysts isolated from brains of chronically infected mice than in the rapidly replicating tachyzoites. A knock-out of the TgAP2XI-4 gene in both T. gondii virulent type I and avirulent type II strains reveals its role in modulating expression and promoter activity of genes involved in stage conversion of the rapidly replicating tachyzoites to the dormant cyst forming bradyzoites. Furthermore, mice infected with the type II KO mutants show a drastically reduced brain cyst burden. Thus, our results validate TgAP2XI-4 as a novel nuclear factor that regulates bradyzoite gene expression during parasite differentiation and cyst formation.

PMID: 23240624 [PubMed - as supplied by publisher]

Fierce competition between Toxoplasma and Chlamydia for host cell structures in dually infected cells

Eukaryot Cell. 2012 Dec 14. [Epub ahead of print]

Fierce competition between Toxoplasma and Chlamydia for host cell structures in dually infected cells

Romano JD, de Beaumont C, Carrasco JA, Ehrenman K, Bavoil PM, Coppens I

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

The prokaryote Chlamydia trachomatis and the protozoan Toxoplasma gondii, two obligate intracellular pathogens of humans, have evolved a similar modus operandi to colonize their host cell and salvage nutrients from organelles. In order to gain fundamental knowledge on the pathogenicity of these microorganisms, we have established a cell culture model whereby single fibroblasts are co-infected by C. trachomatis and T. gondii. We previously reported that the two pathogens compete for the same nutrient pools in co-infected cells and that Toxoplasma holds a significant competitive advantage over Chlamydia. Here we have expanded our co-infection studies by examining the respective abilities of Chlamydia and Toxoplasma to co-opt the host cytoskeleton and recruit organelles. We demonstrate that the two pathogen-containing vacuoles migrate independently to the host perinuclear region and rearrange the host microtubular network around each vacuole. However, Toxoplasma out-competes Chlamydia to the host microtubule-organizing center to the detriment of the bacterium, which then shifts to a stress-induced persistent state. Solely in cells preinfected with Chlamydia, the centrosomes become associated with the chlamydial inclusion while the Toxoplasma parasitophorous vacuole displays growth defects. Both pathogens fragment the host Golgi and recruit Golgi elements to retrieve sphingolipids. This study demonstrates that the productive infection by both Chlamydia and Toxoplasma depends on the capability of each pathogen to successfully adhere to a finely tuned developmental program that aims to remodel the host cell for the pathogen's benefit. In particular, this investigation emphasizes the essentiality of host organelle interception by intravacuolar pathogens to facilitate access to nutrients.

 PMID: 23243063 [PubMed - as supplied by publisher]

Saturday, December 15, 2012

Cell division in apicomplexan parasites is organized by a homolog of the striated rootlet fiber of algal flagella

PLoS Biol. 2012 Dec;10(12):e1001444. doi: 10.1371/journal.pbio.1001444. Epub 2012 Dec 11.

Cell division in apicomplexan parasites is organized by a homolog of the striated rootlet fiber of algal flagella

Francia ME, Jordan CN, Patel JD, Sheiner L, Demerly JL, Fellows JD, de Leon JC, Morrissette NS, Dubremetz JF, Striepen B.

Department of Cellular Biology, University of Georgia, Athens, Georgia, United States of America.

Apicomplexa are intracellular parasites that cause important human diseases including malaria and toxoplasmosis. During host cell infection new parasites are formed through a budding process that parcels out nuclei and organelles into multiple daughters. Budding is remarkably flexible in output and can produce two to thousands of progeny cells. How genomes and daughters are counted and coordinated is unknown. Apicomplexa evolved from single celled flagellated algae, but with the exception of the gametes, lack flagella. Here we demonstrate that a structure that in the algal ancestor served as the rootlet of the flagellar basal bodies is required for parasite cell division. Parasite striated fiber assemblins (SFA) polymerize into a dynamic fiber that emerges from the centrosomes immediately after their duplication. The fiber grows in a polarized fashion and daughter cells form at its distal tip. As the daughter cell is further elaborated it remains physically tethered at its apical end, the conoid and polar ring. Genetic experiments in Toxoplasma gondii demonstrate two essential components of the fiber, TgSFA2 and 3. In the absence of either of these proteins cytokinesis is blocked at its earliest point, the initiation of the daughter microtubule organizing center (MTOC). Mitosis remains unimpeded and mutant cells accumulate numerous nuclei but fail to form daughter cells. The SFA fiber provides a robust spatial and temporal organizer of parasite cell division, a process that appears hard-wired to the centrosome by multiple tethers. Our findings have broader evolutionary implications. We propose that Apicomplexa abandoned flagella for most stages yet retained the organizing principle of the flagellar MTOC. Instead of ensuring appropriate numbers of flagella, the system now positions the apical invasion complexes. This suggests that elements of the invasion apparatus may be derived from flagella or flagellum associated structures.

 PMID: 23239939 [PubMed - in process]

Toxoplasma gondii Clonal Strains All Inhibit STAT1 Transcriptional Activity but Polymorphic Effectors Differentially Modulate IFNγ Induced Gene Expression and STAT1 Phosphorylation

PLoS One. 2012;7(12):e51448. doi: 10.1371/journal.pone.0051448. Epub 2012 Dec 11.

