Saturday, September 29, 2007

Toxo possesses a receptor for activated C kinase ortholog

Biochem Biophys Res Commun. 2007 Sep 19; [Epub ahead of print]

Toxoplasma gondii possesses a receptor for activated C kinase ortholog

Moran JM, Smith SS, Hager KM

Receptor for activated C kinase 1 (RACK1) has been implicated in multiple protein-protein interactions including functioning as a scaffolding protein for signaling molecules. We report the cloning and cellular localization of a RACK1 ortholog (TgRACK1) in the opportunistic pathogen Toxoplasma gondii. The full-length transcript possesses a predicted ORF of 966bp and codes for a protein of approximately 35kDa molecular weight. Molecular analysis of TgRACK1 reveals the presence of seven WD40 repeat motifs. TgRACK1 was tagged with a FLAG epitope and stably expressed in RH parasites. FLAG-TgRACK1 localizes to the parasite cytoplasm and nucleus. Immunoprecipitation (IP) of FLAG-TgRACK1 from highly purified extracellular parasites followed by immunoblot analysis reveals an interaction between TgbetaCOP and FLAG-TgRACK1. This is the first demonstration of an interaction between a betaCOP subunit and the RACK1 protein. This result is of interest given that a signaling event precedes protein secretion and parasite invasion.

Friday, September 28, 2007

Localized recrudescence of Toxo infections in the CNS of immunocompromised mice by bioluminescence imaging

Microbes Infect. 2007 Jun 10; [Epub ahead of print]

Localized recrudescence of Toxoplasma infections in the central nervous system of immunocompromised mice assessed by in vivo bioluminescence imaging

Dellacasa-Lindberg I, Hitziger N, Barragan A

Center for Infectious Medicine, Department of Medicine, and Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, 171 77 Stockholm, Sweden; Swedish Institute for Infectious Disease Control, 171 82 Stockholm, Sweden.

Reactivation of infection in the central nervous system (CNS) with the opportunistic parasite Toxoplasma gondii is a major concern in chronically infected immunocompromised individuals. Yet, the pathophysiology associated with recrudescence of infection remains poorly characterized. The onset of acute reactivated Toxoplasma encephalitis in the murine model was assessed using bioluminescence imaging as a spatio-temporal indicator. An uneven distribution of recrudescence of infection in the CNS was found. Foci of recrudescence after immunosuppression were most commonly located in frontal and parietal cortex, whereas little infection was found in the cerebellum. Recrudescence was also more common in grey matter than in white matter. Pathology was exacerbated in mice deficient in interferon gamma receptors (IFNgammaR(-/-)) corroborating the importance of interferon gamma (IFNgamma) for control of CNS infection. Analysis of parasitic foci identified abundant leukocyte infiltration (CD45(+), CD4(+), CD8(+), F4/80(+) cells) in the vicinity of replicating parasites and microvasculature. This is the first report that addresses the suborganic localization of acute Toxoplasma encephalitis in the murine model. Collectively, the findings suggest that the localization of reactivation foci in the CNS, in conjunction with immune responses, influences the outcome of acute reactivated Toxoplasma encephalitis.

PMID: 17897859 [PubMed - as supplied by publisher]

Wednesday, September 26, 2007

Autoantibodies in nonautoimmune individuals during infections

Ann N Y Acad Sci. 2007 Jun;1108:584-93

Autoantibodies in nonautoimmune individuals during infections

Berlin T, Zandman-Goddard G, Blank M, Matthias T, Pfeiffer S, Weis I, Toubi E, Singh S, Asherson R, Fraser A, Gilburd B, Sapir T, Levy Y, Lukac J, Rozman B, Kveder T, Shoenfeld Y

Department of Medicine E, Meir Hospital, Kfar Saba, Israel.

Infections can act as environmental triggers inducing or promoting autoimmune disease in genetically predisposed individuals. Identification of microbial peptides similar to self-tissues may by molecular mimicry, provide the inducing mechanism for an immune response. The aim of this study was to identify autoantibodies (autoAbs) in nonautoimmune individuals during acute bacterial, viral, or parasitic infections. Specific Abs or specific infections with an increased autoAb load may shed insight into the mechanisms of autoimmune disease. Sera from 88 patients with acute infections (41 bacterial, 23 viral, 17 parasitic, and 7 rickettsial) were tested by the ELISA method for antinuclear antibodies (ANA) 8 Pro, and Abs to thyroid peroxidase (TPO), thyroglobulin, phospholipids, annexin-V, laminin, anti-Saccharomyces cervisiae (ASCA), and prothrombin, along with 80 normal controls. Elevated titers of Abs to annexin-V and prothrombin were the most prevalent in viral, parasitic, and rickettsial infections and to laminin in viral and parasitic infections. Elevated titers of ASCA and ANA were found in viral and bacterial infections. Antiphospholipid Abs were found in parasitic and Q-fever infections. Thirty-four individuals harbored elevated titers of at least two Abs. An autoAb burden was detected in individuals with hepatitis A, hepatitis B, toxoplasma or Q-fever infections. In nonautoimmune individuals with various (bacterial, viral, parasitic, and rickettsial) infections, elevated titers of Abs to annexin-V, prothrombin, laminin, ASCA, ANA, and phospholipids were most frequently detected.

PMID: 17894023 [PubMed - in process]

Tuesday, September 25, 2007

siRNA can mediate the suppression of adenosine kinase expression

Exp Parasitol. 2007 Aug 3; [Epub ahead of print]

Toxoplasma gondii: siRNA can mediate the suppression of adenosine kinase expression

Yu L, Gao YF, Qiao ZP, Li CL, Li X, Shen JL

Institute of Clinical Pharmacology and Department of Pathobiology, Anhui Medical University, Hefei, Anhui 230032, PR China; The Key Laboratory of Zoonoses, Anhui Province, Hefei, Anhui 230032, PR China; Key Laboratory of Gene Resource Utilization for Severe Diseases, The Ministry of Education of China and Anhui Province, Hefei, Anhui 230032, PR China.

Adenosine kinase (AK) is one of the most important enzymes in the Toxoplasma gondii purine salvage pathway. Three siRNAs specific to the AK gene were designed in the present study. At 24h following electroporation, two of them (siRNA786 and siRNA1200) significantly reduced the mRNA level compared with mock electroporation (P <0.05). The ability to incorporate [3H]-adenosine in the parasites electroporated with 4muM siRNA786 or 4muM siRNA1200 was decreased to 39+/-11% and 39+/-7% of the mock electroporation, respectively. At the 48th hour of electroporation, the enzyme's activity was still significantly lower than that of mock electroporation. The data show the siRNAs transfected into cells can work efficiently to regulate gene expression in T. gondii. The application of siRNA in interrupting gene expression in T. gondii would be useful for elucidating gene function as a step toward development of anti-toxoplasmasis vaccines and therapeutic reagents.

