HAE were rinsed with PBS to transiently remove apical secretions and supplied with fresh basolateral medium prior to inoculation. Virus inoculum was diluted in PBS and applied to the apical surface of HAE for 2 hrs at either 32uC, 33uC, or 37uC, as indicated. Following incubation, viral inocula were removed and cultures incubated at 32uC, 33uC or 37uC for the duration of the experiment. Viral growth kinetics were determined by performing apical washes with 300 ml of serum-free DMEM for 30 min at either 32uC or 37uC. Washes were harvested and stored at 280uC prior to analysis. Viral titers in the apical washes were determined by standard plaque assay or tissue culture infectious dose (TCID) 50 assay on MDCK cell monolayers as previously described [13, 52, 54] .