ART4 and infection: Apical surface inoculation of CF HAE with PIVCFTR or PIVGFP at 106 plaque-forming units (PFU) (100 μl of 107 PFU/ml for 2 h: multiplicity of infection [MOI] ∼3 for all lumenal cells and ∼5 for ciliated cells) resulted in infection of a significant number of cells 48 h postinoculation (pi) as detected by immunolocalization of PIV fusion (F) glycoprotein viewed en face (Figure 2A and 2B).