The purpose of this study is to evaluate the effects of stopping preventive therapy for DMAC in HIV-positive patients who (1) have been treated for DMAC for at least 12 months and are now free of any signs of DMAC for at least 16 weeks, and (2) have improved immune systems (CD4 cell counts greater than or equal to 100 cells/mm3) due to anti-HIV drug therapy.

DMAC is a serious and sometimes life-threatening infection that usually affects only HIV-positive patients with CD4 cell counts (cells of the immune system that fight infection) less than 50 cells/mm3. It is recommended that people who are likely to get DMAC be placed on preventive medications which help reduce the risk of infection. New anti-HIV combination drug therapies can increase CD4 cell counts and can reduce the level of HIV in the blood. When CD4 counts are increased, risk of DMAC infection is less. This study examines whether it is possible to stop preventive therapy for DMAC when CD4 counts are high without placing individuals at risk for getting DMAC again.

A growing body of evidence suggests AIDS-related morbidity and mortality significantly decrease where potent antiretroviral therapies are used. HAART (highly active antiretroviral therapy) seems to significantly reduce the incidence of MAC. This study tests the validity of those observations.

Peripheral blood cultures and bone marrow (aspirate) samples from 50 eligible patients previously diagnosed with disseminated Mycobacterium avium complex (DMAC) are assessed for microbiologic sterilization of MAC at the time of study entry. If either bone marrow or blood cultures test positive for MAC, patients are discontinued from study. If cultures prove sterile, patients receive 6 weeks of treatment and then discontinue MAC therapy at Week 6 (entry into Step 2 of study). They are then monitored for clinical signs and symptoms of MAC recurrence and for the presence of mycobacteria in blood cultures. In cases of increased viral load during study, modification of antiretroviral therapy is allowed at the discretion of the patient's provider.

Inclusion Criteria

Patients may be eligible for this study if they:

• Are HIV-positive.
• Have 2 CD4 cell counts greater than or equal to 100 cells/mm3 within 60 days and 14 days prior to entry. Measurements must be taken at least 24 hours apart.
• Have been treated for DMAC with a drug regimen including at least 2 antimycobacterial drugs for at least 12 months, and have been free of symptoms for at least 16 weeks prior to study entry.
• Have been on anti-HIV therapy for at least 16 weeks and have been on stable anti-HIV therapy for at least 8 weeks prior to study entry.
• Are at least 13 years old (need consent of parent or guardian if under 18).

Exclusion Criteria

Patients will not be eligible for this study if they:

• Have any active infection (unless they have been on stable chronic suppressive therapy for at least 3 months).
• Are pregnant.