Evaluation of multiple parameters of HIV-1 replication cycle in testing of AIDS drugs in vitro

Evaluation of the activities of antiretroviral agents and an immunoregulatory compound has been made using two models of HIV-1 infection and three measurements of virus expression. Acute infection of Jurkat cells or chronic/inducible infection in U1.1 cells was monitored at multiple time points after drug treatment. The 50% effective concentrations (EC₅₀) of the HIV-1 inhibitors suramin, 3′-azido-3′-deoxythymidine (AZT), and 2′,3′-dideoxycytidine, as measured by HIV-1 RNA hybridization in Jurkat cells two days after infection, were comparable to EC₅₀ values obtained in parallel measurements of extracellular p24 levels and percent HIV-1 IF-positive cells. However, these measurements diverged: at seven days after infection the EC₅₀ of AZT was greater than 10 μM when intracellular HIV-1 RNA was assayed, 0.2 μM by IF, and 0.03 μM by p24 assay. Human thymic humoral factor displayed no direct inductive activity in chronic HIV-1 infection in U1.1 cells, while phorbol ester and lymphocyte supernatants induced all parameters. These observations warrant care when interpreting results of only a single assay and suggest that definitive assay of HIV-1 infection requires measurements of multiple parameters of virus expression.