FIG 1.

IFN-λ inhibited SARS-CoV-2 replication in cultured human lung cells. Human bronchial epithelial cells expressing hACE2 (HBE-hACE2) were either mock treated (black-filled circles), pretreated for 24 h with IFN-λ (pre-IFN-λ) (green open squares), or treated with IFN-λ at the same time of infection (co-IFN-λ) (green-filled circles) with SARS-CoV-2. Culture medium was harvested at 0, 24, and 48 h postinfection, and viral RNA in culture medium was measured by RT-qPCR following infection at MOI of 0.01 PFU/cell (A) or MOI of 0.1 PFU/cell (B). Mature virus released into the culture media was quantified by plaque assay following infection at MOI of 0.01 PFU/cell (C) or MOI of 0.1 PFU/cell (D). Three independent experiments were performed with technical duplicates. *, P < 0.001 (two-way ANOVA). (E) Representative Western blots are shown of proteins expressed in the HBE and HBE-hACE2 cells following treatment with increasing amounts of IFN-λ (200 to 2,000 units/ml) for 24 h. (F) RT-qPCR measurements are shown for ISG mRNAs expressed in HBE-hACE2 cells relative to untreated controls in response to IFN-λ treatment (1,000 units/ml) or relative to mock treatment in response to a SARS-CoV-2 infection for 24 h.