Fig. 2

The comparison of influenza infectivity in MDCK and MDCK/London cell lines. a Cells were infected with H1N1 (upper panel) and H3N2 (lower panel) for 48 h.p.i. followed by fixation and stained with anti-flu NP antibody after BSA blocking. Images were taken by confocal microscopy in a ×680 magnification. Red fluorescence indicates the location of influenza viruses while blue fluorescence stained by DAPI shows the nucleus of the cell. b The corrected total cell fluorescence (CTCF) for H1N1 or H3N2 was calculated by ImageJ software v.1.8.0. ** indicates the p value is less than 0.01. The cytotoxicity of c conventional MDCK and d MDCK/London cells were determined by the concentrations of LDH in culture medium after influenza infections (M.O.I. of 0.1) at indicated time points, measured by LDH assays. The OD values proportionally correspond to the LDH concentration in accordance with the manufacturer’s instructions