FIGURE 3.

Substitution of residues s7–s12 of ALV-A with ALV-E reduced the Tva binding affinity and infectivity in DF-1 cells. (A) Schematic representations of the replacement fragments s7–s12. (B) DF-1 cells were incubated with chimeric gp85 protein s7–s12 and subsequently infected with RCASBP (A)-EGFP supernatants. The percentage of GFP-positive cells was measured by FACS for blocking analysis of the binding of chimeric gp85 proteins to Tva. (C) The interaction of chimeric gp85 protein s1–s6 with Tva-HA-Fc. (D) The gray scale value level of gp85 (IP)/Tva (IP) was calculated. (E) DF-1 cells transfected with recombinant RCASBP (A/E)-s1-s6-EGFP vectors were visualized under a fluorescence microscope and the percentage of GFP-positive cells (indicated with red color letters) was detected by FACS 7 days posttransfection. *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001.