1. Institute of Molecular Virology, Ulm University Medical Center, 89081 Ulm, Germany.
2. Gladstone Institute of Virology and Immunology, University of California, San Francisco, San Francisco, CA 94158, USA.
3. Department of Urology, University of California, San Francisco, San Francisco, CA 94158, USA.
4. Lindsley F. Kimball Research Institute, New York Blood Center, New York, NY 10065, USA.
5. Institute of Epidemiology and Medical Biometry, Ulm University, 89081 Ulm, Germany.
6. Departments of Medicine and Microbiology and Immunology, University of California, San Francisco, San Francisco, CA 94158, USA.