Sunday, June 29, 2008

Genotyping studies of Toxo isolates from Africa revealed that the archetypal clonal lineages predominate as in North America and Europe

Vet Parasitol. 2008 May 10. [Epub ahead of print]

Genotyping studies of Toxoplasma gondii isolates from Africa revealed that the archetypal clonal lineages predominate as in North America and Europe

Velmurugan GV, Dubey JP, Su C.

United States Department of Agriculture, Agricultural Research Service, Animal and Natural Resources Institute, Animal Parasitic Diseases Laboratory, Building 1001, Beltsville, MD 20705-2350, USA.

Until recently, Toxoplasma gondii was considered to be clonal with very little genetic variability. Recent studies indicate that T. gondii isolates from Brazil are genetically and biologically different from T. gondii isolates from USA and Europe. However, little is known of the genetics of T. gondii strains from Africa. In this study, we genotyped 19 T. gondii isolates from chickens from six African countries (Egypt, Kenya, Nigeria, Congo, Mali, and Burkina Fasco) using 10 PCR-RFLP markers (SAG1, SAG2, SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1, and Apico). The results revealed four genotypes. Thirteen isolates belong to the Type III lineage, five isolates have Type II alleles at all loci except apico and they belong to the Type II lineage. One isolate from Nigeria had atypical genotype. In general, these isolates were mostly clonal Type III and II strains that predominate in North American and European. DNA sequencing at several loci for representative isolates confirmed the results of PCR-RFLP genotyping. Taken together with recent studies of T. gondii isolates from Africa, it is clear that the three clonal lineages (Types I, II and III) predominate not only in North America and Europe, but also in Africa.

PMID: 18583059 [PubMed - as supplied by publisher]

Friday, June 27, 2008

Kinetics of systemic cytokine and brain chemokine expression in murine Toxoplasma infection

J Parasitol. 2008 Apr 10:1. [Epub ahead of print]

Kinetics of systemic cytokine and brain chemokine expression in murine Toxoplasma infection

Aviles HO, Stiles J, O P, Orshal J, Leid J, Sonnenfeld G, Monroy FP.

Toxoplasma gondii often migrates to the central nervous system in immunocompromised patients where it induces a severe inflammation referred as Toxoplasma encephalitis. The mechanisms involved in control of parasite multiplication and prevention of Toxoplasma encephalitis remain unclear. The objective of this study was to characterize the inflammatory response in the brain of mice during acute T. gondii infection with emphasis in the expression of chemokine receptors. Susceptible C57BL/6 mice were orally infected with 10 cysts of the low virulent ME49 strain of T. gondii. Levels of cytokines (TNF-alpha, IFN-gamma, IL-10, IL-6 and IL-12p70) and chemokines (CCL/2MCP-1) were measured in plasma at 5, 10, 15, 20, and 30 days after infection. In addition, the mRNA expression of chemokines (CCL5/RANTES, CCL2/MCP-1, CCL4/MIP-1beta) and chemokine receptors (CCR1, CCR2, CCR5, CCR7, CCR8, CXCR4 and CXR5) were measured in brain tissues at the same time points. Plasma levels of IFN-gamma and CCL2/MCP-1 were highly expressed at day 5, while TNF-alpha had a moderate increase at day 5, peaking at day 10 and returning to normal levels by day 30. Plasma levels of IL-10, IL-6, and IL-12p70 were not detected throughout the study. Analyses of mRNA expression of chemokines and chemokine receptors in the brain showed that CCL5/RANTES, CCR7, CXCR4 and CXCR5 were up-regulated, peaking after 10 days of T. gondii infection. Similar pattern of expression was observed for anti-tachyzoite IgG and IgM antibodies. Our results suggest that T. gondii infection is controlled at local and systemic levels and that pro-inflammatory proteins and their receptors may be acting coordinately to induce stage conversion and prevent parasite multiplication and development of Toxoplasma encephalitis. The early production of IFN-gamma and the delayed expression of CXCR4 and CXCR5 indicate that T. gondii induces an early robust cellular immune response followed by a strong and sustained antibody mediated immunity.

PMID: 18576716 [PubMed - as supplied by publisher]

Tuesday, June 24, 2008

The urban house mouse (Mus domesticus) as a reservoir of infection for the human parasite Toxoplasma gondii: an unrecognised public health issue?

Int J Environ Health Res. 2008 Jun;18(3):177-85

The urban house mouse (Mus domesticus) as a reservoir of infection for the human parasite Toxoplasma gondii: an unrecognised public health issue?

Murphy RG, Williams RH, Hughes JM, Hide G, Ford NJ, Oldbury DJ.

Built and Human Research Institute, University of Salford.

Toxoplasma gondii is a protozoan parasite capable of infecting almost all warm-blooded animals. The cat is the definitive host and becomes infected by consuming contaminated meat or infected prey. Humans can act as intermediate hosts and in healthy individuals the infection is mild and self-limiting. In pregnant women it can cause spontaneous abortions and foetal abnormalities and is capable of inducing serious illness in immuno-compromised patients. In infested dwellings, mice could act as intermediate hosts and play a role in the persistence/propagation of the disease. A total of 200 mice were trapped alive in 27 infested properties in Manchester, UK, and screened for Toxoplasma infection; 59% tested positive. Evidence of vertical transmission from infected dams to foetus was found, possibly maintaining the infection in urban areas. These findings have important implications when considering approaches to rodent control.

PMID: 18569146 [PubMed - in process]

The TNF-Family Receptor DR3 is Essential for Diverse T Cell-Mediated Inflammatory Diseases

Immunity. 2008 Jun 18. [Epub ahead of print]

The TNF-Family Receptor DR3 is Essential for Diverse T Cell-Mediated Inflammatory Diseases

Meylan F, Davidson TS, Kahle E, Kinder M, Acharya K, Jankovic D, Bundoc V, Hodges M, Shevach EM, Keane-Myers A, Wang EC, Siegel RM.

Immunoregulation Unit, Autoimmunity Branch, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, MD 20892.

DR3 (TRAMP, LARD, WSL-1, TNFRSF25) is a death-domain-containing tumor necrosis factor (TNF)-family receptor primarily expressed on T cells. TL1A, the TNF-family ligand for DR3, can costimulate T cells, but the physiological function of TL1A-DR3 interactions in immune responses is not known. Using DR3-deficient mice, we identified DR3 as the receptor responsible for TL1A-induced T cell costimulation and dendritic cells as the likely source for TL1A during T cell activation. Despite its role in costimulation, DR3 was not required for in vivo T cell priming, for polarization into T helper 1 (Th1), Th2, or Th17 effector cell subtypes, or for effective control of infection with Toxoplasma gondii. Instead, DR3 expression was required on T cells for immunopathology, local T cell accumulation, and cytokine production in Experimental Autoimmune Encephalomyelitis (EAE) and allergic lung inflammation, disease models that depend on distinct effector T cell subsets. DR3 could be an attractive therapeutic target for T cell-mediated autoimmune and allergic diseases.

