Synergy of immunomodulators delivered by an HSV-1 oncolytic virus can enhance its therapeutic effects in vivo

Oncolytic HSV-1 (oHSV-1) are among the most promising therapies for cancer. Besides the oncolytic activity delivered by the virus against tumor cells, this treatment can also induce a potent immune response against tumor antigens (whether classic TAA, or neoantigens specific to the tumor being targeted). We have constructed an oncolytic HSV-1 virus (VG161) to deliver 2 immunomodulator cytokines, IL12 and IL15, to the tumor micro-environment. These two cytokines can work synergistically to trigger an efficient anti-tumor immune response. A PD-L1 mimic peptide capable of blocking PD-1/PD-L1 interaction is also delivered as a Fc fusion peptide (TF-Fc) to help in maintaining an effective immune response against the tumor. For the construction of the recombinant virus, the exogenous components were cloned under CMV promoter control. The ICP34.5 gene was deleted as a safety measure for the recombinant virus. The expression of Il12, IL15 and TF-Fc were confirmed, in vitro and in vivo, by qRT-PCR, ELISA and Western blot. Upon intra-tumoral injection of VG161, expressed IL12, IL15 and TF-Fc were detected only in the injected tumor mass, but not in the animals9 blood or other organs. The bio-distribution of the virus was tested by qPCR after injecting VG161 intratumorally, and most of the injected virus were concentrated in the tumor mass. Minimal amounts of the virus were detected in the liver and spleen for short periods after virus injection. We have demonstrated the superior activity of the VG161 virus, compared to the back-bone virus (with no payloads) using immune-competent mouse models (CT26) and nude mice implanted with human tumor cells lines (LNCaP and U87). VG161 induced tumor oncolysis resulting in complete tumor regression in nude mice. In the CT26 model, the tumor regressed to undetectable limits upon intra-tumoral injection with VG161. When the treated mice were challenged with the same tumor, the tumor cells did not grow. The added efficacy in CT26 tumor model can be attributed to the immune response generated by the modified virus, as demonstrated by a higher number of tumor-infiltrating CD8 T cells. The specific activity of T cells against the tumor cells was also demonstrated by ELISpot assay. Finally, memory T-cells were evident in the treated animals demonstrated by multiple assays. Conclusions This work has demonstrated the safety and efficacy of VG161, a novel oncolytic virus which can induce a strong anti-tumor immunity and oncolytic activity. We have also demonstrated that the Intra-tumoral expression of multiple immune regulatory factors may significantly change the tumor immune microenvironment to enhance the efficacy of the oncolytic virus. Citation Format: Yanal M. Murad, Jun Ding, Dmitry Chouljenko , Erica Lee, Luke Bu, Guoyu Liu, Ronghua Zhao, Zahid Delwar, Will Liu, William Jia. Synergy of immunomodulators delivered by an HSV-1 oncolytic virus can enhance its therapeutic effects in vivo [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5641.