[1] Vanderbilt Univ, Sch Med, Dept Pediat, Nashville, TN 37232 USA
[2] Vanderbilt Univ, Sch Med, Dept Microbiol & Immunol, Nashville, TN 37232 USA
[3] Vanderbilt Univ, Sch Med, Dept Biostat, Nashville, TN 37232 USA
[4] Aventis Pasteur, Toronto, ON, Canada
[5] US Mil Acad, HIV Res Program, Rockville, MD USA