Immunogenicity of a plasmid DNA vaccine encoding 42kDa fragment of Plasmodium vivax merozoite surface protein-1

Plasmodium vivax is the second major human malaria parasite that inflicts debilitating morbidity and consequent economic impact in South-East Asian countries. The relapsing nature of P. vivax along with the emergence of drug-resistant P. vivax strains has emphasized the urgent need for a vaccine. However, the development of an effective vivax vaccine is seriously hampered due to the diversity and variation in parasite antigens and non-availability of suitable animal models. DNA based vaccines represent an alternative approach in inducing immunity to multiple targets from different stages of malaria parasite. DNA prime-boosting strategies induce both antibody mediated and cell-mediated immune responses that are the major mechanisms of protection against malaria parasites. We have earlier studied the immunogenicity and protective efficacy of the soluble and refolded forms of recombinant 42kDa fragment of Plasmodium vivax merozoite surface protein-1 (PvMSP-142) using P. cynomolgi rhesus monkey model. In the present study, we have constructed a recombinant DNA vaccine encoding 42kDa fragment of P. vivax MSP-1 and studied the immunogenicity of PvMSP-142 DNA vaccine construct in mice. The 42kDa gene fragment of PvMSP-1 was PCR amplified using gene specific primers and subcloned into pcDNA 3.1 (+) eukaryotic expression vector. In vitro expression of PvMSP-142 plasmid construct was checked by transfection in COS-1 cell line. Indirect immunofluorescence of transfected COS-1 cells probed with monoclonal antibodies against PvMSP-142 exhibited positive fluorescence. Immunization of BALB/c mice with PvMSP-142-pcDNA vaccine construct revealed the immunogenicity of recombinant vaccine plasmid that can be enhanced by prime boosting with recombinant protein corresponding to the DNA vaccine as evidenced by significant elevation of antibody and the cytokines responses.