1. B. F. Haynes is with the Department of Medicine, Division of Rheumatology, Allergy and Immunology, Duke Center for AIDS Research, Duke Medical Center, Durham, NC 27710, USA.
2. G. Pantaleo and A. S. Fauci are with the Laboratory of Immunoregulation, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA.