Interluekin-7 to Treat HIV-Infected People Receiving Antiretroviral Treatment

This study will evaluate whether interleukin-7 (IL-7) a drug similar to the natural IL-7 protein produced by the body, is safe to use in people infected with HIV. IL-7 is important in immune system function. In humans, it can extend the life of immune cells called T-cells and increase their function and maturation; in mice, it can speed up immune system recovery following chemotherapy of transplantation; and in monkeys, it can make T-cells increase in numbers. If this study shows that IL-7 is safe, other trials will determine if it can improve the numbers or function of T-cells in HIV-infected people. Patients 18 years of age and older with HIV infection who have been taking anti-HIV medications for at least 12 months, whose CD4 counts are at least 100 cells/microliter, and whose viral load is no more than 50,000 copies/milliliter may be eligible for this study. Candidates are screened with a physical examination, blood and urine tests, including a blood test for HLA type (a genetic test of markers of the immune system), chest x-ray, electrocardiogram, and ultrasound of the spleen. Participants undergo the following tests and procedures during 9 visits, as follows: Pre-entry visit * Brief physical examination, including examination of lymph nodes and spleen. * Medical history, including questions about current and past medications. * Urine pregnancy test for women who are able to become pregnant. * Blood draw for viral load, immune responses, and other routine safety tests. Entry visit * Complete physical examination, including examination of lymph nodes and spleen. * Routine urine test and urine pregnancy test for women who are able to become pregnant. * Blood draw for viral load, immune responses, and other routine safety tests. * IL-7 dosing. Participants are randomly assigned to receive one of five doses of IL-7 (3, 10, 30, 60 or 100 micrograms per kilogram of body weight) or placebo (a salt solution that does not contain IL-7). The dose may be given in on