Southeast Asian J Trop Med Public Health. 2009 Nov;40(6):1158-78.
Toxoplasmosis in HIV/AIDS: a living legacy
Nissapatorn V.
Department of Parasitology, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia. nissapat@gmail.com
Abstract
Toxoplasmosis has historically been considered one of the most important opportunistic infections detected in HIV/AIDS patients. The prevalence rates of latent Toxoplasma infections in HIV-infected patients has been found to vary greatly from 3% to 97%. Prevalence has been found to be related to ethnicity, certain risk factors, and reactivation of toxoplasmosis. Prior to antiretroviral therapy, toxoplasmic encephalitis (TE) was the most common focal cerebral lesion detected in AIDS patients with Toxoplasma infection, occurring in approximately half of Toxoplasma-seropositive patients. Other forms of dissemination have also been reported in AIDS patients in sites such as the eyes, lungs, heart and spinal cord. Anti-Toxoplasma therapy and chemoprophylaxis have shown effectiveness in reducing the incidence of TE, while noncompliance has been identified as a cause of relapse in these settings. Toxoplasmosis is one of the most common neuropathological complications found at autopsy. Rapid progress in the development of highly active antiretroviral therapy (HAART) has changed the observed patterns with TE, for which there has been a marked decrease in overall incidence. Subsequently, TE has been found to be significantly associated with the so-called "neurological immune restoration inflammatory syndrome" (NIRIS). Toxoplasma screening programs are recommended for all newly diagnosed HIV-positive patients. Chemoprophylaxis should be considered in HIV-infected patients who have a CD4 < 200 cells/mm3, particularly in settings where resources are limited and there is not access to HAART. TE remains a cause of morbidity and mortality among AIDS patients.
PMID: 20578449 [PubMed - in process]
Wednesday, June 30, 2010
Diagnosis of Toxoplasma gondii infection after allogeneic stem cell transplant can be difficult and requires intensive scrutiny
Leuk Lymphoma. 2010 Jun 25. [Epub ahead of print]
Diagnosis of Toxoplasma gondii infection after allogeneic stem cell transplant can be difficult and requires intensive scrutiny
Cavattoni I, Ayuk F, Zander AR, Zabelina T, Bacher A, Cayroglu E, Knospe V, Illies T, Aepfelbacher M, Richard G, Kröger N, Bacher U.
Interdisciplinary Clinic for Stem Cell Transplantation, University of Hamburg, Germany.
Abstract
Infectious complications remain a major problem after allogeneic hematopoietic stem cell transplant (HSCT). Specifically Toxoplasma gondii infection is a life-threatening condition in immunocompromised patients. In order to highlight the difficulties in obtaining an early and definitive diagnosis, we report three cases of toxoplasmosis after HSCT for hematologic malignancies: two cases of T. gondii retinochoroiditis, and one case of encephalitis. All patients had unrelated donors and received antithymocyte globulin; none had received trimethoprim/sulfamethoxazole prophylaxis. Toxoplasmosis occurred early post-transplant and diagnosis was obtained by real-time PCR. In one case, the correct diagnosis could only be established by PCR analysis of a retinal biopsy specimen. Rapid diagnosis-by invasive approaches-and an immediate onset of antiparasite treatment are crucial to avoid disseminated and often lethal Toxoplasma infections in the post-transplant period. Post-transplant prevention strategies and treatment to control advanced infection in this setting are discussed.
PMID: 20578813 [PubMed - as supplied by publisher]
Diagnosis of Toxoplasma gondii infection after allogeneic stem cell transplant can be difficult and requires intensive scrutiny
Cavattoni I, Ayuk F, Zander AR, Zabelina T, Bacher A, Cayroglu E, Knospe V, Illies T, Aepfelbacher M, Richard G, Kröger N, Bacher U.
Interdisciplinary Clinic for Stem Cell Transplantation, University of Hamburg, Germany.
Abstract
Infectious complications remain a major problem after allogeneic hematopoietic stem cell transplant (HSCT). Specifically Toxoplasma gondii infection is a life-threatening condition in immunocompromised patients. In order to highlight the difficulties in obtaining an early and definitive diagnosis, we report three cases of toxoplasmosis after HSCT for hematologic malignancies: two cases of T. gondii retinochoroiditis, and one case of encephalitis. All patients had unrelated donors and received antithymocyte globulin; none had received trimethoprim/sulfamethoxazole prophylaxis. Toxoplasmosis occurred early post-transplant and diagnosis was obtained by real-time PCR. In one case, the correct diagnosis could only be established by PCR analysis of a retinal biopsy specimen. Rapid diagnosis-by invasive approaches-and an immediate onset of antiparasite treatment are crucial to avoid disseminated and often lethal Toxoplasma infections in the post-transplant period. Post-transplant prevention strategies and treatment to control advanced infection in this setting are discussed.
PMID: 20578813 [PubMed - as supplied by publisher]
Toxoplasma gondii activates hypoxia inducible factor by stabilizing the HIF-1 alpha subunit via type I activin like receptor kinase receptor signaling
J Biol Chem. 2010 Jun 25. [Epub ahead of print]
Toxoplasma gondii activates hypoxia inducible factor by stabilizing the HIF-1 alpha subunit via type I activin like receptor kinase receptor signaling
Wiley M, Sweeney KR, Chan DA, Brown KM, McMurtrey C, Howard EW, Giaccia AJ, Blader IJ.
University of Oklahoma Health Sciences Center, United States;
Abstract
Toxoplasma gondii is an intracellular protozoan parasite that can cause devastating disease in fetuses and immune-compromised individuals. We previously reported that the alpha subunit of the host cell transcription factor, hypoxia-inducible factor-1 (HIF-1), is upregulated by infection and necessary for Toxoplasma growth. Under basal conditions, HIF-1alpha is constitutively expressed but rapidly targeted for proteasomal degradation after two proline residues are hydroxylated by a family of prolyl hydroxylases (PHDs). The PHDs are alpha-ketoglutarate-dependent dioxygenases that have low Kms for oxygen, making them important cellular oxygen sensors. Thus, when oxygen levels decrease HIF-1alpha is not hydroxylated, its levels increase, and HIF-1 is activated. How Toxoplasma activates HIF-1 under normoxic conditions remains unknown. Here, we report that Toxoplasma infection increases HIF-1alpha stability by preventing HIF-1alpha prolyl hydroxylation. Infection significantly decreases PHD2 abundance, which is the key prolyl hydroxylase for regulating HIF-1alpha. The effects of Toxoplasma on HIF-1alpha abundance and prolyl hydroxylase activity require Activin Like Receptor Kinase signaling.. Finally, parasite growth is severely diminished when signaling from this family of receptors is inhibited. Together, these data indicate that PHD2 is a key host cell factor for Toxoplasma gondii growth and represent a novel mechanism by which a microbial pathogen subverts host cell signaling and transcription to establish its replicative niche.
PMID: 20581113 [PubMed - as supplied by publisher]
Toxoplasma gondii activates hypoxia inducible factor by stabilizing the HIF-1 alpha subunit via type I activin like receptor kinase receptor signaling
Wiley M, Sweeney KR, Chan DA, Brown KM, McMurtrey C, Howard EW, Giaccia AJ, Blader IJ.
University of Oklahoma Health Sciences Center, United States;
Abstract
Toxoplasma gondii is an intracellular protozoan parasite that can cause devastating disease in fetuses and immune-compromised individuals. We previously reported that the alpha subunit of the host cell transcription factor, hypoxia-inducible factor-1 (HIF-1), is upregulated by infection and necessary for Toxoplasma growth. Under basal conditions, HIF-1alpha is constitutively expressed but rapidly targeted for proteasomal degradation after two proline residues are hydroxylated by a family of prolyl hydroxylases (PHDs). The PHDs are alpha-ketoglutarate-dependent dioxygenases that have low Kms for oxygen, making them important cellular oxygen sensors. Thus, when oxygen levels decrease HIF-1alpha is not hydroxylated, its levels increase, and HIF-1 is activated. How Toxoplasma activates HIF-1 under normoxic conditions remains unknown. Here, we report that Toxoplasma infection increases HIF-1alpha stability by preventing HIF-1alpha prolyl hydroxylation. Infection significantly decreases PHD2 abundance, which is the key prolyl hydroxylase for regulating HIF-1alpha. The effects of Toxoplasma on HIF-1alpha abundance and prolyl hydroxylase activity require Activin Like Receptor Kinase signaling.. Finally, parasite growth is severely diminished when signaling from this family of receptors is inhibited. Together, these data indicate that PHD2 is a key host cell factor for Toxoplasma gondii growth and represent a novel mechanism by which a microbial pathogen subverts host cell signaling and transcription to establish its replicative niche.
PMID: 20581113 [PubMed - as supplied by publisher]
Immunogenetics of Toxoplama gondii informs vaccine design
Trends Parasitol. 2010 Jun 25. [Epub ahead of print]
Immunogenetics of Toxoplama gondii informs vaccine design
Henriquez FL, Woods S, Cong H, McLeod R, Roberts CW.
