Daclizumab to Treat HIV-Infected Patients

This study will examine the safety and effectiveness of daclizumab (also called Zenapax or anti-CD25) in reducing viral replication in patients with HIV infection. Although HAART, an intensive anti-HIV treatment regimen, can suppress HIV in blood below the limit of detection, it cannot completely eradicate the virus. This study will focus on the effectiveness of daclizumab in further reducing viral replication in patients with low viral counts. The Food and Drug Administration approved daclizumab in 1997 for preventing kidney transplant rejection, and it has also been studied in people with an eye infection called uveitis. The drug works by binding to a protein on T cells (white blood cells of the immune system) called CD25. This prevents another protein, called interleukin-2 (IL-2), from binding to this site, thus preventing a series of events that normally results in inflammation. Patients between 18 and 65 years of age with HIV infection who have stable HIV levels at less than 30,000 copies/mL of blood and CD4 T cell counts higher than 400 cells/cmm may be eligible for this study. Patients who have taken drugs that affect the immune system, such as IL-2 and interferon, in the past 5 years may not participate. Candidates are screened with a comprehensive medical examination, including physical examination and laboratory studies. X-rays, consultations, and biopsies are done only if medically indicated. Participants will undergo the following tests and procedures: * Daclizumab therapy: Patients receive daclizumab as a 25-minute infusion through an intravenous catheter (plastic tube placed in a vein) at the NIH Clinical Center outpatient clinic. A total of three doses of drug are given. The first dose is given on study day 1, the second dose is given 2 weeks later, and the third dose is given 4 weeks later. Patients are observed for at least 1 hour after each infusion before being discharged from the clinic. * Follow-up visits: Patients return to the outpatient cl