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. 2023 Mar 10;193(6):690–701. doi: 10.1016/j.ajpath.2023.02.013

Figure 3.

Figure 3

Photomicrographs of immunofluorescence (IFA) antibody– and in situ hybridization (ISH)–labeled sections of lung from uninfected and SARS-CoV-2–inoculated hamsters. A–C: IFA with antibodies against SARS-CoV-2 nucleocapsid protein (NP; red) at 3 days post inoculation (dpi) shows the presence of viral antigen (arrowheads) within hamster terminal bronchiolar epithelium (A–C), alveolar septa (B), and, less commonly, alveolar macrophages (B and C). A: Anti–endothelial cell antibody CD31 (green) highlights endothelial cells lining a small pulmonary artery, which lacks red SARS-CoV-2 NP signal. B and C: Anti-platelet antibody CD41 (green) highlights platelet marginalization along the arteriolar endothelium (double-headed arrow; B), and the presence of intracytoplasmic green signal within mononuclear cells (B and C) is consistent with platelet phagocytosis by alveolar macrophages (arrows). A–C: Viral NP is not associated with pulmonary vessels. D–L: Distribution of SARS-CoV-2 RNA-positive cells in ISH-labeled sections of lung. Cells labeled by riboprobe in situ hybridization stain red. D–F: Lung from uninfected hamster is negative for ISH signal. G and H: In lung sections from a SARS-CoV-2–inoculated hamster euthanized at 3 dpi, SARS-CoV-2 RNA is most prominent within airways, extending from mainstem bronchi to bronchiolar epithelial cells of smaller airways and multifocally into type I and II pneumocytes of peribronchiolar alveolar septa. J and K: In lung sections from a SARS-CoV-2–inoculated hamster euthanized at 6 dpi, the number of positive cells has decreased dramatically, with scattered signal in pneumocytes lining alveolar septa, and occasional weak signal remaining in airway epithelial cells. F, I, and L: No signal is identified within pulmonary vessels. DAPI binds DNA. Scale bars: 20 μm (A–C, E, F, H, I, K, and L); 1 mm (D, G, and J). A, arteriole; B, bronchiole; vRNA, viral RNA.