*2.5. Type I IFN Bioassay*

To measure type I IFN bioactivity, HEK293 cells stably expressing the pGF1-ISRE reporter [26]—in which firefly luciferase expression is driven by interferon-stimulated response elements—were incubated with untreated supernatants of infected cells. Relative light units (RLUs) were measured with a luminometer after 24 h using ONE-Glo Luciferase Assay System (Promega) according to the manufacturer's instructions and OptiPlateTM 96-well plates (Perkin Elmer, cat. nb.: 6005299).
