1. U.S. Military HIV Research Program, Henry M. Jackson Foundation, Rockville, Maryland 20850
2. U.S. Naval Medical Research Center Detachment, Lima, Peru
3. Ludwig-Maximilians University, 80539 Munich, Germany
4. National Reference Center for AIDS, Buenos Aires, Argentina
5. National Reference Laboratory, Montevideo, Uruguay
6. National AIDS Program, Ministry of Health, Montevideo, Uruguay
7. National Institute of Hygiene and Tropical Medicine "Leopoldo Izquieta Perez," Guayaquil, Ecuador
8. National AIDS Program, Ministry of Health, Quito, Ecuador
9. Centro Nacional de Enfermedades Tropicales, Santa Cruz, Bolivia
10. Instituto Nacional de Laboratorios de Salud, La Paz, Bolivia
11. Asociacion Civil Impacta Salud y Educacion, Lima, Peru
12. Division of Retrovirology, Walter Reed Army Institute of Research, Rockville, Maryland 20892