Fig. 5.

High-avidity CD8 T cells drive viral escape. (a) Low-avidity T cells exert low immune pressure on the infecting virus. This results in a low rate of virus mutation, no viral fitness cost and chronic infection. (b) High-avidity T cells exert immune pressure on the infecting virus and drive viral escape. Two outcomes can be observed: viral control, where viral escape results in mutations at a cost to viral fitness, and chronic infection, where viral escape occurs without fitness costs and the host CD8 T cells are unable to control infection. MHC, major histocompatibility complex; CTLs, cytotoxic T lymphocytes.