Can Immune Checkpoint Inhibitors Keep JC Virus in Check

Three groups are now reporting in the Journal descriptions of the clinical course of 10 patients with progressive multifocal leukoencephalopathy (PML) who were treated with the immune checkpoint inhibitor pembrolizumab or nivolumab,1-3 both of which are monoclonal antibodies that target programmed cell death protein 1 (PD-1). This protein is an inhibitory T-cell surface receptor that keeps the immune system from attacking the body’s own tissues and organs (often called self-tolerance) and is a marker of T-cell exhaustion. When PD-1 binds with its ligand, it inhibits T-cell proliferation and cytokine production. Pembrolizumab and nivolumab block this inhibitory reaction and have been . . .