Abstract B181: Adenovirus, Semliki Forest virus and vaccinia virus-induced immunogenic cell death augments oncolytic virus immunotherapy

Oncolytic viruses represent new immunotherapy agents with therapeutic effects consisting of direct oncolysis of cancer cells and anticancer immune responses induced upon oncolysis. However, the exact pathways of cell death and the subsequent immune response initiations after oncolysis are not fully elucidated. We have examined the cell death pathways and immune-stimulatory pathways involved in adenovirus (Ad), Semliki Forest virus (SFV) and vaccinia virus (VV) infection. The three viruses activate distinct but different pathways but all of them induced immunogenic cell death (ICD), which is depicted by elevated cell surface exposure of calreticulin (CRT) and extracellular secretion of ATP. Oncolysis-mediated ICD grants dying cells to be phagocytosed and it promotes DC maturation and activation with a Th1-polarized cytokine secretion profile. As a proof of concept, we validated that when DCs are incubated with Ad- or SFV-, but not VV-infected tumor cells expressing a surrogate antigen (CMVpp65), they can efficiently process and cross-present peptides of this antigen to CD8+ T-cells, as shown by specific IFN-γ production. Mice immunized with SFV- or VV-infected murine glioblastoma cells (GL261) elicit a strong and specific T-cell response against GL261. This adaptive immune response can control tumor growth and prolong mice survival after GL261 rechallenge. Citation Format: Mohanraj Ramachandran, Magnus Essand. Adenovirus, Semliki Forest virus and vaccinia virus-induced immunogenic cell death augments oncolytic virus immunotherapy [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 B181.