Analysis of Plasmodium vivax merozoite surface protein-1 gene sequences from resurgent Korean isolates.

The merozoite surface protein-1 (MSP-1) of Plasmodium vivax exhibits great antigenic diversity among different isolates of this parasite. This antigen is a useful genetic marker for studying the polymorphism of natural P. vivax parasite populations. One or more of these populations has been responsible for resurgent malaria now occurring in Korea. This paper reports the analysis of a highly polymorphic region between interspecies conserved blocks 5 and 6 of the MSP-1 gene, using the polymerase chain reaction to amplify the DNA fragment encompassing these regions from 25 Korean isolates, followed by sequencing. Almost all amino acid sequences of Korean isolates were nearly identical to that of Thai isolates TD525A (96.6-99.7%) and TD424 (96.3-99.5%), and very similar to that of the France-Belem strain when compared with other isolates (Sal-1, Sri Lanka, and Colombia). Interallelic recombination was found in the poly-Q repeat and a Sal-1 type amino acid structure was observed in all isolates. This study shows that the MSP gene nucleotide sequence of resurgent P. vivax in Korea is most similar to that of Thai isolates; however, the Korean strains are phylogenetically unique.