Fig. 6: Membrane-tethered mucins restrict infection of SARS-CoV-2 variants in vitro and mouse-adapted SARS-CoV-2 in vivo.

a, RT–qPCR measuring relative levels of viral N gene copies in mucin-overexpressing Calu-3 cells infected with the indicated SARS-CoV-2 variants at an MOI of 0.05 for 24 h. The dotted line indicates the NTG average for two separate guides each with n = 3 biological replicates. A two-tailed t-test was performed for each viral variant relative to its own NTG control. b, SARS-CoV-2 infection of WT Calu-3 cells with or without pretreatment with StcE across variants. Two-sided t-test performed for +StcE versus −StcE for each viral variant, n = 5 biological replicates. c–h, Muc1^−/−/Muc4^−/−/Muc16^−/− triple KO and control mice were infected with 10³ p.f.u. of mouse-adapted SARS-CoV-2 intranasally and viral loads were analyzed in the lungs 2 d postinfection. c, Schematic depicting experimental conditions for in vivo infection, and subsequent analysis of SARS-CoV-2 infection in either WT or mucin KO mice. d, IHC staining for SARS-CoV-2 nucleocapsid followed by DAB development and hematoxylin II staining on paraffin-embedded lung sections. Shown are representative lungs from n = 8 mice. Scale bars, 1 mm (upper) and 100 µm (lower). e, Quantification of d. A two-tailed t-test was performed between mucin WT and KO groups, n = 8 mice. f. RNA-ISH probing for SARS-CoV-2 RNA on paraffin-embedded lung sections. Shown are representative lungs from n = 8 mice. Scale bars, 2 mm (upper) and 500 µm (lower). DAPI, 4,6-diamidino-2-phenylindole. g, Quantitation of f. A two-tailed t-test was performed between mucin WT and KO groups, n = 8 mice. h, Quantitation of infectious viral particles per lung lobe by plaque assay from n = 8 mice. A two-tailed t-test was performed between mucin WT and KO groups. Error bars denote mean ± s.e.m. NS, not significant; *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001.