Part II: Juvenile rhesus macaques are divided into 4 groups and are infused with IgG from human participants of Groups I and II at Day 0. At Day 1, the macaques are exposed to SHIV-89.6P. At Days 3, 7, 10, and weekly up to Day 73, the CD4 lymphocyte count, plasma viremia, and antibodies of the macaques are measured.