1. Division of Virology, Department of Pathology, University of Cambridge, Cambridge CB2 1QP, UK
2. Viral Pathogenesis and Evolution Section, Laboratory of Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA
3. The Roslin Institute, University of Edinburgh, Easter Bush, Midlothian EH25 9RG, UK
4. Mass Spectrometry and Proteomics Core Facility, University of Utah, Salt Lake City, UT 84112, USA
5. Department of Human Genetics, University of Utah, Salt Lake City, UT 84112, USA
6. BioSciences Institute, University College Cork, Cork, Republic of Ireland