Inter- and intra-genotype differences in induced cystogenesis of recombinant strains of Toxoplasma gondii isolated from chicken and pigs

The ability to differentiate from the proliferative (tachyzoite) to the latent (bradyzoite) stage of isolates of Toxoplasma gondii recombinant genotypes (I/II/III and I/III) and reference strains from a clonal line (RH and ME49) was investigated in this study. Two isolates from chicken (#114 and #277; ToxoDB) and 3 from pigs (#114; ToxoDB) were the subjects for evaluation. The isolates were grown in cell culture under 2 different conditions: culture medium at pH 7.0 (neutral, without stress induction) or pH 8.0 (alkaline, stress inducing). After 4 days, the cultures were fixed and the events resulting from infection and induction were labeled. T. gondii cysts were labeled using Dolichos biflorus-FITC lectin (DBL-cysts) and free tachyzoites or vacuolar were labeled using an anti-T. gondii polyclonal antibody followed by an Alexa 594-conjugated secondary antibody (DBL-negative structures compatible with parasite structures - lysis plaques or vacuole). Differences in DBL-cysts formation in vitro in response to exogenous stress were observed between recombinant genotype isolates and the typical genotypes. The differences in conversion rates and the patterns of lysis plate production between genotype I/III isolates (#114) indicate that care should be taken when extrapolating the in vitro phenotypic characteristics of parasites from the same genotype.