Adjuvants and Immune Enhancement

Abstract

Adjuvants increase cell-mediated and humoral immune responses to specific antigens. Used with recombinant viral antigens, they can elicit the production of T lymphocytes that lyse target cells, expressing the antigen in a genetically restricted fashion. Adjuvants can augment the production of interferon-gamma, thereby favoring the production of protective antibody isotopes, such as immuno-globulin G2a in the mouse. Modern adjuvants display the efficacy of Freund's complete adjuvant without its side effects. One such adjuvant is Syntex adjuvant formulation, a synthetic analogue of muramyl dipeptide in a microfluidized squalane/squalene-in-water emulsion. Monophosphoryl lipid A in a similar lipid emulsion is also effective. Immune-stimulating complexes of saponin and antigens elicit potent cell-mediated and humoral responses. A purified saponin component has adjuvant activity with reduced side effects; liposomes also can have adjuvant activity. Administering antigens in adjuvants can overcome low responsiveness in very young and old experimental animals and in those that are genetically low responders. Adjuvants are likely components of a new generation of recombinant and subunit vaccines.