Vaccines for mucosal immunity to combat emerging infectious diseases

The mucosal immune system consists of molecules, cells, and organized lymph oid structures intended to provide immunity to pathogens that impinge upon mucosal surfaces. Mucosal infection by intracellular pathogens results in t he induction of cell-mediated immunity, as manifested by CD4-positive (CD4( +)) T helper-type 1 cells, as well as CD8(+) cytotoxic T-lymphocytes. These responses are normally accompanied by the synthesis of secretory immunoglo bulin A (S-IgA) antibodies, which provide an important first line of defens e against invasion of deeper tissues by these pathogens. New-generation liv e, attenuated viral vaccines, such as the cold-adapted, recombinant nasal i nfluenza and oral rotavirus vaccines, optimize this form of mucosal immune protection. Despite these advances, new and reemerging infectious diseases are tipping the balance in favor of the parasite; continued mucosal vaccine development will be needed to effectively combat these new threats.