Toxoplasma gondii Clonal Strains All Inhibit STAT1 Transcriptional Activity but Polymorphic Effectors Differentially Modulate IFNγ Induced Gene Expression and STAT1 Phosphorylation

Rosowski EE, Saeij JP

Massachusetts Institute of Technology, Department of Biology, Cambridge, Massachusetts, United States of America.

Host defense against the parasite Toxoplasma gondii requires the cytokine interferon-gamma (IFNγ). However, Toxoplasma inhibits the host cell transcriptional response to IFNγ, which is thought to allow the parasite to establish a chronic infection. It is not known whether all strains of Toxoplasma block IFNγ-responsive transcription equally and whether this inhibition occurs solely through the modulation of STAT1 activity or whether other transcription factors are involved. We find that strains from three North American/European clonal lineages of Toxoplasma, types I, II, and III, can differentially modulate specific aspects of IFNγ signaling through the polymorphic effector proteins ROP16 and GRA15. STAT1 tyrosine phosphorylation is activated in the absence of IFNγ by the Toxoplasma kinase ROP16, but this ROP16-activated STAT1 is not transcriptionally active. Many genes induced by STAT1 can also be controlled by other transcription factors and therefore using these genes as specific readouts to determine Toxoplasma inhibition of STAT1 activity might be inappropriate. Indeed, GRA15 and ROP16 modulate the expression of subsets of IFNγ responsive genes through activation of the NF-κB/IRF1 and STAT3/6 transcription factors, respectively. However, using a stable STAT1-specific reporter cell line we show that strains from the type I, II, and III clonal lineages equally inhibit STAT1 transcriptional activity. Furthermore, all three of the clonal lineages significantly inhibit global IFNγ induced gene expression.

 PMID: 23240025 [PubMed - in process]

Friday, December 14, 2012

GABAergic Signaling Is Linked to a Hypermigratory Phenotype in Dendritic Cells Infected by Toxoplasma gondii

PLoS Pathog. 2012 Dec;8(12):e1003051. doi: 10.1371/journal.ppat.1003051. Epub 2012 Dec 6.

GABAergic Signaling Is Linked to a Hypermigratory Phenotype in Dendritic Cells Infected by Toxoplasma gondii

Fuks JM, Arrighi RB, Weidner JM, Kumar Mendu S, Jin Z, Wallin RP, Rethi B, Birnir B, Barragan A.

Center for Infectious Medicine, Department of Medicine, Karolinska Institutet, Karolinska University Hospital Huddinge, Stockholm, Sweden ; Swedish Institute for Communicable Disease Control, Stockholm, Sweden

During acute infection in human and animal hosts, the obligate intracellular protozoan Toxoplasma gondii infects a variety of cell types, including leukocytes. Poised to respond to invading pathogens, dendritic cells (DC) may also be exploited by T. gondii for spread in the infected host. Here, we report that human and mouse myeloid DC possess functional γ-aminobutyric acid (GABA) receptors and the machinery for GABA biosynthesis and secretion. Shortly after T. gondii infection (genotypes I, II and III), DC responded with enhanced GABA secretion in vitro. We demonstrate that GABA activates GABA(A) receptor-mediated currents in T. gondii-infected DC, which exhibit a hypermigratory phenotype. Inhibition of GABA synthesis, transportation or GABA(A) receptor blockade in T. gondii-infected DC resulted in impaired transmigration capacity, motility and chemotactic response to CCL19 in vitro. Moreover, exogenous GABA or supernatant from infected DC restored the migration of infected DC in vitro. In a mouse model of toxoplasmosis, adoptive transfer of infected DC pre-treated with GABAergic inhibitors reduced parasite dissemination and parasite loads in target organs, e.g. the central nervous system. Altogether, we provide evidence that GABAergic signaling modulates the migratory properties of DC and that T. gondii likely makes use of this pathway for dissemination. The findings unveil that GABA, the principal inhibitory neurotransmitter in the brain, has activation functions in the immune system that may be hijacked by intracellular pathogens.

 PMID: 23236276 [PubMed - in process]

Thursday, December 13, 2012

Molecules to modeling: Toxoplasma gondii oocysts at the human-animal-environment interface

Comp Immunol Microbiol Infect Dis. 2012 Dec 3. pii: S0147-9571(12)00120-8. doi: 10.1016/j.cimid.2012.10.006. [Epub ahead of print]

Molecules to modeling: Toxoplasma gondii oocysts at the human-animal-environment interface

Vanwormer E, Fritz H, Shapiro K, Mazet JA, Conrad PA.

One Health Institute, School of Veterinary Medicine, University of California, Davis, One Shields Avenue, Davis, CA 95616, United States. Electronic address:

Environmental transmission of extremely resistant Toxoplasma gondii oocysts has resulted in infection of diverse species around the world, leading to severe disease and deaths in human and animal populations. This review explores T. gondii oocyst shedding, survival, and transmission, emphasizing the importance of linking laboratory and landscape from molecular characterization of oocysts to watershed-level models of oocyst loading and transport in terrestrial and aquatic systems. Building on discipline-specific studies, a One Health approach incorporating tools and perspectives from diverse fields and stakeholders has contributed to an advanced understanding of T. gondii and is addressing transmission at the rapidly changing human-animal-environment interface.

