Genetic polymorphisms of Plasmodium vivax ookinete (sexual stage) surface proteins (Pvs25 and Pvs28) from Thailand.

ABSTRACT

Plasmodium vivax is the most geographically widespread malaria parasite in human presently. The ookinete surface proteins of sexual stage of malaria parasites, Pvs25 and Pvs28, are candidates for the transmission blocking vaccine. The antigenic variation in population might be barrier for vaccine development. The objective of this study was to investigate the genetic diversity of Pvs25 and Pvs28 in endemic areas of Thailand. P. vivax clinical isolates collected from Thai-neighboring border areas were analyzed using polymerase chain reaction and sequencing method. Three and 14 amino acid substitutions were observed in 43 Pvs25 and 48 Pvs28 sequences, respectively. Three haplotypes in Pvs25 and 14 haplotypes with 5-7 GSGGE/D tandem repeats in Pvs28 were identified. The nucleotide diversity of pvs25 (π = 0.00059) had lower level than pvs28 (π = 0.00517). Tajima's D value for both pvs25 and pvs28 genes were negative while no significant difference was found (P > 0.10). Low genetic diversity was found in pvs25 and pvs28 genes in Thailand. The finding of the most frequent amino acid substitutions was consistent with global isolates. Therefore, the data could be helpful in developing of effective transmission blocking vaccine in malaria endemic areas.