Fig. 4

Overexpression of the wild-type (WT) TVA receptor restores susceptibility of tva-modified DF-1 clones to infection by ALV subgroup A. a Schematic representation showing the wild-type TVA receptor (WT TVA) overexpression cassette. 5′-TR: piggyBac 5′-terminal repeat; Neo: neomycin resistant gene; CMV: cytomegalovirus promoter; WT TVA: WT TVA coding sequence; 3′-TR: piggyBac 3′-terminal repeat; Amp: ampicillin resistant gene; CAGG: cytomegalovirus (CMV) enhancer fused to the chicken beta-actin promoter; PBase: piggyBac transposase coding sequence. b Analysis of genomic DNA to confirm integration of the WT TVA overexpression cassette under specific PCR conditions. GAPDH was used as a control. c Expression of GFP by virus-infected DF-1 clones. Three DF-1 clones (TVA#1–5, TVA#1–6, and TVA#4–4) and WT DF-1 cells were transfected with the WT TVA overexpression cassette and then infected with ALV subgroup A. GFP expression by each group was examined under a fluorescence microscope. Scale bar = 100 μm. d, e Flow cytometry analysis of virus-infected DF-1 clones. Gray peaks indicate the population of WT cells not infected with ALV subgroup A (negative control) and green peaks indicate the population of DF-1 clones infected with ALV subgroup A. The numbers on the histograms represent the mean percentage of cells within that population of triplicate replications. WT DF-1 fibroblasts were used as the control (positive control). Different letters (a, b and c) indicate significant differences (P < 0.05)