A Pilot Study to Evaluate the Immunologic Consequences of a Highly Active Antiretroviral Therapy Regimen (HAART) Consisting of Ritonavir (ABT-538), Zidovudine (AZT), and Lamivudine (3TC) in Moderately Advanced HIV-1 Disease

Inclusion Criteria Concurrent Medication: Allowed: Recombinant erythropoietin and/or G-CSF for AZT-related bone marrow suppression. Antibiotics other than metronidazole. PCP prophylaxis. Regularly prescribed medications such as antipyretics, analgesics, allergy medicine, and oral contraceptives. Vitamins and herbal therapies. Concurrent Treatment: Allowed: Acupuncture. Visualization techniques. Patients must have: Documented HIV infection. CD4 count 100-300 cells/mm3. At least 3 consecutive months of prior AZT at a dosage of 500-600 mg bid, but with 5 weeks of antiretroviral washout prior to study entry. Consent of parent or guardian if less than 18 years old. Prior Medication: Required: Prior AZT at 500-600 mg bid at any time. PCP prophylaxis during antiretroviral washout. Allowed: Prior ddI and/or ddC. Prior recombinant erythropoietin and/or G-CSF for AZT-related bone marrow suppression. Exclusion Criteria Co-existing Condition: Patients with the following symptoms or conditions are excluded: Chronic pancreatitis. Psychological conditions that would affect compliance. Intolerance to 500-600 mg/day AZT. Concurrent participation on another antiretroviral research treatment study (study treatment for opportunistic infection or complications of HIV is allowed). Considered likely to be noncompliant on study. Concurrent Medication: Excluded: Immunomodulators such as systemic corticosteroids, thalidomide, or cytokines. Rifabutin. Disulfiram (Antabuse) or other medications with similar effects, including metronidazole. Other drugs contraindicated with ritonavir. [AS PER AMENDMENT 8/27/96: Immunization must be avoided during the antiretroviral washout period.] Patients with the following prior conditions are excluded: Active opportunistic infection or febrile illness with temperature >= 38.5 C within 3 days prior to study entry. History of acute pancreatitis within the past 2 years. Prior Medication: Excluded: Prior 3TC or a protease inhibitor. Experimental drugs except those for HIV-related conditions, within the past 30 days. [AS PER AMENDMENT 8/27/96: Immunization must be avoided prior to the antiretroviral washout period.] Active substance abuse.