Researchers at Mass General Brigham and Dana-Farber demonstrated that a single injection of a genetically engineered oncolytic virus can reshape the glioblastoma tumor microenvironment, increasing immune-cell infiltration and persistence inside otherwise immunosuppressive brain tumors. The team reported enhanced antitumor immunity in treated models and identified markers of durable immune engagement. The results—reported by clinicians and scientists at two major cancer centers—provide a translational proof-of-concept for combining oncolytic virotherapy with immune modulators in high-grade brain tumors and may inform upcoming clinical strategies for glioblastoma, where outcomes remain poor.