Genotypes of Circumsporozoite of Plasmodium vivax in Korea

Choi, Jong Seong; Lim, Chae Seung; Lee, Kap No

Abstract

BACKGROUND: More than 200 million people suffer from malaria worldwide. In Korea this infectious disease had been on a decreasing trend since 1930s and was considered to be eradicated from 1985. However, since 1993 when a case of malaria was reported, its incidence is progressively increased. Recent efforts have been focused on the development of vaccine against the infective sporozoite stage of Plasmodium vivax. It has been found that sporozoites are complicated with genetic variation within the circumsporozoite gene and phenotypic heterogeneity in the protein it encodes. So, we investigated the distribution of circumsporozoite gene of Plasmodium vivax in Korea.
METHODS
Polymerase chain reactions (PCR) were performed on samples confirmed with microscopic examination for P. vivax and negative samples with clinical and microscopic examination. The amplified products were analyzed by dot hybridization with oligonucleotide probes VK210 and VK247 which are respectively complementary to the predominant and variant strains of the circumsporozoite gene of P. vivax.
RESULTS
The incidence of isolation in VK210 and VK247 strains were 96.3%, respectively and individuals who were infected with both strains were 92.7%. Compared to the microscopic examination, the results of PCR showed 82% in sensitivity, 100% in specificity.
CONCLUSIONS
The present study suggests that a single-epitope vaccine based on either one circumsporozoite domain is unlikely to be protective because both VK210 and VK247 strains of P. vivax were found widely in Korea. The PCR method appears not to be feasible as a screening, but suitable as a confirmatory test for the identification of Plasmodium species.