Saturday, August 30, 2008

Cutaneous toxoplasmosis after bone marrow transplantation

J Am Acad Dermatol. 2008 Aug 22. [Epub ahead of print]

Cutaneous toxoplasmosis after bone marrow transplantation with molecular confirmation

Amir G, Salant H, Resnick IB, Karplus R.

Department of Pathology, Hadassah University Hospital, Jerusalem, Israel.

Toxoplasmosis is a rare and often fatal complication of hematopoietic stem cell transplantation (HSCT). The diagnosis of toxoplasmosis is usually made at autopsy because of the variety of systemic manifestations and the difficulty of diagnosis by serologic methods in the severely immunocompromised patient. Cutaneous toxoplasmosis in this setting is extremely rare and is difficult to diagnose with certainty because of the morphologic similarity of Toxoplasma gondii to other organisms, such as Leishmania and Histoplasma species. We report a patient who developed systemic toxoplasmosis, manifested as encephalitis and cutaneous lesions, after HSCT. Findings of a skin biopsy led to a tentative histologic diagnosis of toxoplasmosis, confirmed by polymerase chain reaction (PCR) examination of the skin biopsy and cerebrospinal fluid. This is, to our knowledge, the first report of cutaneous toxoplasmosis diagnosed by skin biopsy confirmed by PCR and sequencing. This disease may be more common than is generally appreciated in severely immunocompromised patients. PCR is a valuable adjunct to diagnosis.

PMID: 18723241 [PubMed - as supplied by publisher]

7-Deaza-6-benzylthioinosine analogues as subversive substrate of Toxoplasma gondii adenosine kinase

Biochem Pharmacol. 2008 Aug 7. [Epub ahead of print]

7-Deaza-6-benzylthioinosine analogues as subversive substrate of Toxoplasma gondii adenosine kinase: Activities and selective toxicities

Al Safarjalani ON, Rais RH, Ah Kim Y, Chu CK, Naguib FN, El Kouni MH.

Department of Pharmacology and Toxicology, Center for AIDS Research, Comprehensive Cancer Center, University of Alabama at Birmingham, Birmingham, AL 35294, USA.

Toxoplasma gondii adenosine kinase (EC.2.7.1.20) is the major route of adenosine metabolism in this parasite. The enzyme is significantly more active than any other enzyme of the purine salvage in T. gondii and has been established as a potential chemotherapeutic target for the treatment of toxoplasmosis. Certain 6-benzylthioinosines act as subversive substrates of T. gondii, but not human, adenosine kinase. Therefore, these compounds are preferentially metabolized to their respective nucleotides and become selectively toxic against the parasites but not their host. Moreover, 7-deazaadenosine (tubercidin) was shown to be an excellent ligand of T. gondii adenosine kinase. Therefore, we synthesized 7-deaza-6-benzylthioinosine, and analogues with various substitutions at their phenyl ring, to increase the binding affinity of the 6-benzylthioinosines to T. gondii adenosine kinase. Indeed, the 7-deaza-6-benzylthioinosine analogues were better ligands of T. gondii adenosine kinase than the parent compounds, 6-benzylthioinosine and 7-deazainosine. Herein, we report the testing of the metabolism of these newly synthesized 7-deaza-6-benzylthioinosines, as well as their efficacy as anti-toxoplasmic agents in cell culture. All the 7-deaza-6-benzylthioinosine analogues were metabolized to their 5'-monophosphate derivatives, albeit to different degrees. These results indicate that these compounds are not only ligands but also substrates of T. gondii adenosine kinase. All the 7-deaza-6-benzylthioinosine analogues showed a selective antitoxoplasmic effect against wild type parasites, but not mutants lacking adenosine kinase. The efficacy of these compounds varied with the position and nature of the substitution on their phenyl ring. Moreover, none of these analogues exhibited host toxicity. The best compounds were 7-deaza-6-(p-methoxybenzylthio)inosine (IC(50)=4.6muM), 7-deaza-6-(p-methoxycarbonylbenzylthio)inosine (IC(50)=5.0muM), and 7-deaza-6-(p-cyanobenzylthio)inosine (IC(50)=5.3muM). These results further confirm that T. gondii adenosine kinase is an excellent target for chemotherapy and that 7-deaza-6-benzylthioinosines are potential antitoxoplasmic agents.

PMID: 18755159 [PubMed - as supplied by publisher]

Saturday, August 23, 2008

Performance characteristics of the new ARCHITECT Toxo IgG and Toxo IgG Avidity assays

Diagn Microbiol Infect Dis. 2008 Aug 19. [Epub ahead of print]

Performance characteristics of the new ARCHITECT Toxo IgG and Toxo IgG Avidity assays

Sickinger E, Gay-Andrieu F, Jonas G, Schultess J, Stieler M, Smith D, Hausmann M, Stricker R, Stricker R, Dhein J, Braun HB.

Abbott GmbH & Co. KG, Max-Planck-Ring 2, D-65205 Wiesbaden-Delkenheim, Germany.

The ARCHITECT Toxo IgG and IgG Avidity assays have been developed as a fully automated panel for immune status determination and acute infection exclusion. Resolved relative specificity and sensitivity of the ARCHITECT Toxo IgG assay were 99.6% (1359/1365) and 99.7% (1096/1099) as determined on pregnant females, blood donor, and diagnostic specimens. Seroconversion sensitivity of the ARCHITECT assay was comparable with the AxSYM Toxo IgG assay. The ARCHITECT Toxo IgG Avidity assay detected 100.0% (124/124) of acute phase specimens (<4 months after infection) as low avidity, whereas the Vidas Toxo IgG Avidity assay detected 98.9% (89/90) as low avidity. In summary, the ARCHITECT Toxo IgG assay, using recombinant antigens, showed excellent specificity and sensitivity for acute phase as well as past infection specimens. The ARCHITECT Toxoplasmosis panel can be reliably used to rule out acute Toxoplasma gondii infection in pregnant women.

PMID: 18715735 [PubMed - as supplied by publisher]

Role of spiramycin/cotrimoxazole association in the mother-to-child transmission of toxoplasmosis infection in pregnancy

Eur J Clin Microbiol Infect Dis. 2008 Aug 21. [Epub ahead of print]

Role of spiramycin/cotrimoxazole association in the mother-to-child transmission of toxoplasmosis infection in pregnancy

Valentini P, Annunziata ML, Angelone DF, Masini L, De Santis M, Testa A, Grillo RL, Speziale D, Ranno O.

