Fig. 1. SARS-CoV-2 MA10 infection causes lung damage in aged surviving mice.

1-year-old female BALB/c mice were infected with 10³ PFU SARS-CoV-2 MA10 (n=74) or PBS (n=24) and monitored for (A) percent starting weight and (B) survival. (C) Log transformed infectious virus lung titers were assayed at indicated time points. Dotted line represents LOD. Undetected samples are plotted at half the LOD. (D to F) Lung function was assessed by whole body plethysmography for (D) PenH, (E) Rpef, and (F) EF50. (G) Histopathological analysis of lungs at indicated time points are shown. H&E indicates hematoxylin and eosin staining. SMA indicates DAB-labeling (brown) immunohistochemistry for α-smooth muscle actin. Picrosirius Red staining (bright pink-red) highlights collagen fibers. Image scale bars represents 1000 μm for low magnification and 100 μm for 400X images. (H) Disease incidence scoring is shown for indicated time points: 0 = 0% of total area of examined section, 1 = less than 5%; 2 = 6 to 10%; 3 = 11 to 50%; 4 = 51 to 95%; 5 = greater than 95%. Graphs represent individuals necropsied at each time point (C and H), with the average value for each treatment and error bars representing standard error of the mean. Mock infected animals represented by open black circles and SARS-CoV-2 MA10 infected animals are represented by closed red circles.