CURRENT OPTIONS FOR VACCINE DELIVERY SYSTEMS BY MUCOSAL ROUTES

Infectious diseases continue to be the leading cause of morbidity and mortality worldwide. Increased awareness of the fact that mucosal memb ranes are the most frequent portals of entry of pathogenic microorgani sms has prompted studies aimed at the development of vaccination proto cols and antigen delivery systems that would lead to an increased prot ection of mucosae. Although systemic and strictly local (e.g., intrava ginal or conjunctival) immunizations are of limited effectiveness in t he induction of generalized mucosal protection, ingestion or inhalatio n of antigens results in a disseminated immune response manifested by the appearance of specific antibodies of the secretory immunoglobulin (Ig) A isotype in external secretions due to the dissemination of IgA precursor cells from IgA-inductive lymphoid tissues. Furthermore, addi tional inductive sites strategically positioned at the opening of the respiratory and digestive tracts may also be suitable targets for indu ction of immune responses at desired effector sites. To prevent degrad ation and increase the absorption of ingested antigens, novel strategi es including enclosure of antigens in biodegradable microspheres or li posomes, or their expression in viral and bacterial vectors and in pla nts, are currently being considered. Forthcoming technological advance s in antigen preparation and routes of delivery will undoubtedly have a profound impact on immunization practices in the future. (C) 1997 El sevier Science B.V.