Plasma Viremia Titration and RNA Quantitation in ICD-p24 Negative HIV Type-1-Infected Patients

Quantitative culture of human immunodeficiency virus (HIV) was performed on 202 plasma samples obtained from asymptomatic and early symptomatic HIV-1 infected patients (mean CD4⁺ count: 186/mm³) before antiretroviral therapy was started. HIV could be isolated from 84% of the plasma samples (titers ranging from 10⁰ to 10^2.75 TCID₅₀/ml). Immune complex dissociated p24 antigen (ICD-p24) was detected in 66% of the samples. Only 23 samples (11%) were negative for both ICD-p24 as well as HIV culture. Discordant results were obtained in 55 samples, and 45 samples negative for ICD-p24 were positive for HIV culture. A significant proportion (42%) of patients that were negative for ICD-p24 belonged to a very advanced group with very low CD4⁺ cell count. However, almost 90% of these ICD-p24 negative samples were positive for HIV plasma viremia, stressing the value of this virological marker in patients with low CD4⁺ cell count and without any detectable ICD-p24 antigenemia. HIV-1 RNA was detected in all ICD-p24 negative plasma samples tested by the branched DNA (bDNA) assay. A very good correlation was found between high RNA copy number and HIV plasma isolation in samples obtained from patients with low CD4⁺ cell count, suggesting that HIV-1 RNA quantitation may also reflect viral infectivity of plasma.