New approaches to mucosal immunization.

Every year more than 17 million deaths worldwide are caused by infectious diseases. The great majority of these deaths occur in underdeveloped countries and are attributed to diseases preventable by existing vaccines, or diseases that could potentially be prevented with new vaccines. The fact that most human and veterinary pathogens establish infection in the host by initiating contact at a mucosal surface, provide the rationale for the development of mucosal vaccines. An increasing number of strategies have been proposed to facilitate mucosal immunization. Among the most widely investigated strategies are the use of attenuated microorganisms; the inclusion of immunizing antigens in lipid-based carriers, the genetic creation of transgenic plants and the use of mucosal adjuvants derived from bacterial toxins. This review provides a brief summary of the most recent advances in the field of mucosal immunization with an special emphasis on a promising genetically detoxified mucosal adjuvant, LT(R192G), derived from the heat-labile toxin of enterotoxigenic E. coli. We present evidence regarding the safety, immunogenicity, and efficacy of LT(R192G) for the development of a new generation of mucosal vaccines.