Monday, June 23, 2008

Evaluation of the mood-stabilizing agent valproic acid as a preventative for toxoplasmosis in mice

J Parasitol. 2008 Apr;94(2):555-7

Evaluation of the mood-stabilizing agent valproic acid as a preventative for toxoplasmosis in mice and activity against tissue cysts in mice

Goodwin DG, Strobl J, Mitchell SM, Zajac AM, Lindsay DS

Department of Biomedical Science and Pathology, Virginia Tech, 1410 Prices Fork Road, Blacksburg, Virginia 24061, USA.

Toxoplasma gondii is a common intracellular protozoan infection of humans worldwide. Severe disease can occur in immunocompromised individuals and the in the fetuses of nonimmune pregnant women. Chronic infection is associated with vision and hearing problems, and functional mental alterations, including schizophrenia. The mood-stabilizing agent valproic acid has been shown to inhibit the development of T. gondii in vitro at dosages that are normally achieved in the serum and cerebral spinal fluid of human patients and to have positive effects on the behavior of rats chronically infected with T. gondii. The present study was done to examine the in vivo activity of valproic acid against acute toxoplasmosis in mice. Two studies were done with valproic acid given in the drinking water at concentrations of 1.5 mg/ml (Experiment 1) or 3.0 mg/ml (Experiment 2). In a third experiment (Experiment 3), valproic acid was injected intraperitoneally (i.p.) at doses of 200 or 300 mg/kg every 12 hr. Valproic acid was not effective in preventing acute toxoplasmosis. All mice treated with valproic acid died or were killed and did not (P > 0.05) live significantly longer than the controls. Tachyzoites were demonstrated in the tissues of infected valproic-acid-treated mice. A fourth study was done to determine if valproic acid has activity against T. gondii tissue cysts in chronically infected mice. Mice were chronically infected with the ME-49 strain of T. gondii for 8 wk and then treated orally with valproic acid at approximately 6.6 mg/ml (800 mg/kg/day) in the drinking water for 10 wk (amount was varied due to increasing mouse weights). No significant differences (P > 0.05) were present in tissue cyst numbers in valproic-acid-treated T. gondii chronically infected mice and in mice chronically infected with T. gondii but not given valproic acid. Our results indicate that valproic acid, although effective in vitro against T. gondii tachyzoites, is not effective as a preventative in mice inoculated with T. gondii tachyzoites. Additionally, no activity against tissue cysts was observed in chronically T. gondii-infected valproic-acid-treated mice.

PMID: 18564764 [PubMed - in process]

Related ArticlesVaccination of mice with Neospora caninum: response to oral challenge with Toxoplasma gondii oocysts. [J Parasitol. 1998] Parasites as causative agents of human affective disorders? The impact of anti-psychotic, mood-stabilizer and anti-parasite medication on Toxoplasma gondii's ability to alter host behaviour. [Proc Biol Sci. 2006] Remarkable in vitro and in vivo activities of the hydroxynaphthoquinone 566C80 against tachyzoites and tissue cysts of Toxoplasma gondii. [Antimicrob Agents Chemother. 1991] Recombinant bactericidal/permeability-increasing protein (rBPI21) in combination with sulfadiazine is active against Toxoplasma gondii. [Antimicrob Agents Chemother. 1999] Mic1-3 knockout of Toxoplasma gondii is a successful vaccine against chronic and congenital toxoplasmosis in mice. [J Infect Dis. 2006] » See all Related Articles...

Friday, June 20, 2008

Sensorineural hearing loss due to Toxoplasma gondii in children: a case-control study

Clin Otolaryngol. 2008 Jun;33(3):269-73.

Sensorineural hearing loss due to Toxoplasma gondii in children: a case-control study

Noorbakhsh S, Memari F, Farhadi M, Tabatabaei A.

OBJECTIVE: Sensorineural hearing loss (SNHL) can follow congenital toxoplasmosis. Treatment in the first year of life is associated with diminished occurrence of this sequel. In various parts of Iran, the prevalence of antibodies to Toxoplasma gondii ranges from 24% to 57.7%. We evaluate the possible role of Toxoplasma gondii infection on the occurrence of SNHL in children. DESIGN AND SETTING: This case-control study was performed in a tertiary care center in Tehran between 2002 and 2003. This study was carried out based on diagnostic parameters of the American Academy of Otolaryngology criteria for SNHL and a healthy control group. MAIN OUTCOME MEASURES: We compared the specific Toxoplasma gondii antibodies (IgM & IgG) measured by ELISA in 95 blood samples of infants with SNHL and 63 healthy matched infants. RESULTS: Acute (IgM) and previous (IgG) immunity to Toxoplasma gondii was found in 12 and 21.2% of SNHL children, respectively. Most cases with previous infections (IgG positive) were children aged less than 1 year old (i.e. maternal immunity), but acute infection (IgM positive) was higher in 3-5 year old age group. Acute infection (IgM) was significantly more frequent in the SNHL group, and previous immunity was higher in the controls (CI 95%, P-value = 0.01; 0.01). CONCLUSION: With respect to seropositive children, as we were unable to differentiate congenital from acquired cases, we recommend prevention of congenital toxoplasmosis by treatment of Toxoplasma infection in pregnant women and treatment of acquired Toxoplasma gondii infection after birth to minimise the risk of SNHL in children.

Publication Types:
Research Support, Non-U.S. Gov't

PMID: 18559038 [PubMed - in process]

Evaluation of the immune response elicited by multi-antigenic DNA vaccine expressing SAG1, ROP2 and GRA2

Parasitol Int. 2008 May 16. [Epub ahead of print]

Evaluation of the immune response elicited by multi-antigenic DNA vaccine expressing SAG1, ROP2 and GRA2 against Toxoplasma gondii

Xue M, He S, Cui Y, Yao Y, Wang H.

Department of Parasitology, Medical School, Shandong University, PR China.

The parasite Toxoplasma gondii can infect most mammals and birds, sometimes causing severe pathology. Previous studies have reported that multi-antigenic vaccines were more effective than single-antigenic vaccine. It was also reported that the a single-gene vaccine with SAG1 or ROP2, GRA2 could only produce partial protection against T. gondii. In this study, we constructed a multi-antigenic DNA vaccine containing SAG1, ROP2 and GRA2, and evaluated its immune response. We used IL-12 as an adjuvant to enhance the immune response. We immunized BALB/c mice intramuscularly. After immunization, we evaluated the immune response using lymphocyte proliferation assay, cytokine and antibody measurements. The results showed that the group immunized with pcDNA3.1-SAG1-ROP2-GRA2 produced high Th1 immune response compared to other groups immunized with double-gene plasmid, empty plasmid or phosphate-buffered saline, respectively. Moreover, the co-immunization with IL-12 genes enhanced the immune response significantly and prolonged survival time. The current study showed that multi-antigenic DNA with IL-12 produced potent, effective and long-term protection against T. gondii challenge.

