Mucosal immunization with DNA vaccines.

The mucosal surface area of the gastrointestinal, genitourinary and respiratory tracts is more than 200 times greater than that of the skin and is the primary site of transmission of numerous diseases. The entry of pathogenic organisms at mucosal surfaces can be prevented by mucosal, but not systemic immunity. Vaccines which are delivered by intramuscular (IM) or subcutaneous (SC) injection induce strong systemic responses but generally no mucosal immunity. In contrast, vaccines delivered at mucosal surfaces trigger both mucosal (at local and distant sites) and systemic responses (1,2). Other advantages of mucosal immunization include a broader age range of recipients, the vaccines are easy and non-invasive to administer and there is no risk of needle stick injury and cross contamination (3).