Dados do Trabalho

Título

Pulmonary alterations associated with SARS-CoV-2 in the Syrian hamster (Mesocricetus auratus) experimental model: comparative histopathology A.2 and Omicron variants

Introdução

Since the beginning of the outbreaks caused by SARS-CoV-2, several studies have been carried out to better understand the physiopathology of COVID-19 in humans. Macroscopic and microscopic changes in the lungs help to understand the pathophysiology of the organ of SARS-CoV-2 predilection, both to assess the extent/severity of the disease and to test the safety and efficacy of vaccines, antivirals and other potential therapies.

Objetivo (s)

This study aims to investigate lung histopathological changes in Syrian hamsters, comparing A.2 and the Omicron variants for pulmonary severity

Material e Métodos

Syrian hamsters infected with A.2 or Omicron variants were divided and euthanized 3, 5, 10 and 15 days after infection. Lung samples were submitted to routine histological processing and analyzed blindly with the application of observation scores of the most frequent microscopic changes described in humans, ranging from 0 to 4. Additional information was also added when pertinent.

Resultados e Conclusão

Lung injury earliest microscopic aspect was segmentary interstitial mononuclear pneumonia, apparently random distribution of hepatized areas through the lung, without side or lobe predilection. At 3-7DPI we observed epithelial upper airway and bronchial desquamation with a subepithelial infiltration, presence of megakaryocytes and eosinophils. Vasculitis/endothelitis was detected in association with large lymphocytes, reactive endothelial cells, sub-endothelial mononuclear infiltration, degeneration and edema of vascular wall. Atypical epithelial hyperplasia was observed from 5-15DPI, with  cariomegaly, anisocytosis, prominent nucleoli and cellular pleomorphism, associated with interstitial inflammation. Diffuse alveolar injury was frequently observed at 5DPI. The regenerative aspect of SARS-CoV-2 injury may be confirmed by bronchial epithelial cell replacement. Hyperinflated areas were associated with a mononuclear infiltrate reduction in the lung interstitial space. Lymphangitis and lymphangiectasia were most evident around the bronchial hilum. All inoculated animals showed differential thickening of the alveolar septum (inflammatory cells). Among the variants, A.2 obtained higher histopathologic scores. This experimental model mimics the histopathologic changes seen in humans, with greater severity in animals infected with A.2 and milder lesions with Omicron variant. These findings contribute to the consolidation of the Syrian hamster as a robust experimental model for SARS-CoV-2 infection.

Palavras Chave

COVID-19; Hamster; Lung; Pathology; Microscopy; Variants