FIG 4.
TgPHYb is not required for growth or survival at low O2 levels. (A and B) TgPHYbDDHA parasites grown for 24 h with or without Shield-1 were harvested, exposed to stress for 0 or 8 h at 21% or 0.5% O2, and then added to HFF monolayers for 5 days, at which time plaque numbers (A) and area (B) were determined. (C) Equal numbers of parasites were added to HFF monolayers and grown in the absence or presence of 0.2 mM H2O2. After 5 days, monolayers were fixed, numbers of plaques were counted, and % inhibition was calculated by dividing numbers of plaques formed by parasites grown with H2O2/numbers of plaques formed by parasites grown without H2O2. *, P < 0.05, Student’s t test. (D) qPCR was used to measure parasite burdens in peritoneal cavities, spleens, and lungs of mice intraperitoneally infected with TgPHYb-depleted TgPHYbDDHA or RHΔΔ parasites. Shown are means and standard deviations from a total of 8 to 9 mice collected from 3 independent experiments. Significant differences were observed only in lungs (P < 0.05, one-way ANOVA).