An oncolytic virus expressing IL-15/IL-15Rα combined with off-the-shelf EGFR-CAR NK cells targets glioblastoma.

Interleukin (IL)-15 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 IL-15 or its complex with the IL-15Rα 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 IL-15/IL-15Rα sushi domain fusion protein (named OV-IL15C), as well as off-the-shelf EGFR-CAR NK cells, and studied their monotherapy and combination efficacy in vitro and in multiple glioblastoma (GBM) mouse models. In vitro, soluble IL-15/IL-15Rα 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 to 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 to parental OV. OV-IL15C plus EGFR-CAR NK cells synergistically suppressed tumor growth and significantly improved survival compared to 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.