Fig. 4: Attenuation of virus propagation, macrophage accumulation, and epithelial damage in Nsp1-K164A/H165A-infected hamster lungs.

a Representative images of serial lung sections immunostained for Iba1 and prosurfactant protein C (ProSPC) or SARS-CoV-2 nucleocapsid protein after infection with PBS (a), WA1/2020 (b), ΔPRRA (c), Nsp1-K164A/H165A (d), Nsp1-N128S/K129E (e). Consolidated regions in WA1/2020-infected lungs with massive Iba1 positive macrophage infiltration around affected bronchioles (b). Alveolar epithelium surrounding consolidated regions in WA1/2020 stains prominently for viral nucleocapsid (b), while nucleocapsid staining is limited to bronchiolar epithelium in Nsp1-K164A/H165A (inset, d). f Digitally magnified images of macrophage-rich consolidation regions in WA1/2020-infected lungs show loss of ProSPC-stained alveolar type 2 cells. Viral antigen staining of infiltrates within and surrounding affected bronchioles with loss of RAGE-expressing type 1 epithelium in the same regions with consolidated macrophages (asterisk, g). Nuclei were counterstained with Hoechst 33342 dye (blue). Scale bars: 500 mm (a–e), 100 mm (f, g). Experiments were conducted once, with multiple biological replicates.