Abstract
Cancer vaccines aim to prevent or inhibit tumor growth by inducing an immune response to tumor-associated antigens (TAAs) encoded by or present in the vaccine. Previous work has demonstrated that effective antitumor immunity can be induced using a codelivery system in which nonspecific immunostimulatory molecules are administered together with TAAs. In this study, we investigated the antitumor effects of a solid-in-oil (S/O) nanodispersion system containing a model TAA, ovalbumin (OVA), and resiquimod (R-848), a small molecular Toll-like receptor 7/8 ligand, which induces an antigen-nonspecific cellular immune response that is crucial for the efficacy of cancer vaccines. R-848 was contained in the outer oil phase of S/O nanodispersion. Analysis of OVA and R-848 permeation in mouse skin after application of an R-848 S/O nanodispersion indicated that R-848 rapidly permeated the skin and preactivated Langerhans cells, resulting in efficient uptake of OVA and migration of antigen-loaded Langerhans cells to the draining lymph nodes. Transcutaneous immunization of mice with an R-848 S/O nanodispersion inhibited the growth of E.G7-OVA tumors and prolonged mouse survival to a greater extent than did immunization with an S/O nanodispersion containing OVA alone. Consistent with this observation, antigen-specific secretion of the Th1 cytokine interferon-γ and cytolytic activity were both high in splenocytes isolated from mice immunized with R-848 S/O. Our results thus demonstrate that codelivery of R-848 significantly amplified the antitumor immune response induced by antigen-containing S/O nanodispersions and further suggest that S/O nanodispersions may be effective formulations for codelivery of TAAs and R-848 in transcutaneous cancer vaccines.