PMID: 17888425 [PubMed - as supplied by publisher]

Friday, September 21, 2007

BALB/c mice resistant to Toxo infection proved to be highly susceptible when previously infected with Myocoptes musculinus fur mites.

Int J Exp Pathol. 2007 Oct;88(5):325-35

BALB/c mice resistant to Toxoplasma gondii infection proved to be highly susceptible when previously infected with Myocoptes musculinus fur mites

Welter A, Mineo JR, de Oliveira Silva DA, Lourenço EV, Vieira Ferro EA, Roque-Barreira MC, Maria da Silva N

Laboratory of Immunoparasitology, Institute of Biomedical Sciences, Federal University of Uberlândia, Uberlândia, MG 38400-902, Brazil.

The immune response induced by Toxoplasma gondii is characterized by Th1 immune mechanisms. We previously demonstrated that C57BL/6 mice infested with Myocoptes musculinus and infected with T. gondii by intraperitoneal route undergo accelerated mortality according to Th2 immune mechanisms induced by the acarian. To evaluate whether infection with M. musculinus influences T. gondii-induced Th1 response in a resistant mouse lineage, BALB/c, which develops latent chronic toxoplasmosis in a way similar to that observed in immunocompetent humans, this study was done. The animals were infected with T. gondii ME-49 strain 1 month after M. musculinus infestation, being the survival and the immune response monitored. The double-infected displayed higher mortality rate if compared with the mono-infected mice. In addition, infection with M. musculinus changed the T. gondii-specific immune response, converting BALB/c host to a susceptible phenotype. Spleen cells had increased the levels of IL-4 in double-infected mice. This alteration was associated with severe pneumonia, encephalitis and wasting condition. In addition, a higher tissue parasitism was observed in double-infected animals. It can be concluded that infection with these two contrasting parasites, M. musculinus and T. gondii, may convert an immunocompetent host into a susceptible one, and such a host will develop severe toxoplasmosis.

PMID: 17877534 [PubMed - in process]

B Cells Amplify IFN-{gamma} Production By T Cells via a TNF-{alpha}-Mediated Mechanism

J Immunol. 2007 Oct 1;179(7):4857-66

B Cells Amplify IFN-{gamma} Production By T Cells via a TNF-{alpha}-Mediated Mechanism

Menard LC, Minns LA, Darche S, Mielcarz DW, Foureau DM, Roos D, Dzierszinski F, Kasper LH, Buzoni-Gatel D

Departments of Microbiology and Immunology, Dartmouth Medical School, Lebanon, NH 03756.

Aside from being the precursors of the Ab-secreting cells, B cells are engaged in other immune functions such as Ag presentation to T cells or cytokine production. These functions may contribute to the pathogenic role of B cells in a wide range of autoimmune diseases. We demonstrate that B cells acquire the capacity to amplify IFN-gamma production by CD4 and CD8 T cells during the course of the Th1 inflammatory response to Toxoplasma gondii infection. Using the two following different strategies, we observed that B cells from T. gondii-infected mice, but not from naive mice, induce higher IFN-gamma expression by splenic host T cells: 1) reconstitution of B cell-deficient mice with B cells expressing an alloantigen different from the recipients, and 2) adoptive transfer of B and T cells into RAG(-/-) mice. In vitro assays allowing the physical separation of T and B cells demonstrate that Ag-primed B cells enhance IFN-gamma production by T cells in a contact-dependent fashion. Using an OVA-transgenic strain of T. gondii and OVA-specific CD4 T cells, we observed that the proinflammatory effect of B cells is neither Ag specific nor requires MHCII expression. However, TNF-alpha expressed on the surface of B cells appears to mediate in part the up-regulation of IFN-gamma by the effector T cells.

PMID: 17878385 [PubMed - in process]

Proteomic analysis of calcium-dependent secretion in Toxo

Proteomics. 2007 Sep 19; [Epub ahead of print]

Proteomic analysis of calcium-dependent secretion in Toxoplasma gondii

Kawase O, Nishikawa Y, Bannai H, Zhang H, Zhang G, Jin S, Lee EG, Xuan X

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

Toxoplasma gondii is an intracellular protozoan parasite that invades a wide range of nucleated cells. In the course of intracellular parasitism, the parasite releases a large variety of proteins from three secretory organelles, namely, micronemes, rhoptries and dense granules. Elevation of intracellular Ca(2+) in the parasite causes microneme discharge, and microneme secretion is essential for the invasion. In this study, we performed a proteomic analysis of the Ca(2+)-dependent secretion to evaluate the protein repertoire. We found that Ca(2+)-mobilising agents, such as thapsigargin, NH(4)Cl, ethanol and a Ca(2+) ionophore, A23187, promoted the secretion of the parasite proteins. The proteins, artificially secreted by A23187, were used in a comparative proteomic analysis by 2-DE followed by PMF analysis and/or N-terminal sequencing. Major known microneme proteins (MICs), such as MIC2, MIC4, MIC6 and MIC10 and apical membrane antigen 1 (AMA1), were identified, indicating that the proteomic analysis worked accurately. Interestingly, new members of secretory proteins, namely rhoptry protein 9 (ROP9) and Toxoplasma SPATR (TgSPATR), which was a homologue of a Plasmodium secreted protein with an altered thrombospondin repeat (SPATR), were detected in Ca(2+)-dependent secretion. Thus, we succeeded in detecting Ca(2+)-dependent secretory proteins in T. gondii, which contained novel secretory proteins.

PMID: 17880006 [PubMed - as supplied by publisher]

Mutations in {alpha}-Tubulin Confer Dinitroaniline Resistance at a Cost to Microtubule Function

Mol Biol Cell. 2007 Sep 19; [Epub ahead of print]

Mutations in {alpha}-Tubulin Confer Dinitroaniline Resistance at a Cost to Microtubule Function

Ma C, Li C, Ganesan L, Oak J, Tsai S, Sept D, Morrissette NS

Department of Molecular Biology and Biochemistry, University of California, Irvine, Irvine, CA 92697; Department of Biomedical Engineering and the Center for Computational Biology, Washington University School of Medicine, St. Louis, MO 63110.

