Immunisation against gametes and asexual erythrocytic stages of a rodent malaria parasite

Abstract

INVESTIGATIONS into the feasibility of vaccinating against malaria have centred mainly on the use of the sporozoite^1,2 or the asexual blood stages^3–6. Immunisation using sexual stages of malaria parasites has been demonstrated with Plasmodium gallinaceum in chickens^7,8. Gamete vaccines have been used to produce an effective immunity against transmission of the avian malaria parasite, with little or no effect on its asexual erythrocytic stages. More recently, this study has been extended to P. knowlesi infections in rhesus monkeys⁹; transmission-blocking immunity and resistance to asexual infection were obtained, but were fully effective only when the vaccine was combined with Freund's complete adjuvant. We report here successful immunisation of mice against the sexual stages of P. yoelii using formalin-fixed gametes. In addition to very effective transmission-blocking immunity, the vaccinated mice were strongly protected against asexual erythrocytic stages of the parasite.