Plasmodium vivax merozoite surface protein-3 alpha: a high-resolution marker for genetic diversity studies.

BACKGROUND & OBJECTIVES Malaria, an ancient human infectious disease caused by five species of Plasmodium, among them Plasmodium vivax is the most widespread human malaria species and causes huge morbidity to its host. Identification of genetic marker to resolve higher genetic diversity for an ancient origin organism is a crucial task. We have analyzed genetic diversity of P. vivax field isolates using highly polymorphic antigen gene merozoite surface protein-3 alpha (msp-3 alpha) and assessed its suitability as high-resolution genetic marker for population genetic studies. METHODS 27 P. vivax field isolates collected during chloroquine therapeutic efficacy study at Chennai were analyzed for genetic diversity. PCR-RFLP was employed to assess the genetic variations using highly polymorphic antigen gene msp-3 alpha. RESULTS We observed three distinct PCR alleles at msp-3 alpha, and among them allele A showed significantly high frequency (53%, chi2 = 8.22, p = 0.001). PCR-RFLP analysis revealed 14 and 17 distinct RFLP patterns for Hha1 and Alu1 enzymes respectively. Further, RFLP analysis revealed that allele A at msp-3 alpha is more diverse in the population compared with allele B and C. Combining Hha1 and Alu1 RFLP patterns revealed 21 distinct genotypes among 22 isolates reflects higher diversity resolution power of msp-3 alpha in the field isolates. INTERPRETATION & CONCLUSION P. vivax isolates from Chennai region revealed substantial amount of genetic diversity and comparison of allelic diversity with other antigen genes and microsatellites suggesting that msp-3 alpha could be a high-resolution marker for genetic diversity studies among P. vivax field isolates.