[DNA sequencing of circumsporozoite protein genes of Plasmodium vivax from four different countries in west Pacific region: comparative study on the flank sequences].

: P. vivax CSP gene of 18 isolates from infected blood of patients living in China, Philippines, Solomon Islands and Papua New Guinea in West Pacific region has been sequenced from both terminal end. The total readable sequence in most isolates was about 725 base pair (bp), including the first two repeat units (70-330 bp) to the N terminus, and the last two repeat units to the C terminus (763-1,228 bp). Comparison and analysis of these obtained sequences with the published sequences of N.K., Thai., Belem, Sal-l. and BZL strains showed that:the N and C terminus sequences flanking the centre repeats in CSP gene were highly conserved in all isolates and identical with the 5 published sequences but a double base pair substitution in each end and a remarkable polymorphism in the postrepeat variable region in C terminus were found, including some diversities with obvious geographic characteristics which have not been reported previously.