Monitoring Editor: Kerry Bloom Protozoan microtubules are sensitive to disruption by dinitroanilines, compounds that kill intracellular Toxoplasma gondii parasites without affecting microtubules in vertebrate host cells. We previously isolated a number of resistant Toxoplasma lines that harbor mutations to the alpha1-tubulin gene. Some of the mutations are localized in or near the M and N loops, domains that coordinate lateral interactions between protofilaments. Other resistance mutations map to a computationally identified binding site beneath the N loop. Allelic replacement of wild-type alpha1-tubulin with the individual mutations is sufficient to confer dinitroaniline resistance. Some mutations appear to increase microtubule length, suggesting that they increase subunit affinity. All mutations are associated with replication defects that decrease parasite viability. When parasites bearing the N loop mutation Phe52Tyr are grown without dinitroaniline selection, they spontaneously acquired secondary mutations in the M loop (Ala273Val) or in an alpha-tubulin-specific insert that stabilizes the M loop (Asp367Val). Parasites with the double mutations have both reduced resistance and diminished incidence of replication defects, suggesting that the secondary mutations decrease protofilament affinity to increase parasite fitness.

PMID: 17881728 [PubMed - as supplied by publisher]

Thursday, September 20, 2007

Nucleolar translocalization of GRA10 transfectionally expressed in HeLa cells

Korean J Parasitol. 2007 Sep;45(3):165-74

Nucleolar translocalization of GRA10 of Toxoplasma gondii transfectionally expressed in HeLa cells

Ahn HJ, Kim S, Nam HW

Department of Parasitology and the Catholic Institute of Parasitic Diseases, College of Medicine, Catholic University of Korea, Seoul, Republic of Korea.

Toxoplasma gondii GRA10 expressed as a GFP-GRA10 fusion protein in HeLa cells moved to the nucleoli within the nucleus rapidly and entirely. GRA10 was concentrated specifically in the dense fibrillar component of the nucleolus morphologically by the overlap of GFP-GRA10 transfection image with IFA images by monoclonal antibodies against GRA10 (Tg378), B23 (nucleophosmin) and C23 (nucleolin). The nucleolar translocalization of GRA10 was caused by a putative nucleolar localizing sequence (NoLS) of GRA10. Interaction of GRA10 with TATA-binding protein associated factor 1B (TAF1B) in the yeast two-hybrid technique was confirmed by GST pull-down assay and immunoprecipitation assay. GRA10 and TAF1B were also co-localized in the nucleolus after co-transfection. The nucleolar condensation of GRA10 was affected by actinomycin D. Expressed GFP-GRA10 was evenly distributed over the nucleoplasm and the nucleolar locations remained as hollows in the nucleoplasm under a low dose of actinomycin D. Nucleolar localizing and interacting of GRA10 with TAF1B suggested the participation of GRA10 in rRNA synthesis of host cells to favor the parasitism of T. gondii.

PMID: 17876161 [PubMed - in process]

Wednesday, September 12, 2007


Infect Immun. 2007 Sep 10; [Epub ahead of print]


Dzierszinski F, Pepper M, Stumhofer JS, Larosa DF, Wilson EH, Turka LA, Halonen SK, Hunter CA, Roos DS

Departments of Biology, Pathobiology, and Medicine, University of Pennsylvania, Philadelphia, PA 19104; Department of Microbiology, Montana State University, Bozeman, MT 59717.

Challenge with the intracellular protozoan parasite Toxoplasma gondii induces a potent CD8(+) T-cell response that is required for resistance to infection, but many questions remain about the factors that regulate presentation of class I-restricted parasite antigens, and the role of professional and non-professional accessory cells. In order to address these issues, transgenic parasites expressing ovalbumin (OVA), reagents that track OVA/MHC-I presentation and OVA-specific CD8(+) T-cells were exploited to compare the ability of different infected cell types to stimulate CD8(+) T-cells and to define the factors that contribute to antigen processing. These studies reveal that a variety of infected cell types, including haematopoetic and non-haematopoetic cells, are capable of activating an OVA-specific CD8(+) T-cell hybridoma, and that this phenomenon is TAP-dependent and requires live T. gondii. Several experimental approaches indicate that T-cell activation is a consequence of direct presentation by infected host cells, rather than cross-presentation. Surprisingly, non-professional antigen presenting cells were at least as efficient as dendritic cells at activating this class I-restricted response. Studies to assess whether these cells are involved in initiation of the CD8(+) T-cell response to T. gondii in vivo show that chimeric mice expressing MHC-I only in non-haematopoietic compartments are able to activate OVA-specific CD8(+) T-cells upon challenge. These findings associate non-professional APCs with the initial activation of CD8(+) T-cells during toxoplasmosis.

PMID: 17846116 [PubMed - as supplied by publisher]

The timing of sulfadiazine therapy impacts the reactivation of latent Toxo infection in IRF-8(-/-) mice

Parasitol Res. 2007 Sep 12; [Epub ahead of print]

The timing of sulfadiazine therapy impacts the reactivation of latent Toxoplasma infection in IRF-8(-/-) mice

Jost C, Reiter-Owona I, Liesenfeld O

Institut für Medizinische Mikrobiologie, Immunologie und Parasitologie, Universität Bonn, Sigmund-Freud Str. 25, 53105, Bonn, Germany,

The process of reactivation of latent infection with Toxoplasma gondii in immunosuppressed hosts is yet not fully understood. In the past, a number of murine models of reactivation in immunocompromised mice have been described using sulfadiazine to establish latent infection before withdrawal and subsequent reactivation. We studied the process of reactivation in brains of mice with a targeted mutation in the interferon-regulatory factor (IRF)-8 gene after withdrawal of sulfadiazine therapy. IRF-8(-/-) mice were orally infected with five cysts of the ME 49 strain of T. gondii. To allow establishment of latent infection with cyst formation, mice were treated with sulfadiazine starting either 3, 5, 6, or 7 days postinfection. Sulfadiazine was withdrawn after 14-21 days to allow reactivation. We observed that timing of sulfadiazine therapy had a marked impact on the course of infection and reactivation. Mice treated late after infection (days 5-7) showed increased mortality and decreased time to death compared to mice treated early after infection (group A). In the blood of mice with late (days 5-7) but not early (day 3) initiation of treatment, T. gondii-specific deoxyribonucleic acid was detected by polymerase chain reaction. Using double staining with stage-specific antibodies, tachyzoites were detectable in brains of mice with late initiation of sulfadiazine treatment but rarely within cysts thus indicating continued invasion of parasites across the blood-brain barrier. Intracerebral cyst rupture or bradyzoite-tachyzoite conversion was not detectable in IRF-8(-/-) mice when sulfadiazine therapy was initiated late after infection. These results indicate that continued invasion of tachyzoites rather than reactivation of latent cerebral infection impacts the course of infection in this model of reactivated toxoplasmosis. In conclusion, the timing of sulfadiazine therapy is of utmost importance for the course of infection in immunocompromised mice.

