CLONING AND CHARACTERIZATION OF A NOVEL PLASMODIUM-FULCIPARUM SPOROZOITE SURFACE-ANTIGEN, STARP

A novel Plasmodium falciparum sporozoite antigen, STARP (Sporozoite Th reonine and Asparagine-Rich Protein), detected consistently on the sur face of sporozoites obtained from laboratory strains and field isolate s, has been identified and cloned, following a systematic approach aim ed at isolating novel non-CS sporozoite surface antigens. The 2.0-kb S TARP gene has a 5' miniexon/large central exon structure and contains a complex repetitive region encoding multiple dispersed motifs and tan dem 45- and 10-amino acid repeats. In sporozoites, transcription of th e STARP gene has been conclusively demonstrated by reverse PCR and Nor thern blot hybridisation and the 78-kDa protein has been localized by immunofluorescence and immunoelectron microscopy to the sporozoite sur face. STARP is also expressed in liver stages, as revealed by immunofl uorescence assays using antisera raised either to the central repetiti ve region or the C-terminal non-repetitive region. Expression is also detected in early ring stages, though not in mature erythrocytic or se xual stages. Identification and elucidation of this novel antigen is a step forward in current efforts aimed at developing an effective pree rythrocytic-stage malaria vaccine.