TOWARDS A VACCINE AGAINST MALARIA

In many countries malaria is rapidly regaining its status as one of ma nkind's most important diseases, affecting not only indigenous populat ions but also travellers to endemic areas. This has stimulated much re search into the mechanisms by which immunity is acquired to plasmodial infections and into the feasibility of producing effective vaccines a gainst these. Four possible vaccines are under study, each targeted at a different stage of the complete life cycle of the Plasmodium. A vac cine targeted against the sporozoite could totally protect humans agai nst mosquito-borne infection, while a vaccine against asexual erythroc ytic forms would limit the morbidity and mortality of malaria rather t han totally preventing it. In contrast, vaccines directed against the sexual forms of the parasite would not induce protection against infec tion, 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 d emanded the deployment of sophisticated and recently developed techniq ues, especially in immunology and molecular biology. However, man's ca pacity to acquire effective immunity to malaria has long been recognis ed and attempts to induce it artificially by means of vaccines have be en made since the beginning of this century.