FIG 6.

Mice infected with AMA1^KO parasites seroconvert and are protected against new infections. (a) (Left panel) Reactivity of sera from AMA1^KO-inoculated mice 6 to 8 weeks p.i. Western blots show results from 1 representative mouse for each dose of AMA1^KO parasites injected. The inoculation doses are indicated on top of each lane: 0 and + refer to the reactivity of sera from a naive mouse and a mouse infected with the cystogenic type II PruΔKU80 strain, respectively. (Right panel) Histogram showing the rate of seroconversion of mice. The number of mice analyzed is indicated on top of each column. (b) Mouse survival curves after immunization with different doses of AMA1^KO tachyzoites and challenges with various amounts of type I virulent AMA1⁺ tachyzoites. The numbers indicated in the graphs are the inoculum doses at which mice survived. The mice were then challenged with 10⁵ AMA1⁺ parasites for BALB/c and CD1 mice and 10³ AMA1⁺ parasites for C57BL6 mice. (c) Parasite burden in the brain of infected BALB/c mice challenged (n = 5) or not (n = 2) by AMA1^KO parasites and then i.p. injected with 10³ type II (ME49) tachyzoites 8 weeks later. A T. gondii RT-PCR assay was performed on brain tissue extracts 6 weeks postinfection, and data are calibrated with known numbers of parasites.