PLASMODIUM-FALCIPARUM - ALLELIC VARIATION IN THE MEROZOITE SURFACE PROTEIN-1 GENE IN WILD ISOLATES FROM SOUTHERN VIETNAM

Allelic variation in the Plasmodium falciparum merozoite surface prote in 1 (MSP1) gene is expressed as an association of allelic types in va riable blocks. In this study, a PCR strategy that can detect 24 differ ent MSP1 association types was used to investigate allelic Variation i n the MSP1 gene. We identified 236 distinct association type clones in 136 wild isolates collected from southern Vietnam, analysis of which revealed that (1) recombination between two representative allelic typ es in the central part of the MSPI gene did not exist, (2) frequency d istribution of MSP1 association types did not differ indifferent popul ation groups, and (3) particular MSP1 association types were predomina nt. Statistical analysis for the association of allelic types indicate d significant, nonrandom associations between blocks 4 and 6 but not b etween blocks 2 and 4, and 2 and 6. These results suggest that selecti on operates in favor of particular MSPI association types. In addition , direct sequencing of 31 isolates confirmed reported sequence substit utions in the C-terminal 19-kDa Cys-rich region of MSPI, supporting a notion of limited variations in this region, a strong vaccine candidat e molecule. (C) 1997 Academic Press.