School of Science, University of the West of Scotland, Paisley, PA1 2BE, UK.
Abstract
A series of studies over 20 years mapped resistance to toxoplasmic encephalitis in mice to major histocompatibility complex class I (MHC I) and ultimately, more precisely the Ld region. This is consistent with contemporary functional studies that demonstrated a protective role for CD8(+) T cells. Recent studies have demonstrated that the Ld gene product presents a number of immunodominant Toxoplasma gondii-derived peptides in the murine models, providing a paradigm for vaccine design. The almost complete sequencing of the genomes of the predominant strains of T. gondii in conjunction with the development of predictive binding algorithms for MHC I peptides in humans now offers a new opportunity for vaccine development against this medically important pathogen. Copyright © 2010. Published by Elsevier Ltd.
PMID: 20580611 [PubMed - as supplied by publisher]
Immunogenetics of Toxoplama gondii informs vaccine design
Henriquez FL, Woods S, Cong H, McLeod R, Roberts CW.
School of Science, University of the West of Scotland, Paisley, PA1 2BE, UK.
Abstract
A series of studies over 20 years mapped resistance to toxoplasmic encephalitis in mice to major histocompatibility complex class I (MHC I) and ultimately, more precisely the Ld region. This is consistent with contemporary functional studies that demonstrated a protective role for CD8(+) T cells. Recent studies have demonstrated that the Ld gene product presents a number of immunodominant Toxoplasma gondii-derived peptides in the murine models, providing a paradigm for vaccine design. The almost complete sequencing of the genomes of the predominant strains of T. gondii in conjunction with the development of predictive binding algorithms for MHC I peptides in humans now offers a new opportunity for vaccine development against this medically important pathogen. Copyright © 2010. Published by Elsevier Ltd.
PMID: 20580611 [PubMed - as supplied by publisher]
Monday, June 28, 2010
Interleukin 17 Receptor Signaling Is Deleterious during Toxoplasma gondii Infection in Susceptible BL6 Mice
J Infect Dis. 2010 Jun 24. [Epub ahead of print]
Interleukin 17 Receptor Signaling Is Deleterious during Toxoplasma gondii Infection in Susceptible BL6 Mice
Guiton R, Vasseur V, Charron S, Arias MT, Van Langendonck N, Buzoni-Gatel D, Ryffel B, Dimier-Poisson I.
Unité Mixte de Recherche (UMR), 0483 Université, Institut National de la Recherche Agronomique (INRA), Immunologie Parasitaire et Vaccinologie, Biothérapies Anti-Infectieuses, Université François Rabelais, Unité de Formation et de Recherche des Sciences Pharmaceutiques, and 2Service de Parasitologie-Mycologie-Médecine Tropicale, Centre Hospitalier Régional et Universitaire, Tours, 3Unité de Recherche, 1282 Infectiologie Animale et Santé Publique, INRA-Centre de Tours, Nouzilly, and 4UMR 6218 Université-Centre National de la Recherche Scientifique, Immunologie et Embryologie Moléculaire, Orléans, France; and 5Institute of Infectious Diseases and Molecular Medicine, University of Cape Town, South Africa.
Abstract
Th17 cells are involved in host defense against several pathogens. Using interleukin (IL) 17RA-deficient mice, we demonstrated reduced ileitis with diminished neutrophil recruitment and inflammatory lesions in the ileum, in the regional lymph node, in the spleen, and in the liver at day 7 and prolonged survival after Toxoplasma gondii infection. In addition, IL-17A antibody neutralization reduced inflammation and enhanced survival in BL6 mice. Diminished inflammation is associated with augmented interferon (IFN) gamma serum levels and enhanced production of IL-10 and IFN-gamma in cultured splenocytes upon antigen restimulation. Finally, cyst load and inflammation in the brain at 40 days are greater in surviving BL6 mice than in IL-17RA-deficient mice. In conclusion, oral T. gondii infection increases IL-17 expression and contributes to the inflammatory response, and IL-17 neutralization has a partial protective effect against fatal T. gondii-associated inflammation.
PMID: 20575661 [PubMed - as supplied by publisher]
Interleukin 17 Receptor Signaling Is Deleterious during Toxoplasma gondii Infection in Susceptible BL6 Mice
Guiton R, Vasseur V, Charron S, Arias MT, Van Langendonck N, Buzoni-Gatel D, Ryffel B, Dimier-Poisson I.
Unité Mixte de Recherche (UMR), 0483 Université, Institut National de la Recherche Agronomique (INRA), Immunologie Parasitaire et Vaccinologie, Biothérapies Anti-Infectieuses, Université François Rabelais, Unité de Formation et de Recherche des Sciences Pharmaceutiques, and 2Service de Parasitologie-Mycologie-Médecine Tropicale, Centre Hospitalier Régional et Universitaire, Tours, 3Unité de Recherche, 1282 Infectiologie Animale et Santé Publique, INRA-Centre de Tours, Nouzilly, and 4UMR 6218 Université-Centre National de la Recherche Scientifique, Immunologie et Embryologie Moléculaire, Orléans, France; and 5Institute of Infectious Diseases and Molecular Medicine, University of Cape Town, South Africa.
Abstract
Th17 cells are involved in host defense against several pathogens. Using interleukin (IL) 17RA-deficient mice, we demonstrated reduced ileitis with diminished neutrophil recruitment and inflammatory lesions in the ileum, in the regional lymph node, in the spleen, and in the liver at day 7 and prolonged survival after Toxoplasma gondii infection. In addition, IL-17A antibody neutralization reduced inflammation and enhanced survival in BL6 mice. Diminished inflammation is associated with augmented interferon (IFN) gamma serum levels and enhanced production of IL-10 and IFN-gamma in cultured splenocytes upon antigen restimulation. Finally, cyst load and inflammation in the brain at 40 days are greater in surviving BL6 mice than in IL-17RA-deficient mice. In conclusion, oral T. gondii infection increases IL-17 expression and contributes to the inflammatory response, and IL-17 neutralization has a partial protective effect against fatal T. gondii-associated inflammation.
PMID: 20575661 [PubMed - as supplied by publisher]
Monday, June 21, 2010
TLR9-dependent induction of intestinal alpha-defensins by Toxoplasma gondii
J Immunol. 2010 Jun 15;184(12):7022-9. Epub 2010 May 19.
TLR9-dependent induction of intestinal alpha-defensins by Toxoplasma gondii
Foureau DM, Mielcarz DW, Menard LC, Schulthess J, Werts C, Vasseur V, Ryffel B, Kasper LH, Buzoni-Gatel D.
Department of Medicine, Dartmouth Medical School, Lebanon, NH 03756, USA.
Abstract
Alpha-defensins (or Cryptdins [Crps]) are a group of antimicrobial peptides produced as a component of Paneth cell (PC) secretory granules in the small intestine. In vivo ligation of TLR9 by synthetic agonists leads to PC degranulation, although the mechanism by which this occurs remains uncertain. In this report, we investigated TLR9-dependent mechanisms, triggered by the parasite Toxoplasma gondii, inducing Crp release in the lumen. Oral challenge of C57BL/6J (B6) wild-type (WT) mice with T. gondii induced TLR9 mRNA upregulation associated with a marked increase of type I IFN mRNA expression. PC secretory granules were released, and Crp-3/-5 mRNA expression by purified epithelial cells was increased following oral challenge of B6 WT mice. Although PCs failed to degranulate in infected B6 TLR9-/- mice, i.p. injection of mouse IFN-beta alone led to Crp-3/-5 mRNA upregulation in B6 WT and TLR9-/- mice. In addition, modulation of Crp mRNA expression in response to T. gondii infection was abrogated in B6 IFNAR-/- mice, which lack a functional type I IFN receptor. Taken together, these data demonstrate that T. gondii induces Crp-3/-5 production and release by PCs via a TLR9-dependent production of type I IFNs. Crps have a limited direct effect against T. gondii but may indirectly affect the early control of T. gondii invasiveness by promoting the initiation of a protective Th1 response against the parasite.
PMID: 20488791 [PubMed - indexed for MEDLINE]
TLR9-dependent induction of intestinal alpha-defensins by Toxoplasma gondii
Foureau DM, Mielcarz DW, Menard LC, Schulthess J, Werts C, Vasseur V, Ryffel B, Kasper LH, Buzoni-Gatel D.
Department of Medicine, Dartmouth Medical School, Lebanon, NH 03756, USA.
Abstract
Alpha-defensins (or Cryptdins [Crps]) are a group of antimicrobial peptides produced as a component of Paneth cell (PC) secretory granules in the small intestine. In vivo ligation of TLR9 by synthetic agonists leads to PC degranulation, although the mechanism by which this occurs remains uncertain. In this report, we investigated TLR9-dependent mechanisms, triggered by the parasite Toxoplasma gondii, inducing Crp release in the lumen. Oral challenge of C57BL/6J (B6) wild-type (WT) mice with T. gondii induced TLR9 mRNA upregulation associated with a marked increase of type I IFN mRNA expression. PC secretory granules were released, and Crp-3/-5 mRNA expression by purified epithelial cells was increased following oral challenge of B6 WT mice. Although PCs failed to degranulate in infected B6 TLR9-/- mice, i.p. injection of mouse IFN-beta alone led to Crp-3/-5 mRNA upregulation in B6 WT and TLR9-/- mice. In addition, modulation of Crp mRNA expression in response to T. gondii infection was abrogated in B6 IFNAR-/- mice, which lack a functional type I IFN receptor. Taken together, these data demonstrate that T. gondii induces Crp-3/-5 production and release by PCs via a TLR9-dependent production of type I IFNs. Crps have a limited direct effect against T. gondii but may indirectly affect the early control of T. gondii invasiveness by promoting the initiation of a protective Th1 response against the parasite.
