To determine whether administration of a highly active antiretroviral treatment regimen consisting of ritonavir (ABT-538), zidovudine (AZT), and lamivudine (3TC) is associated with the restoration of delayed type hypersensitivity and lymphocyte proliferative responses in patients with moderately advanced HIV-1 infection. To better characterize in these patients the phenotype of the expanded lymphocyte subpopulations, as well as the genotype, phenotype, and cellular origin of viruses that persist after initiation of therapy, and the genotype and phenotype of drug-resistant isolates that emerge during therapy.