Extended Data Figure 3. Lung pathology of Δ3678 virus-immunized and WT SARS-CoV-2-challenged hamsters.

a, Lung sections show typical interstitial pneumonia with moderate to severe inflammatory changes in mock-immunized and WT virus-challenged animals (mock-WT) or in WT virus-inoculated and WT virus-challenged animals (WT-WT). Reduced inflammatory changes are observed in Δ3678 virus-immunized and WT virus-challenged animals (Δ3678-WT). b, Higher magnification images show large inflammatory cells in the airways and prominent septal thickening in the mock-WT and WT-WT groups. Such changes are minimal or absent in the Δ3678-WT group. c-f, Comparative pathology scores calculated based on the criteria described in Table S1. The Δ3678-WT group shows a significant reduction in total pathology score (c), extent of inflammation (d), alveolar septa changes (e), and airway changes (f). Dots represent individual animals (n=5). The values of mean ± standard error of mean are presented. A non-parametric two-tailed Mann-Whitney test was used to determine the statistical differences between Δ3678-WT and mock-WT or WT-WT groups. P values were adjusted using the Bonferroni correction to account for multiple comparisons. *, P<0.025.