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Alessandra G. Commodaro, Sundar Natarajan, Claudio Silveira, Luiz V. Rizzo, Cristina Muccioli, Rubens Belfort, Jr., Michael E. Grigg; Serological And Molecular Characterization Of Toxoplasma Gondii Strains In Brazilian Patients With Ocular Toxoplasmosis. Invest. Ophthalmol. Vis. Sci. 2011;52(14):4313.
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More than 2 billion people worldwide are infected with T. gondii. In the endemic region of Erechim, RS/ Brazil, about 88% of the population is toxoplasmosis positive and about 18% of these individuals have ocular lesions with clinical manifestations. The majority of T. gondii strains circulating globally are genetically classified into 3 distinct clonal lineages, Types I, II and III respectively. However, this is not the case in Brazil, where atypical genotypes of T. gondii are increasingly. In the present study, we tested whether parasite genotype is a significant risk factor for the development of ocular toxoplasmosis (OT).
A serological strain-typing assay was performed using plasma obtained from 516 patients who were seropositive with (n=364) or without (n=152) OT. The assay utilized synthetic peptides that identify strain-specific antibodies circulating in infected patients. Peripheral blood DNA was extracted from 95 OT patients and tested for the presence of parasite DNA by PCR using single/multi-copy genetic markers to determine parasite genotype to correlate with serotype results.
Eight serotypes were identified among the 516 patients investigated. The majority of these samples possessed a "Non-Reactive" (NR) serotype (n=193) that did not react with archetypal strain-specific peptides, but did react with TgSAG1; the antigen for diagnosing Toxoplasma infection. Further, the majority of patients with severe OT possessed the NR serotype (n=141/ 189). In contrast, the majority of patients without OT possessed a nonarchetypal (neither Type I/III or II) serotype (n=64/ 152). Six patients with severe OT were PCR positive from peripheral blood at the BI typing locus, only non-archetypal alleles were amplified. This result indicates that these patients were not infected with Type I, II or III strains when compared to patients from North America and Europe.
Our data suggests an atypical serotype strain that is more often associated with severe ocular toxoplasmosis disease in patients in Brazil. Genotyping confirmed that these patients were infected with non-archetypal strains of T gondii.
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