PMID: 17846793 [PubMed - as supplied by publisher]

Tuesday, September 11, 2007

Toxo: Chimeric Dr fimbriae as a recombinant vaccine against toxoplasmosis

Exp Parasitol. 2007 Aug 3; [Epub ahead of print]

Toxoplasma gondii: Chimeric Dr fimbriae as a recombinant vaccine against toxoplasmosis

Gatkowska J, Gasior A, Kur J, Dlugonska H

Department of Immunoparasitology, University of Lodz, Banacha Str. 12/16, 90-237 Lodz, Poland.

Toxoplasma gondii is responsible for fetopathy in farm animals and humans and severe disease in immunocompromised individuals (i.e. AIDS patients). Effective vaccines, inducing protective and long-lasting immunity to this global parasite, are still desired. In the work, we evaluated the immunogenic and immunoprotective activity of Escherichia coli chimeric Dr fimbriae bearing selected antigenic epitopes of three T. gondii antigens (SAG1, GRA1 and MAG1), in comparison with conventional recombinant antigens obtained in E. coli expression system. Our data demonstrate a very high protective efficacy of recombinant antigens supplemented with Freund's adjuvants, whereas chimeric Dr fimbriae as a vaccine proved non-protective. The recombinant antigen vaccine induced a strong specific antibody response and prevented the brain cysts formation by 89%. The results are promising and should be confirmed in further study on farm animals by use of less aggressive than Freund's adjuvant preparations.

PMID: 17825290 [PubMed - as supplied by publisher]

Toxo effect of infection on expression of 14-3-3 proteins in human epithelial cells

Exp Parasitol. 2007 Aug 3; [Epub ahead of print]

Toxoplasma gondii: Effect of infection on expression of 14-3-3 proteins in human epithelial cells

Monroy FP

Department of Biological Sciences, Northern Arizona University, P.O. Box 5640, Flagstaff, AZ 86011, USA.

14-3-3 Proteins are expressed in most eukaryotes organisms and play varied and crucial roles in a wide range of regulatory processes. In mammalian cells, seven 14-3-3 isoforms have been identified. However, it is not known what effect infection has on 14-3-3 isoform expression. In this study human colonic carcinoma cell lines were infected with Toxoplasma gondii for 24h and expression of 14-3-3 proteins was determined by RT-PCR. HT-29 cells only expressed 3 out of the 7 isoforms while 5 and all 7 isoforms were found in HCT-116 and Caco-2 cells, respectively. Infection had little or no effect in the expression of 14-3-3gamma, epsilon, sigma, and xi; but in HCT-116 cells induced expression of 14-3-3eta and sigma, while 14-3-3beta, eta, and xi were induced in HT-29 cells. If 14-3-3 proteins are involved in cell survival and/or prevention of parasite replication, longer incubation times may be required as no differences in percentage of infection were found among the cell lines at 24h post-infection.

PMID: 17825295 [PubMed - as supplied by publisher]

Molecular genetic tools in Toxoplasma and Plasmodium: achievements and future needs

Curr Opin Microbiol. 2007 Sep 6; [Epub ahead of print]

Molecular genetic tools in Toxoplasma and Plasmodium: achievements and future needs

Meissner M, Breinich MS, Gilson PR, Crabb BS

Hygieneinstitut Heidelberg, Abteilung Parasitologie, Universitätsklinikum Heidelberg, Im Neuenheimer Feld 324, D-69120 Heidelberg, Germany.

The recent awarding of the Nobel prize to Andrew Fire and Craig Mello for the discovery of RNA-interference (RNAi) in plants once more demonstrated the importance of basic science in understanding biological mechanisms. Importantly, this discovery led to the establishment of powerful approaches to study gene function in a wide array of organisms. While a robust RNAi-technology remains elusive in apicomplexan parasites, other molecular genetic technologies have been introduced in recent years. Now, in the post genomic era, the task is to apply these methods to validate and functionally dissect an ever-expanding list of putative vaccine and drug candidates. The ultimate aim of such studies is to transform our knowledge of the genome to the knowledge of the phenome and ultimately new intervention strategies in these important pathogenic organisms. However, substantial limitations remain to the current repertoire of available molecular tools, which limits a comprehensive analysis of these candidates, especially of essential genes. This review summarises the methodologies available for functional gene analysis in apicomplexan parasites and discusses further needs in tool development.

PMID: 17826309 [PubMed - as supplied by publisher]

Modeling the molecular basis of atovaquone resistance in parasites and pathogenic fungi

Trends Parasitol. 2007 Sep 6; [Epub ahead of print]

Modeling the molecular basis of atovaquone resistance in parasites and pathogenic fungi

Kessl JJ, Meshnick SR, Trumpower BL

Center for Retrovirus Research, College of Pharmacy, Ohio State University, Columbus, OH 43210, USA.

Atovaquone is a substituted hydroxynaphthoquinone that is used therapeutically for treating Plasmodium falciparum malaria, Pneumocystis jirovecii pneumonia and Toxoplasma gondii toxoplasmosis. It is thought to act on these organisms by inhibiting parasite and fungal respiration by binding to the cytochrome bc(1) complex. The recent, growing failure of atovaquone treatment and increased mortality of patients with malaria or Pneumocystis pneumonia has been linked to the appearance of mutations in the cytochrome b gene. To better understand the molecular basis of drug resistance, we have developed the yeast and bovine bc(1) complexes as surrogates to model the molecular interaction of atovaquone with human and resistant pathogen enzymes.

PMID: 17826334 [PubMed - as supplied by publisher]

Toxo Infection in the United States, 1999 2004

Am J Trop Med Hyg. 2007 Sep;77(3):405-410

Toxoplasma gondii Infection in the United States, 1999 2004, Decline from the Prior Decade

Jones JL, Kruszon-Moran D, Sanders-Lewis K, Wilson M

Division of Parasitic Diseases, National Center for Zoonotic, Vectorborne, and Enteric Diseases, CCID, Centers for Disease Control and Prevention, Atlanta, Georgia; Division of Health and Nutrition Examination Statistics, National Center for Health Statistics, Centers for Disease Control and Prevention, Hyattsville, Maryland.