PMID: 18562245 [PubMed - as supplied by publisher]

The schizophrenia and Toxoplasma gondii connection: Infectious, immune or both?

Adv Ther. 2008 Jun 12. [Epub ahead of print]

The schizophrenia and Toxoplasma gondii connection: Infectious, immune or both?

Tamer GS, Dundar D, Yalug I, Caliskan S, Yazar S, Aker A.

Department of Clinical Microbiology, Kocaeli University, Medical Faculty, Kocaeli, Turkey,


PMID: 18563312 [PubMed - as supplied by publisher]

Structure-Activity Relationships of 7-Deaza-6-benzylthioinosine Analogues as Ligands of Adenosine Kinase

J Med Chem. 2008 Jun 19. [Epub ahead of print]

Structure-Activity Relationships of 7-Deaza-6-benzylthioinosine Analogues as Ligands of Toxoplasma gondii Adenosine Kinase

Kim YA, Sharon A, Chu CK, Rais RH, Al Safarjalani ON, Naguib FN, El Kouni MH.

Several 7-deaza-6-benzylthioinosine analogues with varied substituents on aromatic ring were synthesized and evaluated against Toxoplasma gondii adenosine kinase (EC. Structure-activity relationships indicated that the nitrogen atom at the 7-position does not appear to be a critical structural requirement. Molecular modeling reveals that the 7-deazapurine motif provided flexibility to the 6-benzylthio group as a result of the absence of H-bonding between N7 and Thr140. This flexibility allowed better fitting of the 6-benzylthio group into the hydrophobic pocket of the enzyme at the 6-position. In general, single substitutions at the para or meta position enhanced binding. On the other hand, single substitutions at the ortho position led to the loss of binding affinity. The most potent compounds, 7-deaza- p-cyano-6-benzylthioinosine (IC 50 = 5.3 muM) and 7-deaza- p-methoxy-6-benzylthioinosine (IC 50 = 4.6 muM), were evaluated in cell culture to delineate their selective toxicity.

PMID: 18563892 [PubMed - as supplied by publisher]

Lipidomic analysis of Toxo tachyzoites rhoptries: further insights into the role of cholesterol

Biochem J. 2008 Jun 16. [Epub ahead of print]

Lipidomic analysis of Toxoplasma gondii tachyzoites rhoptries: further insights into the role of cholesterol

Besteiro S, Bertrand-Michel J, Lebrun M, Vial H, Dubremetz JF.

Rhoptries are secretory organelles involved in the virulence of the human pathogen Toxoplasma gondii. We have used high performance liquid chromatography and capillary gas-liquid chromatography to isolate and quantify lipids from whole Toxoplasma cells and their purified rhoptries. This comparative lipidomic analysis revealed an enrichment of cholesterol, sphingomyelin and, most of all, saturated fatty acids in the rhoptries. These lipids are known, when present in membranes, to be contributing to their rigidity and, interestingly, fluorescence anisotropy measurements confirmed that rhoptry-derived membranes have a lower fluidity than membranes from whole T. gondii cells. Moreover, while rhoptries were initially thought to be highly enriched in cholesterol, we demonstrated it is present in lower proportions and provided additional evidence towards a lack of involvement of rhoptry cholesterol in the process of host cell invasion by the parasite. Indeed, depleting the cholesterol content of the parasites did not prevent the secretion of protein-containing rhoptry-derived vesicles and the parasites could still establish a structure called the moving junction, which is necessary for invasion. Instead, the crucial role for host cholesterol for invasion, which has already been demonstrated (Coppens, I. and Joiner, K. A. (2003), Mol.Biol.Cell 14, 3804-3820), might be explained by the need of a cholesterol-rich region of the host cell we could visualise at the point of contact with the attached parasite, in conditions where parasite motility was blocked.

PMID: 18564055 [PubMed - as supplied by publisher]

Tuesday, June 17, 2008

Expression QTL mapping of Toxoplasma genes reveals multiple mechanisms for strain-specific differences in gene expression

Eukaryot Cell. 2008 Jun 13. [Epub ahead of print]

Expression QTL mapping of Toxoplasma genes reveals multiple mechanisms for strain-specific differences in gene expression

Boyle JP, Saeij JP, Harada SY, Ajioka JW, Boothroyd JC.

Department of Microbiology and Immunology, Stanford University School of Medicine, Fairchild Building Room D305, Stanford, CA 94305, USA; Department of Pathology, Cambridge University, Cambridge, CB2 1QP, UK.

Toxoplasma gondii is an intracellular parasite with a significant impact on human health, especially in cases where individuals are immunocompromised (e.g., due to HIV/AIDS). In Europe and North America only a few clonal genotypes appear to be responsible for the vast majority of Toxoplasma infections, and these clonotypes have been intensely studied to identify strain-specific phenotypes that may play a role in the manifestation of more severe disease. To identify and genetically map strain-specific differences in gene expression, we have carried out expression quantitative trait locus (eQTL) analysis on Toxoplasma gene expression phenotypes using spotted cDNA microarrays. This led to the identification of 16 Toxoplasma genes that had significant and mappable strain-specific variation in hybridization intensity. While the analysis should identify both cis and trans-mapping hybridization profiles, we only identified loci with strain-specific hybridization differences that are most likely due to differences in the locus itself (i.e., cis-mapping). Interestingly, a larger number of these cis-mapping genes than would be expected by chance encode either confirmed or predicted secreted proteins, many of which are known to localize to the specialized secretory organelles characteristic of members of the phylum Apicomplexa. For 6 of the cis-mapping loci we determined if the strain-specific hybridization differences were due to true transcriptional differences or rather strain-specific differences in hybridization efficiency because of extreme polymorphism and/or deletion, and we found examples of both scenarios.

PMID: 18552283 [PubMed - as supplied by publisher]

Schizophrenia Susceptibility Genes Directly Implicated in the Life Cycles of Pathogens

Schizophr Bull. 2008 Jun 13. [Epub ahead of print]

Schizophrenia Susceptibility Genes Directly Implicated in the Life Cycles of Pathogens: Cytomegalovirus, Influenza, Herpes simplex, Rubella, and Toxoplasma gondii

Carter CJ.

