Engineered vesicular cancer vaccines for immunosuppressive microenvironment reversion and in situ vaccine generation

It is crucial to reverse immunosuppressive tumor microenvironment (TME) and effectively activate both cellular and humoral immunity in cancer immunotherapy. We have found that decitabine, an epigenetic regulator, can increase antigen exposure and induce double-stranded RNA (dsRNA) accumulation in tumor cells. The corresponding cell-derived nanovesicles (NV) have the ability to stimulate both cellular and humoral immunity due to the internal dsRNA. However, the efficacy of dsRNA-containing NV (dsRNA@NV) remains constrained by the inadequate activation efficiency of immune cells in immunosuppressive TME. In this study, CD40L, an immune cell regulator, was incorporated on the surface of dsRNA@NV (dsRNA@NV_CD40L) through lentiviral transfection to further reverse the immunosuppressive TME, by activating dendritic cells and regulating macrophages phenotypes via CD40-CD40L interaction. In addition, CD40L could induce immunogenic death of tumor cells, and the administration of dsRNA@NV_CD40L effectively elicited an in situ cancer vaccine response in B16-OVA tumor. This proposed NV-based vaccine was expected to solve the problems of low immunogenicity, insufficient activation of immune responses and lack of effective regulation of immunosuppressive TME of existing tumor vesicular vaccines.