Fig. 2

Establishment of ST3GAL1-overexpressing cell lines and challenge with viruses. a Comparison of ST3GAL1 expression in chicken tissues and WT DF-1 cells by qRT-PCR. Data were normalized to expression of chicken ACTB and are expressed as the mean ± standard deviation (n = 3). Significant differences (compared with WT DF-1 cells) were determined by one-way ANOVA (****P < 0.0001, and *P < 0.05). b Schematic representation of the piggyBac transposon based expression vector harboring ST3GAL1. The vector was used to express ST3GAL1 in WT DF-1 cells, termed O/E-ST3. c (top) Expression of ST3GAL1 in O/E-ST3 and WT DF-1 cells, as detected by qRT-PCR. Data were normalized to expression of chicken ACTB and are expressed as the mean ± standard deviation (n = 3). Significant differences (compared with WT DF-1 cells) were determined by Student’s t-test (***P < 0.001, **P < 0.01, and *P < 0.05) (bottom) Expression of ST3GAL1 in O/E-ST3 and in WT DF-1 cells, as measured by RT-PCR. The chicken ACTB was used as a reference gene. The full length (uncut) gel electrophoresis image is shown in Additional file 2: Fig. S2. d Cell proliferation at 24 h, 48 h, and 72 h. Error bars indicate the mean ± standard deviation of triplicate analyses. e Relative titer of PR8-H5N8 (PB2-627E) or PR8-H9N2 (PB2-627E) after treatment with trypsin (+) in O/E-ST3 cells (O/E-ST3(+)) compared with that in WT DF-1 (WT DF-1(+)) cells treated with trypsin at 24 h post-infection. Significant differences were determined by Student’s t-test (**P < 0.01 and *P < 0.05). Error bars indicate the mean ± standard deviation of triplicate analyses