Fig 2. Histopathological examination of SARS-CoV-2-infected AC70 hACE2 Tg⁺ mice showed inflammatory infiltrates and tissue damage to varying extents.

Various tissue specimens harvested at 4 d.p.i. from AC70 hACE2 Tg⁺ mice challenged with 10⁵ TCID₅₀ of SARS-CoV-2 were subjected to the histopathology study. Briefly, paraffin-embedded, and formalin-fixed tissue sections were stained with hematoxylin and eosin (H&E), as described in Materials and Methods. Mild perivascular infiltrations were seen in the lung (A, blue arrowheads) with areas of congestion/thrombosis (inset). In the brain (B), peri-vascular infiltration and microglial activation (B, black arrows), albeit weak, could be occasionally seen in infected AC70 hACE2 Tg⁺ mice compared to a similar area of their Tg^- littermates (C). Small foci of infiltrates in the heart with eosinophilic myocytes (D, white arrows). Tissue necrosis was seen in the liver (E, black stars) and the small intestine (F, black arrowheads). Note: Bar = 80μm for A, E and F; Bar = 40μm for B, C and D. Representative images from two independent experiments.