Fig. 5.
Pathological findings in infected Syrian hamsters. (A) Histopathological examination of the lungs of infected hamsters. Syrian hamsters were inoculated with 105.6 PFU (in 110 μL) or with 103 PFU (in 110 μL) of UT-NCGM02 via a combination of the intranasal (100 μL) and ocular (10 μL) routes. Syrian hamsters infected with the high or low dose were killed on days 3, 6, and 10 postinfection for pathological examinations (n = 2, except for 1 in the high-dose group on day 10). Shown are representative pathological findings in the lungs of hamsters infected with the virus on days 3, 6, and 10 postinfection (Left and Middle, hematoxylin and eosin staining; Right, immunohistochemistry for SARS-CoV-2 antigen detection). Middle and Right show enlarged views of the area circled in red in Left. (Scale bars, 2 mm [Left] and 200 μm [Middle and Right].) (B and C) Pathological severity scores in infected hamsters. To evaluate comprehensive histological changes, lung tissue sections were scored based on (B) pathological changes and (C) viral antigen detection levels. (B) Scores were determined based on the percentage of inflammation area for each section of the five lobes collected from each animal in each group by using the following scoring system: 0, no pathological change; 1, affected area (≤10%); 2, affected area (<50%, >10%); 3, affected area (≥50%); an additional point was added when pulmonary edema and/or alveolar hemorrhage was observed. The total score for the five lobes is shown for individual animals. (C) Scores were also determined based on the percentage of virus antigen-positive cells, as determined by immunohistochemistry, for each section of the five lobes collected from each animal in each group by using the following scoring system: 0, no positive cells; 1, positive cells (≤10%); 2, positive cells (<50%, >10%); 3, positive cells (≥50%). The total score for the five lobes is shown for individual animals.