ROLE OF MUCOSAL ADJUVANTS IN MUCOSAL IMMUNIZATION

Although the bacterial enterotoxins cholera toxin (CT) and Eschericia coli heat labile toxin (LT) are the most potent mucosal adjuvants curr ently known, their enterotoxicity may preclude their use in humans. St udies conducted with genetically engineered mutant molecules demonstra te that target cell binding is necessary but not sufficient for adjuva nt activity and suggest that some degree of toxin activity is required for oral immunization. Although toxin activity may not be required fo r intranasal adjuvanticity, further studies are needed. Several studie s have demonstrated that CT and LT can enhance the expression of costi mulatory molecules on antigen-presenting cells and thus indirectly inf luence subsequent T-cell responses. Direct effects on B and T cells ma y also be important. Although they have not been as extensively studie d as CT and LT, compounds such as liposomes, immune-stimulating comple xes, microparticles and bacterial membrane proteins have also been sho wn to have mucosal adjuvant activity.