2176 Downs Road, Hastings, East Sussex, TN34 2DZ, UK.

Many genes implicated in schizophrenia can be related to glutamatergic transmission and neuroplasticity, oligodendrocyte function, and other families clearly related to neurobiology and schizophrenia phenotypes. Others appear rather to be involved in the life cycles of the pathogens implicated in the disease. For example, aspartylglucosaminidase (AGA), PLA2, SIAT8B, GALNT7, or B3GAT1 metabolize chemical ligands to which the influenza virus, herpes simplex, cytomegalovirus (CMV), rubella, or Toxoplasma gondii bind. The epidermal growth factor receptor (EGR/EGFR) is used by the CMV to gain entry to cells, and a CMV gene codes for an interleukin (IL-10) mimic that binds the host cognate receptor, IL10R. The fibroblast growth factor receptor (FGFR1) is used by herpes simplex. KPNA3 and RANBP5 control the nuclear import of the influenza virus. Disrupted in schizophrenia 1 (DISC1) controls the microtubule network that is used by viruses as a route to the nucleus, while DTNBP1, MUTED, and BLOC1S3 regulate endosomal to lysosomal routing that is also important in viral traffic. Neuregulin 1 activates ERBB receptors releasing a factor, EBP1, known to inhibit the influenza virus transcriptase. Other viral or bacterial components bind to genes or proteins encoded by CALR, FEZ1, FYN, HSPA1B, IL2, HTR2A, KPNA3, MED12, MED15, MICB, NQO2, PAX6, PIK3C3, RANBP5, or TP53, while the cerebral infectivity of the herpes simplex virus is modified by Apolipoprotein E (APOE). Genes encoding for proteins related to the innate immune response, including cytokine related (CCR5, CSF2RA, CSF2RB, IL1B, IL1RN, IL2, IL3, IL3RA, IL4, IL10, IL10RA, IL18RAP, lymphotoxin-alpha, tumor necrosis factor alpha [TNF]), human leukocyte antigen (HLA) antigens (HLA-A10, HLA-B, HLA-DRB1), and genes involved in antigen processing (angiotensin-converting enzyme and tripeptidyl peptidase 2) are all concerned with defense against invading pathogens. Human microRNAs (Hsa-mir-198 and Hsa-mir-206) are predicted to bind to influenza, rubella, or poliovirus genes. Certain genes associated with schizophrenia, including those also concerned with neurophysiology, are intimately related to the life cycles of the pathogens implicated in the disease. Several genes may affect pathogen virulence, while the pathogens in turn may affect genes and processes relevant to the neurophysiology of schizophrenia. For such genes, the strength of association in genetic studies is likely to be conditioned by the presence of the pathogen, which varies in different populations at different times, a factor that may explain the heterogeneity that plagues such studies. This scenario also suggests that drugs or vaccines designed to eliminate the pathogens that so clearly interact with schizophrenia susceptibility genes could have a dramatic effect on the incidence of the disease.

PMID: 18552348 [PubMed - as supplied by publisher]

Anatomopathological study in BALB/c mice brains experimentally infected with Toxoplasma gondii

Braz J Infect Dis. 2008 Feb;12(1):52-6

Anatomopathological study in BALB/c mice brains experimentally infected with Toxoplasma gondii

Silva MG, Lino Junior Rde S, Costa TL, Soares JD, Amaral WN, Avelino MM, Castro AM.

Postgraduate program from the Tropical Pathology and Public Health Institute, Federal University of Goias.

Toxoplasmosis is one of the most important diseases of the nervous central system, leading to severe symptoms and, many times, irreversible sequelae. This work demonstrated the main anatomopathological lesions caused by Toxoplasma gondii in brains from experimentally infected BALB/c mice. We analyzed 51 cases of mice that developed toxoplasmosis after experimental infection by intraperitoneal inoculation of blood, amniotic liquid and cerebrospinal fluid from fetuses, newly born children and pregnant women with clinical and laboratory signals of toxoplasmosis. In all experiments where we detected the parasite in mice we also detected pathological lesions in the animal brains with great polymorphism between experiments. Edema was the most found lesion in all cases. Besides, it was possible to demonstrate the inflammatory process in 82.4% of cases and necrosis in 64.7% of cases, in agreement with the literature that describes severe neurological damage in its hosts.

PMID: 18553015 [PubMed - in process]

Specific differentiation of H. hammondi from Toxoplasma gondii by PCR

Mol Cell Probes. 2008 May 8. [Epub ahead of print]

Characterization of a repetitive DNA fragment in Hammondia hammondi and its utility for the specific differentiation of H. hammondi from Toxoplasma gondii by PCR

Schares G, Herrmann DC, Beckert A, Schares S, Hosseininejad M, Pantchev N, Globokar Vrhovec M, Conraths FJ.

Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Institute of Epidemiology, Seestrasse 55, D-16868 Wusterhausen, Germany.

Hammondia hammondi and Toxoplasma gondii are closely related protozoan parasites. Both species use felids as definitive hosts and a broad spectrum of warm-blooded animals as intermediate hosts. Morphologically and serologically, the two parasites are difficult to differentiate. While T. gondii is an important pathogen of humans and a broad range of other vertebrates, disease has not yet been associated with H. hammondi infection. The aim of the present study was to identify and characterize a repetitive DNA fragment in H. hammondi and to evaluate its suitability for diagnostic purposes. With two primers considered to be specific for a 529bp repetitive DNA fragment in T. gondii, weak products were amplified by polymerase chain reaction (PCR) from genomic DNA from H. hammondi oocysts. These amplicons (of approximately 150, 300 and 450bp) were sequenced. The 292bp consensus sequence of these three fragments revealed 84% identity with parts of the 529-bp repeat in T. gondii. Based on this sequence, a pair of primers was selected which amplified products of 98 and 630bp from genomic DNA from H. hammondi oocysts but not from DNA from T. gondii. The 630-bp product was purified and cloned into a plasmid vector and the consensus sequence determined from seven randomly selected clones; comparison of this sequence with those available in current databases for T. gondii revealed an 84.0-88.1% identity over a length of 529bp. The sequence data obtained was used for the development of a sensitive PCR which is entirely specific for H. hammondi and incorporates an internal control. The sequence data for the repetitive DNA element of H. hammondi provides a foundation for the design of primers specific to T. gondii, and the future optimisation of conventional and real-time PCR assays for the specific diagnosis of toxoplasmosis in definitive and intermediate hosts.

PMID: 18554866 [PubMed - as supplied by publisher]

Multi-epitope DNA vaccine linked to the A(2)/B subunit of cholera toxin protect mice

Vaccine. 2008 May 20. [Epub ahead of print]

Multi-epitope DNA vaccine linked to the A(2)/B subunit of cholera toxin protect mice against Toxoplasma gondii

Cong H, Gu QM, Yin HE, Wang JW, Zhao QL, Zhou HY, Li Y, Zhang JQ.

Department of Parasitology, Medical School, Shandong University, No. 44 Wenhuaxi Road, Jinan, Shandong 250012, PR China.

The search for an effective vaccine against toxoplasmosis remains a challenging and elusive goal. Combination of epitopes from different stages of Toxoplasma gondii life cycle is an optimal strategy to overcome the antigen complexity of the parasite. Based on published epitope derived from several promising candidate vaccine antigens, we construct a DNA vaccine encoding multi-epitope of T. gondii and CpG motif, with or without the A(2)/B subunit of cholera toxin as a genetic adjuvant. The immunity induced by this vaccine in BALB/c mice and the protection afforded against challenge with the highly virulent RH strain of T. gondii is assessed. This vaccine was able to elicit a significant humoral and cellular immune response in vaccinated mice. Furthermore, CTXA(2)/B as a genetic adjuvant could enhance the magnitude of immune responses as well as increased survival rate in mice infected with the lethal RH tachyzoites. This study is the first report of a multi-epitope DNA construct strategy as a potential DNA vaccine against toxoplasmosis.

