Fig. 1.
T. gondii replication is correlated with IEC cytotoxicity. (A) Comparison of levels of replication of the three T. gondii genotype strains. Human IEC cultured in 24-well plates at a density of 3 × 105 cells/well were left noninfected or infected with either type I (RH), type II (76K), or type III (NED) parasites at a MOI of 1. DNA was extracted from noninfected and infected cells at 8-h intervals for a period of 48 h, and a quantitative PCR was performed using T. gondii-specific primers and probe (see Materials and Methods). Results are expressed as numbers of T. gondii parasites/50 ng of DNA. ***, P < 0.0001; **, P < 0.001; and *, P < 0.05. Data are representative of 3 experiments, performed in triplicates at each time point. (B) Distinct levels of IEC cytotoxicity are induced by the three T. gondii genotype strains. Cell cultures were set up as described above, and supernatants were collected from noninfected/infected cells at 8-h time intervals. Lactate dehydrogenase in culture supernatants was measured using a CytoTox kit (Promega), and optical densities (O.D.) were measured at 490 nm. Data are representative of two experiments performed in triplicate at each time point.