Intravenous liposomal vaccine enhances CTL generation, but not until antigen presentation

Adjuvant loaded nanoparticles are a potent strategy for developing effective combined cancer immunotherapies. A polyinosinic-polycytidylic acid (poly I:C) is a ligand for toll-like receptor 3 and a promising cancer adjuvant. However, regarding intravenous administration, the potential for and the mechanism of poly I:C loaded nano particles as a cancer vaccine are largely unknown. We investigated the effects of using a combination of poly I:C and an antigen loaded liposome for cancer immunotherapy and a key process for achieving effective antitumor immunity of the liposome system under conditions of intravenous vaccination. A poly I:C and ovalbumin (OVA) loaded octaarginine (R8) modified liposome (PoIC/OVA-R8L) drastically inhibited the systemic cytokine production derived from the poly I:C intravenous injection. Treatment with PoIC/OVA-R8L improved the immune status in B16-OVA tumors to an inflamed immune status and induced a significant combined antitumor effect with the anti-programmed cell death 1 ligand (PD-L1). In a mechanistic analysis compared with a high dose of the free form of poly I:C, interestingly, local cytokine production, maturation of antigen presenting cells and antigen presentation were comparable. Conversely, significant differences were identified in the processes after OVA-specific CTL generation. Collectively, our findings have implications for the development of intravenous liposomal vaccines.

Automated summary

The combination of polyinosinic-polycytidylic acid (poly I:C) and antigen loaded liposome has been shown to improve cancer immunotherapy and has the potential for effective antitumor immunity. The study investigated the effects of using poly I:C and an antigen loaded liposome for cancer immunotherapy and found that it significantly inhibited systemic cytokine production and improved the immune status in tumors. The findings provide implications for the development of intravenous liposomal vaccines.