FIG 3.

Histopathological analysis of lung tissue from SARS-CoV-2- and SARS-CoV-2-mCherry-infected K18-hACE2 mice. Twenty-one-week-old male and female K18-hACE2-transgenic mice were inoculated intranasally with 4 × 10⁴ PFU SARS-CoV-2 or SARS-CoV-2-mCherry. (A) At day 7 postinfection, lung tissue was harvested and stored in 4% PFA for 24 h prior to macroimaging. White arrows show the dark-red lesions throughout the dorsal region of the lung in infected mice. Hematoxylin and eosin (H&E)-stained lung sections demonstrate thickened interalveolar septa (black arrow) and a hemorrhage (black arrowhead) in SARS-CoV-2- and SARS-CoV-2-mCherry-infected mice. Scale bars, 6 mm (black), 500 μm (red), 100 μm (green). Black dashed boxes indicate the area of magnification. Each image is representative of ≥3 mice. (B) Cell density was quantified using ImageScope software. Statistical analyses were performed using an unpaired t test. Data represent means ± standard errors.