Assessment of The Impact of Oncolytic Virotherapy on The Immunopeptidome Profile of Tumor by Utilizing GEMM Derived Immunocompetent GBM Models

Abstract

Abstract Immunotherapy clinical trials have not shown efficacy in glioblastoma (GBM), arguably the deadliest of all cancers. A microenvironment, characterized by a paucity of T cells recognizing tumor peptides displayed on major histocompatibility complexes of tumor cells is one of the main reasons for GBM’s evasion. Virotherapy provides the opportunity to reshape the GBM TME towards pro-inflammatory phenotype. Data from a recent clinical trial with herpes simplex-1 based oncolytic virus (oHSV) have shown that the administration of these agents leads to a rapid influx of CD8 T cells, and activation of myeloid cells, suggesting that oHSV may offer an in-situ vaccination approach to increase availability of actionable antigens. C57BL/6-derived GBM models do not mimic the outcome observed with patient derived tumors in terms of virus replication. To decipher the impact of oHSV on tumor antigen specific responses, better immunocompetent models are needed. To assess whether oHSV treatment modulates the immunopeptidome profile (IP) of tumor, we used two transplantable GEMM-derived GBM models, 1620 and 1694. Both have wild type human EGFR, loss of Pten and Cdkn2a in BALB/c background. These models were more receptive to infection than CT2A. In vivo, virus persisted in tumors for up to 6 days, but not for 4 days in CT2A. IP analyses revealed that oHSV promotes epitope presentation on tumor cells and in TME. Moreover, low dose of virus efficiently induced antigen availability in both models though it differentially modulated the MHC ligandome. Using two new GBM models, we showed that an oncolytic virus used in clinical trial with recurrent GBM (NCT03152318) modulates IP of tumors, and low dose of virus is sufficient to induce the presentation of tumor epitopes. This project is supported by Bridge Fund given to Drs. Chiocca and White and P01 CA236749 to Dr. Chiocca.