ANALYSIS OF SEQUENCE DIVERSITY IN THE PLASMODIUM-FALCIPARUM MEROZOITESURFACE PROTEIN-1 (MSP-1)

Immunization with the first identified Plasmodium falciparum merozoite surface protein (MSP-1) protected monkeys from an otherwise fatal inf ection. The question of whether the high degree of diversity in MSP-1 among parasite clones will be an impediment to its development as a va ccine candidate needs to be resolved. We.have aligned all published se quences, identifying errors, resequencing a portion of one parasite cl one, and identifying probable duplicate sequences of four pairs of par asite clones. The sequences are displayed in a fashion that facilitate s the study of variation and its potentially diverse origins. The orig inal dimorphic sequences described by Tanabe et al. [22] have been mod ified to include only common sequences throughout the entire gene. The extension of the dimorphic region to the 5' end of block 3 brings int o question the involvement of intragenic crossover as the major mechan ism generating allelic diversity. Additional diversity developed from point mutations and recombination in certain regions of the gene. The regions of variability and conservation should serve as a data base fo r planning vaccine trials.