PMID: 23218130 [PubMed - as supplied by publisher]

Use and abuse of dendritic cells by Toxoplasma gondii

Virulence. 2012 Nov 15;3(7). [Epub ahead of print]

Use and abuse of dendritic cells by Toxoplasma gondii

Sanecka A, Frickel EM.

Division of Parasitology; MRC National Institute of Medical Research; London, UK.

The ubiquitous apicomplexan parasite Toxoplasma gondii stimulates its host's immune response to achieve quiescent chronic infection. Central to this goal are host dendritic cells. The parasite exploits dendritic cells to disseminate through the body, produce pro-inflammatory cytokines, present its antigens to the immune system and yet at the same time subvert their signaling pathways in order to evade detection. This carefully struck balance by Toxoplasma makes it the most successful parasite on this planet. Recent progress has highlighted specific parasite and host molecules that mediate some of these processes particularly in dendritic cells and in other cells of the innate immune system. Critically, there are several important factors that need to be taken into consideration when concluding how the dendritic cells and the immune system deal with a Toxoplasma infection, including the route of administration, parasite strain and host genotype.

 PMID: 23221473 [PubMed - as supplied by publisher]

Toxoplasma gondii infection, from predation to schizophrenia: can animal behaviour help us understand human behaviour?

J Exp Biol. 2013 Jan 1;216(Pt 1):99-112. doi: 10.1242/jeb.074716.

Toxoplasma gondii infection, from predation to schizophrenia: can animal behaviour help us understand human behaviour?

Webster JP, Kaushik M, Bristow GC, McConkey GA.

Department of Infectious Disease Epidemiology, School of Public Health, Imperial College Faculty of Medicine, London, W2 1PG, UK.

We examine the role of the protozoan Toxoplasma gondii as a manipulatory parasite and question what role study of infections in its natural intermediate rodent hosts and other secondary hosts, including humans, may elucidate in terms of the epidemiology, evolution and clinical applications of infection. In particular, we focus on the potential association between T. gondii and schizophrenia. We introduce the novel term 'T. gondii-rat manipulation-schizophrenia model' and propose how future behavioural research on this model should be performed from a biological, clinical and ethically appropriate perspective.

 PMID: 23225872 [PubMed - in process]

Toxoplasma gondii infection and behaviour - location, location, location?

J Exp Biol. 2013 Jan 1;216(Pt 1):113-9. doi: 10.1242/jeb.074153.

Toxoplasma gondii infection and behaviour - location, location, location?

McConkey GA, Martin HL, Bristow GC, Webster JP.

School of Biology, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK.

Parasite location has been proposed as an important factor in the behavioural changes observed in rodents infected with the protozoan Toxoplasma gondii. During the chronic stages of infection, encysted parasites are found in the brain but it remains unclear whether the parasite has tropism for specific brain regions. Parasite tissue cysts are found in all brain areas with some, but not all, prior studies reporting higher numbers located in the amygdala and frontal cortex. A stochastic process of parasite location does not, however, seem to explain the distinct and often subtle changes observed in rodent behaviour. One factor that could contribute to the specific changes is increased dopamine production by T. gondii. Recently, it was found that cells encysted with parasites in the brains of experimentally infected rodents have high levels of dopamine and that the parasite encodes a tyrosine hydroxylase, the rate-limiting enzyme in the synthesis of this neurotransmitter. A mechanism is proposed that could explain the behaviour changes due to parasite regulation of dopamine. This could have important implications for T. gondii infections in humans.

 PMID: 23225873 [PubMed - in process]

Parasite-augmented mate choice and reduction in innate fear in rats infected by Toxoplasma gondii

J Exp Biol. 2013 Jan 1;216(Pt 1):120-6. doi: 10.1242/jeb.072983.

Parasite-augmented mate choice and reduction in innate fear in rats infected by Toxoplasma gondii

Vyas A.

School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore, 637551.

Typically, female rats demonstrate clear mate choice. Mate preference is driven by the evolutionary need to choose males with heritable parasite resistance and to prevent the transmission of contagious diseases during mating. Thus, females detect and avoid parasitized males. Over evolutionary time scales, parasite-free males plausibly evolve to advertise their status. This arrangement between males and females is obviously detrimental to parasites, especially for sexually transmitted parasites. Yet Toxoplasma gondii, a sexually transmitted parasite, gets around this obstacle by manipulating mate choice of uninfected females. Males infected with this parasite become more attractive to uninfected females. The ability of T. gondii to not only advantageously alter the behavior and physiology of its host but also secondarily alter the behavior of uninfected females presents a striking example of the 'extended phenotype' of parasites. Toxoplasma gondii also abolishes the innate fear response of rats to cat odor; this likely increases parasite transmission through the trophic route. It is plausible that these two manipulations are not two distinct phenotypes, but are rather part of a single pattern built around testosterone-mediated interplay between mate choice, parasitism and predation.