PMID: 18555564 [PubMed - as supplied by publisher]

Sunday, June 15, 2008

Protozoan protein tyrosine phosphatases

Int J Parasitol. 2008 Apr 29. Epub ahead of print

Protozoan protein tyrosine phosphatases

Andreeva AV, Kutuzov MA

Department of Pharmacology (MC 868), University of Illinois at Chicago, 909 S. Wolcott Avenue, Chicago, IL 60612, USA.

The aim of this review is to provide a synthesis of the published experimental data on protein tyrosine phosphatases from parasitic protozoa, in silico analysis based on the availability of completed genomes and to place available data for individual phosphatases from different unicellular parasites into the comparative and evolutionary context. We analysed the complement of protein tyrosine phosphatases (PTP) in several species of unicellular parasites that belong to Apicomplexa (Plasmodium; Cryptosporidium, Babesia, Theileria, and Toxoplasma), kinetoplastids (Leishmania and Trypanosoma spp.), as well as Entamoeba histolytica, Giardia lamblia, Trichomonas vaginalis and a microsporidium Encephalitozoon cuniculi. The analysis shows distinct distribution of the known families of tyrosine phosphatases in different species. Protozoan tyrosine phosphatases show considerable levels of divergence compared with their mammalian homologues, both in terms of sequence similarity between the catalytic domains and the structure of their flanking domains. This potentially makes them suitable targets for development of specific inhibitors with minimal effects on physiology of mammalian hosts.

Cloning, sequencing, expression, and antigenic characterization of ROP2, GRA5 and GRA7

Genet Mol Res. 2008 Apr 8;7(2):305-13

Toxoplasma gondii: cloning, sequencing, expression, and antigenic characterization of ROP2, GRA5 and GRA7

Igarashi M, Kano F, Tamekuni K, Kawasaki PM, Navarro IT, Vidotto O, Vidotto MC, Machado RZ, Garcia JL.

Departamento de Medicina Veterinária Preventiva, Universidade Estadual de Londrina, CCA, Campus Universitário, Londrina, PR, Brasil.

Toxoplasma gondii is an intracellular obligate protozoan, which infects humans and warm-blooded animals. The aim of the present study was to clone the rop2, gra5 and gra7 genes from T. gondii RH strain and to produce recombinant proteins. The rop2, gra5 and gra7 gene fragments produced by polymerase chain reaction were cloned into the pET102/D-TOPO vector which contains thioredoxin and polyhistidine tags at the C- and N-ends, respectively, and is expressed in Escherichia coli BL21(DE-3). The expression fusion proteins were found almost entirely in the insoluble form in the cell lysate. These recombinant proteins were purified with an Ni-NTA column. Concentrations of the recombinant antigens produced in the E. coli BL21-star ranged from 300 to 500 microg/ml growth media, which was used to immunize rabbits. We observed an identity ranging from 96 to 97% when nucleotide sequences were compared to GenBank database sequences. Immunocharacterization of proteins was made by indirect immunofluorescence assay. These proteins will be used for serodiagnosis and vaccination.

Publication Types:
Research Support, Non-U.S. Gov't

PMID: 18551396 [PubMed - in process]

Immunity and Toxoplasma retinochoroiditis

Clin Exp Immunol. 2008 Jun 10. [Epub ahead of print]

Immunity and Toxoplasma retinochoroiditis

Wallace GR, Stanford MR.

Academic Unit of Ophthalmology, Division of Immunity and Infection, University of Birmingham, Birmingham, UK.

Toxoplasma infection accounts for up to 50% of all cases of posterior uveitis worldwide. In this review the control of Toxoplasma infection generally, and specific in the eye, by the immune system is discussed.

PMID: 18549442 [PubMed - as supplied by publisher]

Thursday, June 12, 2008

Deciphering the ubiquitin-mediated pathway in apicomplexan parasites: a potential strategy to interfere with parasite virulence

PLoS ONE. 2008 Jun 11;3(6):e2386

Deciphering the ubiquitin-mediated pathway in apicomplexan parasites: a potential strategy to interfere with parasite virulence

Ponts N, Yang J, Chung DW, Prudhomme J, Girke T, Horrocks P, Le Roch KG.

Department of Cell Biology and Neurosciences, University of California at Riverside, Riverside, California, United States of America.

BACKGROUND: Reversible modification of proteins through the attachment of ubiquitin or ubiquitin-like modifiers is an essential post-translational regulatory mechanism in eukaryotes. The conjugation of ubiquitin or ubiquitin-like proteins has been demonstrated to play roles in growth, adaptation and homeostasis in all eukaryotes, with perturbation of ubiquitin-mediated systems associated with the pathogenesis of many human diseases, including cancer and neurodegenerative disorders. METHODOLOGY/PRINCIPAL FINDINGS: Here we describe the use of an HMM search of functional Pfam domains found in the key components of the ubiquitin-mediated pathway necessary to activate and reversibly modify target proteins in eight apicomplexan parasitic protozoa for which complete or late-stage genome projects exist. In parallel, the same search was conducted on five model organisms, single-celled and metazoans, to generate data to validate both the search parameters employed and aid paralog classification in Apicomplexa. For each of the 13 species investigated, a set of proteins predicted to be involved in the ubiquitylation pathway has been identified and demonstrates increasing component members of the ubiquitylation pathway correlating with organism and genome complexity. Sequence homology and domain architecture analyses facilitated prediction of apicomplexan-specific protein function, particularly those involved in regulating cell division during these parasite's complex life cycles. CONCLUSIONS/SIGNIFICANCE: This study provides a comprehensive analysis of proteins predicted to be involved in the apicomplexan ubiquitin-mediated pathway. Given the importance of such pathway in a wide variety of cellular processes, our data is a key step in elucidating the biological networks that, in part, direct the pathogenicity of these parasites resulting in a massive impact on global health. Moreover, apicomplexan-specific adaptations of the ubiquitylation pathway may represent new therapeutic targets for much needed drugs against apicomplexan parasites.

PMID: 18545708 [PubMed - in process]

Specific DNA-binding by Apicomplexan AP2 transcription factors

Proc Natl Acad Sci U S A. 2008 Jun 9. [Epub ahead of print]

Specific DNA-binding by Apicomplexan AP2 transcription factors

De Silva EK, Gehrke AR, Olszewski K, León I, Chahal JS, Bulyk ML, Llinás M.

