Active immunization and passive transfer of resistance against sporozoite-induced malaria in infant mice

Abstract

Immunization attempts using a variety of plasmodial preparations have identified several developmental stages and vaccination procedures which can protect against malaria^1–3. These indicate that immunoprophylaxis against malaria may also be possible in man. The immune response to these vaccines has only been investigated in adult animals, but in countries where malaria is prevalent, children are most at risk of developing lethal infections. Thus we must ask whether vaccination against malaria would be effective when applied early in life. Here we report the use of intramuscular (i.m.) immunization of very young mice with radiation-attenuated sporozoites of Plasmodium berghei as a vaccination procedure, and that these animals can be effectively protected against sporozoite challenge. This approach avoids the intravenous (i.v.) immunization, which although highly effective in adult animals, is barely acceptable for use in man. Another important aspect of the host–parasite relationship in endemic areas is the role of immunity transmitted congenitally from mother to infants. We therefore investigated whether sporozoite-immunized adult female mice could transfer this immunity to their litters. It was found that the offspring acquired antisporozoite antibodies from their mothers through the milk. Furthermore, most of these offspring resisted challenge by infective sporozoites.