CD274 and infectious disease: Monoclonal antibodies (MAbs) designed to interfere with checkpoint molecules, such as programmed death-1 (PD-1) and programmed death-ligand 1 (PD-L1), are currently being investigated for the treatment of infectious diseases and cancer.1, 2, 3 The immune system of patients with chronic viral infections or cancer is often impaired in function and is unable to mount an effective response against the virus or to recognize and eliminate malignant cells.