Department of Pediatrics, Pediatric Infectious Diseases Unit, Catholic University of the Sacred Heart, L.go A. Gemelli, 8, 00168, Rome, Italy, pvalentini@rm.unicatt.it.

The purpose of this report is to evaluate the efficacy and safety of spiramycin/cotrimoxazole in the mother-to-child transmission of Toxoplasma gondii infection. We retrospectively analysed 76 infants born to mothers with toxoplasmosis during pregnancy and estimated the risk of mother-to-child transmission considering the gestational age at the time of infection. Seventy-six mothers were given spiramycin, cotrimoxazole and folinic acid; only two babies (2.6%) were infected by Toxoplasma and none of them showed signs or symptoms of congenital infection or interference of sulphamid on tetrahydrofolate reductase (THFR) either at birth or during follow-up. Treatment did not need to be stopped in any mother because of adverse drug effects. Our results seem to encourage the use of spiramycin/cotrimoxazole in women with toxoplasmosis during pregnancy.

PMID: 18716804 [PubMed - as supplied by publisher]

Thursday, August 21, 2008

TLR adaptor MyD88 is essential for pathogen control during oral Toxo infection but not adaptive immunity induced by a vaccine strain

J Immunol. 2008 Sep 1;181(5):3464-73

TLR adaptor MyD88 is essential for pathogen control during oral toxoplasma gondii infection but not adaptive immunity induced by a vaccine strain of the parasite

Sukhumavasi W, Egan CE, Warren AL, Taylor GA, Fox BA, Bzik DJ, Denkers EY.

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

TLR adaptor MyD88 activation is important in host resistance to Toxoplasma gondii during i.p. infection, but the function of this signaling pathway during oral infection, in which mucosal immunity assumes a predominant role, has not been examined. In this study, we show that MyD88(-/-) mice fail to control the parasite and succumb within 2 wk of oral infection. Early during infection, T cell IFN-gamma production, recruitment of neutrophils and induction of p47 GTPase IGTP (Irgm3) in the intestinal mucosa were dependent upon functional MyD88. Unexpectedly, these responses were MyD88-independent later during acute infection. In particular, CD4(+) T cell IFN-gamma reached normal levels independently of MyD88, despite continued absence of IL-12 in these animals. The i.p. vaccination of MyD88(-/-) mice with an avirulent T. gondii uracil auxotroph elicited robust IFN-gamma responses and protective immunity to challenge with a high virulence T. gondii strain. Our results demonstrate that MyD88 is required to control Toxoplasma infection, but that the parasite can trigger adaptive immunity without the need for this TLR adaptor molecule.

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

PMID: 18714019 [PubMed - in process]

Tuesday, August 19, 2008

Evaluation of immunization with tachyzoite excreted-secreted proteins in a novel susceptible mouse model (AS/n) for Toxoplasma

Exp Parasitol. 2008 Jul 31. [Epub ahead of print]

Evaluation of immunization with tachyzoite excreted-secreted proteins in a novel susceptible mouse model (AS/n) for Toxoplasma gondii

Costa-Silva TA, Meira CS, Ferreira IM, Hiramoto RM, Pereira-Chioccola VL.

Department of Parasitology, Instituto Adolfo Lutz, Laboratorio de Parasitologia, Av. Dr. Arnaldo, 351, 8 andar, CEP 01246-902, São Paulo, SP, Brazil.

Toxoplasma gondii is an important food-borne parasite transmitted primarily from animals to humans through meat consumption, mainly pork and lamb, as well as through oocysts shed by cats. Infection in humans can cause severe neonatal malformations, ocular complications or encephalitis. Toxoplasmosis infection during pregnancy, especially in sheep, often results in abortion, representing considerable economic loss. The aim of this study was to investigate whether Toxoplasma gondii pooled excreted-secreted antigens (ESA), recovered from infected culture supernatants with tachyzoites used as immunogen, can protect experimental mice against T. gondii infection. For immunization experiments, we evaluated AS/n inbred mice, a novel susceptible mouse model for T. gondii and a virulent strain (RH) for challenge experiments. The antigen selection was based on those produced by tachyzoites since they are responsible for disseminating the infection as well as stimulating the humoral and cellular immune responses. ESA were recovered from VERO cell-culture supernatants infected with virulent RH strain tachyzoites harvested after 48h. Groups of 5 female mice were intraperitoneally (i.p.) immunized with 4 doses at 2week intervals with 20mug of ESA adsorbed to 0.5mg of alum. The control group received only the adjuvant in PBS on the same dates. Pooled serum collected from chronically infected mice was used as positive control. Blood samples were collected from tail veins 14 days after each immunization. Antibody was detected using ELISA, indirect immunofluorescence and immunoblotting. Anti-ESA antibodies were also evaluated by agglutination, complement-mediated lysis and antibody-mediated cellular toxicity. Fifteen days after the last immunization, both groups were challenged (i.p.) with 103 RH strain tachyzoites. The parasitemia was evaluated by PCR, and survival was followed daily. The results showed an increase of antibody levels after each immunization. Anti-ESA antibodies also reacted with a crude tachyzoite antigen and bonded on the parasite surface, with particularly high intensity at the apical region. Anti-ESA antibodies were also able to agglutinate and kill tachyzoites in vitro through interactions with complement and cellular pathways. Even though the tachyzoite challenge was lethal to the mice, PCR results suggested that immunized mice had lower parasitemia as well as longer survival (72h) than mice from the control group.

PMID: 18706414 [PubMed - as supplied by publisher]

Alterations of concentrations of calcium and arachidonic acid and agglutinations of microfilaments in host cells during Toxo invasion

Vet Parasitol. 2008 Jul 23. [Epub ahead of print]

Alterations of concentrations of calcium and arachidonic acid and agglutinations of microfilaments in host cells during Toxoplasma gondii invasion

Li L, Li X, Yan J.

Department of Medical Microbiology and Parasitology, Medical School of Zhejiang University, Hangzhou, 310058, China.

