1. Department of Immunology,2 Chelsea and Westminster Hospital, Imperial College School of Medicine, and
2. Departments of Oncology and Molecular Pathology, Royal Free and University College Medical School, University College London,1 London, and
3. Department of Genitourinary Medicine3 and
4. Institut für Klinische und Molekulare Virologie, Universität Erlangen-Nürnberg, D-91054 Erlangen, Germany,4 and
5. Dunn School of Pathology, University of Oxford, Oxford,5 United Kingdom