Figure 4. Vaccine protection requires an intact rbc membrane.

The role of the spleen early (5 weeks) after vaccination. (A) To determine whether the rbc membrane must remain intact for vaccine efficacy, cohorts of 5 A/J mice were vaccinated with a single dose of 10⁶P. chabaudi prbcs attenuated with centanamycin or a vaccine lysed with distilled water, then returned to isotonicity with 2× PBS. Naive mice served as a control. Five weeks later, mice were challenged with 10⁵P. chabaudi prbcs i.v. and parasitemia monitored. Plus signs indicate that mice succumbed to the infection. (B) To determine the importance of the spleen to immunity early after vaccination, A/J mice were splenectomized and others had a sham splenectomy. Four weeks later, half were immunized i.v. with 3 doses of 10⁶P. chabaudi prbcs attenuated by treatment with centanamycin, each 2 weeks apart. The other half received no treatment. Five weeks after the final dose of vaccine, all mice were challenged with 10⁵ prbcs i.v. and parasitemia monitored. Plus signs indicate that mice succumbed to the infection.