Vaccination with dendritic cells pulsed ex vivo with gp100 peptide-decorated liposomes enhances the efficacy of anti PD-1 therapy in a mouse model of melanoma.

Background: Targeting antigens to dendritic cells (DCs) via nanoparticles is a powerful strategy which improves the efficacy of ex vivo antigen-pulsed DC vaccines.

Methods: In this study, liposomes were first decorated with gp100 self-antigen and then characterized. Then, DCs were pulsed ex vivo with liposomal gp100 and injected subcutaneously in mice bearing B16F10 established melanoma tumors in combination with anti-PD-1 therapy.

Results: Treatment with liposomal pulsed DC vaccine elicited the strongest anticancer immunity and enhanced intratumoral immune responses based on infiltration of gp100-specific CD4+ and CD8+ T cells to the tumor leading to significant tumor growth regression and prolonged survival rate. Treatment with liposomal pulsed DC vaccine also markedly enhanced specific cytotoxic T lymphocytes (CTL) responses with a significant higher titer of IFN-γ in the spleen. Moreover, a significant increase of PD-1 expressing CD8+ tumor infiltrating lymphocytes (TILs) was detected in tumors.

Conclusion: Our results demonstrate an optimum dose of liposomal gp100 significantly increases the efficacy of anti-PD-1 therapy in mice and might be an effective strategy to overcome resistance to anti-PD-1 therapy.