Toxoplasma gondii can cause congenital, neurologic, ocular, and mild or asymptomatic infection. To determine the U.S. prevalence of T. gondii infection, we tested sera collected from the National Health and Nutrition Examination Survey (NHANES) 1999-2004 for T. gondii immunoglobulin G antibodies in persons 6-49 years old and contrasted the results to those comparable in NHANES III (1988-1994) (ages 12-49 years). Of the 17,672 persons examined in NHANES 1999-2004, 15,960 (90%) were tested. The age-adjusted T. gondii seroprevalence among persons 6-49 years old was 10.8% (95% confidence limits [CL] 9.6%, 11.9%), and among women 15-44 years old, 11.0% (95% CL 9.5%, 12.4%). T. gondii seroprevalence declined from 14.1% to 9.0% (P < 0.001) from NHANES III to NHANES 1999-2004 among U.S.-born persons ages 12-49 years. Although T. gondii infects many persons in the U.S., the prevalence has declined in the past decade.

PMID: 17827351 [PubMed - as supplied by publisher]

Parasites Make Scaredy-Rats Foolhardy

Science. 2000 Jul 28;289(5479):525b-527b

EVOLUTION: Parasites Make Scaredy-Rats Foolhardy

Zimmer C

In the 7 August issue of the Proceedings of the Royal Society of London B, researchers offer a striking demonstration of the ability of some parasites to alter the behavior of their hosts for their own benefit. Rats, the intermediate hosts of the protozoan Toxoplasma gondii, appear to lose their fear of cats, Toxoplasma's final host, when the parasite infects them. By precisely altering rat brains, the parasite potentially increases its chances of completing its life cycle.

PMID: 17832058 [PubMed - as supplied by publisher]

Monday, September 10, 2007

Dual targeting of antioxidant and metabolic enzymes to the mitochondrion and the apicoplast of Toxo

PLoS Pathog. 2007 Aug 31;3(8):e115

Dual targeting of antioxidant and metabolic enzymes to the mitochondrion and the apicoplast of Toxoplasma gondii

Pino P, Foth BJ, Kwok LY, Sheiner L, Schepers R, Soldati T, Soldati-Favre D

Department of Microbiology and Molecular Medicine, Centre Medical Universitaire, University of Geneva, Geneva, Switzerland.

Toxoplasma gondii is an aerobic protozoan parasite that possesses mitochondrial antioxidant enzymes to safely dispose of oxygen radicals generated by cellular respiration and metabolism. As with most Apicomplexans, it also harbors a chloroplast-like organelle, the apicoplast, which hosts various biosynthetic pathways and requires antioxidant protection. Most apicoplast-resident proteins are encoded in the nuclear genome and are targeted to the organelle via a bipartite N-terminal targeting sequence. We show here that two antioxidant enzymes-a superoxide dismutase (TgSOD2) and a thioredoxin-dependent peroxidase (TgTPX1/2)-and an aconitase are dually targeted to both the apicoplast and the mitochondrion of T. gondii. In the case of TgSOD2, our results indicate that a single gene product is bimodally targeted due to an inconspicuous variation within the putative signal peptide of the organellar protein, which significantly alters its subcellular localization. Dual organellar targeting of proteins might occur frequently in Apicomplexans to serve important biological functions such as antioxidant protection and carbon metabolism.

PMID: 17784785 [PubMed - in process]

Toxo brain granuloma in a cat

J Small Anim Pract. 2007 Sep 3; [Epub ahead of print]

Toxoplasma gondii brain granuloma in a cat: diagnosis using cytology from an intraoperative sample and sequential magnetic resonance imaging

Falzone C, Baroni M, De Lorenzi D, Mandara MT

San Marco Veterinary Clinic, 35100 Padua, Italy.

A cat with a history of seizures and clinical suspicion of forebrain disorder underwent a brain magnetic resonance imaging. A space-occupying lesion was identified in the left temporal lobe. The mass was surgically removed, and cytological, histological and immunohistochemical examinations documented the presence of Toxoplasma gondii. A definitive diagnosis of an intracranial T gondii granuloma was made. The cat was treated with clindamycin and phenobarbital and the seizures did not recur. After 10 months, a second magnetic resonance imaging showed severe brain atrophy, but T gondii granuloma recurrence was not noted. Twenty-one months after surgery, the cat's condition deteriorated, and another magnetic resonance imaging showed a presumptive recurrence of T gondii granuloma. In cats, T gondii granuloma must be considered as a differential diagnosis even when only a single intracranial mass is present. Cytology and magnetic resonance imaging can be useful in making a definitive diagnosis and to follow the evolution of the lesion.

PMID: 17784931 [PubMed - as supplied by publisher]

Mouse Neutrophils Require JNK2 MAPK for Toxo-Induced IL-12p40 and CCL2/MCP-1 Release

J Immunol. 2007 Sep 15;179(6):3570-7

Mouse Neutrophils Require JNK2 MAPK for Toxoplasma gondii-Induced IL-12p40 and CCL2/MCP-1 Release

Sukhumavasi W, Egan CE, Denkers EY

Department of Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853.

The MAPK family member JNK/stress-activated MAPK (SAPK) is involved in extracellular stress and proinflammatory cytokine responses, including production of cytokines such as IL-12. The JNK1 and 2 isoforms are widely expressed, but JNK3 is largely restricted to tissues of the brain, testis, and heart. In this study, we focus on mouse neutrophils, a cell type in which JNK/SAPK expression and activity has been given little study. We used Western blot analysis to examine expression patterns of JNK/SAPK in wild-type and JNK2(-/-) polymorphonuclear leukocytes (PMN). Surprisingly, neutrophils displayed a major deficiency in JNK1 expression, in contrast to macrophages that expressed high levels of both JNK1 and JNK2 MAPK. JNK1 expression was steadily reduced during the neutrophil maturation in bone marrow. We used PMN infection with the protozoan parasite Toxoplasma gondii to determine whether neutrophil JNK2 was functional. The parasite induced rapid JNK2 phosphorylation and intracellular FACS staining demonstrated preferential activation in infected neutrophils. Use of JNK2(-/-) neutrophils revealed that this MAPK family member was required for PMN IL-12p40 and CCL2/MCP-1 production. The chemotactic response displayed a minor JNK2 dependence but phagocytosis and oxidative burst activity did not require this MAPK. These findings are important because they demonstrate 1) a previously unrecognized unusual JNK expression pattern in mouse neutrophils, 2) JNK2 in PMN is activated by Toxoplasma invasion, and 3) a requirement for JNK2 in PMN IL-12p40 and CCL2/MCP-1 production in response to a microbial pathogen.

