Fig. 1.

Construction and antiviral activity of defective interfering genes (DIG). a The plasmid construction of DI-PB2, DI-PB1, and DI-PA. The indicated sequences of shortened viral polymerase gene PB2, PB1, and PA were inserted into phw2000, respectively. Dotted lines indicate the internal deletion of wild-type (WT) viral polymerase genes. b, c DI RNA expression in 293T and A549 cells. The plasmids of DI-PB2, DI-PB1, and DI-PA were co-transfected into cells with the indicated concentrations. At 24 h post transfection, DI RNAs were extracted from cells and digested by DNase I for RT-qPCR. Empty vector was used as a negative control for RT-qPCR. d Anti-A(H7N7) virus activity of individual plasmid of DI-PB2, DI-PB1, and DI-PA or three combined plasmid DIG (DIG-3, 0.6 μg per well). e, f Dose-dependent anti-A(H7N7) virus activity of DIG-3 in 293T and A549 cells. g Anti-A(H5N1) virus activity of DIG-3. Empty vector phw2000 and plasmids with DIG were individually transfected to cells. At 24 h post transfection, cells were infected with A(H7N7) or A(H5N1) virus at MOI = 0.005 and cell supernatants were collected at 40 h post infection. Viral titers in the supernatants were detected by plaque assay. Data were presented as mean ± SD of three independent experiments. * Indicates P < 0.05. ** Indicates P < 0.01. P values were calculated by the two-tailed Student’s t test