1. Centro Nacional de Referencia para el SIDA, School of Medicine, University of Buenos Aires, Buenos Aires, Argentina.
2. Hospital General de Agudos Jose Maria Ramos Mejia, Buenos Aires, Argentina.
3. Westat, Rockville, Maryland.
4. Pediatric, Adolescent, and Maternal AIDS Branch, CRMC, NICHD, NIH, DHHS, Bethesda, Maryland.
5. University of Sao Paulo at Ribeirao Preto, Ribeirao Preto, Brazil.
6. University of Caxias do Sul, Caxias do Sul, Brazil.
7. Instituto Nacional de la Nutricion Salvador Zubiran, Department of Infectious Diseases, Mexico, D.F., Mexico.