Oncolytic Vaccinia Virus-Engineered EVs Convert Tumor-Promoting Macrophages into Anti-Tumor Effectors

Extracellular vesicles (EVs) play a critical role in shaping the tumor immune microenvironment (TME) by mediating intercellular communication and transferring oncogenic proteins, microRNAs, and immunosuppressive molecules. Tumor-derived EVs (TDEVs) typically promote immune evasion by inducing M2 macrophage polarization, suppressing cytotoxic T-cell activity, and enhancing angiogenesis. Recent evidence suggests that oncolytic viruses (OVs) can reprogram EV secretion, generating OV-derived EVs (OV-EVs) with immunostimulatory properties capable of activating antitumor immune responses.

In this study, we investigated how infection with oncolytic vaccinia virus (OVV) alters the EV secretion profile of colon cancer cells. EVs derived from OVV-infected tumor cells were isolated and characterized, and their effects on macrophage polarization were evaluated using in vitro assays.

Our results demonstrate that OVV infection significantly alters the composition and immunological properties of tumor-derived EVs. OV-EVs were enriched with pathogen-associated and damage-associated molecular patterns (PAMPs/DAMPs), which promoted macrophage reprogramming toward a pro-inflammatory M1 phenotype and enhanced immune activation associated with antitumor responses.

These findings indicate that OVV-induced EVs can reshape the tumor immune microenvironment by modulating macrophage polarization. This study provides new insights into the EV-mediated mechanisms of oncolytic virotherapy and highlights the potential of OV-derived EVs as a novel strategy for EV-based cancer immunotherapy.