Abstract B030: IL-27 expressing oncolytic HSV prolongs survival in a syngeneic murine malignant glioma model in a CD8 T cell-dependent manner

Field: Medicine (Health Sciences)

Abstract Introduction: Malignant gliomas (MG) are the most common primary malignancy of the central nervous system, and for which there currently is no cure. Oncolytic HSVs (oHSV) are experimental immunotherapeutics that directly lyse cancer cells and shift the tumor microenvironment towards a pro-inflammatory state. We recently identified from Phase Ib clinical trial gene expression studies (RNASeq) that IL-27 expression in oHSV-treated and then resected tumors directly correlated with survival. IL-27 is a pleiotropic cytokine with both pro- and anti-inflammatory effects in a context specific manner making its potential to enhance oHSV anti-tumor effects while limiting adverse inflammation appealing. Hypothesis and Approach: To determine whether the association between IL-27 expression and prolonged survival is causal, we developed an IL-27 expressing oHSV. We hypothesize that viral expression of IL-27 will improve survival in a syngeneic murine MG model by enhancing T cell effector function. To test this, CT-2A murine MG brain tumors were implanted in syngeneic immunocompetent (C57BL/6) and T cell deficient (athymic nude NU/J) mice. Mice were intracerebrotumorally (ICT) treated 7d later with saline or equivalent doses (1x107 plaque forming units [PFU]) of C027 (C134+IL27) or parent virus (C134) and monitored for tumor growth and survival. To assess immunophenotypic changes, tumors were harvested 12d post-treatment, immune cells isolated, and analyzed by spectral flow cytometry. To determine the requirement for CD8 T cells, experiments were repeated in mice depleted of CD8 T cells alongside isotype controls. To evaluate the effect IL-27 expression by oHSV on T cell effector function, conditioned media (CM) was generated from viral or mock infected CT-2A cells, splenocytes stimulated (anti-CD3/CD28) in vitro +/- CM (C027, C134, mock), and analyzed by flow cytometry. Results: Treatment with C027 significantly improved survival in immune competent mice relative to saline and C134 (Log-rank p=0.005; p=0.002) and this therapeutic response was abrogated in athymic nude mice (NS: p=0.70). oHSV-treatment response was associated with increased CD8 T cell memory populations and decreased suppressed CD8 T cells (PD1 high, effector cytokine negative) in the tumor. Relative to isotype controls, C027 treated mice lacking CD8 T cells (p=0.009) had a significant decrease in survival. In vitro, C027 CM significantly increased CD8 T cell activation (CD25) and effector molecule production (interferon gamma, granzyme B) relative to controls. Conclusions: IL-27 expression by oHSV significantly prolongs survival in a syngeneic murine MG model and CD8 T cells are required for the C027 anti-glioma activity. In vitro studies suggest IL-27 expression by oHSV may be improving CD8 T cell effector function. The results from these studies suggest the anti-glioma efficacy of C134, currently in phase 1b clinical trial, may be enhanced by IL-27 expression. Future studies include further in vivo and in vitro immunophenotypic, transcriptomic, and T cell functional analyses. Citation Format: Alexia Martin, Jack Hedberg, Ilse Hernandez-Aguirre, Doyeon Kim, Ravi Dhital, Yeaseul Kim, Meisam Naeimi Kararoudi, Kevin Cassady. IL-27 expressing oncolytic HSV prolongs survival in a syngeneic murine malignant glioma model in a CD8 T cell-dependent manner [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor Immunology and Immunotherapy; 2024 Oct 18-21; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2024;12(10 Suppl):Abstract nr B030.