Genetic diversity of vaccine candidate gene, merozoite surface protein 1, block 2 of Plasmodium. falciparum in Thailand

Abstract

In 2030, WHO target is to eliminate malaria in 35 countries at least. At the present, Thailand country
is low risk of malaria. So that, it has the potential to eliminate. About 10 years ago, malaria prevalence was high
in border area. To prevent the recurrence in those areas, evaluation of drug susceptibility and vaccine are
important. Merozoite surface protein 1(msp1) gene is useful for monitoring and the potential gene of vaccine.
However, high diversity of block 2 region in msp1 is the barrier of vaccine design. Therefore, in this study,
genotyping of different alleles from endemic area of Thailand is crucial for control program. One-hundred and
ninety-one P. falciparum-infected blood samples from five endemic regions were amplified by nested PCR to
detect K1, MAD20 and RO33. These alleles were screened with 2.5% gel electrophoresis and fragment sizes were
analyzed. The overall prevalence of K1, MAD20 and RO33 allelic types in P. falciparum isolates from Thailand
were 19.0 %, 53.0% and 28.0%, respectively, of samples under study. MAD20 type is the most prevalent and
diverse one. The fluctuations of alleles were observed in Thailand. High diversity of block 2 results indicates that
high transmission intensity of parasites still present and enforce to the population with drug resistance.