Human immunodeficiency virus type 1 quantitative cell microculture as a measure of antiviral efficacy in a multicenter clinical trial

A Quantitative cell microculture assay (QMC) was used to measure the human immunodeficiency virus type 1 (HIV-1) peripheral blood mononuclear cell (PBMC)-associated titer in 109 subjects enrolled in an open-label phase I/II study of didanosine monotherapy or combination therapy with zidovudine, The titer was inversely correlated with C04⁺cell count at baseline (r =.37, P =.001). After 12 weeks of therapy, subjects showed a significant decreases in virus titer and those with the highest baseline virus titers had the greatest increase in C04⁺cell number (r =.430, P =.002). The QMC assay was more sensitive (98%) for assessing the antiretroviral effect of therapy than was immune complex-dissociated HIV p24 antigen (32%) or plasma culture (3.4%). Estimated sample sizes for phase I/II clinical trials were derived using the within-subject QMC SO of.72 log₁₀infectious units per 10⁶PMBC.