Transgenic viral expression of PH-20, IL-12, and sPD1-Fc enhances immune cell infiltration and anti-tumor efficacy of an oncolytic virus

Oncolytic viruses are of significant clinical interest due to their ability to directly infect and kill tumors and enhance the anti-tumor immune response. Previously, we developed KLS-3010, a novel oncolytic virus derived from the International Health Department-White (IHD-W) strain vaccinia virus, which has robust tumoricidal effects. In the present study, we generated a recombinant oncolytic virus, KLS-3020, by inserting three transgenes (hyaluronidase [PH-20], interleukin-12 [IL-12], and soluble programmed cell death 1 fused to the Fc domain [sPD1-Fc]) into KLS-3010 and investigated its anti-tumor efficacy and ability to induce anti-tumor immune responses in CT26.WT and B16F10 mouse tumor models. A single injection of KLS-3020 significantly decreased tumor growth. The roles of the transgenes were investigated using viruses expressing each single transgene alone and KLS-3020. PH-20 promoted virus spread and tumor immune cell infiltration, IL-12 activated and reprogrammed T cells to inflammatory phenotypes, and sPD1-Fc increased intra-tumoral populations of activated T cells. The tumor-specific systemic immune response and the abscopal tumor control elicited by KLS-3020 were demonstrated in the CT26.WT tumor model. The insertion of transgenes into KLS-3020 increased its anti-tumor efficacy, supporting further clinical investigation of KLS-3020 as a novel oncolytic immunotherapy.