John Frater is Professor of Infectious Diseases at the University of Oxford. His research focuses on the human immune system: how it can control chronic infection, and how it changes over a lifetime. His laboratory has developed single-cell immune-repertoire sequencing methods to study T and B cell responses in fine detail, and these are now applied across infection, autoimmunity and cancer. Much of his work has been in HIV, where he leads the HIV Reservoir and Cure Group and is a lead investigator on major clinical studies including RIO, AbVax, RIVER and HEATHER, which explore how immune responses might be harnessed to control the virus without lifelong antiretroviral therapy. Through the Oxford Martin Programme on Immune Ageing he is now applying the same approaches to understand how immunity changes with age and why those changes differ between people. He is also clinically active as an Honorary Consultant Physician in Infectious Diseases in the NHS.