Fig. 7: Histopathological analysis of rVSV-∆G-spike i.m. vaccinated and infected hamsters’ lungs at 3 and 7 dpi.

General histology (H&E) and SARS-CoV-2 DAB immunolabeling of naive, unvaccinated infected (5 × 10⁶), and vaccinated (10⁶ pfu) hamsters’ lungs, at 3 and 7 dpi. Lungs were isolated and processed for paraffin embedding from naive (a, f), infected (5 × 10⁶ pfu) (b, g for 3 dpi and d, i for 7 dpi) and vaccinated and infected (c, h for 3 dpi and e, j for 7 dpi). Sections (4 µm) were taken for H&E staining (a–e) and SARS-CoV-2 DAB immunolabeling (f–j, positive SARS-CoV-2—brown, hematoxylin counterstaining—blue). An asterisk (*) indicates cellular debris in bronchiolar lumen. Black arrow heads indicate congestion of blood in blood vessels. Black arrows indicate positive stained cells. a–e: scale bar = 200 µm; f–j: scale bar = 20 µm. k Histopathological severity analysis of hamsters lungs of naive, vaccinated, and infected lungs, at 3 and 7 dpi. l Digital morphometric analysis of DAB immunohistochemical staining for SARS-CoV-2 in lungs of naive, infected, and vaccinated lungs, at 3 and 7 dpi. m Tissue/air space analysis of naive, infected, and vaccinated lungs, at 3 and 7 dpi. Data for a–j was taken for five groups. Each group includes four animals. For each animal, five fields were imaged and analyzed. Data for k–m are presented as mean values ± SEM. Statistical analyses for k–m were performed by one-way ANOVA with Tukey’s multiple comparisons test, with p < 0.0001, p = 0.0006, p < 0.0001, respectively. Source data are provided as a Source Data file.