Mucosal vaccines: the promise and the challenge

Mucosal immunization could be our best hope for protection against pathogens that infect mucosal tissues. Here, the authors describe how our accumulating knowledge of the mechanisms of mucosal immune defence is being applied to mucosal vaccine design, in particular against HIV. Most infectious agents enter the body at mucosal surfaces and therefore mucosal immune responses function as a first line of defence. Protective mucosal immune responses are most effectively induced by mucosal immunization through oral, nasal, rectal or vaginal routes, but the vast majority of vaccines in use today are administered by injection. As discussed in this Review, current research is providing new insights into the function of mucosal tissues and the interplay of innate and adaptive immune responses that results in immune protection at mucosal surfaces. These advances promise to accelerate the development and testing of new mucosal vaccines against many human diseases including HIV/AIDS.