Viral evolution under the pressure of an adaptive immune system: Optimal mutation rates for viral escape

Based on a recent model of evolving viruses competing with an adapting immune system (Kamp and Bornholdt, Co‐evolution of quasispecies: B‐cell mutation rates maximize viral error catastrophes. Phys Rev Lett 88, 2002), we study the conditions under which a viral quasispecies can maximize its growth rate. We find that a virus is most viable if it generates on average precisely one mutation within the time it takes for the immune system to adapt to a new viral epitope. Experimental viral mutation rates, in particular for HIV (human immunodeficiency virus), seem to suggest that many viruses have achieved their optimal mutation rate. © 2003 Wiley Periodicals, Inc.