Figure 2.

Viral replication is necessary but not sufficient to induce IFN-β expression. (A) Fractional IFN-β expression among productively infected cells. Reporter cells were infected with 40 HAU/ml NDV for 1 h. IFN-β–tGFP reporter expression and intracellular NDV HN protein was measured by flow cytometry at indicated time post-infection. Dot plots show IFN-β–tGFP expression among productively infected (NDV HN⁺) cells at indicated time post-infection. (B) Separate kinetics of viral replication and IFN-β expression. Frequency of IFN-β–tGFP (black circles) and NDV HN expression (grey squares) over time. (C) Unresponsiveness is not caused by the absence of inducing viral RNA. NDV-infected (80 HAU/ml) IFN-β–tGFP reporter cells were separated into GFP⁺ and GFP⁻ fractions. Total RNA was isolated and transfected into naive IFN-β–tGFP reporter cells (lower graphs). RNA from non-infected cells served as a control (upper graph). The frequency of IFN-β–tGFP-expressing cells 20 h after transfection is presented. Source data is available for this figure in the Supplementary Information.

Source data for Figure 2B ^{(298B, txt)}