FIG 9.

Vaccination of CBA/J mice with 10⁷ CFU of live or heat-killed (HK) cda1Δ2Δ3Δ cells conferred attenuated protective immunity to subsequent infection with wild-type R265 C. gattii cells. (A) Mice were immunized with either 10⁷, 10⁶, or 10⁵ live CFU of cda1Δ2Δ3Δ cells through inhalation. PBS-inoculated mice served as control. Animals were left for 40 days to resolve the infection. Subsequently, both groups of mice were challenged with 50,000 CFU of virulent R265 cells. Virulence was recorded as mortality of mice. Mice that lost 20% of starting body weight at the time of inoculation were considered to be moribund and sacrificed. The percentage of mice that survived was plotted against the day postinfection. Each survival curve is the average of two independent experiments that had five mice per experimental group. (B) Mice were immunized with an inoculum of HK cells with a dose equivalent to 10⁷ CFU of either the wild-type R265 or the cda1Δ2Δ3Δ strain. Control mice were inoculated with PBS. After 40 days, mice were challenged with 50,000 CFU of wild-type R265 cells. Survival of the animals was recorded as described above. The data shown are from a single experiment with five mice per experimental group. A second experiment showed similar results.