The significant differences between groups were tested by Student’s t-test (***, p < 0.001). The plaques were stained with crystal violet at 4 dpi (E) and the plaque diameters were measured and plotted (D). (D and E) Monolayers of DEF were infected with the indicated chimeric viruses and the respective parental viruses at 100 PFU for analysis of plaque morphology. The significant difference between rGI/SH15NS4A and rGIII/SH7NS4A at different time points is labeled (δ, p < 0.05 δδ, p < 0.01). The significant difference between rGI/SH15NS2B/NS3 and rGIII/SH7NS2B/NS3 at different time points is labeled (φ, p < 0.05). The significant difference between rGI/SH15NS2A and rGIII/SH7NS2A at different time points is labeled (&, p < 0.05 &, p < 0.01). The significant difference between rGI/SH15NS1 and rGIII/SH7NS1 at different time points is labeled (#, p < 0.05 #, p < 0.01). The significant difference between rGI/SH15CPrME and rGIII/SH7CPrME at different time points is marked (*, p < 0.05 **, p <0.01). All data are presented as mean ± SD from three independent experiments and were tested by Student’s t-test. (C) DEF were infected with the indicated chimeric recombinant viruses at 0.01 MOI and harvested at the indicated time points for measurement of viral replication with TCID 50 assays in BHK cells. (B) Chimeric recombinant viruses with exchange of non-structural proteins. (A) Chimeric recombinant viruses with exchange of structural proteins. All data are presented as mean ± SD from three independent experiments. (A and B) DEF were infected with the indicated chimeric recombinant viruses at 1 MOI and harvested at 24 hpi for measurement of IFN-α and β expression at the mRNA level by qRT-PCR. S4 Fig: Detection of IFN-α and β expression and replication efficiency of chimeric recombinant viruses in DEF.