Towards a vaccine against malaria.

In many countries malaria is rapidly regaining its status as one of mankind's most important diseases, affecting not only indigenous populations but also travellers to endemic areas. This has stimulated much research into the mechanisms by which immunity is acquired to plasmodial infections and into the feasibility of producing effective vaccines against these. Four possible vaccines are under study, each targeted at a different stage of the complete life cycle of the Plasmodium. A vaccine targeted against the sporozoite could totally protect humans against mosquito-borne infection, while a vaccine against asexual erythrocytic forms would limit the morbidity and mortality of malaria rather than totally preventing it. In contrast, vaccines directed against the sexual forms of the parasite would not induce protection against infection, but would produce a transmission-blocking action, preventing the parasite developing in the mosquito vector. The construction of such vaccines and the measurement of the immune responses they induce has demanded the deployment of sophisticated and recently developed techniques, especially in immunology and molecular biology. However, man's capacity to acquire effective immunity to malaria has long been recognised and attempts to induce it artificially by means of vaccines have been made since the beginning of this century.