Fig. 3

Analysis of the growth properties of rIBV, rIBV-ΔPL1pro, and rIBV-ΔPL1pro-N. (a) Plaque formation in rIBV, rIBV-ΔPL1pro, and rIBV-ΔPL1pro-N infected Vero cells. Three viral stock supernatants were serially diluted and inoculated onto the Vero cells for plaque assays, the dilution of the viral stock is indicated. The original images of virus plaque formation are in Additional file 1: Supplemental Fig. 3a. (b) CPE formation in rIBV, rIBV-ΔPL1pro, and rIBV-ΔPL1pro-N infected H1299 cells. Scale bars: 50 μm. (c) Growth kinetics of the recombinant viruses in Vero cells and H1299 cells. The raw data is presented in Additional file 2. (d) Western blot analysis IBV N protein expression. The expression of IBV N protein in H1299 cells infected with rIBV and rIBV-ΔPL1pro-N at a MOI of 0.5 was assessed by Western blot at the indicated times post-infection, respectively, and β-actin was used as an internal control from the same experiment. The full-length blots are in Additional file 1: Supplemental Fig. 3b. Numbers below the image was IBV N/β-actin ratios of band optical density values from Image J software