 PMID: 23225874 [PubMed - in process]

Influence of latent Toxoplasma infection on human personality, physiology and morphology

J Exp Biol. 2013 Jan 1;216(Pt 1):127-33. doi: 10.1242/jeb.073635.

Influence of latent Toxoplasma infection on human personality, physiology and morphology: pros and cons of the Toxoplasma-human model in studying the manipulation hypothesis

Flegr J

Faculty of Science, Charles University, Department of Philosophy and History of Science, Prague, Czech Republic.

The parasitic protozoan Toxoplasma gondii infects about one-third of the population of developed countries. The life-long presence of dormant stages of this parasite in the brain and muscular tissues of infected humans is usually considered asymptomatic from the clinical point of view. In the past 20 years, research performed mostly on military personnel, university students, pregnant women and blood donors has shown that this 'asymptomatic' disease has a large influence on various aspects of human life. Toxoplasma-infected subjects differ from uninfected controls in the personality profile estimated with two versions of Cattell's 16PF, Cloninger's TCI and Big Five questionnaires. Most of these differences increase with the length of time since the onset of infection, suggesting that Toxoplasma influences human personality rather than human personality influencing the probability of infection. Toxoplasmosis increases the reaction time of infected subjects, which can explain the increased probability of traffic accidents in infected subjects reported in three retrospective and one very large prospective case-control study. Latent toxoplasmosis is associated with immunosuppression, which might explain the increased probability of giving birth to a boy in Toxoplasma-infected women and also the extremely high prevalence of toxoplasmosis in mothers of children with Down syndrome. Toxoplasma-infected male students are about 3 cm taller than Toxoplasma-free subjects and their faces are rated by women as more masculine and dominant. These differences may be caused by an increased concentration of testosterone. Toxoplasma also appears to be involved in the initiation of more severe forms of schizophrenia. At least 40 studies confirmed an increased prevalence of toxoplasmosis among schizophrenic patients. Toxoplasma-infected schizophrenic patients differ from Toxoplasma-free schizophrenic patients by brain anatomy and by a higher intensity of the positive symptoms of the disease. Finally, five independent studies performed in blood donors, pregnant women and military personnel showed that RhD blood group positivity, especially in RhD heterozygotes, protects infected subjects against various effects of latent toxoplasmosis, such as the prolongation of reaction times, an increased risk of traffic accidents and excessive pregnancy weight gain. The modern human is not a natural host of Toxoplasma. Therefore, it can only be speculated which of the observed effects of latent toxoplasmosis are the result of the manipulation activity of the Toxoplasma aimed to increase the probability of its transmission from a natural intermediate to the definitive host by predation, and which are just side effects of chronic infection.

PMID: 23225875 [PubMed - in process]

TgCDPK3 Regulates Calcium-Dependent Egress of Toxoplasma gondii from Host Cells

PLoS Pathog. 2012 Dec;8(12):e1003066. doi: 10.1371/journal.ppat.1003066. Epub 2012 Dec 4.

TgCDPK3 Regulates Calcium-Dependent Egress of Toxoplasma gondii from Host Cells

McCoy JM, Whitehead L, van Dooren GG, Tonkin CJ.

The Walter and Eliza Hall Institute of Medical Research, Melbourne, Australia ; Department of Medical Biology, University of Melbourne, Melbourne, Australia.

The phylum Apicomplexa comprises a group of obligate intracellular parasites of broad medical and agricultural significance, including Toxoplasma gondii and the malaria-causing Plasmodium spp. Key to their parasitic lifestyle is the need to egress from an infected cell, actively move through tissue, and reinvade another cell, thus perpetuating infection. Ca(2+)-mediated signaling events modulate key steps required for host cell egress, invasion and motility, including secretion of microneme organelles and activation of the force-generating actomyosin-based motor. Here we show that a plant-like Calcium-Dependent Protein Kinase (CDPK) in T. gondii, TgCDPK3, which localizes to the inner side of the plasma membrane, is not essential to the parasite but is required for optimal in vitro growth. We demonstrate that TgCDPK3, the orthologue of Plasmodium PfCDPK1, regulates Ca(2+) ionophore- and DTT-induced host cell egress, but not motility or invasion. Furthermore, we show that targeting to the inner side of the plasma membrane by dual acylation is required for its activity. Interestingly, TgCDPK3 regulates microneme secretion when parasites are intracellular but not extracellular. Indeed, the requirement for TgCDPK3 is most likely determined by the high K(+) concentration of the host cell. Our results therefore suggest that TgCDPK3's role differs from that previously hypothesized, and rather support a model where this kinase plays a role in rapidly responding to Ca(2+) signaling in specific ionic environments to upregulate multiple processes required for gliding motility.

 PMID: 23226109 [PubMed - in process]

De novo reconstruction of the Toxoplasma gondii transcriptome

BMC Genomics. 2012 Dec 12;13(1):696. [Epub ahead of print]

De novo reconstruction of the Toxoplasma gondii transcriptome improves on the current genome annotation and reveals alternatively spliced transcripts and putative long non-coding RNAs

Hassan MA, Melo MB, Haas B, Jensen KD, Saeij JP.