Toxoplasma gondii (T. gondii) invasion of host cells is a complicated process of interaction between parasites and host cells. In the present study we investigated the alterations of free Ca(2+) concentration ([Ca(2+)](i)) and cytoskeletons in phagocytic and non-phagocytic host cells and arachidonic acid (AA) concentration in cells supernatant during T. gondii invasion. T. gondii invasion induced significant elevation of intracellular [Ca(2+)](i) in phagocytic cells (J774A.1) but not in non-phagocytic cells (L929). Pre-treatment of J774A.1 cells with Phospholipase C (PLC) inhibitor (U73122), or Ca(2+) chelators (EGTA, BAPTA/AM) did not block elevations of [Ca(2+)](i) but the elevations were lower and of shorter duration than that in untreated cells. Pre-treatment of tachyzoites with Phospholipases A (PLA) inhibitors (4-BPB and AACOCF3) resulted in a similar pattern of increasing of [Ca(2+)](i) as that in Ca(2+) chelators treated cells. Agglutinations of microfilaments were observed in J774A.1 cells but not in L929 cells. No changes of microtubules were observed in either cell. Treatment of cells with cytoskeleton inhibitors (colchicines, cytochalasin-D) resulted in reduced cell infection ratios. AA concentration in J774A.1 cells supernatant reached 8.44-fold of basal concentration after T. gondii infection and those in 4-BPB or AACOCF3 pre-treated cells reached 7.70-fold and 8.09-fold of basal concentration, respectively. However, elevation of AA concentrations induced by 4-BPB or AACOCF3 treated tachyzoites were 3.02-fold and 2.65-fold of basal AA concentration. AA concentration in L929 cells supernatant reached 5.02-fold of basal concentration after T. gondii infection and those in 4-BPB or AACOCF3 pre-treated cells reached 4.75-fold and 4.78-fold of basal concentration, respectively. However, elevation of AA concentrations induced by 4-BPB or AACOCF3 treated tachyzoites were 2.06-fold and 2.43-fold of basal AA concentration. Results indicated that elevations of [Ca(2+)](i) and AA induced by T. gondii invasion were from both host cells and parasites. T. gondii invasion activated host cell PLC and triggered the PLC-PKC signal pathway, which resulted in the flowing of extracellular Ca(2+) and the releasing of intracellular Ca(2+) pool. Elevated [Ca(2+)](i) induced reorganization of host cell microfilaments. The invasion also activated secretory PLA(2) (sPLA(2)) and cytosolic PLA(2) (cPLA(2)) of the parasite to release AA, which increased the permeability of cell membrane.

PMID: 18706765 [PubMed - as supplied by publisher]

Sunday, August 17, 2008

The cell cycle and Toxoplasma gondii cell division: Tightly knit or loosely stitched?

Int J Parasitol. 2008 Jul 24. [Epub ahead of print]

The cell cycle and Toxoplasma gondii cell division: Tightly knit or loosely stitched?

Gubbels MJ, White M, Szatanek T.

Department of Biology, Boston College, 355 Higgins Hall, 140 Commonwealth Avenue, Chestnut Hill, MA 02467, USA.

The flexibility displayed by apicomplexan parasites to vary their mode of replication has intrigued biologists since their discovery by electron microscopy in the 1960s and 1970s. Starting in the 1990s we began to understand the cell biology of the cytoskeleton elements driving cytokinesis. By contrast, the molecular mechanisms that regulate the various division modes and how they translate into the budding process that uniquely characterizes this parasite family are much less understood. Although growth mechanisms are a neglected area of study, it is an important pathogenic parameter as fast division rounds are associated with fulminant infection whereas slower growth attenuates virulence, as is exploited in some vaccine strains. In this review we summarize a recent body of cell biological experiments that are rapidly leading to an understanding of the events that yield successful mitosis and cytokinesis in Toxoplasma. We place these observations within a cell cycle context with comments on how these events may be regulated by known eukaryotic checkpoints active in fission and budding yeasts as well as mammalian cells. The presence of cell cycle control mechanisms in the Apicomplexa is supported by our findings that identify several cell cycle checkpoints in Toxoplasma. The progress of the cell cycle is ultimately controlled by cyclin-Cdk pair activities, which are present throughout the Apicomplexa. Although many of the known controllers of cyclin-Cdk activity are present, several key controls cannot readily be identified, suggesting that apciomplexan parasites deviate at these points from the higher eukaryotic models. Altogether, new insights in Toxoplasma replication are reciprocally applied to hypothesize how other division modes in the Toxoplasma life cycle and in other Apicomplexa species could be controlled in terms of cell cycle checkpoint regulation.

PMID: 18703066 [PubMed - as supplied by publisher]

Use of SAG2A recombinant Toxoplasma gondii surface antigen as a diagnostic marker for human acute toxoplasmosis

Diagn Microbiol Infect Dis. 2008 Aug 12. [Epub ahead of print]

Use of SAG2A recombinant Toxoplasma gondii surface antigen as a diagnostic marker for human acute toxoplasmosis: analysis of titers and avidity of IgG and IgG1 antibodies


Béla SR, Oliveira Silva DA, Cunha-Júnior JP, Pirovani CP, Chaves-Borges FA, Reis de Carvalho F, Carrijo de Oliveira T, Mineo JR.

Laboratory of Immunoparasitology, Institute of Biomedical Sciences, Federal University of Uberlândia, Uberlândia, MG, 38401-136, Brazil.

We evaluated the reactivity of IgG and IgG1 antibodies by immunoassays in sera from patients with acute and chronic phases of toxoplasmosis against 2 recombinant antigens, SAG2A (full molecule) and SAG2ADelta (truncated molecule from the epitope recognized by A4D12 monoclonal antibody [mAb]), in comparison with soluble Toxoplasma antigen (STAg). Results demonstrated higher IgG reactivity in acute sera with both STAg and SAG2A than in chronic phase sera, and this difference was more evident for IgG1 antibodies to SAG2A. Low reactivity to SAG2ADelta was found in sera from both phases. ELISA-IgG-SAG2A showed high sensitivity (95%) and specificity (100%). ELISA-IgG1-SAG2A sensitivity was significantly higher (90%) for acute than for chronic (67%) phases. ELISA-IgG avidity using STAg demonstrated high performance for characterizing sera with high avidity (>60%), whereas the ELISA-IgG1 avidity-SAG2A immunoassay was the best to define chronic phase infection. It can be concluded that SAG2A is an antigen that may be used as a diagnostic tool to characterize the acute phase Toxoplasma gondii infection. Also, the epitope recognized by A4D12 mAb may be critical for the recognition of this molecule.