Department of Molecular Biology and Lewis–Sigler Institute for Integrative Genomics, Princeton University, 246 Carl Icahn Laboratory, Princeton, NJ 08544;

Malaria remains one of the most prevalent infectious diseases worldwide, affecting more than half a billion people annually. Despite many years of research, the mechanisms underlying transcriptional regulation in the malaria-causing Plasmodium spp., and in Apicomplexan parasites generally, remain poorly understood. In Plasmodium, few regulatory elements sufficient to drive gene expression have been characterized, and their cognate DNA-binding proteins remain unknown. This study characterizes the DNA-binding specificities of two members of the recently identified Apicomplexan AP2 (ApiAP2) family of putative transcriptional regulators from Plasmodium falciparum. The ApiAP2 proteins contain AP2 domains homologous to the well characterized plant AP2 family of transcriptional regulators, which play key roles in development and environmental stress response pathways. We assayed ApiAP2 protein-DNA interactions using protein-binding microarrays and combined these results with computational predictions of coexpressed target genes to couple these putative trans factors to corresponding cis-regulatory motifs in Plasmodium. Furthermore, we show that protein-DNA sequence specificity is conserved in orthologous proteins between phylogenetically distant Apicomplexan species. The identification of the DNA-binding specificities for ApiAP2 proteins lays the foundation for the exploration of their role as transcriptional regulators during all stages of parasite development. Because of their origin in the plant lineage, ApiAP2 proteins have no homologues in the human host and may prove to be ideal antimalarial targets.

PMID: 18541913 [PubMed - as supplied by publisher]

Population Structure of Toxoplasma gondii: Clonal Expansion Driven by Infrequent Recombination and Selective Sweeps

Annu Rev Microbiol. 2008 Jun 10. [Epub ahead of print]

Population Structure of Toxoplasma gondii: Clonal Expansion Driven by Infrequent Recombination and Selective Sweeps

Sibley LD, Ajioka JW.

Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, 63130; email:

Toxoplasma gondii is among the most successful parasites. It is capable of infecting all warm-blooded animals and causing opportunistic disease in humans. T. gondii has a striking clonal population structure consisting of three predominant lineages in North America and Europe. Clonality is associated with the recent emergence of a monomorphic version of Chr1a, which drove a selective genetic sweep within the past 10,000 years. Strains from South America diverged from those in North America some 1-2 mya; recently, however, the monomorphic Chr1a has extended into regions of South America, where it is also associated with clonality. The recent spread of a few dominant lineages has dramatically shaped the population structure of T. gondii and has resulted in most lineages sharing a highly pathogenic nature. Understanding the factors that have shaped the population structure of T. gondii has implications for the emergence and transmission of human pathogens. Expected final online publication date for the Annual Review of Microbiology Volume 62 is September 08, 2008. Please see for revised estimates.

PMID: 18544039 [PubMed - as supplied by publisher]

Avidity of IgG antibodies against excreted/secreted antigens of Toxoplasma

Rev Soc Bras Med Trop. 2008 Apr;41(2):142-147

Avidity of IgG antibodies against excreted/secreted antigens of Toxoplasma gondii: immunological marker for acute recent toxoplasmosis

Araújo PR, Ferreira AW.

IInstitute of Tropical Medicine, Faculty of Medicine, University of São Paulo, São Paulo, SP.

Detection of anti-toxoplasma IgM antibodies has frequently been used as a serological marker for diagnosing recently acquired toxoplasmosis. However, the persistence of these antibodies in some patients has complicated the interpretation of serological results when toxoplasmosis is suspected. The purpose of the present study was to evaluate the avidity of IgG antibodies against excreted/secreted antigens of Toxoplasma gondii by means of immunoblot, to establish a profile for acute recent infection in a single serum sample and confirm the presence of residual IgM antibodies obtained in automated assays. When we evaluated the avidity of IgG antibodies against excreted/secreted antigens of Toxoplasma gondii by means of immunoblot, we observed phase-specific reactivity, i.e. cases of acute recent toxoplasmosis presented low avidity and cases of non-acute recent toxoplasmosis presented high avidity towards the 30kDa protein fraction, which probably corresponds to the SAG-1 surface antigen. Our results suggest that the avidity of IgG antibodies against excreted/secreted antigens of Toxoplasma gondii is an important immunological marker for distinguishing between recent infections and for determining the presence of residual IgM antibodies obtained from automated assays.

PMID: 18545833 [PubMed - as supplied by publisher]

Sunday, June 08, 2008

The prodomain of GPI-anchored subtilase TgSUB1 mediates its targeting to micronemes

Traffic. 2008 Jun 2. [Epub ahead of print]

The prodomain of Toxoplasma gondii GPI-anchored subtilase TgSUB1 mediates its targeting to micronemes

Binder EM, Lagal V, Kim K

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

Subtilisin-like proteases have been proposed to play an important role for parasite survival in Toxoplasma gondii and Plasmodium falciparum. The T. gondii subtilase TgSUB1 is located in the microneme, an apical secretory organelle whose contents mediate adhesion to the host during invasion. TgSUB1 is predicted to contain a glycosyl-phosphatidylinositol anchor (GPI). This is unusual, as Toxoplasma GPI anchored proteins are targeted to the parasite's surface. Here, we report that the subtilase TgSUB1 is indeed a GPI anchored protein, but contains dominant microneme targeting signals. Accurate targeting of TgSUB1 to the micronemes is dependent upon several factors including promoter strength and timing, accurate processing, and folding. We analyzed the targeting domains of TgSUB1 using TgSUB1 deletion constructs and chimeras made between TgSUB1 and reporter proteins. The TgSUB1 prodomain is responsible for trafficking to the micronemes and is sufficient for targeting a reporter protein to the micronemes. Trafficking is dependent upon correct folding or other context-dependent conformation, as the prodomain expressed alone is unable to reach the micromenes. Therefore, TgSUB1 is a novel example of a GPI anchored protein in T. gondii that bypasses the GPI dependent surface trafficking pathway to traffic to micronemes, specialized regulated secretory organelles.

PMID: 18532988 [PubMed - as supplied by publisher]

Thursday, June 05, 2008


Pediatr Infect Dis J. 2008 May;27(5):469-474


Cañedo-Solares I, Galván-Ramírez MD, Luna-Pastén H, Rodríguez Pérez LR, Ortiz-Alegría LB, Rico-Torres CP, Vela-Amieva M, Pérez-Andrade M, Figueroa-Damián R, Correa D.

From the *Inmunología Experimental, Subdirección de Medicina Experimental, Instituto Nacional de Pediatría, Secretaría de Salud, México DF; †Centro Universitario de Ciencias de la Salud de la Universidad de Guadalajara; and ‡Instituto Nacional de Perinatología, Secretaría de Salud, México DF, México.

Anti-Toxoplasma gondii antibodies of all IgG subclasses were studied in mother/newborn pairs. IgG1 in the mothers and IgG3 in the newborns were related to offspring clinical problems; IgG2 and IgG3 in the babies were markers of vertical transmission, and IgG4 in mothers or children were associated to clinical problems. IgG subclasses may be markers of congenital infection or clinical outcome.

