ANTIBODY MEDIATED MECHANISMS OF IMMUNITY TO MALARIA INDUCED BY VACCINATION WITH PLASMODIUM-KNOWLESI MEROZOITES

Abstract

Rhesus monkeys vaccinated with merozoites in FCA [Freund''s complete adjuvant] are protected against challenge with several strains and variants of P. knowlesi. Vaccination induces sterilizing immunity which is species specific. Merozoite-blocking (inhibitory) antibody usually correlates with clinical immunity and protection can be passively transferred with immune sera provided these contain high levels of inhibitory antibody. Vaccination using adjuvants other than FCA may induce inhibitory antibody without clinical protection. Vaccinated animals may become susceptible to challenge 4-5 wk after splenectomy, although inhibitory antibody levels are not reduced. Immunity induced by merozoite vaccination apparently involves merozoite blocking (inhibitory) antibody, or specific antibody or immune complexes acting synergistically with cytotoxic splenic cells stimulated by FCA.