PMID: 18703303 [PubMed - as supplied by publisher]

Friday, August 15, 2008

Ocular Sequelae of Congenital Toxoplasmosis in Brazil Compared with Europe

PLoS Negl Trop Dis. 2008 Aug 13;2(8):e277

Ocular Sequelae of Congenital Toxoplasmosis in Brazil Compared with Europe

Gilbert RE, Freeman K, Lago EG, Bahia-Oliveira LM, Tan HK, Wallon M, Buffolano W, Stanford MR, Petersen E; for The European Multicentre Study on Congenital Toxoplasmosis (EMSCOT).

Centre for Paediatric Epidemiology and Biostatistics, Institute of Child Health, London, United Kingdom.

BACKGROUND: Toxoplasmic retinochoroiditis appears to be more severe in Brazil, where it is a leading cause of blindness, than in Europe, but direct comparisons are lacking. Evidence is accumulating that more virulent genotypes of Toxoplasma gondii predominate in South America. METHODS: We compared prospective cohorts of children with congenital toxoplasmosis identified by universal neonatal screening in Brazil and neonatal or prenatal screening in Europe between 1992 and 2003, using the same protocol in both continents. RESULTS: Three hundred and eleven (311) children had congenital toxoplasmosis: 30 in Brazil and 281 in Europe, where 71 were identified by neonatal screening. Median follow up was 4.1 years in Europe and 3.7 years in Brazil. Relatively more children had retinochoroiditis during the first year in Brazil than in Europe (15/30; 50% versus 29/281; 10%) and the risk of lesions by 4 years of age was much higher: the hazard ratio for Brazil versus Europe was 5.36 (95%CI: 3.17, 9.08). Children in Brazil had larger lesions, which were more likely to be multiple and to affect the posterior pole (p<0.0001). In Brazil, visual impairment (<6/12 Snellen) was predicted for most affected eyes (87%, 27/31), but not in Europe (29%; 20/69, p<0.0001). The size of newly detected lesions decreased with age (p = 0.0007). CONCLUSIONS: T. gondii causes more severe ocular disease in congenitally infected children in Brazil compared with Europe. The marked differences in the frequency, size and multiplicity of retinochoroidal lesions may be due to infection with more virulent genotypes of the parasite that predominate in Brazil but are rarely found in Europe.

PMID: 18698419 [PubMed - as supplied by publisher]

Thursday, August 14, 2008

Control of the risk of human toxoplasmosis transmitted by meat

Int J Parasitol. 2008 Jul 23. [Epub ahead of print]

Control of the risk of human toxoplasmosis transmitted by meat

Kijlstra A, Jongert E.

Animal Sciences Group, Wageningen UR, P.O. Box 65, 8200 AB Lelystad, The Netherlands; Department Ophthalmology, Maastricht University, Maastricht, The Netherlands.

One-third of the human world population is infected with the protozoan parasite Toxoplasma gondii. Recent calculations of the disease burden of toxoplasmosis rank this foodborne disease at the same level as salmonellosis or campylobacteriosis. The high disease burden in combination with disappointing results of the currently available treatment options have led to a plea for more effective prevention. In this review we describe Toxoplasma as a hazard associated with the consumption of undercooked meat or meat products and provide an analysis of the various options to control the risk of human toxoplasmosis via this source. Monitoring and surveillance programs may be implemented for pre-harvest control of Toxoplasma infection of farm animals, with the reduction of environmental oocyst load as the most important milestone. Alternatively, Toxoplasma safe meat can be obtained through simple post-harvest decontamination procedures, whereby freezing the meat may currently be the best option, although new technologies using irradiation or high-pressure treatment may offer promising alternatives. Influence of culture, religion and food handling customs may predispose a certain type of meat as an important source of infection, indicating that prevention needs to be tailored according to social habits in different regions in the world. The rationale for more stringent control measures to prevent toxoplasmosis both from disease and economic points of view is emphasized.

PMID: 18694755 [PubMed - as supplied by publisher]

Wednesday, August 13, 2008

Postdoctoral Position

An NIH sponsored postdoctoral position is available beginning Dec. 1, 2008 or soon thereafter to investigate the function of cathepsin proteases in Toxoplasma gondii, an opportunistic protozoan parasite that can cause severe disease (encephalitis, retinitis, birthdefects)in humans and animals. T. gondii is a tractable parasite that is easily grown in culture, has excellent animal models, and is amenable genetic manipulation. The parasite expresses two cathepsin endoproteases that appear to function together to activate invasion related proteins in a novel multivesicular endosome within the parasite. Cathepsin function will be investigated by a variety of in vitro and in vivo approaches including analysis of recombinant proteins, targeted gene-disruption and gene-tagging, use of small molecule inhibitors, etc.

Candidates must have a Ph.D. and/or M.D., or equivalent degree and a strong background in protein biochemistry and molecular cell biology. Experience with fluorescence microscopy would also be advantageous.

The University of Michigan is currently ranked second among top American public research universities (http://mup.asu.edu/research.html). The university is located in Ann Arbor, Michigan, which is widely considered one of the most livable mid-sized cities in the USA. With its abundance of parks, restaurants, recreational opportunities, and moderate cost of living, residents of Ann Arbor enjoy a high quality of life. Ann Arbor is situated within a 30 min drive of Detroit International Airport, thus providing easy air travel access to destinations in the USA and throughout the world.

Please send by e-mail a cover letter stating interests and career goals, a C.V. including list of publications, and the contact information for three individuals who are willing to provide letters of recommendation.

Vern B. Carruthers, Ph.D.
Associate Professor
Department of Microbiology & Immunology
University of Michigan Medical School
5740A Medical Science Bldg. II, Box 5620
1150 West Medical Center Dr.
Ann Arbor, Michigan 48109-5620
Telephone (734) 763-2081
FAX (734) 764-3562
http://www.med.umich.edu/microbio/bio/carruthers.htm
vcarruth@umich.edu

Tuesday, August 12, 2008

Ovine toxoplasmosis: transmission, clinical outcome and control

Parassitologia. 2007 Dec;49(4):219-21

Ovine toxoplasmosis: transmission, clinical outcome and control

Buxton D, Maley SW, Wright SE, Rodger S, Bartley P, Innes EA.

Moredun Research Institute, Edinburgh, Scotland, UK. david.buxton@moredun.ac.uk

Toxoplasma gondii is a significant cause of abortion in sheep. Infection is picked up from the environment and if initiated during pregnancy may cause fetal mortality. Infected sheep remain persistently infected with tissue cysts in brain and muscle (meat), and are also immune and would not be expected to abort again. The live tachyzoite vaccine (Toxovax) protects against abortion and this allows the suggestion that it may also reduce or prevent tissue cyst development in muscle. If this were so it raises the question of whether the vaccine could be used to make meat safer for human consumption.

