Abstract B059: Synergistic activation of antitumor immunity by an oncolytic virus VG161 armed with multiple immune-stimulating genes

Oncolytic viruses (OVs) are among the most powerful approaches in cancer immunotherapy. OVs not only cause cancer cell lysis but more importantly, their infection in tumors induces anti-tumor immune response from the host, resulting in lasting anti-tumor immunity. It has been recognized that anti-tumor immune response requires multiple immune regulatory factors that act synergistically and tumor microenvironment is critical for tumor to grow. Herpes simplex virus type-1 (HSV-1) has been approved by FDA as an oncolytic viral drug to treat melanoma. One advantage of HSV-1 is its large genomic capacity for carrying multiple exogenous genes.A HSV-1 oncolytic viral vector (VG161) was constructed to simultaneously express IL12, IL15 with its receptor alpha unit and a PDL-1 blocking peptide. Antitumor activity of VG161 was tested in both immune competent mice (CT26 and A20 tumor models) and nude mice for human tumor models (LNCaP and U87). Since CT26 and A20 are poorly permissive for HSV-1 replication, the mouse tumor models were able to demonstrate the antitumor immune response induced by VG161 while oncolytic activity of VG161 was demonstrated in LNCaP and U87 models since the immune system is compromised in those models.VG161 completely inhibited tumors in all the models tested and the animals survived tumor-free for many months till sacrificed. VG161 induced tumor oncolysis in both LNCaP and U87 tumors. In the CT26 model, animals were protected from the second challenging with CT26 cells following previous virally induced tumor regression. Furthermore, in a A20 double tumor model, intratumoral injection into the tumor on one side caused tumor regression on both sides. Transcriptome analysis showed significant change in tumor microenvironment. Finally, tumor specific memory T-cells were evident in the treated animals. The anti-tumor immune response by VG161 was significantly stronger than similar viruses that did not express any immune stimulating gene or only express GM-CSF. These results showed that intratumorally expressed multiple immune regulatory factors by an oncolytic virus may significantly change the tumor immune microenvironment to enhance efficacy of the oncolytic virus. Citation Format: Ronghua Zhao, Jun Ding, Dmitry Choujenko, Yanal Murad, Erica Lee, Guoyu Liu, Luke Bu, William Jia. Synergistic activation of antitumor immunity by an oncolytic virus VG161 armed with multiple immune-stimulating genes [abstract]. In: Proceedings of the Fourth CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; Sept 30-Oct 3, 2018; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2019;7(2 Suppl):Abstract nr B059.