Fig. 1

Bat respiratory epithelial cells were less susceptible than MDCK cells to influenza A virus infections but showed differential susceptibility between human and avian influenza viruses. Epithelial cells of T. brasiliensis (TB1-Lu), E. helvum, C. perspic and control MDCK cells were separately infected with human (USSR H1N1 and pdm H1N1) and avian (H2N3 and H6N1) viruses at 1.0 MOI for 6 h and 24 h, and immunostained (brown) for viral NP. Expectedly, MDCK cells were extensively infected showing nuclear localisation of NP at 6 hpi, and widespread cytoplasmic spread of NP at 24 hpi with each virus type (a). TB1-Lu cells, by contrast, were not readily infected by human or avian viruses; even at 24 hpi only a limited number of cells showed intranuclear NP localisation (b). E. helvum and C. perspic cells showed differential infection susceptibility between human and avian viruses. Cells from the two bat species, like TB1-Lu cells, were not readily infected with human viruses (USSR H1N1 or pdm H1N1 virus) such that relatively few cells showed intranuclear NP localisation at 24 hpi (c and d). However, E. helvum and C. perspic cells were extensively infected by 6 hpi with avian viruses (H2N3 or H6N1 virus), and by 24 hpi exhibited extensive cell loss and cytoplasmic spread of NP (c and d)