En face staining of HAE at 24 hr intervals after inoculation showed PR8+Chick HA/NA spread to additional target cells at 37uC at a rate similar to that of PR8+Vic HA/NA at 32uC and correlated with the titers measured for these two viruses under those conditions ( Figure 6C and 6D ). At 32uC, however, PR8+Chick HA/NA spread was severely compromised and resembled the infection characteristics shown for A/Dk/Eng/62 (H4N6) in Figure 2A . Thus, by replacing human glycoproteins with those from an avian virus isolate, we have recapitulated the effect of temperature on infection and growth kinetics as well as the degree of cytotoxicity produced by wholly avian influenza virus interactions in human ciliated airway epithelium. The relative contributions of reduced cell-cell spread and reduced CPE by avian-like influenza viruses at temperatures of the proximal airways to in vivo infection and pathology will, however, require further investigation.