The Effects of Anti-HIV Therapy on the Immune Systems of Children and Young Adults Infected With HIV

The purpose of this study is to determine the number of newly formed CD4 cells in children who have taken anti-HIV drugs. The study will also evaluate the effectiveness of the new CD4 cells in producing an immune response to hepatitis A and tetanus toxoid vaccination. Study hypothesis: 1) Immunologic reconstitution of individuals who have less than 15% CD4 cells may or may not be associated with functional activity. 2) The functional immunologic responses to recall and newly experienced antigens may be different. 3) The functional responses to antigens delivered in vaccine format may be a function of CD4 level, viral load, or both.