To block the activity of phosphatases after infection with influenza virus, sodium vanadate was used. Dilutions were prepared using infection medium. Sodium vanadate was added to the virus-containing infection medium at the time points indicated. After 10 minutes of incubation IFNb, diluted in infection medium, was added to the medium containing virus and sodium vanadate. The cells were stimulated with IFNb for 15 minutes. Incubation with sodium vanadate started 25 min before cells were lysed and subjected to Western blotting as described.