PMID: 18689230 [PubMed - in process]

Undercooked meat consumption remains the major risk factor for Toxoplasma infection in Serbia

Parassitologia. 2007 Dec;49(4):227-30

Undercooked meat consumption remains the major risk factor for Toxoplasma infection in Serbia

Bobić B, Nikolić A, Klun I, Vujanić M, Djurković-Djaković O.

Belgrade University Institute for Medical Research, Toxoplasmosis Research Laboratory, Belgrade, Serbia. bobicb@imi.bg.ac.yu

Toxoplasma gondii infection prevalence and infection risk factors were analyzed in a series of 765 women of generative age from throughout Serbia tested at the Institute for Medical Research Toxoplasmosis Laboratory between 2001 and 2005. The infection risk factors were additionally analyzed in a group of 53 women with acute infection (cases) compared to a group of seronegative women matched for age and education level (controls). The overall prevalence of infection was 33%. Infection risk factors in the whole series were undercooked meat consumption (RR = 1.77, 95% CI = 1.16-2.7, P = 0.008) and exposure to soil (RR = 1.63, 95% CI = 1.17-2.29, P = 0.004), particularly in less educated women. Moreover, undercooked meat consumption was the single predictor of infection in women with acute infection, with an 11-fold increased risk of infection in women who acknowledged consumption of undercooked meat (RR = 11.21, 95% CI = 3.10-40.53, P = 0.000). These data prompted us to analyze the significance of consumption of particular meat types as sources of infection. Of all the meat types mostly consumed in Serbia, only consumption of beef (RR = 1.006, 95% CI = 1.001-1.011, P = 0.027) was shown to influence Toxoplasma infection rates.

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

PMID: 18689232 [PubMed - in process]

Gr1(+) Inflammatory Monocytes Are Required for Mucosal Resistance to the Pathogen Toxoplasma

Immunity. 2008 Aug 6. [Epub ahead of print]

Gr1(+) Inflammatory Monocytes Are Required for Mucosal Resistance to the Pathogen Toxoplasma gondii

Dunay IR, Damatta RA, Fux B, Presti R, Greco S, Colonna M, Sibley LD.

Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO 63110, USA.

The enteric pathogen Toxoplasma gondii is controlled by a vigorous innate T helper 1 (Th1) cell response in the murine model. We demonstrated that after oral infection, the parasite rapidly recruited inflammatory monocytes [Gr1(+) (Ly6C(+), Ly6G(-)) F4/80(+)CD11b(+)CD11c(-)], which established a vital defensive perimeter within the villi of the ileum in the small intestine. Mice deficient of the chemokine receptor CCR2 or the ligand CCL2 failed to recruit Gr1(+) inflammatory monocytes, whereas dendritic cells and resident tissue macrophages remained unaltered. The selective lack of Gr1(+) inflammatory monocytes resulted in an inability of mice to control replication of the parasite, high influx of neutrophils, extensive intestinal necrosis, and rapid death. Adoptive transfer of sorted Gr1(+) inflammatory monocytes demonstrated their ability to home to the ileum in infected animals and protect Ccr2(-/-) mice, which were otherwise highly susceptible to oral toxoplasmosis. Collectively, these findings illustrate the critical importance of inflammatory monocytes as a first line of defense in controlling intestinal pathogens.

PMID: 18691912 [PubMed - as supplied by publisher]

Sunday, August 10, 2008

Role of lipoxin in the modulation of immune response during infection

Int Immunopharmacol. 2008 Oct;8(10):1316-9. Epub 2008 Jan 18

Role of lipoxin in the modulation of immune response during infection

Machado FS, Aliberti J.

Division of Molecular Immunology, Cincinnati Children's Hospital Medical Center and University of Cincinnati College of Medicine, Cincinnati, Ohio, USA.

Pro-inflammatory mediators such as IL-12, IFN-gamma and TNF are essential in controlling parasite growth during Toxoplasma gondii infection. However, it is clear that the exacerbate production of these cytokines results in the host tissue damage. Investigation into the immune response modulation during infectious disease, has revealed that lipoxin (LXA), an anti-inflammatory eicosanoids, plays an important role in regulation of immune response to different pathogens, including T. gondii and Mycobacterium tuberculosis. Here, we review the pro-resolution pathways triggered by LXA that are responsible for control of pro-inflammatory response during chronic disease.

PMID: 18687293 [PubMed - in process]

CCR2 Receptor Is Essential to Activate Microbicidal Mechanisms to Control Toxo Infection in the CNS

Am J Pathol. 2008 Aug 7. [Epub ahead of print]

CCR2 Receptor Is Essential to Activate Microbicidal Mechanisms to Control Toxoplasma gondii Infection in the Central Nervous System

Benevides L, Milanezi CM, Yamauchi LM, Benjamim CF, Silva JS, Silva NM.

From the Department of Biochemistry and Immunology,* School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, São Paulo; the State University of Londrina, Londrina, Paraná; the Institute of Biomedical Sciences, Federal University of Rio de Janeiro, Rio de Janeiro; and the Department of Morphology, Institute of Biomedical Sciences, Federal University of Uberlândia, Uberlândia, Minas Gerais, Brazil.

Chemokines comprise a structurally related family of cytokines that regulate leukocyte trafficking. Because infection with Toxoplasma gondii can induce an important inflammatory reaction that, if left uncontrolled, can lead to death, we investigated the role of the chemokine receptor CCR2 in T. gondii infection. We orally infected CCR2(-/-) mice with five ME-49 T. gondii cysts and monitored morbidity, survival, and immune response thereafter. The CCR2(-/-) mice displayed higher susceptibility to infection as all mice died on day 28 after infection. Despite similar Th1 responses, a more evident anti-inflammatory response was induced in the peripheral organs of CCR2(-/-) mice compared with wild-type C57BL/6 mice. Additionally, CCR2(-/-) mice presented greater parasitism and a milder inflammatory reaction in their peripheral organs with lesser CD4(+) and MAC-1(+) and greater CD8(+) cell migration. The parasite load decreased in these organs in CCR2(-/-) mice but remained uncontrolled in the central nervous system. Additionally, we observed down-regulated inducible nitric oxide synthase expression in peripheral organs from CCR2(-/-) mice that was associated with a small nitric oxide production by spleen macrophages. In conclusion, in the absence of CCR2, another mechanism is activated to control tissue parasitism in peripheral organs. Nevertheless, CCR2 is essential for the activation of microbicidal mediators that control T. gondii replication in the central nervous system.