PMID: 20488791 [PubMed - indexed for MEDLINE]
P2X7 receptor-mediated killing of an intracellular parasite, Toxoplasma gondii, by human and murine macrophages
J Immunol. 2010 Jun 15;184(12):7040-6. Epub 2010 May 19.
P2X7 receptor-mediated killing of an intracellular parasite, Toxoplasma gondii, by human and murine macrophages
Lees MP, Fuller SJ, McLeod R, Boulter NR, Miller CM, Zakrzewski AM, Mui EJ, Witola WH, Coyne JJ, Hargrave AC, Jamieson SE, Blackwell JM, Wiley JS, Smith NC.
Institute for the Biotechnology of Infectious Diseases, University of Technology, Sydney, Broadway, NSW, Australia.
Abstract
The P2X7R is highly expressed on the macrophage cell surface, and activation of infected cells by extracellular ATP has been shown to kill intracellular bacteria and parasites. Furthermore, single nucleotide polymorphisms that decrease receptor function reduce the ability of human macrophages to kill Mycobacterium tuberculosis and are associated with extrapulmonary tuberculosis. In this study, we show that macrophages from people with the 1513C (rs3751143, NM_002562.4:c.1487A>C) loss-of-function P2X7R single nucleotide polymorphism are less effective in killing intracellular Toxoplasma gondii after exposure to ATP compared with macrophages from people with the 1513A wild-type allele. Supporting a P2X7R-specific effect on T. gondii, macrophages from P2X7R knockout mice (P2X7R-/-) are unable to kill T. gondii as effectively as macrophages from wild-type mice. We show that P2X7R-mediated T. gondii killing occurs in parallel with host cell apoptosis and is independent of NO production.
PMID: 20488797 [PubMed - indexed for MEDLINE]
P2X7 receptor-mediated killing of an intracellular parasite, Toxoplasma gondii, by human and murine macrophages
Lees MP, Fuller SJ, McLeod R, Boulter NR, Miller CM, Zakrzewski AM, Mui EJ, Witola WH, Coyne JJ, Hargrave AC, Jamieson SE, Blackwell JM, Wiley JS, Smith NC.
Institute for the Biotechnology of Infectious Diseases, University of Technology, Sydney, Broadway, NSW, Australia.
Abstract
The P2X7R is highly expressed on the macrophage cell surface, and activation of infected cells by extracellular ATP has been shown to kill intracellular bacteria and parasites. Furthermore, single nucleotide polymorphisms that decrease receptor function reduce the ability of human macrophages to kill Mycobacterium tuberculosis and are associated with extrapulmonary tuberculosis. In this study, we show that macrophages from people with the 1513C (rs3751143, NM_002562.4:c.1487A>C) loss-of-function P2X7R single nucleotide polymorphism are less effective in killing intracellular Toxoplasma gondii after exposure to ATP compared with macrophages from people with the 1513A wild-type allele. Supporting a P2X7R-specific effect on T. gondii, macrophages from P2X7R knockout mice (P2X7R-/-) are unable to kill T. gondii as effectively as macrophages from wild-type mice. We show that P2X7R-mediated T. gondii killing occurs in parallel with host cell apoptosis and is independent of NO production.
PMID: 20488797 [PubMed - indexed for MEDLINE]
Wednesday, June 16, 2010
Toxoplasma gondii transmembrane microneme proteins and their modular design
Mol Microbiol. 2010 Jun 9. [Epub ahead of print]
Toxoplasma gondii transmembrane microneme proteins and their modular design
Sheiner L, Santos JM, Klages N, Parussini F, Jemmely N, Friedrich N, Ward GE, Soldati-Favre D.
Department of Microbiology and Molecular Medicine, CMU, University of Geneva, 1 rue Michel-Servet, 1211 Geneva 4, Switzerland Phone: + 41 22 379 5656, Fax: + 41 22 379 5702.
Abstract
Summary Host cell invasion by the Apicomplexa critically relies on regulated secretion of transmembrane micronemal proteins (TM-MICs). Toxoplasma gondii possesses functionally non-redundant MICs complexes that participate in gliding motility, host cell attachment, moving junction formation, rhoptry secretion and invasion. The TM-MICs are released onto the parasite's surface as complexes capable of interacting with host cell receptors. Additionally, TgMIC2 simultaneously connects to the actomyosin system via binding to aldolase. During invasion these adhesive complexes are shed from the surface notably via intramembrane cleavage of the TM-MICs by a rhomboid protease. Some TM-MICs act as escorters and assure trafficking of the complexes to the micronemes. We have investigated the properties of TgMIC6, TgMIC8, TgMIC8.2, TgAMA1 and the new micronemal protein TgMIC16 with respect to interaction with aldolase, susceptibility to rhomboid cleavage and presence of trafficking signals. We conclude that several TM-MICs lack targeting information within their C-terminal domains, indicating that trafficking depends on yet unidentified proteins interacting with their ectodomains. Most TM-MICs serve as substrates for a rhomboid protease and some of them are able to bind to aldolase. We also show that the residues responsible for binding to aldolase are essential for TgAMA1 but dispensable forTgMIC6 function during invasion.
PMID: 20545864
Toxoplasma gondii transmembrane microneme proteins and their modular design
Sheiner L, Santos JM, Klages N, Parussini F, Jemmely N, Friedrich N, Ward GE, Soldati-Favre D.
Department of Microbiology and Molecular Medicine, CMU, University of Geneva, 1 rue Michel-Servet, 1211 Geneva 4, Switzerland Phone: + 41 22 379 5656, Fax: + 41 22 379 5702.
Abstract
Summary Host cell invasion by the Apicomplexa critically relies on regulated secretion of transmembrane micronemal proteins (TM-MICs). Toxoplasma gondii possesses functionally non-redundant MICs complexes that participate in gliding motility, host cell attachment, moving junction formation, rhoptry secretion and invasion. The TM-MICs are released onto the parasite's surface as complexes capable of interacting with host cell receptors. Additionally, TgMIC2 simultaneously connects to the actomyosin system via binding to aldolase. During invasion these adhesive complexes are shed from the surface notably via intramembrane cleavage of the TM-MICs by a rhomboid protease. Some TM-MICs act as escorters and assure trafficking of the complexes to the micronemes. We have investigated the properties of TgMIC6, TgMIC8, TgMIC8.2, TgAMA1 and the new micronemal protein TgMIC16 with respect to interaction with aldolase, susceptibility to rhomboid cleavage and presence of trafficking signals. We conclude that several TM-MICs lack targeting information within their C-terminal domains, indicating that trafficking depends on yet unidentified proteins interacting with their ectodomains. Most TM-MICs serve as substrates for a rhomboid protease and some of them are able to bind to aldolase. We also show that the residues responsible for binding to aldolase are essential for TgAMA1 but dispensable forTgMIC6 function during invasion.
PMID: 20545864
Determining UV Inactivation of Toxoplasma gondii Oocysts Using Cell Culture and a Mouse Bioassay
Appl Environ Microbiol. 2010 Jun 11. [Epub ahead of print]
Determining UV Inactivation of Toxoplasma gondii Oocysts Using Cell Culture and a Mouse Bioassay
Ware MW, Augustine SA, Erisman DO, See MJ, Wymer L, Hayes SL, Dubey JP, Villegas EN.
National Exposure Research Laboratory, National Risk Management Research Laboratory, U.S. Environmental Protection Agency, Cincinnati, OH 45268; Department of Biological Sciences, McMicken College of Arts and Sciences, University of Cincinnati, Cincinnati, OH 45220; Animal Parasitic Disease Laboratory, Agricultural Research Service, U.S. Department of Agriculture, Beltsville, MD, 20705.
Abstract
The effect of UV exposure on Toxoplasma gondii oocysts has not been completely defined for use in water disinfection. This study evaluated UV irradiated oocysts by three assays: a SCID mouse bioassay, an in vitro T. gondii oocyst plaque assay (TOP-assay), and a quantitative reverse-transcriptase real-time PCR (RT-qPCR) assay. The results from the animal bioassay show that 1 and 3 log10 inactivation is achieved with 4 mJ/cm(2) UV and 10 mJ/cm(2) low pressure UV, respectively. TOP-assay results, but not RT-qPCR results, correlate well with bioassay results. In conclusion, a 3 log10 inactivation of T. gondii oocysts is achieved by a 10 mJ/cm(2) low pressure UV, and the in vitro TOP-assay is a promising alternative to the mouse bioassay.
