Although no gross cytopathic effects were observed in HBoV1infected B-HAE, histology analysis of mock-vs. HBoV1-infected epithelia (B33-11) revealed morphological differences: infected B-HAE did not feature obvious cilia at 7 days p.i., and was significantly thinner than the mock-infected one on average at 22 days p.i. ( Figure 4B ). We further monitored the transepithelial electrical resistance (TEER) during infection of B-HAE, and found that at 6 days p.i., it was reduced from a value of ,1,200 to ,400 V.cm 2 , while the mock-infected B-HAE maintained the initial TEER ( Figure 4C) . Notably, the decrease in TEER in the infected B-HAE was accompanied by an increase in HBoV1 secretion ( Figure 4A ).