A single virus injection may finally turn the immune system loose on one of the toughest brain cancers. Credit: Shutterstock Researchers from Mass General Brigham and Dana-Farber Cancer Institute report that a single dose of an oncolytic virus, a genetically engineered virus designed to infect and kill cancer cells, can draw immune cells deep into brain tumors and keep them active there. Their findings, published in Cell , explain how this approach improved survival in patients with