PMID: 20543052
Determining UV Inactivation of Toxoplasma gondii Oocysts Using Cell Culture and a Mouse Bioassay
Ware MW, Augustine SA, Erisman DO, See MJ, Wymer L, Hayes SL, Dubey JP, Villegas EN.
National Exposure Research Laboratory, National Risk Management Research Laboratory, U.S. Environmental Protection Agency, Cincinnati, OH 45268; Department of Biological Sciences, McMicken College of Arts and Sciences, University of Cincinnati, Cincinnati, OH 45220; Animal Parasitic Disease Laboratory, Agricultural Research Service, U.S. Department of Agriculture, Beltsville, MD, 20705.
Abstract
The effect of UV exposure on Toxoplasma gondii oocysts has not been completely defined for use in water disinfection. This study evaluated UV irradiated oocysts by three assays: a SCID mouse bioassay, an in vitro T. gondii oocyst plaque assay (TOP-assay), and a quantitative reverse-transcriptase real-time PCR (RT-qPCR) assay. The results from the animal bioassay show that 1 and 3 log10 inactivation is achieved with 4 mJ/cm(2) UV and 10 mJ/cm(2) low pressure UV, respectively. TOP-assay results, but not RT-qPCR results, correlate well with bioassay results. In conclusion, a 3 log10 inactivation of T. gondii oocysts is achieved by a 10 mJ/cm(2) low pressure UV, and the in vitro TOP-assay is a promising alternative to the mouse bioassay.
PMID: 20543052
Carbocyclic 6-benzylthioinosine analogues as subversive substrates of Toxoplasma gondii adenosine kinase
Biochem Pharmacol. 2010 Jun 9. [Epub ahead of print]
Carbocyclic 6-benzylthioinosine analogues as subversive substrates of Toxoplasma gondii adenosine kinase: Biological activities and selective toxicities
Safarjalani ON, Rais RH, Kim YA, Chu CK, Naguib FN, Kouni MH.
Department of Pharmacology and Toxicology, Center for AIDS Research, Comprehensive Cancer Center, University of Alabama at Birmingham, Birmingham, AL 35294.
Abstract
Toxoplasma gondii adenosine kinase (EC.2.7.1.20) is the major route of adenosine metabolism in this parasite. The enzyme is significantly more active than any other enzyme of the purine salvage in T. gondii and has been established as a potential chemotherapeutic target for the treatment of toxoplasmosis. Several 6-benzylthioinosines have already been identified as subversive substrates of the T. gondii but not human adenosine kinase. Therefore, these compounds are preferentially metabolized to their respective nucleotides and become selectively toxic against the parasites but not its host. In the present study, we report the testing of the metabolism of several carbocyclic 6-benzylthioinosines, as well as their efficacy as anti-toxoplasmic agents in cell culture. All the carbocyclic 6-benzylthioinosine analogues were metabolized to their 5'-monophosphate derivatives, albeit to different degrees. These results indicate that these compounds are not only ligands but also substrates of T. gondii adenosine kinase. All the carbocyclic 6-benzylthioinosine analogues showed a selective anti-toxoplasmic effect against wild type parasites, but not mutants lacking adenosine kinase. These results indicate that the oxygen atom of the sugar is not critical for substrate-binding. The efficacy of these compounds varied with the position and nature of the substitution on their phenyl ring. Moreover, none of these analogues exhibited host toxicity. The best compounds were carbocyclic 6-(p-methylbenzylthio)inosine (IC(50)=11.9muM), carbocyclic 6-(p-methoxybenzylthio)inosine (IC(50)=12.1muM), and carbocyclic 6-(p-methoxycarbonylbenzylthio)inosine (IC(50)=12.8muM). These compounds have about a 1.5-fold better efficacy relative to their corresponding 6-benzylthioinosine analogues (Rais et al., Biochem Pharmacol 2005;69:1409-19). The results further confirm that T. gondii adenosine kinase is an excellent target for chemotherapy and that carbocyclic 6-benzylthioinosines are potential antitoxoplasmic agents. Copyright © 2010. Published by Elsevier Inc.
PMID: 20541538
Carbocyclic 6-benzylthioinosine analogues as subversive substrates of Toxoplasma gondii adenosine kinase: Biological activities and selective toxicities
Safarjalani ON, Rais RH, Kim YA, Chu CK, Naguib FN, Kouni MH.
Department of Pharmacology and Toxicology, Center for AIDS Research, Comprehensive Cancer Center, University of Alabama at Birmingham, Birmingham, AL 35294.
Abstract
Toxoplasma gondii adenosine kinase (EC.2.7.1.20) is the major route of adenosine metabolism in this parasite. The enzyme is significantly more active than any other enzyme of the purine salvage in T. gondii and has been established as a potential chemotherapeutic target for the treatment of toxoplasmosis. Several 6-benzylthioinosines have already been identified as subversive substrates of the T. gondii but not human adenosine kinase. Therefore, these compounds are preferentially metabolized to their respective nucleotides and become selectively toxic against the parasites but not its host. In the present study, we report the testing of the metabolism of several carbocyclic 6-benzylthioinosines, as well as their efficacy as anti-toxoplasmic agents in cell culture. All the carbocyclic 6-benzylthioinosine analogues were metabolized to their 5'-monophosphate derivatives, albeit to different degrees. These results indicate that these compounds are not only ligands but also substrates of T. gondii adenosine kinase. All the carbocyclic 6-benzylthioinosine analogues showed a selective anti-toxoplasmic effect against wild type parasites, but not mutants lacking adenosine kinase. These results indicate that the oxygen atom of the sugar is not critical for substrate-binding. The efficacy of these compounds varied with the position and nature of the substitution on their phenyl ring. Moreover, none of these analogues exhibited host toxicity. The best compounds were carbocyclic 6-(p-methylbenzylthio)inosine (IC(50)=11.9muM), carbocyclic 6-(p-methoxybenzylthio)inosine (IC(50)=12.1muM), and carbocyclic 6-(p-methoxycarbonylbenzylthio)inosine (IC(50)=12.8muM). These compounds have about a 1.5-fold better efficacy relative to their corresponding 6-benzylthioinosine analogues (Rais et al., Biochem Pharmacol 2005;69:1409-19). The results further confirm that T. gondii adenosine kinase is an excellent target for chemotherapy and that carbocyclic 6-benzylthioinosines are potential antitoxoplasmic agents. Copyright © 2010. Published by Elsevier Inc.
PMID: 20541538
Synthesis and evaluation of anti-Toxoplasma gondii and antimicrobial activities of thiosemicarbazides, 4-thiazolidinones and 1,3,4-thiadiazoles
Eur J Med Chem. 2010 May 31. [Epub ahead of print]
Synthesis and evaluation of anti-Toxoplasma gondii and antimicrobial activities of thiosemicarbazides, 4-thiazolidinones and 1,3,4-thiadiazoles
Liesen AP, de Aquino TM, Carvalho CS, Lima VT, de Araújo JM, de Lima JG, de Faria AR, de Melo EJ, Alves AJ, Alves EW, Alves AQ, Góes AJ.
Departamento de Antibióticos, Universidade Federal de Pernambuco, Recife 50670-901, Brazil.
Abstract
In this work we reported the synthesis and evaluation of anti-Toxoplasma gondii and antimicrobial activities in vitro of three new compound series obtained from ethyl(5-methyl-1-H-imidazole-4-carboxylate): acylthiosemicarbazide analogues 3a-d, 4-thiazolidinone analogues 4a-d and 1,3,4-thiadiazole analogues 5a-d. All synthesized compounds were characterized by IR, (1)H, (13)C NMR and HRMS. The majority of the tested compounds show excellent anti-T. gondii activity when compared to hydroxyurea and sulfadiazine. In addition it was also shown that most of the compounds in this study have a better performance against intracellular tachyzoites. The results for antimicrobial activity evaluation showed weak antibacterial and antifungal activities for all the tested molecules, when compared with the standard drugs (chloramphenicol and rifampicin for antibacterial activity; nistatin and ketoconazole for antifungal activity). Copyright © 2010 Elsevier Masson SAS. All rights reserved.
PMID: 20541294
Synthesis and evaluation of anti-Toxoplasma gondii and antimicrobial activities of thiosemicarbazides, 4-thiazolidinones and 1,3,4-thiadiazoles
Liesen AP, de Aquino TM, Carvalho CS, Lima VT, de Araújo JM, de Lima JG, de Faria AR, de Melo EJ, Alves AJ, Alves EW, Alves AQ, Góes AJ.
Departamento de Antibióticos, Universidade Federal de Pernambuco, Recife 50670-901, Brazil.
