NOVEL ADJUVANTS AND VACCINE DELIVERY SYSTEMS

Conventionally the efficiency of an adjuvant is measured by the capaci ty to induce enhanced antibody serum titres and cell mediated immunity (CMI) to a given antigen. Nowadays the capacity of an adjuvant is als o measured by the quality as well as the magnitude of the induced immu ne response, guided by the protective immune response required. Qualit y includes isotype and IgG subclass responses, T-helper cell responses characterized by the cytokine profile and cytotoxic T cells (CTL), In the early phase of immunization some adjuvants influence the antigen administration and uptake by a so-called depot effect exemplified by a luminium hydroxide gel and oil adjuvants, which possibly is not as des ired as alledged. A modem depot is exerted by slow release formulation s continuously releasing the antigen over a period of time or by pulse s at intervals aiming at 'single injection' vaccine. Great efforts are made to formulate efficient delivery formulations targeting the antig ens from the site of administration, to draining lymph nodes or distan t lymphatic tissue or to mucosal surfaces by parenteral or mucosal adm inistrations. Nowadays, non-replicating carriers besides replicating v accines are formulated to induce mucosal immune responses encompassing secretory IgA and CMI. Efforts to evoke immune responses on mucosal m embranes distant from the site of administration have resulted mostly in little success. For a long time it was considered that CTL under th e restriction of MHC Class I only could be evoked by replicating virus es or intracellular parasites, However, novel adjuvant delivery system s readily induce CTL by delivering the antigen to the APC resulting in intracellular transport to the cytosol for the MHC Class I presentati on system, as well as to the endosomal pathway for the MHC Class II pr esentation.