Copolymer adjuvants in malaria vaccine development.

Protection against virulent challenge with murine Plasmodium yoelii malaria was induced by immunization with whole killed blood-stage parasites in copolymer P1004 and detoxified lipopolysaccharide as adjuvant. Similar immunization with Freund's complete adjuvant and other water-in-oil emulsions failed to protect. Protection was associated with the production of antibody of the IgG2a isotype against epitopes measured by immunofluorescence. Several formulations that did not protect elicited high antibody titers measured by enzyme-linked immunosorbent assays or titers of other isotypes measured by indirect immunofluorescent assay. The results provide additional evidence that the adjuvants influenced both the isotype and specificity of antibody. The implications of these findings for vaccine development are discussed.