Immune checkpoint blockade, immunogenic chemotherapy or IFN-{alpha} blockade boost the local and abscopal effects of oncolytic virotherapy

Athough the clinical efficacy of oncolytic viruses has been demonstrated for local treatment, the ability to induce immune-mediated regression of distant metastases is still poorly documented. We report here that the engineered oncolytic vaccinia virus VVWR-TK-RR--Fcu1 can induce immunogenic cell death and generate a systemic immune response. Effects on tumor growth and survival was largely driven by CD8+ T cells, and immune cell infiltrate in the tumor could be reprogrammed towards a higher ratio of effector T cells to regulatory CD4+ T cells. The key role of type 1-IFN pathway in oncolytic virotherapy was also highlighted, as we observed a strong abscopal response in Ifnar-/- tumors. In this model, single administration of virus directly into the tumors one one flank led to regression in the contralateral flank. Moreover, these effects were further enhanced when oncolytic treatment was combined with immunogenic chemotherapy or with immune checkpoint blockade. Taken together, our results suggest how to safely improve the efficacy of local oncolytic virotherapy in patients whose tumors are characterized by dysregulated IFN-α signaling.

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