Genetic diversity in the C-terminal 42 kDa region of merozoite surface protein-1 of Plasmodium vivax (PvMSP-1(42)) among Indian isolates.

Plasmodium vivax merozoite surface protein 1 (PvMSP-1) is a leading malaria vaccine candidate. This protein is processed to give rise to various sized fragments during merozoite maturation. Here, we describe the analysis of genetic diversity in the 42 kDa C-terminal part of this protein among 33 Indian P. vivax isolates. A total of 27 haplotypes with 72 mutations and 0.0212+/-0.0005S.D. over all pi nucleotide diversity were observed among the isolates. Twenty-six of 27 haplotypes reported here were new as they have not been reported so far from any other country. The difference between non-synonymous (dN) and synonymous (dS) mutations was found to be positive (0.0081+/-0.0051) for the entire 42 kDa region. Further analysis revealed that 33 kDa (MSP-1(33)) fragment of the MSP-1(42) was highly polymorphic with pi nucleotide diversity 0.0290+/-0.0007S.D. The dN-dS for this region of MSP-1 was also positive (0.0114+/-0.0071S.E.). On the other hand, there was no non-synonymous mutation in the 19 kDa (MSP-1(19)) fragment of the MSP-1(42) and thus it was highly conserved. In conclusion, MSP-1(33) fragment was highly polymorphic and appeared to be under diversifying selection whereas there was no selection at MSP-1(19) region among the isolates. Present study will be helpful for the development of PvMSP-1 based vaccine against P. vivax malaria.