Table 1.
Histopathology findings in respiratory track of hamsters exposed to SARS-CoV-2 at each day post-exposure.
| Day 2 |
Day 5 |
Day 8 |
|||||||
|---|---|---|---|---|---|---|---|---|---|
| Strain/Age | HE | IHC | ISH | HE | IHC | ISH | HE | IHC | ISH |
| Lung | |||||||||
| Aged WT | Similar lesions as seen in young WT hamsters | +++ 3/3 |
+++ 3/3 |
As same as 2 d, but more severe necrohemorrhagic and lesser interstitial pneumonia | +++ 3/3 |
+++ 3/3 |
As same as 5 d, still predominated by necrohemorrhagic pneumonia | ++ 3/3 |
+ 1/3* - 2/3 |
| Young WT | Multifocal, mild to moderate, necrohemorrhagic pneumonia, bronchiolar intraluminal hemorrhagic exudates and cell debris, and vascular leakage and leukocyte migration in pulmonary veins | +++ 6/6 |
++ 1/6 +++ 5/6 |
Multifocal, mild to moderate mixture of hemorrhagic and interstitial (glandular pattern of hypertrophic and hyperplastic type II pneumocytes) pneumonia, bronchiolar epithelial hypertrophy and hyperplasia forming folds with syncytial cells |
+ 6/6 |
+ 2/6 +++ 1/6 - 3/6 |
Early alveolar and bronchiolar repair characterized by alveoli and bronchioles lined by hyperplastic, flattened type II pneumocytes or cuboidal epithelial cells, respectively, and no or small numbers of intra-alveolar macrophages | + 1/6* |
- 6/6 |
| hACE2 adult | No significant lesions (1/3). Minimal (1/3) to mild (1/3), multifocal, lymphohistiocytic bronchointerstitial pneumonia | +++ 3/3 |
<25% 3/3 |
Multifocal, minimal (2/3) to mild (1/3) hemorrhagic and interstitial pneumonia | +++ 3/3 |
<25% 3/3 |
ND | ND | ND |
| Nasal Turbinates | |||||||||
| WT aged | Similar lesions | +++ 3/3 |
+++ 3/3 |
As same as 2 d, predominated by epithelial cell degeneration and necrosis | +++ 3/3 |
+++ 3/3 |
As same as 5 d, still presented with multifocal, mild (1/3) to severe (2/3) olfactory epithelial degeneration and necrosis | + 1/3 +++ 2/3 |
+ 1/3** |
| WT young | Multifocal, acute rhinitis characterized epithelial (respiratory, olfactory, and submucosal glandular) degeneration and necrosis with loss of cilia, inflammatory infiltrates of mucosa and submucosa, large amount/numbers of hemorrhagic exudates, sloughed epithelial cells, and degenerate neutrophils. | +++ 6/6 |
+++ 6/6 |
Multifocal, moderate to severe respiratory epithelial hypertrophy and hyperplasia or squamous metaplasia, olfactory epithelia attenuation by irregular hyperplastic epithelial cells, and lesser exudate in the nasal cavities. | + 6/6** |
++ 2/6 ++ 2/6 |
Respiratory epithelium was partially repaired either by normal pseudostratified or metaplastic squamous epithelia. The olfactory epithelium was partially repaired by multiple irregular layers of elongated, basophilic, hyperplastic epithelial cells. | − (6/6)** |
− 6/6** |
| hACE2 adult | Mild (1/3) to moderate (2/3), multifocal to locally extensive, neutrophilic and lymphohistiocytic rhinitis | +++ 3/3 |
ND | Minimal (1/3) to mild (1/3) to moderate (1/3), multifocal to locally extensive, neutrophilic rhinitis | +++ 1/3 |
ND | ND | ND | ND |
Abbreviations: WT, wild-type; hACE2, human angiotensin-converting enzyme 2; HE, hematoxylin; IHC, immunohistochemistry; ISH, in situ hybridization; ND, not done.
Notes: +: weakly positive; ++: moderately positive; +++: strongly positive. * focal, <5 positive cells in a young hamster; ** Rare intraluminal cell debris was weakly positive in some hamsters.