Blocking of transmission to mosquitoes by antibody to Plasmodium vivax malaria vaccine candidates Pvs25 and Pvs28 despite antigenic polymorphism in field isolates

We have previously demonstrated that mouse antisera against yeast-produced recombinant forms of the ookinete surface proteins of Plasmodium vivax (Pvs25 and Pvs28) blocks transmission of the homologous P. vivax (Sal I strain). In this study, we developed mouse and rabbit antisera against Pvs25 and Pvs28 and evaluated the efficacy of these vaccine candidates against natural isolates of P. vivax in Thailand. Although both Pvs25 and Pvs28 genes are polymorphic. sera from mice immunized using alum adjuvant completely inhibited oocyst development for most human isolates. whereas sera from rabbits immunized with either alum or Freund's adjuvant were partially inhibitory. All inhibition occurred in an antibody dose dependent fashion. Data from this study clearly demonstrates that antibodies raised against Sal I-based vaccines overcome the genetic polymorphism of Pvs25 and Pvs28 present in natural isolates of P. vivax. suggesting the wide range applicability of Sal I based vaccines.