Figure 5.

Knockdown of IRF7 inhibited influenza-mediated RIG-I induction and innate responses in human alveolar epithelial cells. A549 cells were transfected with IRF7 siRNA for three days. Then, the cells were infected with (A) IAV PR8 at the MOI of 0.2 for 24 h or (B) 500 U/mL of IFN-β for 6 h. Total RNA was extracted and mRNA expression was assessed by qRT-PCR. Data were expressed as the means ± SEM from three separate experiments. Statistical significance was determined by ANOVA. * denotes significant difference compared to data from the siRNA CTL + IAV infected group, p < 0.05. (C) Supernatants from IAV infected cells stimulated RIG-I/IRF7 expression in uninfected cells. Supernatants were collected from IAV infected cells after 24 h poi. Then the supernatants were filtered to remove IAV using a 100 K MW filter (Amicon). The filtered supernatants were added to A549 cells and changes in RIG-I/IRF7 mRNA were assessed by qRT-PCR. (D) RIG-I protein in A549 cells was detected by immunoblotting. The immunoblot shown is representative of three separate experiments, with quantitation of that result depicted below the image.