Dendritic Cell Derived-Extracellular Vesicles Engineered to Express Interleukin-12 and Anti-CTLA-4 on Their Surface for Combinational Cancer Immunotherapy.

Dendritic cell (DC)-derived extracellular vesicles (DEVs) are promising candidates for cancer vaccines, but their therapeutic effects still need further optimization. In this study, we utilized neoantigens, lipopolysaccharide and IFN-γ to induce the maturation of DCs, and then isolated DEVs derived from these mature DCs. We showed that the immune checkpoint inhibitor (anti-CTLA-4 antibody, aCTLA-4) can improve the immunostimulatory function of DEVs by directly activating T cells through immune checkpoint signal blockade. The cytokine interleukin-12 (IL-12), as one of the third signals for T cell activation, can also enhance the capability of DEVs to activate T cells directly. Based on these findings, we designed the engineered DEVs conjugated with IL-12 and aCTLA-4 (DEV@IL-12-aCTLA-4) to improve the therapeutic potential of DEVs by providing sufficient immune regulatory signals. Moreover, the carrier property of DEVs also contributes to the delivery of IL-12 and aCTLA-4 to lymph nodes. This indicates that the conjugation of DEVs with IL-12 and aCTLA-4 constitutes a complementary approach, where IL-12 and aCTLA-4 help to enhance the T cell activation effect of DEVs, and DEVs facilitate the delivery of IL-12 and aCTLA-4. Our results showed that DEV@IL-12-aCTLA-4 can enhance the Th1 immune response and reverse exhausted CD8(+) T cells in the tumour microenvironment, effectively inducing robust T cell immune responses and inhibiting tumour growth in tumour-bearing mice. Overall, this study expands the theoretical foundation of DEVs and provides a universal strategy for optimizing cancer combination immunotherapy by reprogramming DEVs.