PMID: 17785791 [PubMed - in process]

Surveillance of Toxo infection in recipients of thoracic solid organ transplants

New Microbiol. 2007 Jul;30(3):299-302

Surveillance of Toxoplasma gondii infection in recipients of thoracic solid organ transplants

Sarchi E, Genco F, Di Matteo A, Castiglioni B, Minoli L, Meroni V

Infectious Diseases Department, University of Pavia, Fondazione I.R.C.C.S. Policlinico San Matteo, Pavia, Italy.

We evaluated the frequency of seroconversion for toxoplasmosis in seronegative recipients of thoracic solid organ transplants with seronegative or seropositive donors and the efficacy of chemoprophylaxis with pyrimethamine+sulfametopirazine. One hundred and sixty one patients seronegative for toxoplasmosis were followed-up at different intervals. Six patients out of 79 R-/D- and twelve out of 82 R-/D+ seroconverted after chemoprophylaxis interruption. There was no difference between matched and mismatched recipients as to the frequency of seroconversion which therefore could not be related to donor seropositivity. Seroconversions were almost asymptomatic. All positive recipients should be tested if symptoms of infection are present.

PMID: 17802914 [PubMed - in process]

The role of inositol-acylation and inositol-deacylation in the Toxo glycosylphosphatidylinositol biosynthetic pathway

J Biol Chem. 2007 Sep 5; [Epub ahead of print]

The role of inositol-acylation and inositol-deacylation in the Toxoplasma gondii glycosylphosphatidylinositol biosynthetic pathway

Smith TK, Kimmel JF, Azzouz N, Shams-Eldin H, Schwarz RT

College of Life Sciences, University of Dundee, Dundee DD1 5EH.

Toxoplasma gondii is a ubiquitous parasitic protozoan that invades nucleated cells in a process thought to be in part due to several surface, glycosylphosphatidylinositol (GPI)-anchored proteins, like the major surface antigen SAG1 (P30), which dominates the plasma membrane. The serine protease inhibitors phenylmethylsulfonylfluoride and diisopropylfluoride were found to have a profound effect on the T. gondii GPI biosynthetic pathway, leading to the observation and characterization of novel inositol-acylated mannosylated GPI intermediates. This inositol-acylation is acyl-CoA dependent and takes place prior to mannosylation, but uniquely for this class of inositol-acyltransferase it is inhibited by phenylmethylsulfonylfluoride. The subsequent inositol-deacylation of fully mannosylated GPI intermediates is inhibited by both phenylmethylsulfonylfluoride and diisopropylfluoride. The use of these serine protease inhibitors allows observations as to the timing of inositol-acylation and subsequent inositol-deacylation of the GPI intermediates. Inositol-acylation of the non-mannosylated GPI intermediate GlcN-PI precedes mannosylation. Inositol-deacylation of the fully mannosylated GPI intermediate allows further processing, i.e. addition of GalNAc side chain to the first mannose. Characterization of the phosphatidylinositol moieties present on both free GPIs and GPI-anchored proteins shows the presence of a diacyl-glycerol lipid, whose sn-2 position contains almost exclusively an C18:1 acyl chain. The data presented here identifies key novel inositol-acylated mannosylated intermediates, allowing the formulation of an updated T. gondii GPI biosynthetic pathway, along with identification of the putative genes involved.

PMID: 17804418 [PubMed - as supplied by publisher]

Recent transcontinental sweep of Toxo driven by a single monomorphic chromosome

Proc Natl Acad Sci U S A. 2007 Sep 5; [Epub ahead of print]

Recent transcontinental sweep of Toxoplasma gondii driven by a single monomorphic chromosome

Khan A, Fux B, Su C, Dubey JP, Darde ML, Ajioka JW, Rosenthal BM, Sibley LD

Department of Molecular Microbiology, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, MO 63130;

Toxoplasma gondii is a highly prevalent protozoan parasite that infects a wide range of animals and threatens human health by contaminating food and water. A markedly limited number of clonal parasite lineages have been recognized as predominating in North American and European populations, whereas strains from South America are comparatively diverse. Here, we show that strains from North America and Europe share distinct genetic polymorphisms that are mutually exclusive from polymorphisms in strains from the south. A striking exception to this geographic segregation is a monomorphic version of one chromosome (Chr1a) that characterizes virtually all northern and many southern isolates. Using a combination of molecular phylogenetic and phenotypic analyses, we conclude that northern and southern parasite populations diverged from a common ancestor in isolation over a period of approximately 10(6) yr, and that the monomorphic Chr1a has swept each population within the past 10,000 years. Like its definitive feline hosts, T. gondii may have entered South America and diversified there after reestablishment of the Panamanian land bridge. Since then, recombination has been an infrequent but important force in generating new T. gondii genotypes. Genes unique to a monomorphic version of a single parasite chromosome may have facilitated a recent population sweep of a limited number of highly successful T. gondii lineages.

PMID: 17804804 [PubMed - as supplied by publisher]

Opportunistic Infections in Patients With HIV Clade C Infection

J Neuropathol Exp Neurol. 2007 Sep;66(9):799-808

Characterization of Human Immunodeficiency Virus (HIV)-Infected Cells in Infiltrates Associated With CNS Opportunistic Infections in Patients With HIV Clade C Infection

Mahadevan A, Shankar SK, Satishchandra P, Ranga U, Chickabasaviah YT, Santosh V, Vasanthapuram R, Pardo CA, Nath A, Zink MC

From the Departments of Neuropathology (AM, SKS, YTC, VS), Neurology (PS), and Neurovirology (RV), National Institute of Mental Health and Neurological Sciences, Bangalore, India; Molecular Virology Laboratory (UR), Molecular Biology and Genetics Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bangalore, India; and Departments of Neurology (CAP, AN) and Molecular and Comparative Pathobiology (MCZ), The Johns Hopkins University, Baltimore, Maryland.

