Figure 6.
Histopathological Analysis of Hamsters after SARS-CoV-2 Infection
(A) Histopathology of representative hematoxylin-and-eosin-stained, paraffin-embedded bronchi with inserted epithelium (top row) and lung parenchyma with inserted blood vessels (bottom row) at 3 dpi. Severe suppurative bronchitis with immune cell infiltration (hash symbol) is apparent only in the control-treated animals with necrosis of bronchial epithelial cells (diagonal arrows). Necro-suppurative interstitial pneumonia (upward arrows) with endothelialitis (downward arrows) is prominent in control-treated animals. Scale bars, 200 μm in the bronchus overview, 50 μm in all others.
(B) Bronchitis and edema score at 3 dpi. Bars indicate the mean.
(C) Detection of viral RNA (red) using in situ hybridization of representative bronchial epithelium present only in the control group. Scale bars, 50 μm.
(D) Histopathology of representative lung sections from areas comparable with (A) at 5 dpi. Staining of bronchi of control-treated animals showed marked bronchial hyperplasia with hyperplasia of epithelial cells (diagonal arrow) and still existing bronchitis (hash symbol), absent in all prophylactically treated and in 2/3 therapeutically treated animals (top row). Lung parenchyma staining of control-treated animals showed severe interstitial pneumonia with marked type II alveolar epithelial cell hyperplasia and endothelialitis (insets, downward arrows). Compared with control-treated animals, prophylactically treated animals showed only mild signs of interstitial pneumonia with mild type II alveolar epithelial cell hyperplasia (upward arrow), whereas therapeutically treated animals showed a more heterogeneous picture, with 1/3 animals showing no signs of lung pathology, 1/3 animals showing only mild signs of interstitial pneumonia, and 1/3 animals showing moderate multifocal interstitial pneumonia. Scale bars, 200 μm in the bronchus overview, 50 μm in all others.
(E) Bronchitis and edema score at 5 dpi. Bars indicate the mean.