Figure 7.
K18-hACE2 KI mouse infection with SARS-CoV-2 variants. (A) Schematic for SARS-CoV-2 infection. Twelve-week-old K18-hACE2 KI mice were i.n. inoculated with 2.5 × 102 PFU of SARS-CoV-2 WT, Delta, Omicron BA.1, or Omicron BA.2 of SARS-CoV-2. Infected mice were monitored and evaluated at the indicated time for (B) body weight changes (n = 5) and (C) survival (n = 5). At endpoint (n = 5), mice were sacrificed to harvest their lungs, and (D) viral N gene copy numbers were measured by absolute quantification RT-PCR. Mice that lost over 20% of their starting body weight were euthanized. Error bars represent the means with SDs. (E) Pathology scores. (F) Lung H&E staining of K18-hACE2 KI mice. The lungs of K18-hACE2 KI mice collected at endpoint were subjected to H&E staining and histology scoring. The scale bar is shown in each section. The black arrow indicates the lung tissue damage, the yellow arrow indicates the infiltration of monocytes. Two-way ANOVA with Tukey’s multiple comparison test was used. **, P < 0.01; ns, not significant, P > 0.05. Error bars represent the means with SEMs in (B) and the means with SDs elsewhere.