Transcutaneous immunization: T cell responses and boosting of existing immunity

Transcutaneous immunization (TCI) is a novel immunization strategy by which antigen and adjuvant are applied topically to intact, hydrated skin to ind uce potent antibody and cell-mediated immune responses specific for both th e antigen and the adjuvant. Using tetanus toroid as a model antigen, we exa mined the T cell response to tetanus toroid after topical immunization with a variety of adjuvants. TCI readily induced systemic antigen specific T ce ll responses with a mixed Th1/Th2 phenotype but with a Th2 bias. We also in vestigated whether priming by the intramuscular route, which is known to in duce T cell memory, could be followed by a boosting immunization on the ski n to induce secondary responses. TCI could augment existing immunity, but i nterestingly, this strategy induced potent responses only if the antibody t iter was low at the time of TCI boosting. These and previous observations s uggest that TCI follows known immunological principles that govern other ro utes of vaccine delivery. Furthermore. booster immunization using tetanus t oroid may provide a useful model for further development of important patch and formulation concepts for TCI, and act as an early candidate for valida ting product feasibility of TCI in humans. (C) 2001 Elsevier Science Ltd. A ll rights reserved.