Survival curve for pTgASP1-immunized BALB/c mice following challenge with T. gondii . (A) Three groups of mice were challenged with 1 × 104 tachyzoites of the virulent RH strain of T. gondii two weeks after their last immunization. n = 10 per group. Survival was monitored daily for 16 d after challenge. (B) The incidence of infection in the three groups of mice.