Conjugation of TLR7/8 Adjuvants with Cholesteryl Pullulan for a Self-Assembled Nanogel Vaccine: Enhanced Immunostimulatory Activation with Reduced Systemic Inflammation

Therapeutic cancer vaccines are promising treatment strategies capable of specifically eradicating cancer cells. However, their clinical efficacy has been limited due to insufficient cytotoxic T lymphocyte (CTL) responses. Effective CTL induction requires efficient and proper coordination of immune interactions between antigen-presenting cells (APCs) and T cells within lymphoid tissues. Here, we developed a cholesteryl pullulan (CHP) nanogel carrier system that codelivers protein antigens and Toll-like receptor 7/8 (TLR7/8) adjuvants. In this system, the TLR7/8 adjuvants are covalently conjugated to cholesteryl pullulan, while the protein antigens are noncovalently incorporated with the nanogel through host–guest interactions. This dual incorporation strategy enables the simultaneous delivery of both components to lymphoid tissues, enhancing CTL responses while minimizing systemic toxicity. Owing to its small size (approximately 25 nm) and neutral surface charge, the nanogel vaccine efficiently migrated to the lymph nodes after subcutaneous administration, delivering both the antigens and adjuvants to APCs. The nanogel system effectively activated APCs in the draining lymph nodes while minimizing systemic inflammatory responses by restricting adjuvant diffusion at the injection site. This system led to the robust induction of antigen-specific CTLs. Overall, we demonstrated that the adjuvant-conjugated nanogel vaccine effectively controlled the pharmacokinetics of both antigens and adjuvants, resulting in enhanced CTL induction. These findings provide valuable insights for designing safer and more effective vaccines, contributing to advancements in cancer immunotherapy.