Antiviral activities of IDV, an inhibitor of HIV-1 PR, on HIV-1 producer cells, target cells, and isolated virions. (A) Transfected, virus-producing HeLa cells were treated for 24 h with increasing concentrations of IDV, and the culture supernatants were evaluated for HIV infectivity on the basis of a single cycle of virus replication on indicator P4 cells. (B) Target indicator P4 cells were treated overnight with increasing concentrations of IDV and then infected with virus-containing supernatant from untreated, transfected HeLa cells in the presence of the same concentrations of IDV as those used in the pretreatment period. (C) Supernatant from transfected HeLa cells was subjected to treatment with 5 μM IDV for the indicated periods and used to infect P4 cells. The results are the means of results from at least two independent experiments and are expressed as percentages of results for untreated controls. Results are relative to those for untreated HeLa cells (A), untreated P4 cells (B), and untreated virus (C).