Infection with human immunodeficiency virus (HIV) clade C is the most common HIV infection worldwide, yet its impact on the nervous system remains largely unknown. Autopsy studies from regions affected by this virus are scarce, and HIV dementia has only rarely been reported from these countries. Most patients who develop neurologic complications die of opportunistic infections. We thus conducted a neuropathologic study from a single institution in India to characterize the HIV-infected cells in the inflammatory infiltrates in a total of 15 cases (5 patients each who died of either CNS toxoplasmosis, tuberculosis, or cryptococcal meningitis). Nearly, all patients had HIV-infected cells in the brain, although these cells were most abundant in patients with toxoplasma encephalitis. Interestingly, none of the patients had any multinucleated giant cells. HIV-infected cells were found in the parenchyma, perivascular regions, and choroid plexus and found infiltrating the parenchyma from the meninges, suggesting multiple portals of entry into the brain. These findings suggest the possibility that patients, even if successfully treated for an opportunistic inflection, may be at high risk of developing HIV encephalitis and subsequent dementia.

PMID: 17805010 [PubMed - as supplied by publisher]

Fatal outbreak of human toxoplasmosis along the Maroni River

Clin Infect Dis. 2007 Oct 1;45(7):e88-95. Epub 2007 Aug 27

Fatal outbreak of human toxoplasmosis along the Maroni River: epidemiological, clinical, and parasitological aspects

Demar M, Ajzenberg D, Maubon D, Djossou F, Panchoe D, Punwasi W, Valery N, Peneau C, Daigre JL, Aznar C, Cottrelle B, Terzan L, Dardé ML, Carme B

Unit of Parasitology-Mycology, Cayenne Hospital, Equipe EA, Cayenne, French Guiana.

BACKGROUND: Well-documented outbreaks of human toxoplasmosis infection are infrequently reported. Here, we describe a community outbreak of multivisceral toxoplasmosis that occurred in Patam, a Surinamese village near the French Guianan border. METHODS: From the end of December 2003 through the middle of January 2004, 5 adult patients in Patam, including 2 pregnant women, were initially hospitalized for multivisceral toxoplasmosis. A French-Surinamese epidemiological investigation was conducted in the village; inquiries and clinical examinations were performed, and blood and environmental samples were obtained. For all serologically confirmed cases of toxoplasmosis, molecular analysis and mouse inoculations were performed for diagnosis and genetic characterization of Toxoplasma gondii. RESULTS: The hospitalized patients, who did not have any immunodeficiencies, presented with an infectious disease with multivisceral involvement. Serological examination confirmed acute toxoplasmosis. One adult died, and a neonate and a fetus with congenital toxoplasmosis also died. During the investigation, 4 additional acute cases of toxoplasmosis were diagnosed among the 33 villagers. Only 3 inhabitants had serological evidence of previous T. gondii infection. In total, we reported 11 cases of toxoplasmosis: 8 multivisceral cases in immunocompetent adults, resulting in 1 death; 2 cases of lethal congenital toxoplasmosis in a neonate and a fetus; and 1 symptomatic case in a child. Molecular analysis demonstrated that identical isolates of only 1 atypical strain were responsible for at least 5 of the 11 cases of toxoplasmosis in the outbreak. No epidemiological sources could be linked to this severe community-wide outbreak of toxoplasmosis. CONCLUSION: This report is in agreement with the particular features of toxoplasmosis involving atypical strains that were recently described in French Guiana.

PMID: 17806043 [PubMed - in process]

Membrane Protease is Targeted to the Relict Plastid of Toxo via an Internal Signal Sequence

Traffic. 2007 Sep 6; [Epub ahead of print]

A Membrane Protease is Targeted to the Relict Plastid of Toxoplasma via an Internal Signal Sequence

Karnataki A, Derocher AE, Coppens I, Feagin JE, Parsons M

Seattle Biomedical Research Institute, 307 Westlake Avenue North, Seattle, WA 98109, USA.

The apicoplast is a secondary plastid found in Toxoplasma gondii, Plasmodium species and many other apicomplexan parasites. Although the apicoplast is essential to parasite survival, little is known about the protein constituents of the four membranes surrounding the organelle. Luminal proteins are directed to the endoplasmic reticulum (ER) by an N-terminal signal sequence and from there to the apicoplast by a transit peptide domain. We have identified a membrane-associated AAA protease in T. gondii, FtsH1. Although the protein lacks a canonical bipartite-targeting sequence, epitope-tagged FtsH1 colocalizes with the recently identified apicoplast membrane marker APT1 and immunoelectron microscopy confirms the residence of FtsH1 on plastid membranes. Trafficking appears to occur via the ER because deletion mutants lacking the peptidase domain are retained in the ER. When extended to include the peptidase domain, the protein trafficks properly. The transmembrane domain is required for localization of the full-length protein to the apicoplast and a truncation mutant to the ER. Thus, at least two distinct regions of FtsH1 are required for proper trafficking, but they differ from those of luminal proteins and would not be detected by the algorithms currently used to identify apicoplast proteins.

PMID: 17822404 [PubMed - as supplied by publisher]

Impact of foetus and mother on IFNg-induced IDO and inducible NOS expression in murine placenta

Int J Parasitol. 2007 Jul 26; [Epub ahead of print]

Impact of foetus and mother on IFN-gamma-induced indoleamine 2,3-dioxygenase and inducible nitric oxide synthase expression in murine placenta following Toxoplasma gondii infection

Pfaff AW, Mousli M, Sénégas A, Marcellin L, Takikawa O, Klein JP, Candolfi E

Institut de Parasitologie et de Pathologie Tropicale, E.A. 3950: Interaction Cellulaire et Moléculaire Hôte–Parasite, Faculté de Médecine, 3, rue Koeberlé, 67000 Strasbourg, France.

IFN-gamma production is a hallmark of acute infection with the protozoan parasite Toxoplasma gondii. The tryptophan-catabolising enzyme indoleamine 2,3-dioxygenase (IDO), as well as inducible nitric oxide synthase (NOS2) are induced by IFN-gamma and can play extremely diverse roles in immune regulation, defence against pathogens and physiological homeostasis. We investigated the regulation of these two central enzymes in the placenta during acute infection of pregnant female mice. Using IFN-gamma receptor knockout (IFNgammaR(-/-)) mice, we showed that IDO is not constitutively expressed in term placentas. In contrast, NOS2 expression was observed, largely dependent on IFN-gamma signalling. Upon infection with the avirulent PRU strain of T. gondii, IDO mRNA expression was induced in an IFNgammaR-dependent manner. Surprisingly, NOS2 mRNA was severely suppressed. Importantly, we showed in crossing experiments of heterozygote (IFNgammaR(+/-)) mothers with IFNgammaR(-/-) males and vice versa that IDO expression largely depends on the presence of IFN-gamma receptors on foetal cells, and to a lesser extent on maternal cells. Immunohistochemical analysis localised foetal IDO production to invasive trophoblasts within the maternal part of the placenta. The placental vascular endothelium only stained positive when the mothers possessed functional IFN-gamma receptors. In contrast, placental NOS2 expression, but also its suppression following infection, seems to be largely dependent on IFN-gamma signalling in maternal cells. Neither factor appears to regulate placental T. gondii growth, as we observed no difference in parasite numbers between (+/-) and (-/-) foetuses. Taken together, our results demonstrate the crucial role of the foetus in placental IDO, but not NOS2, production following T. gondii infection.

