1. U.S. Naval Medical Research Center Detachment (NMRCD), Lima, Peru.
2. Henry M. Jackson Foundation, Rockville, Maryland 20852.
3. National AIDS Control Program, Montevideo, Uruguay.
4. National AIDS Control Program, Asunción, Paraguay
5. National Reference for AIDS, Buenos Aires, Argentina.
6. National Laboratory of Reference for HIV-AIDS, Montevideo, Uruguay.
7. Tropical Medicine Institute, Asunción, Paraguay.
8. Division of Retrovirology, Walter Reed Army Institute of Research, Rockville, Maryland 20850.