Radiotherapy synergizes with AAV-based immunotherapy to program local and systemic antitumor immunity [scRNA-Seq]

Radiotherapy (RT) primes the immune system against cancer antigens but fails to trigger effective antitumor responses due to concomitant induction of immunosuppressive factors. To expand the benefits of RT, we combine local radiation with immuno-gene therapy by harnessing the ability of ionizing radiation to enhance AAV-mediated tumor transduction. To successfully deliver AAV-based local immunotherapy and restrict transgene expression within tumors, we designed a recombinant AAV that expresses IL-12 through an interferon (IFN)-inducible promoter (AAV-iIL12). Local administration of AAV-iIL12 upon RT results in marked and durable elevation of intratumor IL-12 with minor and transient systemic release. This strategy generates a highly immunostimulatory tumor microenvironment (TME) leading to strong antitumor responses in an IFNg-dependent manner. Moreover, local treatment with RT and AAV-iIL12 elicits systemic antitumor immunity with marked CD8+ T cell infiltration and regression of distant tumors. Our work shows that radiation coupled with AAV-based immuno-gene delivery is a novel, efficient and safe approach that can be exploited as cancer therapy. Overall design: Transcriptomic analysis by scRNA seq of CD45+ tumor infiltrating cells obtained 6 days after treatment with RT + control AAV (n=4) or RT + AAV-iIL12 (n=4).