MALARIA VACCINES

Significant progress has been made in the development of the malaria v accine during the last 20 years. Ninety percent of the 300-500 million clinical cases of malaria per year worldwide occur in Africa. Thus, r esearch must be directed toward the 1 million African children under 5 years of age who die every year of malaria. An asexual blood-stage va ccine, capable of reducing severe and complicated malaria and malaria- related mortality, is therefore an important public health tool in the se countries. Although knowledge of the parasite's biology is incomple te, research has allowed insight into some of the mechanisms that the parasite uses to evade host immunity. This is the basis for adopting a n ''antigenic cocktail'' approach toward obtaining a synthetic or reco mbinant subunit vaccine such as the synthetic Colombian Malaria vaccin e SPf 66. During the development of Spf66, field trials under both low and high malaria endemicity areas in Latin America and Africa have be en carried out. The results from these studies showed a protective eff icacy ranging between 38.8 and 60.2% against Plasmodium falciparum mal aria. Given the characteristics of the normal immune response to malar ia (relatively short-lived and not completely effective), it is unders tandable that the main goal is to try to increase the host's natural i mmunity. The best candidates for designing a malaria vaccine are the p roteins required for parasite survival, those with low mutation rates and conserved epitopes. Because these proteins play an important role in multiple or alternative steps during the invasion process, they sho uld be the targets against which a protective immune response should b e elicited. The interaction between the malaria parasite and its host is complex. It is therefore crucial to define new ways of improving th e immune response-such as directly modifying the chemical structure of epitopes or using new adjuvants or DNA immunization techniques-to pro duce novel vaccines against this disease.