Exploration of Plasmodium vivax merozoite surface proteins 1 and 7 genetic diversity in Brazilian Amazon and Rio de Janeiro Atlantic Forest.

Abstract Plasmodium vivax merozoite surface proteins (PvMSP) 1 and 7 are considered vaccine targets. Genetic diversity knowledge is crucial to assess their potential as immunogens and to provide insights about population structure in different epidemiological contexts. Here, we investigate the variability of pvmsp-142, pvmsp-7E, and pvmsp-7F genes in 227 samples from the Brazilian Amazon (BA) and Rio de Janeiro Atlantic Forest (AF). pvmsp-142 has 63 polymorphisms - 57 nonsynonymous - generating a nucleotide diversity of π = 0.009 in AF, and π = 0.018 in BA. In pvmsp-7E, 134 polymorphisms - 103 nonsynonymous - generate the nucleotide diversity of π = 0.027 in AF, and π = 0.042 in BA. The pvmsp-7F has only two SNPs - A610G and A1054T –, with nucleotide diversity of π = 0.0004 in AF, and π = 0.0007 in BA. The haplotype diversity of pvmsp-142, pvmsp-7E, and pvmsp-7F genes is 0.997, 1.00, and 0.649, respectively. None of the pvmsp-142 or pvmsp-7E sequences are identical to the Salvador 1 strain's sequences. Conversely, most of pvmsp-7F sequences (94/48%) are identical to Sal-1's sequences. We evaluated eight B-cell epitopes in pvmsp-7E, four of them showed higher nucleotide diversity compared to pvmsp-7E's epitopes. Positive selection was detected in pvmsp-142, pvmsp-7E central region, and pvmsp-7F with Tajima's D. In pvmsp-7E, the significant nucleotide and haplotype diversities with low genetic differentiation, could be indicative of balancing selection. The genetic differentiation of pvmsp-142 (0.315) and pvmsp-7F (0.354) genes between AF and BA regions is significant, which is not the case for pvmsp-7E (0.193). We conclude that pvmsp-142 and pvmsp-7E have great genetic diversity even in AF region, an enclosure area with deficient transmission levels of P. vivax zoonotic malaria. In both Brazilian regions, pvmsp-119, pvmsp-7E, and pvmsp-7F are conserved, most likely due to their roles in parasite survival, and could be considered potential targets for a “blood-stage vaccine”.