Transcutaneous immunization is a novel, non-invasive alternative to conventional immunization by injection. Skin immunocompetence composed of abundant antigen-presenting cells in the epidermal and dermal layers of the skin can provide an effective tool for transcutaneous immunization, whereas the outermost, hydrophobic layer of skin, the stratum corneum, hinders the penetration of antigens into the skin. To realize effective transcutaneous delivery of antigens, we have developed a solid-in-oil (S/O) technique that produces an oil dispersion of hydrophilic biomolecules. In this study, we applied the S/O nanodispersions in transcutaneous immunization to induce cancer immunity. The topical application of S/O nanodispersions bearing ovalbumin (OVA) as a model cancer-antigen allowed the penetration of OVA into the deep dermis region of the skin by intercellular and transfollicular pathways. Inhibition of OVA-bearing tumor growth and production of cytokines responsible for cellular immunity were achieved, demonstrating the applicability of S/O nanodispersions to the induction of cancer immunity.
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