Fig. 3: presence of respiratory tract epithelial cell plugs and concomitant occurrence of segmental lesions in the lungs of hamsters infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). (A) Low-magnification histological image showing the contrast between an intensely injured area (top right) and a normal neighbouring area (left). (B) Intensely damaged lung area, highlighting the bronchus semi-obstructed by plug cells (^*yellow), mostly epithelial from the respiratory tract. Black arrows indicate points of contact between plug cells and bronchial wall epithelial cells, which are injured. (C) Immunofluorescence for the nucleocapsid protein of SARS-CoV-2, showing the presence of several cells infected by the virus in a cell plug trapped in a bronchial lumen (^*pink). (D) and (E) Presence of the SARS-CoV-2 nucleocapsid protein, both in remaining plug cells (yellow arrows) and in bronchial epithelial cells where they were installed (blue arrows). (F) Immunofluorescence for pan-cytokeratin shows positive epithelial cells on the bronchial layer and inside the bronchiolar lumen with a more circular morphology, along with lymphocytes (amplified image). Paraffin-embedded lung sections: (A) and (B) HE is staining, brightfield microscopy (Metasystems slide scanner), 20x objective lens/ 0.8 NA; (C), (D) and (E) immunofluorescence for SARS-CoV-2 nucleocapsid protein (green), counterstained with Evans Blue (red blood cells and cytoplasm of some cells in red) and DAPI (nuclei in white). (F) Immunofluorescence for mouse monoclonal pan-cytokeratin (Biocare Medical, cat. CM043-C) in green, counterstained with Evans Blue (red blood cells and cytoplasm of some cells in red) and DAPI (nuclei in white). Confocal laser scanning microscopy (Zeiss LSM 710), objective lens 40x/ 1.3 NA.4.