1. Harvard AIDS Institute, Department of Immunology and Infectious Diseases, Harvard School of Public Health, Boston, Massachusetts 02115,1 and
2. Theoretical Biology and Biophysics, Group T-10, Los Alamos National Laboratory, Los Alamos, New Mexico 87545,2 and
3. AIDS/STD Unit3 and
4. Princess Marina Hospital,4 Gaborone, Botswana