CYTOKINES AND ANTIBODY SUBCLASS ASSOCIATED WITH PROTECTIVE IMMUNITY AGAINST BLOOD-STAGE MALARIA IN MICE VACCINATED WITH THE C-TERMINUS OF MEROZOITE SURFACE PROTEIN-1 PLUS A NOVEL ADJUVANT

A blood-stage malaria antigen comprising the C terminus of merozoite s urface protein 1 fused to glutathione S-transferase, combined with an adjuvant formulation containing squalane, Tween 80, and pluronic L121 (AF), administered subcutaneously protected mice against death from a lethal Plasmodium yoelii infection, The protection induced by this ant igen-adjuvant combination was compared with that induced by the antige n plus saponin in terms of survival from the lethal infection and clea rance of parasitemia, The levels of gamma interferon and interleukin-4 in spleens were measured as indicators of Th1 and Th2 cell activation , and antibody classes and subclasses were determined by immunofluores cence, With a 10-mu g dose of antigen and AF as adjuvant, all mice rec overed, but with saponin as the adjuvant, there were only a few surviv ors, With 30 mu g of antigen plus AF, the peak parasitemias were 10-fo ld lower than those with 10 mu g; with saponin, survival was slightly improved, The levels of both gamma interferon and interleukin-4 rose m ore rapidly and to higher levels with AF as the adjuvant than with sap onin, and the same was true for immunoglobulin G1 (IgG1), IgG2a, and I gG2b subclasses, Thus, in terms of both cytokine production and antibo dy levels, AF is a more potent adjuvant for a malaria vaccine than is saponin.