1. Departments of Medicine and Microbiology, University of Alabama at Birmingham, Birmingham, AL, USA.
2. Laboratoire Retrovirus, UMR145, Institut de Recherche pour le Développement and Department of International Health, University of Montpellier I, 911 Avenue Agropolis, Boite Postale 64501, 34394 Montpellier Cedex 5, France.
3. Institute of Genetics, University of Nottingham, Queens Medical Centre, Nottingham, NG7 2UH, UK.
4. Projet Prevention du Sida au Cameroun (PRESICA), Boite Postale 1857, Yaoundé, Cameroun.
5. Howard Hughes Medical Institute, 720 South 20th Street, KAUL 816, Birmingham, AL 35294, USA.