PMID: 18520342 [PubMed - as supplied by publisher]

Invasion of human retinal vascular endothelial cells by Toxoplasma gondii tachyzoites

Br J Ophthalmol. 2008 Jun;92(6):852-5

Invasion of human retinal vascular endothelial cells by Toxoplasma gondii tachyzoites

Zamora DO, Rosenbaum JT, Smith JR.

Oregon Health and Science University, L467AD, Biomedical Research Building, 3181 S.W. Sam Jackson Park Rd, Portland, OR 97239, USA;

BACKGROUND: Toxoplasma gondii infection is a leading cause of posterior uveitis. Human retinal endothelial cells (HREC) are more susceptible to infection with T gondii tachyzoites than other subpopulations of endothelial cells. It is hypothesised that this phenomenon reflects differences in invasion efficiency. METHODS: YFP-expressing RH strain T gondii tachyzoites were added to confluent HREC or human dermal endothelial cells (HDEC) (MOI = 50:1). Tachyzoite invasion after 1 h was determined by microplate reading of fluorescence intensity or parasite counts obtained using image analysis software. Selected cultures were incubated for three subsequent days, at which time fluorescence intensity indicated intracellular tachyzoite proliferation. RESULTS: HREC-tachyzoite cultures were more fluorescent than HDEC-tachyzoite cultures after 1 h (p = 0.020, paired t test, 3 experiments). Parasite counts also indicated that more tachyzoites invaded HREC than HDEC (p = 0.042, paired t test, 5 experiments). At 3 days, fluorescence intensity remained higher in HREC-tachyzoite cultures (p
PMID: 18523089 [PubMed - in process]

Genetic and Epigenetic Factors at COL2A1 and ABCA4 Influence Clinical Outcome in Congenital Toxoplasmosis

PLoS ONE. 2008 Jun 4;3(6):e2285

Genetic and Epigenetic Factors at COL2A1 and ABCA4 Influence Clinical Outcome in Congenital Toxoplasmosis

Jamieson SE, de Roubaix LA, Cortina-Borja M, Tan HK, Mui EJ, Cordell HJ, Kirisits MJ, Miller EN, Peacock CS, Hargrave AC, Coyne JJ, Boyer K, Bessieres MH, Buffolano W, Ferret N, Franck J, Kieffer F, Meier P, Nowakowska DE, Paul M, Peyron F, Stray-Pedersen B, Prusa AR, Thulliez P, Wallon M, Petersen E, McLeod R, Gilbert RE, Blackwell JM.

Cambridge Institute for Medical Research and Department of Medicine, University of Cambridge School of Clinical Medicine, Addenbrookes Hospital, Cambridge, United Kingdom.

BACKGROUND: Primary Toxoplasma gondii infection during pregnancy can be transmitted to the fetus. At birth, infected infants may have intracranial calcification, hydrocephalus, and retinochoroiditis, and new ocular lesions can occur at any age after birth. Not all children who acquire infection in utero develop these clinical signs of disease. Whilst severity of disease is influenced by trimester in which infection is acquired by the mother, other factors including genetic predisposition may contribute. METHODS AND FINDINGS: In 457 mother-child pairs from Europe, and 149 child/parent trios from North America, we show that ocular and brain disease in congenital toxoplasmosis associate with polymorphisms in ABCA4 encoding ATP-binding cassette transporter, subfamily A, member 4. Polymorphisms at COL2A1 encoding type II collagen associate only with ocular disease. Both loci showed unusual inheritance patterns for the disease allele when comparing outcomes in heterozygous affected children with outcomes in affected children of heterozygous mothers. Modeling suggested either an effect of mother's genotype, or parent-of-origin effects. Experimental studies showed that both ABCA4 and COL2A1 show isoform-specific epigenetic modifications consistent with imprinting. CONCLUSIONS: These associations between clinical outcomes of congenital toxoplasmosis and polymorphisms at ABCA4 and COL2A1 provide novel insight into the molecular pathways that can be affected by congenital infection with this parasite.

PMID: 18523590 [PubMed - in process]

Tuesday, June 03, 2008

Current and emerging approaches to studying invasion in apicomplexan parasites

Subcell Biochem. 2008;47:1-32

Current and emerging approaches to studying invasion in apicomplexan parasites

Mital J, Ward GE.

Department of Microbiology and Molecular Genetics, University of Vermont, Burlington, VT 05405, USA.

In this chapter, we outline the tools and techniques available to study the process of host cell invasion by apicomplexan parasites and we provide specific examples of how these methods have been used to further our understanding of apicomplexan invasive mechanisms. Throughout the chapter we focus our discussion on Toxoplasmagondii, because T. gondii is the most experimentally accessible model organism for studying apicomplexan invasion (discussed further in the section, "Toxoplasma as a Model Apicomplexan") and more is known about invasion in T. gondii than in any other apicomplexan.

Publication Types:
Research Support, N.I.H., Extramural
Research Support, Non-U.S. Gov't

PMID: 18512338 [PubMed - in process]

Calcium regulation and signaling in apicomplexan parasites

Subcell Biochem. 2008;47:70-81.

Calcium regulation and signaling in apicomplexan parasites

Nagamune K, Moreno SN, Chini EN, Sibley LD.

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

Apicomplexan parasites rely on calcium-mediated signaling for a variety of vital functions including protein secretion, motility, cell invasion, and differentiation. These functions are controlled by a variety of specialized systems for uptake and release of calcium, which acts as a second messenger, and on the functions of calcium-dependent proteins. Defining these systems in parasites has been complicated by their evolutionary distance from model organisms and practical concerns in working with small, and somewhat fastidious cells. Comparative genomic analyses of Toxoplasma gondii, Plasmodium spp. and Cryptosporidium spp. reveal several interesting adaptations for calcium-related processes in parasites. Apicomplexans contain several P-type Ca2+ ATPases including an ER-type reuptake mechanism (SERCA), which is the proposed target of artemisinin. All three organisms also contain several genes related to Golgi PMR-like calcium transporters, and a Ca2+/H+ exchanger, while plasma membrane-type (PMCA) Ca2+ ATPases and voltage-dependent calcium channels are exclusively found in T. gondii. Pharmacological evidence supports the presence of IP3 and ryanodine channels for calcium-mediated release. Collectively these systems regulate calcium homeostasis and release calcium to act as a signal. Downstream responses are controlled by a family of EF-hand containing calcium binding proteins including calmodulin, and an array of centrin and caltractin-like genes. Most surprising, apicomplexans contain a diversity of calcium-dependent protein kinases (CDPK), which are commonly found in plants. Toxoplasma contains more than 20 CDPK or CDPK-like proteases, while Plasmodium and Cryptosporidium have fewer than half this number. Several of these CDPKs have been shown to play vital roles in protein secretion, invasion, and differentiation, indicating that disruption of calcium-regulated pathways may provide a novel means for selective inhibition of parasites.

