Infection of BHK-21 with VSVΔG(H5,N1,sNLuc) expressing both the hemagglutinin (HA) and neuraminidase (NA) of the highly pathogenic avian influenza virus A/chicken/Yamaguchi/7/04 (H5N1) was significantly affected by bafilomycin A1, in accordance with the pH-dependent fusion activity of HA (Figure 7a). Here, XK is linked to infection.