A Plasmodium vivax vaccine candidate displays limited allele polymorphism,which does not restrict recognition by antibodies

Background: The 19 kDa C-terminal region of the merozoite surface protein 1 (MSP1(19)) has been suggested as candidate for part of a subunit vaccine a gainst malaria. A major concern in vaccine development is the polymorphism observed in different plasmodial strains. The present study examined the ex tension and immunological relevance of the allelic polymorphism of the MSP1 (19) from Plasmodium vivax, a major human malaria parasite. Materials and Methods: We cloned and sequenced 88 gene fragments representi ng the MSP1(19) from 28 Brazilian isolates of P. vivax. subsequently, we ev aluated the reactivity of rabbit polyclonal antibodies, a monoclonal antibo dy, and a panel of 80 human sera to bacterial and yeast recombinant protein s representing the two allelic forms of P. vivax MSP19 described thus far. Results: We observed that DNA sequences encoding MSP1(19) were not as varia ble as the equivalent region of other species of Plasmodium, being conserve d among Brazillian isolates of P. vivax. Also, we found that antibodies are directed mainly to conserved epitopes present in both allelic forms of the protein. Conclusions: Our findings suggest that the use of MSP1(19) as part of a sub unit vaccine against P, vivax might be greatly facilitated by the limited g enetic polymorphism and predominant recognition of conserved epitopes by an tibodies.