SARS-CoV-2 infection of IFNAR1-deficient patient cells in vitro. (A–C) IF analysis for the SARS-CoV-2 N protein in SV40-fibroblasts from healthy controls (C1 and C2) and patients with IFNAR1 variants including P335del/P335del, P335del/+ (two patients), W73C/W73C, V225fs/+, and V225fs/V225fs. Cells were treated with IFN-α2a (100 or 10 U/ml, A), IFN-ω (1 or 0.1 ng/ml, B), or IFN-β (10, 5, or 1 U/ml, C) overnight and then infected with SARS-CoV-2 at MOI = 0.1, 0.5, or 1.5. Cells were fixed and stained 24 or 48 h after infection. (D) IF analysis for the SARS-CoV-2 N protein in SV40-fibroblasts treated with neutralizing antibodies against IFN-β then stimulated with IFN-α2a (100 U/ml), IFN-ω (1 ng/ml), or IFN-β (100 U/ml). Cells were then infected with SARS-CoV-2 at MOI = 0.5. Cells were fixed and stained 24 h after infection. The graphs depict the mean ± SEM of two or three independent experiments.