Antibodies elicited by LAGAP immunization require complement and FCR binding for complete protection.

A) Survival of C57BL/6 mice (n = 5 mice per group) immunized and depleted of CD4 and CD8 T cells as in Fig 1. Six hours prior to challenge with 104 iRBC, mice were depleted of complement by administration of 30 μg of cobra venom factor with an additional dose at 4 days post challenge. Loss of protection in 3/5 mice following complement depletion indicates a strong role for the classical complement pathway in antibody-mediated BS protection. B) Survival of FcγR-/- given the same immunization, T cell depletion and challenge as in Fig 1 without complement depletion by CVF. Loss of protection from lethal parasitemia also implicates FCR binding in antibody-mediated BS protection. C) The same immunization and challenge was performed with FcγR-/- mice but with complement depletion prior to challenge as in (A). Loss of protection in 4/5 mice further confirms the role of both complement and FCR binding as antibody effector mechanisms. D) Parasitemia of mice in (A) and (C) on day 5 post challenge. A higher peak parasitemia in complement-depleted FcγR-/- mice confirms the role of FCR-binding in controlling parasitemia in LAGAP-immunized mice. Comparisons were performed using one-way ANOVA with Tukey post-hoc analysis with significance indicated by: **0.01≥p>0.001; non-significant (NS) p≥0.05.