Intragenic recombination in the 3 ' portion of the merozoite surface protein 1 gene of Plasmodium vivax

To date, little has been known about the extent of sequence variation in th e C-terminal part of the Plasmodium vivax merozoite surface protein 1 (PvMS P1) which has been considered to be a potential vaccine candidate. Here, we examined the variation in the region encompassing interspecies conserved b locks (ICBs) 8 and 10 of PvMSP1 by DNA sequencing of 14 Thai isolates and t hree Brazilian isolates. Eighteen different alleles were detected. Three ne w sequence types had been identified in polymorphic region between ICB8 and CB9: one was possibly a result of intragenic recombination between the Bel em and Salvador I alleles and the others displayed unique repeats. A striki ng variation was observed in a stretch of 38 codons in polymorphic block be tween conserved block CB9 and ICB10, resulting in eight different sequence types, probably generated by interallelic recombination at a single or mult iple sites. There is no apparent linkage between these two polymorphic site s, On the other hand, a single or stretches of nucleotide substitutions are dimorphic like in Plasmodium falciparum MSP1 (PfMSP1) in the remaining par ts, creating microheterogeneity of sequences. The C-terminal 19 kDa-encodin g region was extremely conserved with a single dimorphic exchange at a know n position. Thus, this study provides evidence of intragenic recombination occurring in the 3' portion of PvMSP1 and suggests that the 3' portion of P vMSP1 is more diverse than that in PfMSP1. (C) 2000 Elsevier Science B.V. A ll rights reserved.