Publication Types:
Research Support, N.I.H., Extramural
Research Support, Non-U.S. Gov't

PMID: 18512342 [PubMed - in process]

Roles of proteases during invasion and egress by Plasmodium and Toxoplasma

Subcell Biochem. 2008;47:121-39.

Roles of proteases during invasion and egress by Plasmodium and Toxoplasma

Dowse TJ, Koussis K, Blackman MJ, Soldati-Favre D.

Department of Biological Sciences, Imperial College, London, UK.

Apicomplexan pathogens replicate exclusively within the confines of a host cell. Entry into (invasion) and exit from (egress) these cells requires an array of specialized parasite molecules, many of which have long been considered to have potential as targets of drug or vaccine-based therapies. In this chapter the authors discuss the current state of knowledge regarding the role of parasite proteolytic enzymes in these critical steps in the life cycle of two clinically important apicomplexan genera, Plasmodium and Toxoplasma. At least three distinct proteases of the cysteine mechanistic class have been implicated in egress of the malaria parasite from cells of its vertebrate and insect host. In contrast, the bulk of the evidence indicates a prime role for serine proteases of the subtilisin and rhomboid families in invasion by both parasites. Whereas proteases involved in egress may function predominantly to degrade host cell structures, proteases involved in invasion probably act primarily as maturases and 'sheddases', required to activate and ultimately remove ligands involved in interactions with the host cell.

PMID: 18512347 [PubMed - in process]

Biogenesis of and activities at the Toxoplasma gondii parasitophorous vacuole membrane

Subcell Biochem. 2008;47:155-64

Biogenesis of and activities at the Toxoplasma gondii parasitophorous vacuole membrane

Sinai AP.

Department of Microbiology Immunology and Molecular Genetics, University of Kentucky College of Medicine, 800 Rose St., Lexington, Kentucky 40536, USA.

Apicomplexan parasites like Toxoplasma gondii are distinctive in their utilization of para site encoded motor systems to invade cells. Invasion results in the establishment of the parasitophorous vacuole (PV) within the infected cell. Most apicomplexans complete their intracellular tenure within the infected cell in the PV that is demarcated from the host cytoplasm by the parasitophorous vacuole membrane (PVM). In this chapter I focus on the events surrounding the formation of the PVM and selected activities attributed to it. Its central role as the interface between the parasite and its immediate environment, the host cytoplasm, is validated by the diversity of functions attributed to it. While functions in structural organization, nutrient acquisitions and signaling have been defined their molecular bases remain largely unknown. Several recent studies and the decoding of the Toxoplasma genome have set the stage for a rapid expansion in our understanding of the role of the PVM in parasite biology. Toxoplasma gondii, like all apicomplexan parasites are obligate intracellular pathogens. This family of parasites utilize their own actin-myosin based motor systems to gain entry into susceptible cells establishing themselves, in some cases transiently (e.g., Theileria spp) in specialized vacuolar compartment, the parasitophorous vacuole (PV). The T. gondii PV is highly dynamic compartment defining the replication permissive niche for the parasite. The delimiting membrane defining the parasitophorous vacuole, the parasitophorous vacuole membrane or PVM is increasingly being recognized as a specialized "organelle" that in the context of the infected cell is extracorporeal to the parent organism, the parasite. A systematic study of this enigmatic organelle has been severely limited by several issues. Primary among these is the fact that it is formed only in the context of the infected cell thereby limiting the amount of material. Secondly, unlike other cellular organelles that can often be purified by conventional approaches, the PVM, cannot be purified away from host cell organelles (see below). In spite of these significant obstacles considerable progress has been made in recent years toward understanding the biogenesis of the PVM, identification of its protein complement and the characterization of activities within it. These studies demonstrate that the PVM, on its own and by virtue of its interactions with cellular components, plays critical functions in the structural integrity of the vacuole, nutrient acquisition and the manipulation of cellular functions. In addition it appears that the repertoire of activities at the PVM is likely to be plastic reflecting temporal changes associated with the replicative phase of parasite growth. Finally, the PVM likely forms the foundation for the cyst wall as the parasite differentiates in the establishment of latent infection. As the critical border crossing between the parasite and invaded cell the study of the PVM provides a fertile area for new investigation aided by the recent decoding of the Toxoplasma genome (available at and the application of proteomic analyses to basic questions in parasite biology.

PMID: 18512349 [PubMed - in process]

Transepithelial migration by Toxoplasma

Subcell Biochem. 2008;47:198-207.

Transepithelial migration by Toxoplasma

Barragan A, Hitziger N.

Swedish Institute for Infectious Disease Control and Center for Infectious Medicine, Karolinska Institutet, SE-141 86 Stockholm, Sweden.

A hallmark of T. gondii infections is passage of parasites across restrictive biological barriers--intestine, blood-brain barrier, blood-retina barrier and placenta-during primary infection or reactivation of chronic disease. Traversal of cellular barriers permits rapid dissemination of parasites to gain access to biologically restricted organs. This process involves active parasite motility and tightly regulated interactions between host cell receptors and parasite adhesins that facilitate paracellular transfer. Mounting evidence also suggests that parasites use migrating leukocytes as Trojan horses to disseminate in the organism while avoiding immune attack. Thus, the interaction of Toxoplasma with biological barriers is a determinant factor of human toxoplasmosis. The elucidation of determinants involved in the process of migration may reveal virulence factors and novel therapeutic targets to combat disease.

Publication Types:
Research Support, Non-U.S. Gov't

PMID: 18512353 [PubMed - in process]

What are the respective host and parasite contributions to toxoplasmosis?

Trends Parasitol. 2008 May 28. [Epub ahead of print]

What are the respective host and parasite contributions to toxoplasmosis?

Maubon D, Ajzenberg D, Brenier-Pinchart MP, Dardé ML, Pelloux H.

Laboratoire Adaptation et Pathogénie des Microorganismes, UMR 5163 CNRS-Université Joseph Fourier, Institut J. Roget, BP 170, 38042 Grenoble Cedex 9, France; Laboratoire de Parasitologie–Mycologie, Département des Agents Infectieux, Pôle de Biologie, Centre Hospitalier Universitaire de Grenoble, France.

The toxoplasmosis pathogenesis mechanism is complex because parasite and host specificities are interrelated. Advances in fundamental research (including strain genotyping, analyzing the progeny from crosses of different strains and exploring the implication of epigenetic effects on the parasite) have contributed greatly to our current knowledge of this mechanism. At the same time new data on the clinical characteristics of the disease have come to light. For example, highly virulent strains have been isolated recently in immunocompetent patients, and some studies suggest that toxoplasmosis also might be implicated in brain disorders. These recent tools and discoveries are likely to cast new light on the pathogenicity of Toxoplasma parasites and provide the key to understanding this unique form of parasitism.

PMID: 18514029 [PubMed - as supplied by publisher]