FIG. 3.

SQLs are active even when added after infection: a time-of-addition experiment. HeLa P4 cells were infected with NL43. The drug was added to the cell culture 14 h before the infection; at the onset of infection; or 2, 3, 5, 10, or 24 h after the onset of infection. FZ41 (▾) was tested, and AZT (○) and nevirapine (▿) were used as controls for inhibition at early replication steps. β-Gal overproduction was quantified by CPRG assay 72 h after infection. Curves are the means of at least three experiments, and IC₅₀s were determined as described in Materials and Methods. The IC₅₀s are expressed as percentages of the IC₅₀ when the drug was added at the same time as the virus.