1. Partners AIDS Research Center and Infectious Disease Unit, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02129
2. Department of Microbiology, University of Washington, Seattle, Washington 98195
3. Positive Health Program, University of California at San Francisco, San Francisco, California 94143
4. Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115
5. Fenway Community Health Center, Boston, Massachusetts 02116
6. Department of Medicine, University of California, San Francisco, California 94143