[Malaria: recent immunological acquisitions and therapeutic prospects]

Malaria remains one of the major health problems in many tropical countries. The asymptomatic carrier status is common and about 100% of the children in highly endemic areas have Plasmodium falciparum parasitaemia at any given time. Consequently a case definition based on the mere presence of parasites in the blood is non-informative in terms of measuring morbidity. Acquired clinical and parasitological immunity develop progressively over several years after repeated exposure to infection. Protection is acquired first again death or severe clinical disease, but protection against infection is never complete, moreover it is still not known why some infections are mild an some fatal. Although virulence markers on the parasite have not been identified with certainty, there are some indications that parasites differ in virulence. The genetic composition of human many also play a role in the defence against the parasite, so the immune mechanisms responsible for the acquired immunity remain uncertain. In fact, an infection by Plasmodium falciparum induces a variety of immune responses, including humoral and cellular, which can be specific or non-specific responses, some of which are protective, but against which the parasite has evolved effective escape measures. Vaccines has proven a most effective measure to control infectious diseases, but no consistently effective vaccine has yet developed against a human parasitic disease. A malaria vaccine aimed at disrupting the parasites life cycle at one or more of the three stages (sporozoite or pre-erythrocytic stage, asexual blood or erythrocytic stage, and sexual or sporogonic stage) might be a long-term solution.