BACKGROUND: Accurate gene model predictions and annotation of alternative splicing events are imperative for genomic studies in organisms that contain genes with multiple exons. Currently most gene models for the intracellular parasite, Toxoplasma gondii, are based on computer model predictions without cDNA sequence verification. Additionally, the nature and extent of alternative splicing in Toxoplasma gondii is unknown. In this study, we used de novo transcript assembly and the published type II (ME49) genomic sequence to quantify the extent of alternative splicing in Toxoplasma and to improve the current Toxoplasma gene annotations.
We used high-throughput RNA-sequencing data to assemble full-length transcripts, independently of a reference genome, followed by gene annotation based on the ME49 genome. We assembled 13,533 transcripts overlapping with known ME49 genes in ToxoDB and then used this set to; a) improve the annotation in the untranslated regions of ToxoDB genes, b) identify novel exons within protein-coding ToxoDB genes, and c) report on 50 previously unidentified alternatively spliced transcripts. Additionally, we assembled a set of 2,930 transcripts not overlapping with any known ME49 genes in ToxoDB. From this set, we have identified 118 new ME49 genes, 18 novel Toxoplasma genes, and putative non-coding RNAs.
RNA-seq data and de novo transcript assembly provide a robust way to update incompletely annotated genomes, like the Toxoplasma genome. We have used RNA-seq to improve the annotation of several Toxoplasma genes, identify alternatively spliced genes, novel genes, novel exons, and putative non-coding RNAs.

 PMID: 23231500 [PubMed - as supplied by publisher]

Parasites and cancers: parasite antigens as possible targets for cancer immunotherapy

Future Oncol. 2012 Dec;8(12):1529-35. doi: 10.2217/fon.12.155.

Parasites and cancers: parasite antigens as possible targets for cancer immunotherapy

Darani HY, Yousefi M.

Department of Parasitology & Mycology, Medicine, Isfahan University of Medical Sciences, Isfahan, Iran.

An adverse relationship between some parasite infections and cancer in the human population has been reported by different research groups. Anticancer activity of some parasites such as Trypanosoma cruzi, Toxoplasma gondii, Toxocara canis, Acantamoeba castellani and Plasmodium yoelii has been shown in experimental animals. Moreover, it has been shown that cancer-associated mucin-type O-glycan compositions are made by parasites, therefore cancers and parasites have common antigens. In this report anticancer activities of some parasites have been reviewed and the possible mechanisms of these actions have also been discussed.

 PMID: 23231515 [PubMed - in process]

Dynein light chain 8a of Toxoplasma gondii, a unique conoid-localized β-strand-swapped homodimer, is required for an efficient parasite growth

FASEB J. 2012 Dec 11. [Epub ahead of print]

Dynein light chain 8a of Toxoplasma gondii, a unique conoid-localized β-strand-swapped homodimer, is required for an efficient parasite growth

Qureshi BM, Hofmann NE, Arroyo-Olarte RD, Nickl B, Hoehne W, Jungblut PR, Lucius R, Scheerer P, Gupta N.

*Department of Molecular Parasitology, Humboldt University, Berlin, Germany;

Dynein light chain 8 (DLC8) is a ubiquitous eukaryotic protein regulating diverse cellular functions. We show that the obligate intracellular parasite Toxoplasma gondii harbors 4 DLC8 proteins (TgDLC8a-d), of which only TgDLC8a clusters in the mainstream LC8 class. TgDLC8b-d proteins form a divergent and alveolate-specific clade. TgDLC8b-d proteins are largely cytosolic, whereas TgDLC8a resides in the conoid at the apical end of T. gondii. The apical location of TgDLC8a is also not shared by its nearly identical Eimeria (EtDLC8a), Plasmodium (PfDLC8), or human (HsDLC8) orthologs. Notwithstanding an exclusive conoid targeting, TgDLC8a exhibits a classical LC8 structure. It forms a homodimer by swapping of the β(2) strands that interact with the antiparallel β(1)' strands of the opposing monomers. The TgDLC8a dimer contains two identical binding grooves and appears to be adapted for multitarget recognition. By contrast, the previously reported PfDLC8 homodimer is shaped by binding of the β(0) strand with the parallel β(2)' strand and lacks such a distinct binding interface. Our comparisons suggest an unexpected structural and functional divergence of the two otherwise conserved proteins from apicomplexan parasites. Finally, we demonstrate that a phosphomimetic S88E mutation renders the TgDLC8a-S88E mutant monomeric and cytosolic in T. gondii, and its overexpression inhibits the parasite growth in human fibroblasts.

PMID: 23233536 [PubMed - as supplied by publisher]

Thursday, December 06, 2012

Induction of sulfadiazine resistance in vitro in Toxoplasma gondii

Exp Parasitol. 2012 Nov 30. pii: S0014-4894(12)00357-8. doi: 10.1016/j.exppara.2012.11.019. [Epub ahead of print]

Induction of sulfadiazine resistance in vitro in Toxoplasma gondii

Doliwa C, Escotte-Binet S, Aubert D, Velard F, Schmid A, Geers R, Villena I.

