Genotyping of polymorphic marker (MSP3α and MSP3β) genes of Plasmodium vivax field isolates from malaria endemic of Thailand.

Two polymorphic marker genes, merozoite surface protein 3α (PvMSP3α) and merozoite surface protein 3β (PvMSP3β), from 100 Plasmodium vivax field isolates, were investigated using polymerase chain reaction and restriction fragment length polymorphism (PCR/RFLP). Genotyping of PvMSP3α and PvMSP3β revealed marked polymorphisms in length and sequence. Three major types of PvMSP3α (Type A, B and C) and two major types of PvMSP3β (Type A and B) were detected based on the length of PCR products. Fourteen alleles of both genes with difference frequencies were distinguished by restriction fragment length polymorphism, and these results strongly support that P. vivax isolates in Thailand are markedly diverse. PvMSP3α and PvMSP3β are reliable polymorphic markers for population genetic analysis of P. vivax, and PCR/RFLP provides a powerful method for genotyping and identification of mixed parasite infections without requirement of gene sequencing.