PMID: 18688032 [PubMed - as supplied by publisher]

Antibody response of HIV-infected patients to latent, cerebral and recently acquired toxoplasmosis

Eur J Clin Microbiol Infect Dis. 2008 Aug 8. [Epub ahead of print]

Antibody response of HIV-infected patients to latent, cerebral and recently acquired toxoplasmosis

Machala L, Malý M, Hrdá S, Rozsypal H, Staňková M, Kodym P.

University Hospital Bulovka, AIDS Center, Budínova 2, Prague 8, 180 81, Czech Republic.

The aim of this longitudinal study with 626 HIV-infected patients was to evaluate the capability of serological tests in diagnosing the presence of Toxoplasma gondii infection in HIV-infected patients, as well as the potential impact of various treatment regimes on serological results. Low IgG antibody levels and stable or declining titres predominated. IgM positivity occurred in ten patients (one seroconversion, seven latent, two cerebral toxoplasmosis). Complement fixation test (CFT) titres >/=1:32 imply that the relative risk of cerebral toxoplasmosis is 6.84 (95% confidence interval [CI] 1.44-32.5) but with a predictive value of only 14.0% (95% CI 5.3-27.9). Values of specific antibodies are not biassed by antiretroviral treatment and/or prophylaxis for toxoplasmosis, and the detection of specific antibodies is very useful in the identification of T. gondii infection in the HIV-infected population, but the role of serology in predicting the clinical manifestation of T. gondii infection is limited.

PMID: 18688665 [PubMed - as supplied by publisher]

Friday, August 08, 2008

A qualitative assessment of Toxoplasma gondii risk in ready-to-eat smallgoods processing

J Food Prot. 2008 Jul;71(7):1442-52

A qualitative assessment of Toxoplasma gondii risk in ready-to-eat smallgoods processing

Mie T, Pointon AM, Hamilton DR, Kiermeier A.

Department for Food Safety and Infection Biology, Section for Food Safety, Norwegian School of Veterinary Science, P.O. Box 8146, Ullevaalsveien 72, 0033 Oslo, Norway.

Toxoplasma gondii is one of the most common parasitic infections of humans and other warm-blooded animals. In most adults, it does not cause serious illness, but severe disease may result from infection in fetuses and immunocompromised people. Consumption of raw or undercooked meats has consistently been identified as an important source of exposure to T. gondii. Several studies indicate the potential failure to inactivate T. gondii in the processes of cured meat products, This article presents a qualitative risk-based assessment of the processing of ready-to-eat smallgoods, which include cooked or uncooked fermented meat, pâté, dried meat, slow cured meat, luncheon meat, and cooked muscle meat including ham and roast beef. The raw meat ingredients are rated with respect to their likelihood of containing T. gondii cysts and an adjustment is made based on whether all the meat from a particular source is frozen. Next, the effectiveness of common processing steps to inactivate T. gondii cysts is assessed, including addition of spices, nitrates, nitrites and salt, use of fermentation, smoking and heat treatment, and the time and temperature during maturation. It is concluded that processing steps that may be effective in the inactivation of T. gondii cysts include freezing, heat treatment, and cooking, and the interaction between salt concentration, maturation time, and temperature. The assessment is illustrated using a Microsoft Excel-based software tool that was developed to facilitate the easy assessment of four hypothetical smallgoods products.

PMID: 18680945 [PubMed - in process]

Astrocyte gp130 Expression Is Critical for the Control of Toxoplasma Encephalitis

J Immunol. 2008 Aug 15;181(4):2683-93

Astrocyte gp130 Expression Is Critical for the Control of Toxoplasma Encephalitis

Drögemüller K, Helmuth U, Brunn A, Sakowicz-Burkiewicz M, Gutmann DH, Mueller W, Deckert M, Schlüter D.

Institut für Medizinische Mikrobiologie, Otto-von-Guericke-Universität, Magdeburg, Germany;

Toxoplasma gondii infects astrocytes, neurons and microglia cells in the CNS and, after acute encephalitis, persists within neurons. Robust astrocyte activation is a hallmark of Toxoplasma encephalitis (TE); however, the in vivo function of astrocytes is largely unknown. To study their role in TE we generated C57BL/6 GFAP-Cre gp130(fl/fl) mice (where GFAP is glial fibrillary acid protein), which lack gp130, the signal-transducing receptor for IL-6 family cytokines, in their astrocytes. In the TE of wild-type mice, the gp130 ligands IL-6, IL-11, IL-27, LIF, oncostatin M, ciliary neurotrophic factor, B cell stimulating factor, and cardiotrophin-1 were up-regulated. In addition, GFAP(+) astrocytes of gp130(fl/fl) control mice were activated, increased in number, and efficiently restricted inflammatory lesions and parasites, thereby contributing to survival from TE. In contrast, T. gondii- infected GFAP-Cre gp130(fl/fl) mice lost GFAP(+) astrocytes in inflammatory lesions resulting in an inefficient containment of inflammatory lesions, impaired parasite control, and, ultimately, a lethal necrotizing TE. Production of IFN-gamma and the IFN-gamma-induced GTPase (IGTP), which mediate parasite control in astrocytes, was even increased in GFAP-Cre gp130(fl/fl) mice, indicating that instead of the direct antiparasitic effect the immunoregulatory function of GFAP-Cre gp130(fl/fl) astrocytes was disturbed. Correspondingly, in vitro infected GFAP-Cre gp130(fl/fl) astrocytes inhibited the growth of T. gondii efficiently after stimulation with IFN-gamma, whereas neighboring noninfected and TNF-stimulated GFAP-Cre gp130(fl/fl) astrocytes became apoptotic. Collectively, these are the first experiments demonstrating a crucial function of astrocytes in CNS infection.

PMID: 18684959 [PubMed - in process]

Thursday, August 07, 2008

Rhoptry Discharge Correlates with Activation of the EGR2 Host Cell Transcription Factor

Infect Immun. 2008 Aug 4. [Epub ahead of print]

Toxoplasma gondii Rhoptry Discharge Correlates with Activation of the EGR2 Host Cell Transcription Factor

Phelps ED, Sweeney KR, Blader IJ.

Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104.

