Detached epithelial cell plugs from the upper respiratory tract favour distal lung injury in Golden Syrian hamsters (Mesocricetus auratus) when experimentally infected with the A.2 Brazilian SARS-CoV-2 strain.

Abstract

Background: The Golden Syrian hamster (Mesocricetus auratus), Ferrets (Mustela putorius furo), and macaques have been described as useful laboratory animals naturally susceptible to SARS-CoV-2 infection. Objectives: To study the mechanism of lung injury, we describe the histopathological features of SARS-CoV-2 infection in Golden Syrian hamsters inoculated intranasally with the A.2 Brazilian strain. Methods: Hamsters were intranasally inoculated with the A.2 variant and euthanized at 3-, 5-, 10-and 15-days post-inoculation. The physical examination and body weight were recorded daily. Neutralizing antibodies and viral RNA load of the respiratory tract were assessed during necropsies. Findings: The COVID-19 model presented body weight loss, high levels of respiratory viral RNA load, severe segmentary pneumonitis, and bronchial fistula besides lymphatic trapping and infiltration, like the human SARS-COV-2 pathogenesis. The presence of subepithelial lymphoeosinophilic infiltrate was highlighted in our results; it contributed to the detachment of SARS-CoV-2 nucleocapsid-positive epithelial cells resulting in the infectious cell plugs. Main conclusions: The SARS-CoV-2 caused segmentary pneumonia and vascular damage. In our comprehension, the infectious cell plugs, as being aspirated from the upper respiratory tract into the terminal bronchial lumen, work as a “Trojan horse”, thus contributing to the dissemination of the SARS-CoV-2 infection into specific regions of the deep lung parenchyma.