1. Centro Nacional de Microbiología, Instituto de Salud Carlos III, Majadahonda, Madrid, Spain.
2. Division of Viral Pathogenesis, Beth Israel Deaconess Medical Center, Boston, Massachusetts.
3. Complejo Hospitalario Xeral-Cíes, Vigo, Pontevedra, Spain.
4. Complejo Hospitalario Provincial de Pontevedra, Pontevedra, Spain.
5. Hospital de Txagorritxu, Vitoria, Álava, Spain.
6. Complejo Hospitalario Santa María Madre, Ourense, Spain.
7. Hospital Arquitecto Marcide, Ferrol, A Coruña, Spain.
8. Hospital Donostia, San Sebastián, Guipúzcoa, Spain.
9. Hospital de Basurto, Bilbao, Vizcaya, Spain.
10. Hospital de Fuenlabrada, Fuenlabrada, Madrid, Spain.
11. Botkin's Infectious Diseases Hospital, St. Petersburg, Russia.
12. St. Petersburg AIDS Center, St. Petersburg, Russia.
13. National Reference Center of HIV/AIDS, Public Health Institute of Chile, Santiago, Chile.
14. Department of Surgery, Laboratory for AIDS Vaccine Research and Development, Duke University Medical Center, Durham, North Carolina.