Viral Protein-Pseudotyped and siRNA-Electroporated Extracellular Vesicles for Cancer Immunotherapy

Extracellular vesicles (EVs) have shown great potential in drug delivery, disease diagnosis, and treatment owing to their versatile native features and functions. RNA interference (RNAi) therapeutics that block the programmed death-1 (PD-1) and programmed death-ligand 1 (PD-L1) pathway have attracted increasing interest for the treatment of various cancers. Here, immunoregulatory EVs are developed by decorating M1-macrophage-derived EVs (M1 EV) with vesicular stomatitis virus glycoprotein (VSV-G), a pH-responsive viral fusion protein, and electroporating anti-PD-L1 siRNA (siPD-L1) into the EVs. After administration to CT26 tumor-bearing mice, this virus-mimic nucleic acid engineered EVs (siRNA@V-M1 EV) can target tumor tissues, which is attributed to the natural tumor-homing property of M1 EV. Then, the fusion of VSV-G with cells facilitates the direct release of siPD-L1 into the cytoplasm and triggers robust gene silencing, leading to the efficient block of PD-L1/PD-1 interaction and then the elevation of CD8(+)T cell population. Meanwhile, the M1 EVs and IFN-gamma secreted by the CD8(+)T cells promote the repolarization of M2 tumor-associated macrophages to M1 macrophages. The combination of PD-L1/PD-1 pathway blocking, T cell recognition reconstructing, and M1 macrophage repolarization via multifunctional EVs can achieve satisfactory antitumor efficacy in this tumor model, showing potential as a new modality to fight cancers.