Abstract
In this work we reported the synthesis and evaluation of anti-Toxoplasma gondii and antimicrobial activities in vitro of three new compound series obtained from ethyl(5-methyl-1-H-imidazole-4-carboxylate): acylthiosemicarbazide analogues 3a-d, 4-thiazolidinone analogues 4a-d and 1,3,4-thiadiazole analogues 5a-d. All synthesized compounds were characterized by IR, (1)H, (13)C NMR and HRMS. The majority of the tested compounds show excellent anti-T. gondii activity when compared to hydroxyurea and sulfadiazine. In addition it was also shown that most of the compounds in this study have a better performance against intracellular tachyzoites. The results for antimicrobial activity evaluation showed weak antibacterial and antifungal activities for all the tested molecules, when compared with the standard drugs (chloramphenicol and rifampicin for antibacterial activity; nistatin and ketoconazole for antifungal activity). Copyright © 2010 Elsevier Masson SAS. All rights reserved.
PMID: 20541294
Tuesday, June 15, 2010
POSTDOCTORAL POSITION Biochemistry, Molecular Parasitology
POSTDOCTORAL POSITION: Biochemistry, Molecular Parasitology
POSTDOCTORAL POSITION available to investigate the molecular basis of epigenetics and gene expression during development of the protozoan parasite Toxoplasma gondii. Related to the malaria parasite, Toxoplasma causes serious disease in immunocompromised (AIDS) patients due to the ability of the parasite to develop into cysts in the body. We have shown that epigenetics plays an important role in this critical developmental transition (for a recent review, see Dixon et al., 2010, Mol Biochem Parasitol). Potential projects include molecular and biochemical analyses of chromatin remodeling complexes and functional characterization of parasite mutants defective in histone modifying enzymes. See www.sullivanlab.com for more information.
Position requires a Ph.D., expertise in biochemistry and molecular biology, and excellent communication skills (speaking and writing English). Experience in molecular parasitology or chromatin biology is a plus. Submit CV and contact information for three references to Dr. Bill Sullivan (wjsulliv@iupui.edu).
Located in downtown Indianapolis, Indiana University School of Medicine (IUSM) is the second largest medical school in the US and boasts an outstanding intellectual atmosphere and core facilities. IUSM was nationally ranked in the Top 30 Best Places to Work for Postdocs. IUSM is an equal opportunity employer.
POSTDOCTORAL POSITION available to investigate the molecular basis of epigenetics and gene expression during development of the protozoan parasite Toxoplasma gondii. Related to the malaria parasite, Toxoplasma causes serious disease in immunocompromised (AIDS) patients due to the ability of the parasite to develop into cysts in the body. We have shown that epigenetics plays an important role in this critical developmental transition (for a recent review, see Dixon et al., 2010, Mol Biochem Parasitol). Potential projects include molecular and biochemical analyses of chromatin remodeling complexes and functional characterization of parasite mutants defective in histone modifying enzymes. See www.sullivanlab.com for more information.
Position requires a Ph.D., expertise in biochemistry and molecular biology, and excellent communication skills (speaking and writing English). Experience in molecular parasitology or chromatin biology is a plus. Submit CV and contact information for three references to Dr. Bill Sullivan (wjsulliv@iupui.edu).
Located in downtown Indianapolis, Indiana University School of Medicine (IUSM) is the second largest medical school in the US and boasts an outstanding intellectual atmosphere and core facilities. IUSM was nationally ranked in the Top 30 Best Places to Work for Postdocs. IUSM is an equal opportunity employer.
Sunday, June 13, 2010
Thymosin alpha1 to harness immunity to pathogens after haploidentical hematopoietic transplantation
Ann N Y Acad Sci. 2010 Apr;1194:153-61.
Thymosin alpha1 to harness immunity to pathogens after haploidentical hematopoietic transplantation
Perruccio K, Bonifazi P, Topini F, Tosti A, Bozza S, Aloisi T, Carotti A, Aversa F, Martelli MF, Romani L, Velardi A.
Division of Hematology and Clinical Immunology, University of Perugia, Perugia, Italy.
Abstract
We designed a phase I/II clinical study to determine safety and efficacy of thymosin alpha1 (Talpha1) administration in recipients of one HLA haplotype (haploidentical) stem cell transplants for hematologic malignancies. Talpha1 administration did not cause acute or chronic graft versus host disease and was associated with significant improvement in polymorphonuclear (phagocytosis) and dendritic cell (phagocytosis, expression of costimulatory molecules, and cytokine production) functions. It was also associated with increased T-cell counts and earlier appearance of functional pathogen-specific T cell responses (by a sensitive limiting dilution assay that detects frequency of T cells specific for Aspergillus, Candida, CMV, ADV, VZV, HSV, Toxoplasma). Five of six haploidentical transplant recipients who received Talpha1 are alive and disease free at a median follow-up of 10 months after transplantation (range: 5-20). They experienced only a single nonlethal infectious episode and one patient developed fatal immune hemolytic anemia. At this very early stage of the clinical trial, we conclude Talpha1 administration is safe and may impact favorably on immune function. Larger numbers of patients and longer follow-up are, of course, needed to assess its impact on survival.
PMID: 20536464 [PubMed - in process]
Thymosin alpha1 to harness immunity to pathogens after haploidentical hematopoietic transplantation
Perruccio K, Bonifazi P, Topini F, Tosti A, Bozza S, Aloisi T, Carotti A, Aversa F, Martelli MF, Romani L, Velardi A.
Division of Hematology and Clinical Immunology, University of Perugia, Perugia, Italy.
Abstract
We designed a phase I/II clinical study to determine safety and efficacy of thymosin alpha1 (Talpha1) administration in recipients of one HLA haplotype (haploidentical) stem cell transplants for hematologic malignancies. Talpha1 administration did not cause acute or chronic graft versus host disease and was associated with significant improvement in polymorphonuclear (phagocytosis) and dendritic cell (phagocytosis, expression of costimulatory molecules, and cytokine production) functions. It was also associated with increased T-cell counts and earlier appearance of functional pathogen-specific T cell responses (by a sensitive limiting dilution assay that detects frequency of T cells specific for Aspergillus, Candida, CMV, ADV, VZV, HSV, Toxoplasma). Five of six haploidentical transplant recipients who received Talpha1 are alive and disease free at a median follow-up of 10 months after transplantation (range: 5-20). They experienced only a single nonlethal infectious episode and one patient developed fatal immune hemolytic anemia. At this very early stage of the clinical trial, we conclude Talpha1 administration is safe and may impact favorably on immune function. Larger numbers of patients and longer follow-up are, of course, needed to assess its impact on survival.
PMID: 20536464 [PubMed - in process]
Monocytes mediate mucosal immunity to Toxoplasma gondii
Curr Opin Immunol. 2010 May 26. [Epub ahead of print]
Monocytes mediate mucosal immunity to Toxoplasma gondii
Dunay IR, Sibley LD.
Department of Neuropathology, University of Freiburg, Breisacherstrasse 64, Freiburg 79106, Germany.
Abstract
Toxoplasma gondii is a widespread protozoan parasite that causes water and foodborne infections in humans. The parasite not only infects intestinal enterocytes but also spreads by migration across the epithelial layer and entry into the submucosa. Within the lamina propria, innate immune responses lead to initial parasite control, although the infection disseminates widely and persists chronically despite adaptive immunity. Inflammatory monocytes exit the bone marrow and home to the lamina propria where they express antimicrobial effector functions that control infection. Ablation of the signals for recruitment of inflammatory monocytes in the mouse results in uncontrolled parasite replication, extensive infiltration of neutrophils, intestinal necrosis, and rapid death. Inflammatory monocytes play a pivotal role in mucosal immunity against T. gondii, and likely other enteric pathogens. Copyright © 2010 Elsevier Ltd. All rights reserved.
PMID: 20537517 [PubMed - as supplied by publisher]
Monocytes mediate mucosal immunity to Toxoplasma gondii
Dunay IR, Sibley LD.
Department of Neuropathology, University of Freiburg, Breisacherstrasse 64, Freiburg 79106, Germany.
Abstract
Toxoplasma gondii is a widespread protozoan parasite that causes water and foodborne infections in humans. The parasite not only infects intestinal enterocytes but also spreads by migration across the epithelial layer and entry into the submucosa. Within the lamina propria, innate immune responses lead to initial parasite control, although the infection disseminates widely and persists chronically despite adaptive immunity. Inflammatory monocytes exit the bone marrow and home to the lamina propria where they express antimicrobial effector functions that control infection. Ablation of the signals for recruitment of inflammatory monocytes in the mouse results in uncontrolled parasite replication, extensive infiltration of neutrophils, intestinal necrosis, and rapid death. Inflammatory monocytes play a pivotal role in mucosal immunity against T. gondii, and likely other enteric pathogens. Copyright © 2010 Elsevier Ltd. All rights reserved.
PMID: 20537517 [PubMed - as supplied by publisher]
Apicomplexan perforin-like proteins
Commun Integr Biol. 2010 Jan;3(1):18-23.
Apicomplexan perforin-like proteins
Kafsack BF, Carruthers VB.
Department of Microbiology and Immunology; University of Michigan; Ann Arbor, MI USA.
