Limited Polymorphism of the Plasmodium vivax Merozoite Surface Protein 1 Gene in Isolates from Turkey

The 200-kD merozoite surface protein of Plasmodium vivax (PvMSP-1) is one of the leading vaccine candidates against P vivax malaria. However, the gene encoding PvMSP-1 (pvmspl) is highly polymorphic and is a major obstacle to effective vaccine development. To further understand polymorphism in pvmspl, we obtained 30 full-length pvmspl sequences from southeastern Turkey. Comparative analysis of sequences from Turkey and other areas showed substantially limited polymorphism. Substitutions were found at 280 and 162 amino acid sites in samples from other regions and those from Turkey, respectively. Eight substitutions were unique to Turkey. In one of them, DIE at position 1706 in the C-terminal 19-kD region, the K/E change at 1709 was the only polymorphism previously known. Limited diversity was also observed in microsatellites. Data suggest a recent population bottleneck in Turkey that may have obscured a signature for balancing selection in the C-terminal 42-kD region, which was otherwise detectable in other areas.