IFNB1 and infection: To evaluate the potential of IFN-λs alone or in combination with type I IFNs against SARS-CoV infection, we pretreated 2B4 cells with IFN-β, IFN-λ1 and IFN-λ2, either individually or in combination at indicated concentrations prior to infection with SARS-CoV (MOI = 0.01).