Abstract
Numerous perforin-like proteins are encoded in the genomes of apicomplexan parasites, where they are expressed in various life-cycle stages and play critical roles in pathogenesis and lifecycle progression. These ApiPLPs are characterized by the presence of a MACPF domain, responsible for pore-formation in target membranes in a number of systems, including many bacterial pathogens and effector cells of the immune response. ApiPLP MACPF domains maintain the critical structural elements but are often present in new and intriguing domain arrangements. Recent work in Toxoplasma and Plasmodium has shown that ApiPLPs are important for breaching membranes during parasite egress and cell traversal. Here we present an overview of this important protein family from a structural, functional and phylogenetic perspective across the Apicomplexa.
PMID: 20539776 [PubMed - in process]
Apicomplexan perforin-like proteins
Kafsack BF, Carruthers VB.
Department of Microbiology and Immunology; University of Michigan; Ann Arbor, MI USA.
Abstract
Numerous perforin-like proteins are encoded in the genomes of apicomplexan parasites, where they are expressed in various life-cycle stages and play critical roles in pathogenesis and lifecycle progression. These ApiPLPs are characterized by the presence of a MACPF domain, responsible for pore-formation in target membranes in a number of systems, including many bacterial pathogens and effector cells of the immune response. ApiPLP MACPF domains maintain the critical structural elements but are often present in new and intriguing domain arrangements. Recent work in Toxoplasma and Plasmodium has shown that ApiPLPs are important for breaching membranes during parasite egress and cell traversal. Here we present an overview of this important protein family from a structural, functional and phylogenetic perspective across the Apicomplexa.
PMID: 20539776 [PubMed - in process]
Saturday, June 12, 2010
A common red algal origin of the apicomplexan, dinoflagellate, and heterokont plastids
Proc Natl Acad Sci U S A. 2010 Jun 1. [Epub ahead of print]
A common red algal origin of the apicomplexan, dinoflagellate, and heterokont plastids
Janouskovec J, Horák A, Oborník M, Lukes J, Keeling PJ.
Department of Botany, University of British Columbia, Vancouver, BC, Canada V6T1Z4.
Abstract
The discovery of a nonphotosynthetic plastid in malaria and other apicomplexan parasites has sparked a contentious debate about its evolutionary origin. Molecular data have led to conflicting conclusions supporting either its green algal origin or red algal origin, perhaps in common with the plastid of related dinoflagellates. This distinction is critical to our understanding of apicomplexan evolution and the evolutionary history of endosymbiosis and photosynthesis; however, the two plastids are nearly impossible to compare due to their nonoverlapping information content. Here we describe the complete plastid genome sequences and plastid-associated data from two independent photosynthetic lineages represented by Chromera velia and an undescribed alga CCMP3155 that we show are closely related to apicomplexans. These plastids contain a suite of features retained in either apicomplexan (four plastid membranes, the ribosomal superoperon, conserved gene order) or dinoflagellate plastids (form II Rubisco acquired by horizontal transfer, transcript polyuridylylation, thylakoids stacked in triplets) and encode a full collective complement of their reduced gene sets. Together with whole plastid genome phylogenies, these characteristics provide multiple lines of evidence that the extant plastids of apicomplexans and dinoflagellates were inherited by linear descent from a common red algal endosymbiont. Our phylogenetic analyses also support their close relationship to plastids of heterokont algae, indicating they all derive from the same endosymbiosis. Altogether, these findings support a relatively simple path of linear descent for the evolution of photosynthesis in a large proportion of algae and emphasize plastid loss in several lineages (e.g., ciliates, Cryptosporidium, and Phytophthora).
PMID: 20534454 [PubMed - as supplied by publisher]
A common red algal origin of the apicomplexan, dinoflagellate, and heterokont plastids
Janouskovec J, Horák A, Oborník M, Lukes J, Keeling PJ.
Department of Botany, University of British Columbia, Vancouver, BC, Canada V6T1Z4.
Abstract
The discovery of a nonphotosynthetic plastid in malaria and other apicomplexan parasites has sparked a contentious debate about its evolutionary origin. Molecular data have led to conflicting conclusions supporting either its green algal origin or red algal origin, perhaps in common with the plastid of related dinoflagellates. This distinction is critical to our understanding of apicomplexan evolution and the evolutionary history of endosymbiosis and photosynthesis; however, the two plastids are nearly impossible to compare due to their nonoverlapping information content. Here we describe the complete plastid genome sequences and plastid-associated data from two independent photosynthetic lineages represented by Chromera velia and an undescribed alga CCMP3155 that we show are closely related to apicomplexans. These plastids contain a suite of features retained in either apicomplexan (four plastid membranes, the ribosomal superoperon, conserved gene order) or dinoflagellate plastids (form II Rubisco acquired by horizontal transfer, transcript polyuridylylation, thylakoids stacked in triplets) and encode a full collective complement of their reduced gene sets. Together with whole plastid genome phylogenies, these characteristics provide multiple lines of evidence that the extant plastids of apicomplexans and dinoflagellates were inherited by linear descent from a common red algal endosymbiont. Our phylogenetic analyses also support their close relationship to plastids of heterokont algae, indicating they all derive from the same endosymbiosis. Altogether, these findings support a relatively simple path of linear descent for the evolution of photosynthesis in a large proportion of algae and emphasize plastid loss in several lineages (e.g., ciliates, Cryptosporidium, and Phytophthora).
PMID: 20534454 [PubMed - as supplied by publisher]
Evidence for associations between the purinergic receptor P2X(7) (P2RX7) and toxoplasmosis
Genes Immun. 2010 Jun 10. [Epub ahead of print]
Evidence for associations between the purinergic receptor P2X(7) (P2RX7) and toxoplasmosis
Jamieson SE, Peixoto-Rangel AL, Hargrave AC, Roubaix LA, Mui EJ, Boulter NR, Miller EN, Fuller SJ, Wiley JS, Castellucci L, Boyer K, Peixe RG, Kirisits MJ, Elias LD, Coyne JJ, Correa-Oliveira R, Sautter M, Smith NC, Lees MP, Swisher CN, Heydemann P, Noble AG, Patel D, Bardo D, Burrowes D, McLone D, Roizen N, Withers S, Bahia-Oliveira LM, McLeod R, Blackwell JM.
[1] Cambridge Institute for Medical Research and Department of Medicine, University of Cambridge School of Clinical Medicine, Cambridge, UK [2] Telethon Institute for Child Health Research, Centre for Child Health Research, The University of Western Australia, Subiaco, Western Australia, Australia.
Abstract
Congenital Toxoplasma gondii infection can result in intracranial calcification, hydrocephalus and retinochoroiditis. Acquired infection is commonly associated with ocular disease. Pathology is characterized by strong proinflammatory responses. Ligation of ATP by purinergic receptor P2X(7), encoded by P2RX7, stimulates proinflammatory cytokines and can lead directly to killing of intracellular pathogens. To determine whether P2X(7) has a role in susceptibility to congenital toxoplasmosis, we examined polymorphisms at P2RX7 in 149 child/parent trios from North America. We found association (FBAT Z-scores +/-2.429; P=0.015) between the derived C(+)G(-) allele (f=0.68; OR=2.06; 95% CI: 1.14-3.75) at single-nucleotide polymorphism (SNP) rs1718119 (1068T>C; Thr-348-Ala), and a second synonymous variant rs1621388 in linkage disequilibrium with it, and clinical signs of disease per se. Analysis of clinical subgroups showed no association with hydrocephalus, with effect sizes for associations with retinal disease and brain calcifications enhanced (OR=3.0-4.25; 0.004
PMID: 20535134 [PubMed - as supplied by publisher]
Evidence for associations between the purinergic receptor P2X(7) (P2RX7) and toxoplasmosis
Jamieson SE, Peixoto-Rangel AL, Hargrave AC, Roubaix LA, Mui EJ, Boulter NR, Miller EN, Fuller SJ, Wiley JS, Castellucci L, Boyer K, Peixe RG, Kirisits MJ, Elias LD, Coyne JJ, Correa-Oliveira R, Sautter M, Smith NC, Lees MP, Swisher CN, Heydemann P, Noble AG, Patel D, Bardo D, Burrowes D, McLone D, Roizen N, Withers S, Bahia-Oliveira LM, McLeod R, Blackwell JM.
[1] Cambridge Institute for Medical Research and Department of Medicine, University of Cambridge School of Clinical Medicine, Cambridge, UK [2] Telethon Institute for Child Health Research, Centre for Child Health Research, The University of Western Australia, Subiaco, Western Australia, Australia.
Abstract
Congenital Toxoplasma gondii infection can result in intracranial calcification, hydrocephalus and retinochoroiditis. Acquired infection is commonly associated with ocular disease. Pathology is characterized by strong proinflammatory responses. Ligation of ATP by purinergic receptor P2X(7), encoded by P2RX7, stimulates proinflammatory cytokines and can lead directly to killing of intracellular pathogens. To determine whether P2X(7) has a role in susceptibility to congenital toxoplasmosis, we examined polymorphisms at P2RX7 in 149 child/parent trios from North America. We found association (FBAT Z-scores +/-2.429; P=0.015) between the derived C(+)G(-) allele (f=0.68; OR=2.06; 95% CI: 1.14-3.75) at single-nucleotide polymorphism (SNP) rs1718119 (1068T>C; Thr-348-Ala), and a second synonymous variant rs1621388 in linkage disequilibrium with it, and clinical signs of disease per se. Analysis of clinical subgroups showed no association with hydrocephalus, with effect sizes for associations with retinal disease and brain calcifications enhanced (OR=3.0-4.25; 0.004
PMID: 20535134 [PubMed - as supplied by publisher]
Sunday, June 06, 2010
High-Resolution Characterization of Toxoplasma gondii Transcriptome with a Massive Parallel Sequencing Method
DNA Res. 2010 Jun 3. [Epub ahead of print]
High-Resolution Characterization of Toxoplasma gondii Transcriptome with a Massive Parallel Sequencing Method
Yamagishi J, Wakaguri H, Ueno A, Goo YK, Tolba M, Igarashi M, Nishikawa Y, Sugimoto C, Sugano S, Suzuki Y, Watanabe J, Xuan X.
