FIG. 5.

Survival plots demonstrating that immunization of mice with SOF2 protects against challenge infections with SOF-positive group A streptococci. Groups of five mice were immunized by i.v. injections of SOF2(38-1047) or SOF2(494-1047). Ten days later all 10 immunized mice received an i.p. injection of SOF2(494-1047). At day 21 the immunized mice were challenged i.p. with ∼5 × 10⁷ CFU of S. pyogenes strain T2MR. Nonimmunized control mice received an i.p. injection of ∼5 × 10⁷ CFU. Both groups of mice that were immunized were combined since there was no difference in their rates of survival. The difference in survival between immunized and nonimmunized mice was significant (Fisher's exact test; P = 0.005).