PMID: 17822706 [PubMed - as supplied by publisher]

Thursday, September 06, 2007

Bilateral acute acquired toxoplasmic retinochoroiditis after steroid therapy for hantavirus pulmonary syndrome: case report

Arq Bras Oftalmol. 2007 Jun;70(3):513-516.

Bilateral acute acquired toxoplasmic retinochoroiditis after steroid therapy for hantavirus pulmonary syndrome: case report

Siqueira RC, Jorge R, Figueiredo LT.
Faculdade de Medicina de Catanduva, Catanduva, SP, Brasil.

Description of a case of acute acquired ocular toxoplasmosis following hantavirus pulmonary syndrome. A 41-year-old man presenting hantavirus pulmonary syndrome, confirmed in the laboratory by detection of IgM antibodies to the virus, was submitted to high doses of intravenous corticosteroids for two months. After clinical improvement of hantavirus pulmonary syndrome the patient presented visual loss in both eyes that was secondary to a toxoplasmosis retinitis. The retinitis resolved with anti-toxoplasma therapy. Acquired toxoplasmic retinochoroiditis can occur following steroid therapy for hantavirus pulmonary syndrome.

PMID: 17768562 [PubMed - as supplied by publisher]

Toxo induces changes in intracellular calcium in macrophages

Parasitology. 2007 Sep 4;:1-7 [Epub ahead of print]

Toxoplasma gondii induces changes in intracellular calcium in macrophages

Masek KS, Zhu P, Freedman BD, Hunter CA

Department of Pathobiology, School of Veterinary Medicine, Room 313, Hill Pavilion, 380 South University Avenue, University of Pennsylvania, Philadelphia, PA 19104, USA.

SUMMARYToxoplasma gondii is an obligate intracellular parasite that interacts with calcium storage organelles and induces calcium-dependent signalling in macrophages. This study was performed to determine whether Toxoplasma induces changes in intracellular calcium in these cells. Ratiometric imaging of live, Fura-2 loaded macrophages challenged with T. gondii revealed robust elevations in intracellular calcium. These elevations were late in onset, beginning 15-20 min after addition of parasites and occurred in up to 20% of macrophages in an imaging field. Further characterization of these events revealed that they follow from challenge with live T. gondii, but not heat-killed parasites or soluble Toxoplasma antigen (STAg). Parasite-induced calcium elevations derived from extracellular sources, and were independent of host recognition factors MyD88 and CCR5. These findings indicate that Toxoplasma gondii alters calcium homeostasis in macrophages and this activity is independent of known pathways involved in the innate recognition of this organism.

PMID: 17767794 [PubMed - as supplied by publisher]

Tuesday, September 04, 2007

Artemisinin induces calcium-dependent protein secretion in Toxo

Eukaryot Cell. 2007 Aug 31; [Epub ahead of print]

Artemisinin induces calcium-dependent protein secretion in the protozoan parasite Toxoplasma gondii

Nagamune K, Beatty WL, Sibley LD

Department of Molecular Microbiology, Washington University School of Medicine, 660 S. Euclid Ave., St. Louis, MO 63110.

Intracellular calcium controls several crucial cellular events in apicomplexan parasites including protein secretion, motility, invasion into and egress from host cells. The plant compound thapsigargin inhibits the sarcoplasmic-endoplasmic reticulum calcium ATPase (SERCA), resulting in elevated calcium and induction of protein secretion in Toxoplasma gondii. Artemisinins are also natural products that show potent and selective activity against parasites, making them useful for the treatment of malaria. While the mechanism of action is uncertain, previous studies have suggested that artemisinin may inhibit SERCA, thus disrupting calcium homeostasis. We cloned the single copy gene encoding SERCA in T. gondii and demonstrate that the protein localizes to the ER in the parasite. In extracellular parasites, TgSERCA partially relocalized to the apical pole, a highly active site for regulated secretion of micronemes. TgSERCA complemented a calcium ATPase-defective yeast mutant and this activity was inhibited by either thapsigargin or artemisinin. Treatment of T. gondii with artemisinin triggered calcium-dependent secretion of microneme proteins, similar to the SERCA inhibitor thapsigargin. Artemisinin treatment also altered intracellular calcium in parasites by increasing the periodicity of calcium oscillations and inducing recurrent, strong calcium spikes, as imaged using fluo-4 labeling. Collectively, these results demonstrate that artemisinin perturbs calcium homeostasis in T. gondii, supporting the idea that Ca(2+)-ATPases are potential drug targets in parasites.

PMID: 17766463 [PubMed - as supplied by publisher]

Sunday, September 02, 2007

Acidocalcisomes in Apicomplexan parasites

Exp Parasitol. 2007 Aug 3; [Epub ahead of print]

Acidocalcisomes in Apicomplexan parasites

Miranda K, Souza WD, Plattner H, Hentschel J, Kawazoe U, Fang J, Moreno SN

Center for Tropical and Emerging Global Diseases and Department of Cellular Biology, 350 Paul D. Coverdell Center, University of Georgia, Athens, GA 30602, USA; Laboratório de Ultraestrutura Celular Hertha Meyer, IBCCF, CCS, UFRJ, Rio de Janeiro, RJ, Brazil.

Acidocalcisomes are acidic calcium stores found in diverse organisms, being conserved from bacteria to man. They posses an acidic matrix that contains several cations bound to phosphates, mainly present in the form of short and long polyphosphate chains. Their matrix is acidified through the action of proton pumps such as a vacuolar proton ATPase and a vacuolar proton pyrophosphatase. The calcium uptake occurs through a Ca(2+)/H(+) counter transporting ATPase located in the membrane of the organelle. Acidocalcisomes have been identified in a variety of microorganisms, including Apicomplexan parasites such as Plasmodium and Eimeria species, and in Toxoplasma gondii. In this paper, we review the structural, biochemical and physiological aspects of acidocalcisomes in Apicomplexan parasites and discuss their functional roles in the maintenance of intracellular ion homeostasis.

PMID: 17761167 [PubMed - as supplied by publisher]