1National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Japan.
Abstract
For the last couple of years, a method that permits the collection of precise positional information of transcriptional start sites (TSSs) together with digital information of the gene-expression levels in a high-throughput manner was established. We applied this novel method, 'tss-seq', to elucidate the transcriptome of tachyzoites of the Toxoplasma gondii, which resulted in the identification of 124 000 TSSs, and they were clustered into 10 000 transcription regions (TRs) with a statistics-based analysis. The TRs and annotated ORFs were paired, resulting in the identification of 30% of the TRs and 40% of the ORFs without their counterparts, which predicted undiscovered genes and stage-specific transcriptions, respectively. The massive data for TSSs make it possible to execute the first systematic analysis of the T. gondii core promoter structure, and the information showed that T. gondii utilized an initiator-like motif for their transcription in the major and novel motif, the downstream thymidine cluster, which was similar to the Y patch observed in plants. This encyclopaedic analysis also suggested that the TATA box, and the other well-known core promoter elements were hardly utilized.
PMID: 20522451
High-Resolution Characterization of Toxoplasma gondii Transcriptome with a Massive Parallel Sequencing Method
Yamagishi J, Wakaguri H, Ueno A, Goo YK, Tolba M, Igarashi M, Nishikawa Y, Sugimoto C, Sugano S, Suzuki Y, Watanabe J, Xuan X.
1National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Japan.
Abstract
For the last couple of years, a method that permits the collection of precise positional information of transcriptional start sites (TSSs) together with digital information of the gene-expression levels in a high-throughput manner was established. We applied this novel method, 'tss-seq', to elucidate the transcriptome of tachyzoites of the Toxoplasma gondii, which resulted in the identification of 124 000 TSSs, and they were clustered into 10 000 transcription regions (TRs) with a statistics-based analysis. The TRs and annotated ORFs were paired, resulting in the identification of 30% of the TRs and 40% of the ORFs without their counterparts, which predicted undiscovered genes and stage-specific transcriptions, respectively. The massive data for TSSs make it possible to execute the first systematic analysis of the T. gondii core promoter structure, and the information showed that T. gondii utilized an initiator-like motif for their transcription in the major and novel motif, the downstream thymidine cluster, which was similar to the Y patch observed in plants. This encyclopaedic analysis also suggested that the TATA box, and the other well-known core promoter elements were hardly utilized.
PMID: 20522451
A Complex Small RNA Repertoire Is Generated by a Plant/Fungal-Like Machinery and Effected by a Metazoan-Like Argonaute in Toxoplasma
PLoS Pathog. 2010 May 27;6(5):e1000920.
A Complex Small RNA Repertoire Is Generated by a Plant/Fungal-Like Machinery and Effected by a Metazoan-Like Argonaute in the Single-Cell Human Parasite Toxoplasma gondii
Braun L, Cannella D, Ortet P, Barakat M, Sautel CF, Kieffer S, Garin J, Bastien O, Voinnet O, Hakimi MA.
Laboratoire Adaptation et Pathogénie des Micro-organismes, CNRS UMR 5163 - ATIP+ group, Université Joseph Fourier, Grenoble, France.
Abstract
In RNA silencing, small RNAs produced by the RNase-III Dicer guide Argonaute-like proteins as part of RNA-induced silencing complexes (RISC) to regulate gene expression transcriptionally or post-transcriptionally. Here, we have characterized the RNA silencing machinery and exhaustive small RNAome of Toxoplasma gondii, member of the Apicomplexa, a phylum of animal- and human-infecting parasites that cause extensive health and economic damages to human populations worldwide. Remarkably, the small RNA-generating machinery of Toxoplasma is phylogenetically and functionally related to that of plants and fungi, and accounts for an exceptionally diverse array of small RNAs. This array includes conspicuous populations of repeat-associated small interfering RNA (siRNA), which, as in plants, likely generate and maintain heterochromatin at DNA repeats and satellites. Toxoplasma small RNAs also include many microRNAs with clear metazoan-like features whose accumulation is sometimes extremely high and dynamic, an unexpected finding given that Toxoplasma is a unicellular protist. Both plant-like heterochromatic small RNAs and metazoan-like microRNAs bind to a single Argonaute protein, Tg-AGO. Toxoplasma miRNAs co-sediment with polyribosomes, and thus, are likely to act as translational regulators, consistent with the lack of catalytic residues in Tg-AGO. Mass spectrometric analyses of the Tg-AGO protein complex revealed a common set of virtually all known RISC components so far characterized in human and Drosophila, as well as novel proteins involved in RNA metabolism. In agreement with its loading with heterochromatic small RNAs, Tg-AGO also associates substoichiometrically with components of known chromatin-repressing complexes. Thus, a puzzling patchwork of silencing processor and effector proteins from plant, fungal and metazoan origin accounts for the production and action of an unsuspected variety of small RNAs in the single-cell parasite Toxoplasma and possibly in other apicomplexans. This study establishes Toxoplasma as a unique model system for studying the evolution and molecular mechanisms of RNA silencing among eukaryotes.
PMID: 20523899
A Complex Small RNA Repertoire Is Generated by a Plant/Fungal-Like Machinery and Effected by a Metazoan-Like Argonaute in the Single-Cell Human Parasite Toxoplasma gondii
Braun L, Cannella D, Ortet P, Barakat M, Sautel CF, Kieffer S, Garin J, Bastien O, Voinnet O, Hakimi MA.
Laboratoire Adaptation et Pathogénie des Micro-organismes, CNRS UMR 5163 - ATIP+ group, Université Joseph Fourier, Grenoble, France.
Abstract
In RNA silencing, small RNAs produced by the RNase-III Dicer guide Argonaute-like proteins as part of RNA-induced silencing complexes (RISC) to regulate gene expression transcriptionally or post-transcriptionally. Here, we have characterized the RNA silencing machinery and exhaustive small RNAome of Toxoplasma gondii, member of the Apicomplexa, a phylum of animal- and human-infecting parasites that cause extensive health and economic damages to human populations worldwide. Remarkably, the small RNA-generating machinery of Toxoplasma is phylogenetically and functionally related to that of plants and fungi, and accounts for an exceptionally diverse array of small RNAs. This array includes conspicuous populations of repeat-associated small interfering RNA (siRNA), which, as in plants, likely generate and maintain heterochromatin at DNA repeats and satellites. Toxoplasma small RNAs also include many microRNAs with clear metazoan-like features whose accumulation is sometimes extremely high and dynamic, an unexpected finding given that Toxoplasma is a unicellular protist. Both plant-like heterochromatic small RNAs and metazoan-like microRNAs bind to a single Argonaute protein, Tg-AGO. Toxoplasma miRNAs co-sediment with polyribosomes, and thus, are likely to act as translational regulators, consistent with the lack of catalytic residues in Tg-AGO. Mass spectrometric analyses of the Tg-AGO protein complex revealed a common set of virtually all known RISC components so far characterized in human and Drosophila, as well as novel proteins involved in RNA metabolism. In agreement with its loading with heterochromatic small RNAs, Tg-AGO also associates substoichiometrically with components of known chromatin-repressing complexes. Thus, a puzzling patchwork of silencing processor and effector proteins from plant, fungal and metazoan origin accounts for the production and action of an unsuspected variety of small RNAs in the single-cell parasite Toxoplasma and possibly in other apicomplexans. This study establishes Toxoplasma as a unique model system for studying the evolution and molecular mechanisms of RNA silencing among eukaryotes.
PMID: 20523899
Type I strains in human toxoplasmosis: myth or reality?
Future Microbiol. 2010 Jun;5:841-3.
Type I strains in human toxoplasmosis: myth or reality?
Ajzenberg D.
Centre National de Référence (CNR) Toxoplasmose/Toxoplasma Biological Resource Center (BRC), Centre Hospitalier-Universitaire Dupuytren, Limoges, 87042, France and Laboratoire de Parasitologie-Mycologie, EA 3174-NETEC, Faculté de Médecine, Université de Limoges, Limoges, 87025, France. ajz@unilim.fr.
PMID: 20521929
Type I strains in human toxoplasmosis: myth or reality?
Ajzenberg D.
