Human airway epithelium cultures. Polarized primary HAE, termed as primary B-HAE, was generated by growing isolated human airway (tracheobronchial) epithelial cells (three HAE cultures were generated from different donors) on collagencoated, semipermeable membrane inserts (0.6 cm 2 , Millicell-PCF; Millipore, Billerica, MA), and then allowing them to differentiate at an air-liquid interface (ALI); this was carried out at the Tissue and Cell Culture Core of the Center for Gene Therapy, University of Iowa [44, 58, 75, 76] . After 3-4 weeks of culture at an ALI, the polarity of the HAE was determined based on the transepithelial electrical resistance (TEER) using an epithelial Volt-Ohm Meter (Millipore) and the relationship to infectability was assessed; a value of over 1,000 V.cm 2 was required for HBoV1 infection. CuFi-and NuLi-HAE were generated following the same method as above, but using the immortalized airway epithelial cell lines, CuFi-8 and NuLi-1, respectively. The primary B-, CuFi-, and NuLi-HAE were cultured, differentiated and maintained in (50%:50%) DMEM:F12 medium containing 2% Ultroser G (Pall BioSepra, Cergy-Staint-Christophe, France).