Effective Combination Immunotherapy using Oncolytic Viruses to Deliver CAR Targets to Solid Tumors

Abstract Chimeric antigen receptor (CAR)-engineered T cell therapy for solid tumors is limited by the lack of tumor-restricted and homogeneous expression of tumor antigens 1,2 . Therefore, we engineered an oncolytic virus to express a non-signaling, truncated CD19 (CD19t) protein for tumor-selective delivery, enabling targeting by CD19-specific CAR T cells. Infecting tumor cells with a chimeric oncolytic vaccinia virus coding for CD19t (OV19t) produced de novo CD19 surface-antigen expression prior to virus-mediated tumor lysis. Co-cultured CD19-CAR T cells secreted cytokines and elicited potent cytolytic activity against infected tumors. Using multiple mouse tumor models, intratumoral delivery of OV19t induced tumor expression of CD19t and improved tumor control following CD19-CAR T cell administration. CAR T cell–mediated tumor killing also promoted release of virus from dying tumor cells, which propogated tumor expression of CD19t. These data demonstrate a novel immunotherapy approach utilizing oncolytic viruses to promote de novo CAR T cell targeting of solid tumors. One Sentence Summary We describe a novel and effective combination immunotherapy utilizing oncolytic viruses to deliver de novo cell surface expression of CD19 antigen promoting CD19-CAR T cell anti-tumor responses against solid tumors.