1. Division of Experimental Virology, Department of Biomedicine, University of Basel, 4003 Basel, Switzerland.
2. Department of Pathology and Immunology, Geneva Faculty of Medicine, Geneva University Hospital, 1211 Geneva 4, Switzerland.
3. Division of Clinical Pathology, Geneva University Hospital, 1 rue Michel Servet, 1211 Geneva 4, Switzerland.
4. Institute of Virology and Immunology, 3147 Mittelhäusern, Switzerland.
5. Department of Biomedicine, Bioinformatics Core Facility, University Hospital Basel, 4031 Basel, Switzerland.
6. Department for Medical Microbiology and Hygiene, Institute for Immunology, University Medical Center Freiburg, 79104 Freiburg, Germany.
7. Fred Hutchinson Cancer Research Center, University of Washington, Seattle, WA 98109, USA.
8. Department of Immunology, University of Washington, Seattle, WA 98109, USA.