FIG. 7.

TrkA signaling is important for influenza virus replication. (A) TrkA inhibitors significantly reduce influenza virus production in vitro. A549 cells were infected with A/WSN at an MOI of 0.1, in the presence of either vehicle control (DMSO alone) or various inhibitors: SKI-606 (10 μM), ZD1839 (10 μM), A9 (4 μM), AG1296 (10 μM), AG879 (10 μM), TAK-165 (10 μM), GW441756 (10 μM), or K252a (2 μM). Virus production at 18 hpi was quantified by plaque assay. (B) TrkA-specific shRNAs decreased the TrkA expression level. A549 cells were transfected with the shRNA-expressing plasmid specific for either LUC or TrkA and then infected with influenza A virus. TrkA protein expression was detected 48 h after transfection by Western blot analysis using anti-TrkA antibody. (C) TrkA-specific shRNAs significantly decreased virus production. A549 cells transfected 48 h previously with either LUC- or TrkA-specific shRNA plasmid were infected with A/WSN at an MOI of 1. Virus production was quantified at 12 hpi. Results shown are the averages from at least three independent experiments. Error bars indicate SD. Statistical analysis was conducted with Student's t test (**, P < 0.01; ***, P < 0.001; ****, P < 0.0001).