Genetic variation among Plasmodium vivax isolates adapted to non-human primates and the implication for vaccine development.

Plasmodium vivax Duffy binding protein (DBP) is vital for parasite development, thereby making this molecule a good vaccine candidate. Preclinical development of a P. vivax vaccine often involves use of primate models prior to testing efficacy in humans, but primate isolates are poorly characterized. We analyzed the complete gene coding for the DBP in several P. vivax isolates that are used for experimental primate infections and compared these sequences with the Salvador I DBP isolate, which is being used for vaccine development. Our results affirm that primate-adapted isolates are genetically similar to P. vivax circulating in humans, but variability is greatest in the putative target of protective antibodies. In addition, some P. vivax isolates contain multiple genetically different clones. Testing a DBP vaccine may therefore be complicated by heterogeneity and diversity of the P. vivax isolates available for in vivo challenge.