[Development of an Immune Regulation Technology Targeting the Skin and Promotion of the Practical Applications of Transcutaneous Vaccination/Immunotherapy]

In the premise of vaccination and allergen-specific immunotherapy, transcutaneous formulations have an advantage over conventional subcutaneous injections in terms of convenience, simplicity of delivery, and painless administration into the skin. Additionally, since transcutaneous formulations can be rendered cold-chain free, they do not require expert handling during transportation, storage, and stockpiling, which enables reductions in costs and distribution to distant areas. Furthermore, transcutaneous formulations are effective for improving adherence in children with phobias toward injection needles and may help in persuading them to perform self-vaccination and home immunotherapy against allergies in the future. We have been promoting the development of innovative "patch-type formulations for vaccination and immunotherapy" which regard skin as an immune organ and utilize our original transcutaneous administration devices (hydrophilic gel patch and microneedle patch) for their delivery. We have confirmed the safety and efficacy of transcutaneous formulations not only in demonstration experiments using animals but also in physician-initiated clinical studies. Additionally, in order to elucidate the mechanism for the induction of immune responses by transcutaneous formulations, we analyzed the immunological events occurring in the skin and regional lymph nodes which accompanied the application of transcutaneous administration devices or the delivery of antigens (vaccines and allergens) to the skin surface layer. This review presents our results from basic to clinical research on the development of transcutaneous formulations for vaccines and allergen-specific immunotherapy.