Sublingual vaccination

The sublingual route has been used for many years to deliver drugs and small molecules to the bloodstream. Surprisingly, the potential of this route for delivering vaccines has received very little if any attention until recently. During the past few years, a number of laboratories have documented the efficacy of sublingual immunization for inducing a broad range of immune responses in different experimental animal systems using a variety of antigens, including soluble proteins, inert particulate antigens (killed viruses, virus-like particles, bacterial extracts) as well as live-attenuated viruses. In most cases, systemic and mucosal immune responses, including humoral and cytotoxic T-cell responses were induced in both mucosal and extra-mucosal tissues. Overall, sublingual immunization was comparable to nasal immunization regarding the magnitude, breadth, and anatomic dissemination of the induced immune responses. Importantly, and contrary to nasal administration, sublingual administration did not redirect antigens and/or adjuvants to the brain. Here we review the results of pre-clinical studies using animal models of respiratory, intestinal and genital infections. These promising results provide a foundation for testing the approach in humans.