Figure 3. The effect of senescence on viral infection-induced IFN expression and IFN-mediated antiviral activities. Host antiviral gene expression was assessed by qRT-PCR. The expression of IFN-β and IFN-γ-Inducible Protein 10 (IP-10) in response to IFV infection (A) and IFN-β and interferon-stimulated gene 15 (ISG15) in response to VZV infection (B) was normalized to GAPDH and shown as fold induction level relative to mock (m) control. The results are representative of three independent experiments. Statistical analysis: ^*p<0.05, ^**p<0.01 compared with virus-infected NS cells. (C, D) Recombinant human IFN-α (10 ng/mL), IFN-β (10 ng/mL), IFN-λ1 (10 ng/mL) and IFN-λ2 (10 ng/mL) were added to cells. Next day, cells were infected with IFV or VZV and plaque assays were performed. Progeny viral titers were calculated and expressed as plaque forming units (PFU)/mL. Control-treated cells were normalized to 100% viral titers and data are presented as the percentage of control treated samples. Data are shown as means±SEM of two independent experiments.