Fig. 2

The design of diverse lengths of influenza DIGs and the antiviral efficiency of DIGs. a Construction of defective interfering genes (DIGs). The diverse defective interfering (DI) genes of DI-PA, DI-PB1 and DI-PB2 with internal deletion were generated by fusion PCR. Dotted lines show the internal deletion in wild-type viral polymerase genes. The solid-line sequences of shortened viral polymerase gene PA, PB1 and PB2 were inserted into phw2000 vector, respectively. b The antiviral activity of single DIG against A(H7N7) virus in A549 cells. c The dose-dependent antiviral efficiency of single PAD4 and combinational DIG-3 (including PAD3, PB2D3, and PB1D3) and DIG-4 (including PAD4, PB2D3, and PB1D3). The plasmid DIG or empty vector (PHW) with indicated concentrations were transfected into A549 cells and then cells were infected by H7N7 virus at 24 h post transfection. Viral titers in cell supernatants were measured by plaque assay at 48 h post infection. Data were presented as mean ± SD of at least three independent experiments. * indicates P < 0.05 and ** indicates P < 0.01. P values were calculated by the two-tailed Student’s t test. d The protection of two doses of DIG on A(H1N1)-infected mice. DIG-4 (5 µg/mouse, n = 5), PAD4 (5 µg/mouse, n = 5), DIG-3 (5 µg/mouse, n = 5), or empty vector (PHW, 5 µg/mouse, n = 5) packaged by TAT-P1 were intratracheally inoculated into mice at 48 h and 24 h before viral challenge. e The protection of one dose DIG on A(H1N1)-infected mice. DIG-4 (5 µg/mouse, n = 10), PAD4 (5 µg/mouse, n = 10), DIG-3 (5 µg/mouse, n = 10), or PHW (5 µg/mouse, n = 10) packaged by TAT-P1 were intratracheally inoculated into mice at 24 h before viral challenge. Survivals were generated from 10 mice in each group. P values were calculated by Gehan–Breslow–Wilcoxon test