Toxoplasma gondii is a ubiquitous Apicomplexan parasite that can cause severe disease in fetuses and immune-compromised patients. Rhoptries, micronemes, and dense granules, which are secretory organelles unique to Toxoplasma and other Apicomplexan parasites, play critical roles in parasite growth and virulence. To understand how these organelles modulate infected host cells, we sought to identify host cell transcription factors triggered by their release. EGR2 is a host cell transcription factor that is rapidly upregulated and activated in Toxoplasma-infected cells but not in cells infected with the closely related Apicomplexan parasite Neospora caninum. EGR2 upregulation only occurred when live parasites were in direct contact with the host cell and not by cell extracts that contain dense granule or micronemal proteins. When microneme-mediated attachment was blocked by pre-treating parasites with a calcium chelator, EGR2 expression was significantly reduced. In contrast, when host cells were infected with parasites in the presence of cytochalasin D, which allows rhoptry secretion but prevents parasite invasion, EGR2 was activated. Finally, we demonstrate that Toxoplasma activation of host p38 MAP kinase is necessary but not sufficient for EGR2 activation. Collectively, these data indicate that EGR2 is specifically upregulated by a parasite-derived secreted factor that is most likely a resident rhoptry protein.

PMID: 18678671 [PubMed - as supplied by publisher]

Enhanced Antimalarial Activity of Novel Synthetic Aculeatin Derivatives

J Med Chem. 2008 Aug 5. [Epub ahead of print]

Enhanced Antimalarial Activity of Novel Synthetic Aculeatin Derivatives

Peuchmaur M, Saïdani N, Botté C, Maréchal E, Vial H, Wong YS.

yung-sing.wong@ujf-grenoble.fr.

We report the design, synthesis, and in vitro evaluation of novel polyspirocyclic structures, inspired by the antimalarial natural products, the aculeatins. A divergent synthetic strategy was conceived for the practical supply and has allowed the discovery of two novel and more potent analogues active on the Plasmodium falciparum 3D7 strain. Moreover, these compounds proved to be potent against Toxoplasma gondii. A number of features that govern these inhibitions were identified.

PMID: 18680278 [PubMed - as supplied by publisher]

Wednesday, August 06, 2008

Protective Th1 immune responses against chronic toxoplasmosis induced by a protein-protein vaccine combination but not by its DNA-protein counterpart

Vaccine. 2008 Jul 31. [Epub ahead of print]

Protective Th1 immune responses against chronic toxoplasmosis induced by a protein-protein vaccine combination but not by its DNA-protein counterpart

Jongert E, Verhelst D, Abady M, Petersen E, Gargano N.

Laboratory for Toxoplasmosis, Pasteur Institute of Brussels, Scientific Institute of Public Health, Brussels, Belgium.

Vaccine-induced protection against toxoplasmosis is correlated with cellular immune responses to Toxoplasma gondii, both in animals and man. The goal of the current study was to evaluate whether the combination of a recombinant protein and a plasmid DNA vaccine could offer an advantage over the protein mixture, and protect outbred mice against infection with T. gondii. To this purpose, the chimeric protein rEC2, encoding antigenic fragments of surface-associated proteins MIC2, MIC3 and SAG1, was combined with pGRA7 plasmid DNA or rGRA7 protein. High levels of antibodies were elicited by both vaccine formulations. The protein-DNA vaccine elicited a polarized Th1/Th2 immune response, characterized by IFN-gamma and IL-10, and afforded low protection (24%) against brain cyst formation. In contrast, the protein-protein vaccine elicited a Th1-focused immune response, characterized by IFN-gamma and IL-2 production, conferring a strong protection (79%) against brain cyst formation in chronic toxoplasmosis. We show here that GERBU adjuvanted protein vaccines confer better protection against toxoplasmosis than the protein-DNA heterologous vaccine.

PMID: 18675872 [PubMed - as supplied by publisher]

Toxoplasma gondii protease inhibitor-1 (TgPI-1) is a novel vaccine candidate against toxoplasmosis

Vaccine. 2008 Jul 31. [Epub ahead of print]

Toxoplasma gondii protease inhibitor-1 (TgPI-1) is a novel vaccine candidate against toxoplasmosis

Cuppari AF, Sanchez V, Ledesma B, Frank FM, Goldman A, Angel SO, Martin V.

Laboratorio de Inmunología, Centro de Salud y Medio Ambiente, E.C.y T., Universidad de Gral. San Martín, Provincia de Buenos Aires, Argentina.

The Toxoplasma gondii serin protease inhibitor-1 (TgPI-1) is a dense granule antigen that showed to specifically inhibit trypsin, chymotrypsin and neutrophil elastase, suggesting a possible modulatory role during the parasite invasion process and on the development of the innate immune response. To study the immune-protective value of TgPI-1, C3H/HeN mice were immunized with a recombinant form of the antigen rTgPI-1 combined with alum. All immunized mice produced specific anti-rTgPI-1 immunoglobulins, with high IgG antibody titers and a mixed IgG(1)/IgG(2a) response, with predominance of IgG(1) production. The cellular immune response was associated with the production of IFN-gamma and IL-10 cytokines. Vaccinated mice displayed significant protection against an oral challenge either after a lethal infection with Me49 cysts (90% survival vs. 50%) and also after a non-lethal infection (58% reduction in brain parasite load) compared to the non-vaccinated control group. In conclusion, rTgPI-1 elicits a strong specific immune response providing partial protection against both T. gondii acute and chronic infection, so it would be a good candidate in a vaccine against toxoplasmosis, which could be combined with other relevant parasite antigens.

PMID: 18675873 [PubMed - as supplied by publisher]

Sunday, August 03, 2008

Toxoplasma rhoptries: unique secretory organelles and source of promising vaccine proteins for immunoprevention of toxoplasmosis

J Biomed Biotechnol. 2008;2008:632424

Toxoplasma rhoptries: unique secretory organelles and source of promising vaccine proteins for immunoprevention of toxoplasmosis

Dlugonska H.

Department of Immunoparasitology, Institute of Microbiology and Immunology, University of Lodz, 90-237 Lodz, Poland.