Laboratoire de Parasitologie-Mycologie, EA 3800, SFR CAP-Santé FED 4231, Université de Reims Champagne-Ardenne, 51 rue Cognacq-Jay, 51095 Reims Cedex, France. Electronic address:

We induced sulfadiazine resistance in two sulfadiazine sensitive strains of T. gondii, RH (Type I) and ME-49 (Type II) in vitro by using drug pressure. At first, sulfadiazine susceptibility of the two sensitive strains and two naturally resistant strains of T. gondii was evaluated on Vero cells using an enzyme-linked immunosorbent assay (ELISA). The IC(50) values of sulfadiazine were 77 μg/mL for RH, 51 μg/mL for ME-49 and higher than 1,000 μg/mL for the two natural resistant strains. Secondly, induced resistance of the strains by gradually increase sulfadiazine concentration was verified by this test, which resulted IC(50) values at higher than 1,000 μg/mL. In conclusion we developed in vitro two sulfadiazine resistant strains called RH-R(SDZ) and ME-49-R(SDZ). These strains resistant to sulfadiazine would be useful to characterize resistance mechanisms to sulfadiazine.

PMID: 23206954 [PubMed - as supplied by publisher]

Chitinase dependent control of protozoan cyst burden in the brain

PLoS Pathog. 2012 Nov;8(11):e1002990. doi: 10.1371/journal.ppat.1002990. Epub 2012 Nov 29.

Chitinase dependent control of protozoan cyst burden in the brain

Nance JP, Vannella KM, Worth D, David C, Carter D, Noor S, Hubeau C, Fitz L, Lane TE, Wynn TA, Wilson EH.

Division of Biomedical Sciences, University of California, Riverside, California, United States of America.

Chronic infections represent a continuous battle between the host's immune system and pathogen replication. Many protozoan parasites have evolved a cyst lifecycle stage that provides it with increased protection from environmental degradation as well as endogenous host mechanisms of attack. In the case of Toxoplasma gondii, these cysts are predominantly found in the immune protected brain making clearance of the parasite more difficult and resulting in a lifelong infection. Currently, little is known about the nature of the immune response stimulated by the presence of these cysts or how they are able to propagate. Here we establish a novel chitinase-dependent mechanism of cyst control in the infected brain. Despite a dominant Th1 immune response during Toxoplasma infection there exists a population of alternatively activated macrophages (AAMØ) in the infected CNS. These cells are capable of cyst lysis via the production of AMCase as revealed by live imaging, and this chitinase is necessary for protective immunity within the CNS. These data demonstrate chitinase activity in the brain in response to a protozoan pathogen and provide a novel mechanism to facilitate cyst clearance during chronic infections.

PMID: 23209401 [PubMed - in process]

A Forward Genetic Screen Reveals that Calcium-dependent Protein Kinase 3 Regulates Egress in Toxoplasma

PLoS Pathog. 2012 Nov;8(11):e1003049. doi: 10.1371/journal.ppat.1003049. Epub 2012 Nov 29.

A Forward Genetic Screen Reveals that Calcium-dependent Protein Kinase 3 Regulates Egress in Toxoplasma

Garrison E, Treeck M, Ehret E, Butz H, Garbuz T, Oswald BP, Settles M, Boothroyd J, Arrizabalaga G.

University of Idaho, Department of Biological Sciences, Moscow, Idaho, United States of America.

Egress from the host cell is a crucial and highly regulated step in the biology of the obligate intracellular parasite, Toxoplasma gondii. Active egress depends on calcium fluxes and appears to be a crucial step in escaping the attack from the immune system and, potentially, in enabling the parasites to shuttle into appropriate cells for entry into the brain of the host. Previous genetic screens have yielded mutants defective in both ionophore-induced egress and ionophore-induced death. Using whole genome sequencing of one mutant and subsequent analysis of all mutants from these screens, we find that, remarkably, four independent mutants harbor a mis-sense mutation in the same gene, TgCDPK3, encoding a calcium-dependent protein kinase. All four mutations are predicted to alter key regions of TgCDPK3 and this is confirmed by biochemical studies of recombinant forms of each. By complementation we confirm a crucial role for TgCDPK3 in the rapid induction of parasite egress and we establish that TgCDPK3 is critical for formation of latent stages in the brains of mice. Genetic knockout of TgCDPK3 confirms a crucial role for this kinase in parasite egress and a non-essential role for it in the lytic cycle.

PMID: 23209419 [PubMed - in process]

Toxoplasma gondii Myocarditis after Adult Heart Transplantation: Successful Prophylaxis with Pyrimethamine

J Trop Med. 2012;2012:853562. doi: 10.1155/2012/853562. Epub 2012 Nov 1.

Toxoplasma gondii Myocarditis after Adult Heart Transplantation: Successful Prophylaxis with Pyrimethamine

Strabelli TM, Siciliano RF, Vidal Campos S, Bianchi Castelli J, Bacal F, Bocchi EA, Uip DE.

Infection Control Unit, Heart Institute (Incor-HCFMUSP), University of São Paulo Medical School, São Paulo, SP, Brazil.

