Studies of Lymphocyte Kinetics Using Bromodeoxyuridine

This study will examine how quickly white blood cells called CD4 lymphocytes reproduce and how long they live in people infected with HIV. It will do this using bromodeoxyuridine (BrDU), a compound that is structurally similar to thymidine, one of the building blocks of DNA. BrDU gets incorporated into DNA instead of thymidine, but it can only get into cells that are replicating. Therefore, measuring the proportion of cells with BrDU indicates how many cells are replicating.

HIV-infected patients 18 years of age and older may be eligible for this study. Candidates will be screened with a medical history, physical examination, chest X-ray, electrocardiogram (EKG) and blood tests.

Participants will be given an infusion of BrDU through a catheter (thin plastic tube) placed in an arm vein. Blood will be drawn up to 4 times in the first 24 hours after the infusion.

Additional samples will then be collected as often as daily for the first week, twice a week for the next 3 weeks and then weekly to monthly for up to 1 year. Some patients may undergo a tissue biopsy (removal of a small tissue sample from a lymph node, tonsil or colon) or computed tomography (CT) scans of the thymus (a small gland between the lungs that manufactures lymphocytes. Some patients will have a second infusion in order to examine changes in the rate of CD4 replication over time or following potent antiretroviral therapy. Patients will be followed in the clinic periodically for the first year and then will be seen in the clinic or contacted by telephone once a year for 4 more years.

The results of this study may provide a better understanding of how HIV causes disease and how therapy affects the immune system.