Fig. 3.

Growth and virulence of mutant and parental strain. (A) Growth of ACP/ACPi and ΔACP/ACPi parasites incubated in the presence and absence of ATc was scored by plaque assay. (B) Plaque number and area were quantified in three independent flasks. (C and D) ATc dependence of growth was also measured by following fluorescence in YFP-YFP-expressing lines derived from parent and mutant (second-passage parasites were cultured for 6 days under ATc before inoculation of multiwell plates). C57BL/6 mice were infected with parent (E) and mutant (F) parasites (note slight delay in killing by the mutant when compared with the parental parasites). Mice received 0.2 mg/ml ATc (red) or placebo (green) in the drinking water, and survival was followed for 100 days. (G) Surviving mice from F were rechallenged with 10,000 RH wild-type parasites (vaccinated parasites) in parallel to a group of naïve control mice. (H) Mice were immunosuppressed by injection of 0.5 mg of an IFNγ-specific antibody on days 0 and 5 (arrows), infected with ΔACP/ACPi, and treated as described for F.