PROTECTION AGAINST MALARIA BY IMMUNIZATION WITH PLASMID DNA ENCODING CHOLERA-TOXIN B-SUBUNIT AND PLASMODIUM-FALCIPARUM EPITOPES

Cholera toxin B subunit is a good carrier protein and an effective adj uvant which can boost both cellular and humoral immunity. DNA fragment s encoding B cell, Th cell and CTL epitopes of P. falciparum CS, MSA-1 , MSA-2 and RESA antigens were cloned down-stream of cholera toxin B s ubunit gene in the same reading frame. Another modification using IL2 as adjuvant was also made. High titer of anti-malaria epitopes antibod ies and strong cellular immunogenicity were elicited after Balb/c mice were immunized three times with 100 mu g recombinant plasmid DNA diss olved in 100 mu L PBS. 200 vaccinees were challenged with mouse Plasmo dium yoelli to investigate if cross protection existed. The protective efficacy was about 50 %. And it is found that the protective efficacy is correlated with CTL activity which was considered to be the primar y effects of anti-sporozoite protective immunity. Better results might be expected when the DNA vaccine candidates were applied to primates.