The relation of virologic and immunologic markers to clinical outcomes after nucleoside therapy in HIV-infected adults with 200 to 500 CD4 cells per cubic millimeter

Background: We studied measures of human immunodeficiency virus (HIV) replication, the viral phenotype, and immune function (CD4 cell counts) and the relation of changes in these indicators to clinical outcomes in a subgroup of patients in a controlled trial of early antiretroviral treatment for HIV, the AIDS Clinical Trials Group Study 175. Methods: The 391 subjects, each of whom entered the study with a single screening CD4 cell count of 200 to 500 per cubic millimeter, were randomly as signed to receive zidovudine alone, didanosine alone, zidovudine plus didanosine, or zidovudine plus zalcitabine. Plasma concentrations of HIV RNA were assessed in 366 subjects, and viral isolates from 332 subjects were assayed for the presence of the syncytium inducing phenotype. Results: After eight weeks, the mean (±SE) decrease from base line in the concentration of HIV RNA, expressed as the change in the base 10 log of the number of copies per milliliter, was 0.26±0.06 for patients treated with zidovudine alone, 0.65±0.07 for didanosine alone, 0.93±0.10 for zidovudine plus didanosine, and 0.89±0.06 for zidovudine plus zalcitabine (P