IFNB1 and infection: As shown in Fig. 3, ΔN146-infected cells, similar to the LPS-treated cells, expressed and secreted copious levels of type I interferon β (IFN-β), IL-1β, IL-6 and tumor necrosis factor α (TNF-α) 12 h post infection whereas these cytokines were barely detectable in supernatants from mock infected cells.