Toxoplasma gondii primary infection/reactivation after solid organ transplantation is a serious complication, due to the high mortality rate following disseminated disease. We performed a retrospective study of all cases of T. gondii infections in 436 adult patients who had received an orthotopic cardiac transplant at our Institution from May 1968 to January 2011. Six patients (1.3%) developed T. gondii infection/reactivation in the post-operative period. All infections/reactivations occurred before 1996, when no standardized toxoplasmosis prophylactic regimen or co-trimoxazole prophylaxis was used. Starting with the 112th heart transplant, oral pyrimethamine 75 mg/day was used for seronegative transplant recipients whose donors were seropositive or unknown. Two patients (33.3%) presented with disseminated toxoplasmosis infection, and all patients (100%) had myocarditis. Five patients (83.3%) were seronegative before transplant and one patient did not have pre-transplant serology available. Median time for infection onset was 131 days following transplantation. Three patients (50%) died due to toxoplasmosis infection. After 1996, we did not observe any additional cases of T. gondii infection/reactivation. In conclusion, toxoplasmosis in heart allographs was more frequent among seronegative heart recipients, and oral pyrimethamine was highly effective for the prevention of T. gondii infection in this population.

PMID: 23209479 [PubMed - in process]

Anti-Gluten Immune Response following Toxoplasma gondii Infection in Mice

PLoS One. 2012;7(11):e50991. doi: 10.1371/journal.pone.0050991. Epub 2012 Nov 29.

Anti-Gluten Immune Response following Toxoplasma gondii Infection in Mice

Severance EG, Kannan G, Gressitt KL, Xiao J, Alaedini A, Pletnikov MV, Yolken RH.

Stanley Division of Developmental Neurovirology, Department of Pediatrics, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America.

Gluten sensitivity may affect disease pathogenesis in a subset of individuals who have schizophrenia, bipolar disorder or autism. Exposure to Toxoplasma gondii is a known risk factor for the development of schizophrenia, presumably through a direct pathological effect of the parasite on brain and behavior. A co-association of antibodies to wheat gluten and to T. gondii in individuals with schizophrenia was recently uncovered, suggesting a coordinated gastrointestinal means by which T. gondii and dietary gluten might generate an immune response. Here, we evaluated the connection between these infectious- and food-based antigens in mouse models. BALB/c mice receiving a standard wheat-based rodent chow were infected with T. gondii via intraperitoneal, peroral and prenatal exposure methods. Significant increases in the levels of anti-gluten IgG were documented in all infected mice and in offspring from chronically infected dams compared to uninfected controls (repetitive measures ANOVAs, two-tailed t-tests, all p≤0.00001). Activation of the complement system accompanied this immune response (p≤0.002-0.00001). Perorally-infected females showed higher levels of anti-gluten IgG than males (p≤0.009) indicating that T. gondii-generated gastrointestinal infection led to a significant anti-gluten immune response in a sex-dependent manner. These findings support a gastrointestinal basis by which two risk factors for schizophrenia, T. gondii infection and sensitivity to dietary gluten, might be connected to produce the immune activation that is becoming an increasingly recognized pathology of psychiatric disorders.

PMID: 23209841 [PubMed - in process]

Neuropsychiatric symptoms are common in immunocompetent adult patients with Toxoplasma gondii acute lymphadenitis

Scand J Infect Dis. 2012 Dec 4. [Epub ahead of print]

Neuropsychiatric symptoms are common in immunocompetent adult patients with Toxoplasma gondii acute lymphadenitis

Wong WK, Upton A, Thomas MG.

Department of Molecular Medicine and Pathology, Faculty of Medical and Health Sciences, The University of Auckland.

Background: Chronic toxoplasmosis has been shown to be strongly associated with a range of neuropsychiatric effects including schizophrenia and suicide. However there have not been any prospective, community-based studies of the neuropsychiatric effects of acute toxoplasmosis in adult immunocompetent patients. Methods: Adult patients with a positive serum IgM anti-Toxoplasma gondii test result, in the context of an acute illness with lymphadenopathy, were invited to complete a questionnaire seeking information relating to the nature, severity, and duration of symptoms in the months following the diagnosis of acute toxoplasmosis. Results: Laboratory testing identified a total of 187 adults who had a positive serum IgM anti-T. gondii test result between 1 January and 30 November 2011. Consent to contact 108/187 (58%) patients was provided by their family doctor; 37 (34%) of these 108 patients completed and returned the questionnaire. Questionnaires from the 31/108 (29%) patients who reported swollen lymph nodes during their illness were included in the study. Fatigue (90%), headache (74%), difficulty concentrating (52%), and muscle aches (52%) were the most commonly reported symptoms. These symptoms commonly persisted for at least 4 weeks. Twenty-seven of 31 (87%) subjects reported a moderate or severe reduction in their overall physical and mental health during the first 2 months of illness. Conclusions: Acute toxoplasmosis in immunocompetent adults commonly causes moderately severe neuropsychiatric symptoms that might result from replication of the organism in the central nervous system with consequent effects on brain function. Patients should be advised that such symptoms are common and reassured that they usually resolve completely within a few months.

