Clues to how a rare group of patients can resist infection by HIV are reported in a paper this week in Nature Immunology. So-called ‘elite controllers’ are able to retain normal immune function and undetectable levels of HIV infection despite regular exposure to the virus.
Suspecting that characteristics of the white blood cell cytotoxic T lymphocyte (CTL) response was responsible for this remarkable immune control, Bruce Walker and colleagues compared the CTL responses of elite controllers and susceptible individuals across numerous highly defined and consistent parameters. Only two clear differences could be seen; the first was that the CTLs of elite controllers had more efficient killing of infected cells, and the second was that these same CTLs could better tackle HIV mutants which are normally able to evade immune responses. These properties appeared to depend on the make-up of the CTL populations found in elite controllers. Specifically, the T cell receptor that the CTLs use to detect virus contained unique features enabling them to kill a wide range of infected target cells.
Understanding how elite controllers keep HIV in check is of critical importance for T cell vaccine design and therapeutic strategies.