1. Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama 35294
2. Laboratoire Retrovirus, IRD, 34032 Montpellier, France
3. Aaron Diamond AIDS Research Center, Rockefeller University, New York, New York 10016
4. Department of Internal Medicine, Seoul National University College of Medicine and Clinical Research Institute, Seoul National University Hospital, Seoul 110-744, South Korea
5. Department of Infectious Disease, National Public Health Institute, FIN-00300 Helsinki, Finland
6. Department of Zoology, University of Oxford, Oxford, OX1 3PB, UK
7. Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama 35294; Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama 35294; Howard Hughes Medical Institute, University of Alabama at Birmingham, Birmingham, Alabama 35294
8. Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama 35294; Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama 35294