Viral evolution under the pressure of an adaptive immune system - optimal mutation rates for viral escape

摘要

Based on a recent model of evolving viruses competing with an adapting immunesystem [1], we study the conditions under which a viral quasispecies canmaximize its growth rate. The range of mutation rates that allows viruses tothrive is limited from above due to genomic information deterioration, and frombelow by insufficient sequence diversity, which leads to a quick eradication ofthe virus by the immune system. The mutation rate that optimally balances thesetwo requirements depends to first order on the ratio of the inverse of thevirus' growth rate and the time the immune system needs to develop a specificanswer to an antigen. We find that a virus is most viable if it generatesexactly one mutation within the time it takes for the immune system to adapt toa new viral epitope. Experimental viral mutation rates, in particular for HIV(human immunodeficiency virus), seem to suggest that many viruses have achievedtheir optimal mutation rate. [1] C.Kamp and S. Bornholdt, Phys. Rev. Lett., 88,068104 (2002)