Determination of Toxoplasma gondii"s genetic variability in cases of maternal seroconversion during pregnancy from Uruguay

The paradigm for transmission and manifestations of human toxoplasmosis arose based on clinical data and experimentation in mice using strains of Toxoplasma gondii circulating in Europe and North America known as "typical." However, we now understand that the severity of human toxoplasmosis depends on the gestational period upon which the infection is acquired, the parasitic load and genotype of the parasite, which is closely linked to its geographic origin. Worldwide genotyping studies describe a higher incidence of atypical strains in South America, but this concept is mainly based on data obtained in Brazil, Colombia, and Argentina. Pioneering work in Uruguay described the existence of "atypical" serotypes in patients and the isolation of a genetically atypical strain of Uruguayan origin. We hypothesize that there is ample genetic variability of circulating T. gondii strains in humans in our country. To address this, we genotyped T. gondii strains in women who acquired the infection during pregnancy, as determined by the patient's seroconversion, detectable during routine pregnancy checkups. We amplified parasite DNA from peripheral blood, placental tissue, umbilical cord blood and newborn babies peripheral blood. T. gondii DNA was detectable in 17 of 32 patients. Positive samples were genotypes using in silico PCR-RFLP and sequence analyses, of nine polymorphic genetic markers. The presence of "atypical" strains was evidenced in 7 samples. We are currently advancing in their genetic characterization and pursuing the isolation of circulating strains with the aim of correlating genotype with phenotype. Preliminary data suggests that the severity of ocular toxoplasmosis is linked to the genotype. In addition, we updated the epidemiological data on T. gondii prevalence for the general population in the country, extrapolating from serological data obtained from pregnant women, and determined the seroconversion rates during pregnancy for the studied population.