Effects of GS4071 on the production of infectious viruses. (A) Progeny viruses accumulated in the medium (assayed at 13 h p.i.). +GS4071: Virus-infected cultures were incubated with or without 2 μM GS4071 from 1 to 13 h p.i. H3/Osaka: human A/Osaka/981/98(H3N2). H10/chick: avian A/chicken/Germany/N/49(H10N7). Error bars represent standard deviations of averages of three independent experiments. (B) Progeny viruses produced from 12 to 13 h p.i. in the absence of GS4071. The virus-infected cell cultures were incubated with or without 2 μM GS4071 from 1 to 12 h p.i., washed to remove GS4071, and incubated in pre-warmed fresh DMEM from 12 to 13 h p.i. (for 1 h) at 36°C in the absence of GS4071. The culture medium was collected and assayed for the virus production. (C) Effect of pulse treatment with GS4071 on infected cells during virus production assay. Infected cells were incubated without GS4071 from 1 to 12 h p.i., and then in fresh medium with or without 2 μM GS4071 from 12 to 13 h p.i. (for 1 h) at 36°C. The culture medium was collected and analyzed for virus production. Statistical analyses were performed using the Student's t-test.