Centre National de Référence (CNR) Toxoplasmose/Toxoplasma Biological Resource Center (BRC), Centre Hospitalier-Universitaire Dupuytren, Limoges, 87042, France and Laboratoire de Parasitologie-Mycologie, EA 3174-NETEC, Faculté de Médecine, Université de Limoges, Limoges, 87025, France. ajz@unilim.fr.
PMID: 20521929
Friday, June 04, 2010
Absence of Both IL-7 and IL-15 Severely Impairs the Development of CD8 T Cell Response against Toxoplasma gondii
PLoS One. 2010 May 26;5(5):e10842.
Absence of Both IL-7 and IL-15 Severely Impairs the Development of CD8 T Cell Response against Toxoplasma gondii
Bhadra R, Guan H, Khan IA.
Department of Microbiology, Immunology and Tropical Medicine, George Washington University, Washington, D. C., United States of America.
Abstract
CD8(+) T cells play an essential role in the protection against both acute as well as chronic Toxoplasma gondii infection. Although the role of IL-15 has been reported to be important for the development of long-term CD8(+) T cell immunity against the pathogen, the simultaneous roles played by both IL-15 and related gamma-chain family cytokine IL-7 in the generation of this response during acute phase of infection has not been described. We demonstrate that while lack of IL-7 or IL-15 alone has minimal impact on splenic CD8(+) T cell maturation or effector function development during acute Toxoplasmosis, absence of both IL-7 and IL-15 only in the context of infection severely down-regulates the development of a potent CD8(+) T cell response. This impairment is characterized by reduction in CD44 expression, IFN-gamma production, proliferation and cytotoxicity. However, attenuated maturation and decreased effector functions in these mice are essentially downstream consequences of reduced number of antigen-specific CD8(+) T cells. Interestingly, the absence of both cytokines did not impair initial CD8(+) T cell generation but affected their survival and differentiation into memory phenotype IL-7Ralpha(hi) cells. Significantly lack of both cytokines severely affected expression of Bcl-2, an anti-apoptotic protein, but minimally affected proliferation. The overarching role played by these cytokines in eliciting a potent CD8(+) T cell immunity against T. gondii infection is further evidenced by poor survival and high parasite burden in anti IL-7 treated IL-15(-/-) mice. These studies demonstrate that the two cytokines, IL-7 and IL-15, are exclusively important for the development of protective CD8(+) T cell immune response against T. gondii. To the best of our knowledge this synergism between IL-7 and IL-15 in generating an optimal CD8(+) T cell immunity against intracellular parasite or any other infectious disease model has not been previously reported.
PMID: 20520779 [PubMed - in process]
Absence of Both IL-7 and IL-15 Severely Impairs the Development of CD8 T Cell Response against Toxoplasma gondii
Bhadra R, Guan H, Khan IA.
Department of Microbiology, Immunology and Tropical Medicine, George Washington University, Washington, D. C., United States of America.
Abstract
CD8(+) T cells play an essential role in the protection against both acute as well as chronic Toxoplasma gondii infection. Although the role of IL-15 has been reported to be important for the development of long-term CD8(+) T cell immunity against the pathogen, the simultaneous roles played by both IL-15 and related gamma-chain family cytokine IL-7 in the generation of this response during acute phase of infection has not been described. We demonstrate that while lack of IL-7 or IL-15 alone has minimal impact on splenic CD8(+) T cell maturation or effector function development during acute Toxoplasmosis, absence of both IL-7 and IL-15 only in the context of infection severely down-regulates the development of a potent CD8(+) T cell response. This impairment is characterized by reduction in CD44 expression, IFN-gamma production, proliferation and cytotoxicity. However, attenuated maturation and decreased effector functions in these mice are essentially downstream consequences of reduced number of antigen-specific CD8(+) T cells. Interestingly, the absence of both cytokines did not impair initial CD8(+) T cell generation but affected their survival and differentiation into memory phenotype IL-7Ralpha(hi) cells. Significantly lack of both cytokines severely affected expression of Bcl-2, an anti-apoptotic protein, but minimally affected proliferation. The overarching role played by these cytokines in eliciting a potent CD8(+) T cell immunity against T. gondii infection is further evidenced by poor survival and high parasite burden in anti IL-7 treated IL-15(-/-) mice. These studies demonstrate that the two cytokines, IL-7 and IL-15, are exclusively important for the development of protective CD8(+) T cell immune response against T. gondii. To the best of our knowledge this synergism between IL-7 and IL-15 in generating an optimal CD8(+) T cell immunity against intracellular parasite or any other infectious disease model has not been previously reported.
PMID: 20520779 [PubMed - in process]
Disseminated toxoplasmosis in an immunocompetent patient from Peruvian Amazon
Rev Inst Med Trop Sao Paulo. 2010 Apr;52(2):107-10.
Disseminated toxoplasmosis in an immunocompetent patient from Peruvian Amazon
Nunura J, Vásquez T, Endo S, Salazar D, Rodriguez A, Pereyra S, Solis H.
Ministerio de Salud, Lima, Perú
Abstract
We report a case of severe toxoplasmosis in an immunocompetent patient, characterized by pneumonia, retinochoroiditis, hepatitis and myositis. Diagnosis was confirmed by serology, T. gondii in thick blood smear and presence of bradyzoites in muscle biopsy. Treatment with pyrimethamine plus sulfadoxine was successful but visual acuity and hip extension were partially recovered. This is the first case report of severe toxoplasmosis in an immunocompetent patient from Peru.
PMID: 20464132 [PubMed - indexed for MEDLINE]
Disseminated toxoplasmosis in an immunocompetent patient from Peruvian Amazon
Nunura J, Vásquez T, Endo S, Salazar D, Rodriguez A, Pereyra S, Solis H.
Ministerio de Salud, Lima, Perú
Abstract
We report a case of severe toxoplasmosis in an immunocompetent patient, characterized by pneumonia, retinochoroiditis, hepatitis and myositis. Diagnosis was confirmed by serology, T. gondii in thick blood smear and presence of bradyzoites in muscle biopsy. Treatment with pyrimethamine plus sulfadoxine was successful but visual acuity and hip extension were partially recovered. This is the first case report of severe toxoplasmosis in an immunocompetent patient from Peru.
PMID: 20464132 [PubMed - indexed for MEDLINE]
Thursday, June 03, 2010
Toxoplasma gondii: determinants of tachyzoite to bradyzoite conversion
Parasitol Res. 2010 Jun 1. [Epub ahead of print]
Toxoplasma gondii: determinants of tachyzoite to bradyzoite conversion
Skariah S, McIntyre MK, Mordue DG.
Department of Microbiology and Immunology, New York Medical College, Valhalla, NY, 10595, USA.
Abstract
Apicomplexa are primarily obligate intracellular protozoa that have evolved complex developmental stages important for pathogenesis and transmission. Toxoplasma gondii, responsible for the disease toxoplasmosis, has the broadest host range of the Apicomplexa as it infects virtually any warm-blooded vertebrate host. Key to T. gondii's pathogenesis is its ability to differentiate from a rapidly replicating tachyzoite stage during acute infection to a relatively non-immunogenic, dormant bradyzoite stage contained in tissue cysts. These bradyzoite cysts can reconvert back to tachyzoites years later causing serious pathology and death if a person becomes immune-compromised. Like the sexual stage sporozoites, bradyzoites are also orally infectious and a major contributor to transmission. Because of the critical role of stage conversion to pathogenesis and transmission, a major research focus is aimed at identifying molecular mediators and pathways that regulate differentiation. Tachyzoite to bradyzoite development can occur spontaneously in vitro and be induced in response to exogenous stress including but not limited to host immunity. The purpose of this review is to explore the potential contributors to stage differentiation in infection and how a determination is made by the parasite to differentiate from tachyzoites to bradyzoites.
PMID: 20514494 [PubMed - as supplied by publisher]
Toxoplasma gondii: determinants of tachyzoite to bradyzoite conversion
Skariah S, McIntyre MK, Mordue DG.
Department of Microbiology and Immunology, New York Medical College, Valhalla, NY, 10595, USA.
Abstract
Apicomplexa are primarily obligate intracellular protozoa that have evolved complex developmental stages important for pathogenesis and transmission. Toxoplasma gondii, responsible for the disease toxoplasmosis, has the broadest host range of the Apicomplexa as it infects virtually any warm-blooded vertebrate host. Key to T. gondii's pathogenesis is its ability to differentiate from a rapidly replicating tachyzoite stage during acute infection to a relatively non-immunogenic, dormant bradyzoite stage contained in tissue cysts. These bradyzoite cysts can reconvert back to tachyzoites years later causing serious pathology and death if a person becomes immune-compromised. Like the sexual stage sporozoites, bradyzoites are also orally infectious and a major contributor to transmission. Because of the critical role of stage conversion to pathogenesis and transmission, a major research focus is aimed at identifying molecular mediators and pathways that regulate differentiation. Tachyzoite to bradyzoite development can occur spontaneously in vitro and be induced in response to exogenous stress including but not limited to host immunity. The purpose of this review is to explore the potential contributors to stage differentiation in infection and how a determination is made by the parasite to differentiate from tachyzoites to bradyzoites.
PMID: 20514494 [PubMed - as supplied by publisher]
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