The purpose of this study is to see if it is safe and effective to give HIV-infected children and teens 1 of 4 anti-HIV drug combinations.

Decreasing HIV levels in infected patients can slow down disease progression. Further study is needed to find out which drug combinations are most effective in doing this.

For PRAM 2: Evidence suggests that as a consequence of antiviral therapy, decreases in plasma HIV-1 RNA are strongly associated with a delay in clinical progression. Therefore, the drug regimens proposed in this study are designed to result in a much larger sustained drop in plasma HIV-1 RNA and greater clinical benefit. Further intent of this study is to evaluate the virologic and therapeutic potential of novel combinations of antiretrovirals and to better define the pharmacokinetics and drug-drug interactions of therapies included in this regimen.

The Master PRAM schema is designed to allow new therapeutic arms to be studied as "rolling screens" through multiple generations of PRAMs. There is a common, "linking" regimen between any 2 sequential PRAM generations that will permit an indirect comparison of included therapies. (NOTE: Due to significant changes in study design between PRAM 1 and PRAM 2, there is no "linking" arm between them. The linkage will be reinstated from PRAM 2 and subsequent PRAM generations.) The therapeutic potential of the treatment arms is assessed by their ability to decrease HIV copy numbers as defined by plasma HIV-1 RNA copy number. Once accrual to a PRAM is complete, a new treatment comparison will open for accrual.

For PRAM 2: This study will compare the following 4 treatment arms:

Arm A - stavudine (d4T)/nevirapine/ritonavir Arm B - d4T/lamivudine (3TC)/nelfinavir Arm C - d4T/nevirapine/nelfinavir Arm D - d4T/3TC/nevirapine/nelfinavir. Prior to randomization to 1 of the PRAM 2 treatment arms, patients are stratified based on their CD4% (less than 25% and greater than or equal to 25%) and by age (less than 24 months and greater than or equal to 24 months). The first 35 subjects/treatment arm are evaluated with special immunologic studies including lymphoproliferative assays and extended panel immunophenotyping. There is an interim analysis after all patients have completed 12 weeks of treatment. Patients are treated for 48 weeks. [AS PER AMENDMENT 6/11/99: The study has been extended for an additional 48 weeks (96 weeks total) to permit long-term follow-up of clinically stable, HIV-infected children.]

Inclusion Criteria

Patients may be eligible for this study if they:

• Are HIV-positive.
• Have received the same continuous anti-HIV treatment for the past 16 weeks (missing no more than 6 weeks of treatment total during those 16 weeks).
• Are between 4 months and 17 years old (consent of parent or guardian required).

Exclusion Criteria

Patients will not be eligible if they:

• Have certain serious conditions such as cancer, an opportunistic (AIDS-related) infection, or other serious infection.
• Have ever taken any of the study drugs or any protease inhibitor.
• Are currently taking any anti-HIV drugs.
• Have taken an investigational drug within 14 days of entry into the study. (Co-enrollment in ACTG 219, ACTG 220 and certain ACTG opportunistic infection studies is allowed.)
• Are taking certain other drugs.
• Are pregnant.