Fully differentiated primary B-(each of the three distinct subtypes), CuFi-and NuLi-HAE were cultured in Millicell inserts (0.6 cm 2 ; Millipore) and inoculated with 150 ml of purified HBoV1 (1610 7 gc/ml in phosphate buffered saline, pH7.4; PBS) from the apical surface (at a multiplicity of infection, MOI, of ,750 gc/cell; an average of 2610 6 cells per insert). For each of the HAE, a 2-h incubation was followed by aspiration of the virus from the apical chamber and by three washes of the cells with 200 ml of PBS to remove unbound virus. The HAEs were then further cultured at an ALI.