Recent advances in tropical medicine

Malaria

A vaccine for malaria is still awaited. In 1993 the results were published of the SPf66 malarial vaccine developed and tested in Columbia by Manuel Patarroyo and his colleagues.1 SPf66 is a synthetic peptide containing the amino acid sequences of three Plasmodium falciparum merozoite proteins linked to each other by a tetrapeptide derived from the circumsporozoite protein. In Columbia, an area of relatively low malaria endemicity, the vaccine had an overall protective efficacy of about 35%, being highest in young children aged 1-4 years and adults over 45 years (at 77% and 67% respectively), but disappointingly only 22% in the 15-44 year age group. Three controlled trials, two in Africa (in the Gambia in children aged 6-12 months and in Tanzania in children aged 1-5 years) and one in Thailand (in children aged 2-15 years) are under way. Although safety and immunogenicity studies are promising, the efficacy of this vaccine in these areas of high transmission will not be known until August 1994. Development of other potential vaccines continues, and five further P falciparum antigens from different stages of the life cycle have been earmarked by the World Health Organisation: three antigens involved in parasite invasion of red cells (merozoite surface protein-1 (MSP-1), apical membrane antigen (AMA-1), and erythrocyte binding antigen (EBA 175)); a soluble antigen (SERA) released when parasitised …