Limited sequence polymorphisms of four transmission-blocking vaccine candidate antigens in Plasmodium vivax Korean isolates

Abstract

Background: Transmission-blocking vaccines (TBVs), which target the sexual stages of malaria parasites to interfere with and/or inhibit the parasite's development within mosquitoes, have been regarded as promising targets for disrupting the malaria transmission cycle. In this study, genetic diversity of four TBV candidate antigens, Pvs25, Pvs28, Pvs48/45, and PvWARP, among Plasmodium vivax Korean isolates was analysed. Methods: A total of 86 P. vivax-infected blood samples collected from patients in Korea were used for analyses. Each of the full-length genes encoding four TBV candidate antigens, Pvs25, Pvs28, Pvs48/45, and PvWARP, were amplified by PCR, cloned into T&A vector, and then sequenced. Polymorphic characteristics of the genes were analysed using the DNASTAR, MEGA4, and DnaSP programs. Results: Polymorphism analyses of the 86 Korean P. vivax isolates revealed two distinct haplotypes in Pvs25 and Pvs48/45, and three different haplotypes in PvWARP. In contrast, Pvs28 showed only a single haplotype. Most of the nucleotide substitutions and amino acid changes identified in all four TBV candidate antigens were commonly found in P. vivax isolates from other geographic areas. The overall nucleotide diversities of the TBV candidates were much lower than those of blood stage antigens. Conclusions: Limited sequence polymorphisms of TBV candidate antigens were identified in the Korean P. vivax population. These results provide baseline information for developing an effective TBV based on these antigens, and offer great promise for applications of a TBV against P. vivax infection in regions where the parasite is most prevalent.