1. Department of Immunology and Infectious Diseases, Harvard School of Public Health and Harvard AIDS Institute, Boston, Massachusetts1; and
2. Laboratoire de Bactériologie-Virologie, Faculté Mixte de Médecine et de Pharmacie, Université Cheikh Anta Diop,2 and
3. Institut Hygiène Sociale,3 Dakar, Senegal; and
4. Division of Biostatistics and Epidemiology, University of Massachusetts Cancer Center, Worcester, Massachusetts4