Mucosal immunisation : successful approaches to targeting different tissues

Vaccines have been developed for clinical and veterinary applications to protect against infectious diseases [1,2], to provide therapies against cancer [3,4], addictions [5], and allergies and autoimmune diseases [6,7], and to prevent pregnancy [4,8,9]. In general, traditional immunisation relies on the production of antibody and cell-mediated responses directed against specific antigens from a pathogen, usually an attenuated or subunit protein/peptide derivative, co-administered with an adjuvant [10]. More recently, DNA, or primed, pre-existing leukocytes or antigen-presenting cells have been used to prime vaccinees [11]. The choice of vaccination procedures is complex, and the results may be dependent on many factors such as dose, type of adjuvant, time between inoculation, and methods used to evaluate efficacy [12,13]. In addition, immune responses to an antigen vary with age, gender, and health status, factors that the vaccination regimen needs to take into account [14–16]. To date, and with a few exceptions, vaccines are generally given by subcutaneous or intramuscular injection. This invasive procedure ensures that the correct dose is given, often forming a depot of antigen and the overall effect is to stimulate the appropriate action by immune cells [10]