Chapter 43

Evolution of Hepatitis Viruses

Peter Simmonds

Peter Simmonds

Infection and Immunity Division, The Roslin Institute, University of Edinburgh, Edinburgh, UK

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Donald B. Smith

Donald B. Smith

Centre for Immunity, Infection and Evolution, Ashworth Laboratories, University of Edinburgh, Edinburgh, UK

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First published: 26 July 2013
Citations: 1

Summary

The evolution of human hepatitis viruses A, B, C, and E (HAV, HBV, HCV, and HEV) can be studied over very different time scales. Very rapid sequence change occurs in response to a variety of selection pressures driven by the immune escape from B and T cell responses and immunization and, in treated individuals, by antiviral therapy. Each shows more gradual accumulation of largely neutral nucleotide substitutions, a process that, over a much longer term period, leads ultimately to their differentiation into genetically distinct types. Thus, hepatitis A, B, C, and E viruses are currently divided into 6, 8, 7, and 4 genotypes respectively with HCV showing the greatest genetic divergence (>30% nucleotide sequence over the length of the genome) and HBV the least (11–15%). Some hepatitis viruses infect nonhuman primates (HAV and HBV) and other mammals (HEV), while HCV infections are restricted to humans. Sequence variability influences their antigenicity, their biology, and host interactions, with implications for vaccine development and antiviral therapy.

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