The adjuvant effect of jacalin on the mouse humoral immune response to trinitrophenyl and Trypanosoma cruzi

We have evaluated the adjuvant action of jacalin, a lectin obtained from se eds of Artocarpus integrifolia, on humoral immune response against the trin itrophenyl (TNP) hapten when conjugated to it and to Trypanosoma cruzi. The protective effect of parasite-specific antibodies generated in mice immuni zed with epimastigote forms of T. cruzi plus jacalin was also evaluated by determining the parasitemia levels of animals after infection with 1000 try pomastigote forms. Immunization of mice with trinitrophenylated jacalin (TN P-JAC) in saline resulted in an antibody response to the TNP hapten that wa s eight and 16 times higher than that found in mice immunized with TNP-huma n gamma globulin (TNP-HGG) or TNP-bovine serum albumin (TNP-BSA), respectiv ely. In addition, immunization with either a lysate or viable epimastigote forms of T. cruzi the presence of jacalin resulted in a marked increase in the levels of anti-T. cruzi antibodies. The protective action of antibodies against acute infection by T. cruzi was evident when mice were immunized w ith 1.0 x 10(5) epimastigotes plus jacalin. These animals had a significant ly lower parasitemia than those immunized with epimastigotes alone. In cont rast, mice immunized with 1.0 x 10(6) epimastigotes developed very low leve ls of parasitemia, regardless of the presence of jacalin. These data sugges t that jacalin is a potent adjuvant in the humoral response to TNP and T. c ruzi, and that the protective action of the T. cruzi-specific antibodies de pends on the number of parasites used in the immunization protocol. (C) 199 9 Elsevier Science B.V. All rights reserved.