Generation, characterization and immunogenicity of a novel chimeric recombinant protein based on Plasmodium vivax AMA-1 and MSP1.

Plasmodium vivax is the most widely distributed malaria species and the most prevalent species of malaria in America and Asia. Vaccine development against P. vivax is considered a priority in the global program for the eradication of malaria. Earlier studies have characterized the Apical Membrane Antigen 1 (AMA-1) ectodomain and the C-terminal region (19kDa) of the Merozoite Surface Protein 1 (MSP-1) of P. vivax as immunodominant antigens. Based on this characterization, we designed a chimeric recombinant protein containing both merozoite immunodominant domains (PvAMA1-MSP1). The recombinant PvAMA1-MSP1 was successfully expressed in Pichia pastoris and used to immunize two different mouse strains (BALB/c and C57BL/6) in the presence of the Poly (I:C) as an adjuvant. Immunization with the chimeric protein induced high antibody titers against both proteins in both strains of mice as detected by ELISA. Antisera also recognized the native proteins expressed on the merozoites of mature P. vivax schizonts. Moreover, this antigen was able to induce IFN-gamma-secreting cells in C57BL/6 mice. These findings indicate that this novel yeast recombinant protein containing PvAMA1 and PvMSP1 is advantageous, because of improved antibody titers and cellular immune response. Therefore, this formulation should be further developed for pre-clinical trials in non-human primates as a potential candidate for a P. vivax vaccine.