1. E. S. Rosenberg, J. M. Billingsley, S. A. Kalams, B. D. Walker, Partners AIDS Research Center and Infectious Disease Unit, Massachusetts General Hospital, and Harvard Medical School, Boston, MA 02114, USA.
2. A. M. Caliendo, Partners AIDS Research Center and Department of Pathology, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114, USA.
3. S. L. Boswell, Fenway Community Health Center, Boston, MA 02115, USA.
4. P. E. Sax, Partners AIDS Research Center and Division of Infectious Diseases, Brigham and Women's Hospital, and Harvard Medical School, Boston, MA 02115, USA.