An Oncolytic Virus Expressing IL15/IL15Rα Combined with Off-the-Shelf EGFR-CAR NK Cells Targets Glioblastoma

IL15 is a pleiotropic cytokine with multiple roles that improve immune responses to tumor cells. Oncolytic viruses (OV) specifically lyse tumors and activate immune responses. Systemic administration of IL15 or its complex with the IL15R alpha and chimeric antigen receptor (CAR) natural killer (NK) cells are currently being tested in the clinic. Here, we generated a herpes simplex 1-based OV-expressing human IL15/IL15R alpha sushi domain fusion protein (named OV-IL15C), as well as off-theshelf EGFR-CAR NK cells, and studied their monotherapy and combination efficacy in vitro and in multiple glioblastoma (GBM) mouse models. In vitro, soluble IL15/IL15R alpha complex was secreted from OV-IL15C-infected GBM cells, which promoted GBM cytotoxicity and improved survival of NK and CD8(+) T cells. Frozen, readily available off-the-shelf EGFR-CAR NK cells showed enhanced killing of tumor cells compared with empty vector-transduced NK cells. In vivo, OV-IL15C significantly inhibited tumor growth and prolonged survival of GBM-bearing mice in the presence of CD8(+) T cells compared with parental OV. OV-IL15C plus EGFR-CAR NK cells synergistically suppressed tumor growth and significantly improved survival compared with either monotherapy, correlating with increased intracranial infiltration and activation of NK and CD8(+) T cells and elevated persistence of CAR NK cells in an immunocompetent model. Collectively, OV-IL15C and off-the-shelf EGFR-CAR NK cells represent promising therapeutic strategies for GBM treatment to improve the clinical management of this devastating disease. Significance: The combination of an oncolytic virus expressing the IL15/IL15R alpha complex and frozen, ready-to-use EGFR-CAR NK cells elicits strong antitumor responses in glioblastoma.