Tune Up <em>In Situ</em> Autovaccination against Solid Tumors with Oncolytic Viruses

With the progress of immunotherapy in cancer, oncolytic viruses (OVs) are getting more and more attention during the past decade. Due to their cancer-selective and immunogenic property, OVs are considered ideal candidates to be combined with immunotherapy to increase both specificity and efficacy in cancer treatment. OVs preferentially replicate in and lyse cancer cells, generating pathogen-associated molecular patterns (PAMPs) and danger (damage)-associated molecular patterns (DAMPs). These signals trigger innate immune response to modulate the solid tumor microenvironment, resulting in in situ autovaccination leading to adaptive anti-virus and anti-tumor immunity. Here, we summarize the conceptual updates of oncolytic virotherapy, immunotherapy, and the strategies to enhance the virus-mediated anti-tumor immune response, including: 1. Arm OVs with cytokines to modulated innate and adaptive immunity; 2. Combine OVs with immune checkpoint inhibitors to release T cell inhibition; 3. Combine OVs with immune co-stimulators to enhance T cell activation.