Toxoplasma gondii is an obligate intracellular protozoan parasite classified in the phylum Apicomplexa, which includes numerous notable human and animal pathogens (Plasmodium species, Cryptosporidium species, Neospora caninum, etc.). The invasive stages of apicomplexans are characterized by the presence of an apical complex composed of specialized cytoskeletal and secretory organelles, including rhoptries. Rhoptries, unique apical secretory organelles shared exclusively by all apicomplexan parasites, are known to be involved in an active parasite's penetration into the host cell associated with the biogenesis of specific intracellular compartment, parasitophorous vacuole in which the parasite multiplies intensively, avoiding intracellular killing. Due to the key biological role of rhoptries, rhoptry proteins have recently become vaccine candidates for the prevention of several parasitoses, toxoplasmosis among them. The article presents current data on T. gondii rhoptries biology and new approaches to the development of effective vaccines against toxoplasmosis using rhoptry antigens.

PMID: 18670609 [PubMed - in process]

Toxoplasma: the next 100 years

Microbes Infect. 2008 Jul 10. [Epub ahead of print]

Toxoplasma: the next 100 years

Kim K, Weiss LM.

Department of Medicine (Division of Infectious Diseases), Albert Einstein College of Medicine, Ullmann 1225, 1300 Morris Park Avenue, Bronx, NY 10461, USA; Department of Microbiology & Immunology, Albert Einstein College of Medicine, Ullmann 1225, 1300 Morris Park Avenue, Bronx, NY 10461, USA.

It has been 100years since Toxoplasma gondii was initially described in Tunis by Nicolle and Manceaux (1908) in the tissues of the gundi (Ctenodoactylus gundi) and in Brazil by Splendore (1908) in the tissues of a rabbit. T. gondii is a ubiquitous, Apicomplexan parasite of warm-blooded animals that can cause several clinical syndromes including encephalitis, chorioretinitis and congenital infection. Due to the extensive repertoire of applicable experimental techniques available for this pathogen it has become a model organism for the study of intracellular pathogens. Data obtained from genome-wide expression studies, including ChIP on chip and proteomics surveys, are refining our understanding of the genetic networks involved in the developmental biology of this pathogen as well as the interactions of the parasite with its host. This review addresses recent advances in our understanding of the developmental biology and host-pathogen relationships of T. gondii.

PMID: 18672085 [PubMed - as supplied by publisher]

Friday, August 01, 2008

Toxoplasma gondii-derived heat shock protein 70 induces lethal anaphylactic reaction

Microbiol Immunol. 2008;52(7):366-74

Toxoplasma gondii-derived heat shock protein 70 induces lethal anaphylactic reaction through activation of cytosolic phospholipase A and platelet-activating factor via Toll-like receptor 4/myeloid differentiation factor 88

Fang H, Mun HS, Kikumura A, Sayama Y, Norose K, Yano A, Aosai F.

Department of Infection and Host Defense, Graduate School of Medicine, Chiba University, Chiba, Japan.

Toxoplasma gondii-derived heat shock protein 70 (T.g.HSP70) was proven to induce IFN-gamma-dependent lethal anaphylactic reaction in T. gondii-infected mice through an alternative PAF-mediated pathway, but not the classical immunoglobulin (Ig)E-dependent pathway. Although marked IFN-gamma production was observed by CD11b(+), CD11c(+), CD4(+) and CD8(+) splenocytes, CD11b(+) and CD11c(+) cells were shown to be the key effecter cells which generated pro-inflammatory lipid such as PAF and caused T.g.HSP70-induced anaphylactic reaction. In the present study, we found that the T.g.HSP70-induced anaphylactic reaction was not observed in TLR 4-deficient ((-/-)) mice, whereas it was observed in WT and TLR2(-/-) mice. The mRNA expression of PAF-AH, the main enzyme for PAF degradation, increased in T. gondii-infected WT and TLR2(-/-) but not in TLR4(-/-) mice after T.g.HSP70 injection. Furthermore, phosphorylation of cPLA(2), which is the key enzyme for pro-inflammatory lipid generation, was detected in CD11b(+) splenocytes of WT and TLR2(-/-) mice but not in TLR4(-/-) mice. Subsequently, cPLA(2) activation was suppressed by inhibiting the TLR4-directed p38 and p44/42 MAPK pathways. However, T.g.HSP70-induced anaphylactic reaction was observed in TRIF(-/-) mice, but not in MyD88(-/-) mice. These findings indicate the cPLA(2) activated-PAF production via TLR4/MyD88-dependent, but not TRIF-dependent, signaling pathway in T.g.HSP70-induced anaphylactic reaction in T. gondii-infected mice.

PMID: 18667035 [PubMed - in process]

Usefulness of GRA6 derived synthetic polymorphic peptides in Toxoplasma serotyping of worldwide human samples by an immunoenzymatic assay

Clin Vaccine Immunol. 2008 Jul 30. [Epub ahead of print]

Usefulness of GRA6 derived synthetic polymorphic peptides in Toxoplasma gondii serotyping of worldwide human samples by an immunoenzymatic assay

Sousa S, Ajzenberg D, Vilanova M, Costa J, Dardé ML.

Center of Parasite Immunology and Biology, INSA, Rua de S. Luis 16, 4000-509 Porto, Portugal; Instituto de Ciências Biomédicas de Abel Salazar, Largo do Professor Abel Salazar 2, 4099-003, Porto, Portugal; Laboratory for Veterinary Research, LNIV-INRB, I.P. Rua dos Lagidos, Lugar da Madalena, 4485-655 Vairão VCD, Portugal; Université de Limoges, EA 3174-NETEC, and National Reference Center and Biological resource Center for Toxoplasmosis, CHU Dupuytren, 2, av Martin Luther King, 87042 Limoges Cedex, France.

Serotyping is a simple typing method that consists in an immunoenzymatic assay (ELISA) using synthetic polymorphic peptides derived from Toxoplasma gondii antigens. We developed a new ELISA assay based on GRA6 C-terminal polymorphic peptides. Serum samples from 41 human infections due to 23 archetypal (type I, II or III) and 18 non-archetypal strains were selected in order to validate this approach. For 20 out of the 23 archetypal infections, there was a clear correlation between microsatellite genotype and GRA6 serotyping. All infections due to non-archetypal strains were misclassified as archetypal strain infections. The GRA6 C-terminal peptides from these strains were analysed to explain this misclassification. A second group of 455 patients with acute and chronic toxoplasmosis due to unknown genotypes from different European, African and Latin American countries were included in this study, and the strain type predicted by this method. The results suggest that serotyping is a promising method for typing strains, although limitations exist for African and South American strains as a consequence of higher peptide polymorphism. Other peptides from different markers must be studied in order to discriminate archetypal from non-archetypal strains.

PMID: 18667636 [PubMed - as supplied by publisher]