FIG 4.
The combination of mutations at positions 603, 633, and 891 of Satt largely determines the Vero cell adaptation of DR13att. (A) Schematic representation of the chimeric S proteins of recombinant PEDVs. The positions of the mutated residues are shown, and their colors are consistent with the colors of their original S proteins. (B) Luciferase expression by recombinant PEDVs. The intracellular Renilla luciferase activities of the first two generations of the recombinant viruses (P0 and P1) (y axis) (relative light units [RLU]) were determined. The results are expressed as the mean values from three parallel tests, and error bars represent the SD. Comparisons were carried out between the luciferase activities of the recombinant viruses and that of the mock treatments. *, P < 0.05; **, P < 0.01.