1. MRC Virology Unit, Institute of Virology, Church Street, Glasgow G11 5JR, UK
2. Department of Immunology and Microbiology, Rush University Medical Center, 1653 West Congress Parkway, Chicago, IL 60612, USA
3. Division of Pathway Medicine, University of Edinburgh Medical School, Chancellor's Building, 49 Little France Crescent, Edinburgh EH16 4SB, UK
4. The Gene Pool, Ashworth Laboratories, Institute of Evolutionary Biology, King's Buildings, Edinburgh EH9 3JT, UK
5. Department of Medical Microbiology, Tenovus Building, School of Medicine, Cardiff University, Heath Park, Cardiff CF14 4XX, UK