Sequence polymorphisms of Plasmodium vivax ookinete surface proteins (Pvs25 and Pvs28) from clinical isolates in Korea.

The Ookinete surface proteins of Plasmodium vivax (P. vivax), Pvs25 and Pvs28, were candidates for the transmission blocking vaccine (TBV), which exhibited great antigenic diversities among various isolates. Polymorphisms of these genes in the isolates from Republic of Korea (ROK) were analysed, which provided valuable baseline data for the field trials of TBV-based vaccines. A total of 98 isolates were collected over 11 years from 1996 to 2007. pvs25 and pvs28 genes from the above isolates were amplified, sequenced and compared against Sal-1 strain. Sequencing analysis of PCR products from P. vivax pvs25 revealed two allelic types, Q97T130 and E97/T130 alleles with the frequencies of 54.5% and 45.5%, respectively, in comparison with Sal I type sequence (E97/I130). From pvs28 gene, polymorphisms at M52L and T140S in the first and third EGF-like domains in comparison to Sal-1 strain were detected, respectively. Six GSGGE tandem repeats followed by GSGGDT or SSGGDT were identified at the end of the fourth EGF-like domain in all Korean isolates. Interestingly, different tandem repeats of amino acid substitutions were observed from isolates collected after 2006 in comparison with preceding years. The ROK isolates revealed limited sequence polymorphisms in pvs25 and tandem repeats in pvs28 in comparison with reported isolates from other nations. Current observations suggested the rapid progresses of genetic changes among Korean isolates.