Fig. 2: Role of S in Omicron pathogenicity.
From: Spike and nsp6 are key determinants of SARS-CoV-2 Omicron BA.1 attenuation
a–c, Male and female K18-hACE2 mice (aged 12–20 weeks) were intranasally inoculated with 1 × 104 PFU of WT (n = 6 mice), Omi-S (n = 10 mice) or Omicron (n = 10 mice) virus. Two independently generated virus stocks were used in this experiment. Body weight (a), clinical score (b) and survival (c) were monitored daily for 14 days. Mice that lost 20% of their initial body weight were euthanized. d,e, K18-hACE2 mice were intranasally inoculated with 1 × 104 PFU of WT (n = 14 mice), Omi-S (n = 14 mice) and Omicron (n = 14 mice). Lung samples of the infected mice were collected at 2 or 4 dpi to determine the viral titre (n = 4 mice) (d) or for immunohistochemistry (IHC) detection of the N protein (n = 3 mice) (e). In e, representative IHC images showing SARS-CoV-2 N (brown colour) in alveoli (arrows) and bronchioles (arrowheads) in mice lungs at 2 dpi are presented. Scale bars, 100 µm. f, Percentage of N-positive bronchioles in the lungs of infected mice (n = 3 mice) at 2 dpi. Each dot represents an infected mouse. Statistical significance was determined using a two-tailed, unpaired t-test with Welch’s correction (a,b,d,f) and log-rank (Mantel-Cox) test (c). *P < 0.05, **P < 0.01, ***P < 0.001 and ****P < 0.0001; NS, not significant.
