Figure 6. Histopathological staining of trachea and lung sections from multi dose nebulization treated Syrian hamsters following SARS-CoV-2 infection.

Representative hematoxylin and eosin-stained tissue sections from day 3 and day 7 post infection groups (n = 4 per group) for trachea, bronchioles, blood vessels, and alveolar parenchyma. Pathology of note for the saline group includes epithelial cell exfoliation and cellular debris accumulation in the bronchiole lumen (3dpi, arrow), mononuclear cell and heterophile infiltration and accumulation of leukocytes in blood vessel smooth muscle layers (3dpi, arrow), severe perivascular edema (3dpi, star) and transmural leukocyte migration and perivascular accumulation (7dpi, arrow). The nanobody treated group pathology remained within normal limits at day 3 post infection, exhibiting minor pathology of note on day 7 including minimal mononuclear cell infiltration in the tracheal subepithelial interstitium (7dpi, arrow) and minimal perivascular accumulation of mononuclear cells (7dpi, arrow). Corresponding pathologist descriptions found in Supplementary Table 5. Representative images for each group column are from the same animal. Images acquired at 200x magnification. Scale bars for all images = 300μm.