PMID: 23210638 [PubMed - as supplied by publisher]

Wednesday, December 05, 2012

Postdoctoral position: Host-pathogen interactions


Biochemistry, Microbiology, Host-Pathogen Interactions

Indiana University School of Medicine

POSTDOCTORAL POSITION available to investigate host-pathogen interactions during infection with 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 investigate proteome-wide changes taking place in the host cell during infection and employ state of the art genetic and biochemical approaches to make the host cell less hospitable for intracellular parasites.

Position requires a Ph.D., expertise in biochemistry & cell biology, and excellent communication skills (speaking and writing English). Experience in host-pathogen interactions and/or bioinformatics is a plus. Submit CV and contact information for three references to Dr. Bill Sullivan (

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 for more information.

Tuesday, December 04, 2012

Toxoplasma histone acetylation remodelers as novel drug targets

Expert Rev Anti Infect Ther. 2012 Oct;10(10):1189-201. doi: 10.1586/eri.12.100.

Toxoplasma histone acetylation remodelers as novel drug targets

Vanagas L, Jeffers V, Bogado SS, Dalmasso MC, Sullivan WJ Jr, Angel SO.

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

Toxoplasma gondii is a leading cause of neurological birth defects and a serious opportunistic pathogen. The authors and others have found that Toxoplasma uses a unique nucleosome composition supporting a fine gene regulation together with other factors. Post-translational modifications in histones facilitate the establishment of a global chromatin environment and orchestrate DNA-related biological processes. Histone acetylation is one of the most prominent post-translational modifications influencing gene expression. Histone acetyltransferases and histone deacetylases have been intensively studied as potential drug targets. In particular, histone deacetylase inhibitors have activity against apicomplexan parasites, underscoring their potential as a new class of antiparasitic compounds. In this review, we summarize what is known about Toxoplasma histone acetyltransferases and histone deacetylases, and discuss the inhibitors studied to date. Finally, the authors discuss the distinct possibility that the unique nucleosome composition of Toxoplasma, which harbors a nonconserved H2Bv variant histone, might be targeted in novel therapeutics directed against this parasite.

PMID: 23199404 [PubMed - in process]

Toxoplasma gondii prevalence in farm animals in the United States

Int J Parasitol. 2012 Nov 27. pii: S0020-7519(12)00300-1. doi: 10.1016/j.ijpara.2012.09.012. [Epub ahead of print]

Toxoplasma gondii prevalence in farm animals in the United States

Hill DE, Dubey JP.

United States Department of Agriculture, Agricultural Research Service, Beltsville Agricultural Research Center Animal Parasitic Diseases Laboratory. BARC-East, Beltsville, Maryland U.S.A., 20705. Electronic address:

Toxoplasmosis, caused by Toxoplasma gondii, is one of the most common parasitic infections of humans and other warmblooded animals. It has been found worldwide and nearly one-third of humans have been exposed to the parasite. Congenital infection occurs when a woman becomes infected during pregnancy and transmits the parasite to the fetus. Besides congenital infection, humans become infected by ingesting food or water contaminated with sporulated oocysts from infected cat feces or through ingestion of tissue cysts in undercooked or uncooked meat. Food animals (pigs, chickens, lambs and goats) become infected by the same routes, resulting in meat products containing tissue cysts, which can then infect consumers. Toxoplasma infection is common in food animals in the United States. Implementation of management factors such as biosecure confinement housing are important in reducing the levels of infection in animals destined for human consumption.

PMID: 23201235 [PubMed - as supplied by publisher]

Matrix metalloproteinase-2 and -9 lead to fibronectin degradation in astroglia infected with Toxoplasma gondii

Acta Trop. 2012 Nov 28. pii: S0001-706X(12)00366-X. doi: 10.1016/j.actatropica.2012.11.002. [Epub ahead of print]

Matrix metalloproteinase-2 and -9 lead to fibronectin degradation in astroglia infected with Toxoplasma gondii

Lu CY, Lai SC.

Institue of Medicine, Chung Shan Medical University, Taichung 402, Taiwan.

Toxoplasma gondii is a zoonotic parasite and its infection in human can induce toxoplasmic encephalitis in immune disorders. In this study, astroglia were infected with the TS-4 strain of T. gondii tachyzoite in vitro to investigate the changes of matrix metalloproteinase (MMP)-2, MMP-9 and their substrate fibronectin. MMP-2 and MMP-9 were significantly increased at 1h, 6h and 12h post-infection (PI) in the cell homogenates, and increased at 6h, 12h, 24h and 48h PI in the cell-cultured supernatants. Fibronectin degradation also occurred at the same time points. In addition, immunocytochemistry showed that MMP-2 and MMP-9 localized in the cytoplasm, and confocal scanning laser microscopy revealed co-labeled patterns of MMP-2 and MMP-9 with fibronectin. MMP-2 and MMP-9 interacted with fibronectin, respectively. These results suggest that MMP-2 and MMP-9 induction from astroglia may contribute to extracellular matrix (ECM) degradation occurring in toxoplasmosis. Thus, we hypothesize that MMP-2 and MMP-9 cleave fibronectin and may contribute to the astroglia reaction and leukocyte migration to the sites of T. gondii replication during toxoplasmic encephalitis.

PMID: 23201304 [PubMed - as supplied by publisher]