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Alessandra Commodaro, Cristina Muccioli, Cláudio Silveira, Luiz V Rizzo, Rubens Belfort, Jr., Michael Grigg; Toxoplasma gondii serotype associated with patients experiencing severe ocular toxoplasmosis in Brazil. Invest. Ophthalmol. Vis. Sci. 2014;55(13):2841.
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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 predominate. 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 448 patients who were seropositive with (n=311) or without (n=137) OT. The assay utilized synthetic peptides that identify strain-specific antibodies circulating in the blood of infected patients. DNA extracted from the peripheral blood of OT patients was tested for the presence of parasite DNA by PCR using single/multi-copy genetic markers to determine parasite genotype to correlate with serotype results.
51% of patients with severe OT possessed the “Non-Reactive” (NR) serotype: no reactivity against archetypal strain-specific peptides, but positive reactivity with TgSAG1; the antigen for diagnosing Toxoplasma infection. In contrast, patients without OT were more frequently infected by atypical serotypes (33%), and presented only 23% of NR serotype. Patients infected with T. gondii were PCR positive from peripheral blood at the B1 (28%) and NTS2 (63%) typing locus, all possessed non-archetypal alleles. Our results indicate that the majority of OT patients in Brazil are not infected with Type I, II or III strains.
Our data suggests that an atypical serotype is more often associated with severe ocular toxoplasmosis in patients in Brazil. Genotyping confirmed that these patients were infected by non-archetypal strains of T gondii.
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