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[Preprint]. 2022 Feb 24:rs.3.rs-1375091. [Version 1] doi: 10.21203/rs.3.rs-1375091/v1

Figure 1. Omicron/BA.2 and Omicron/BA.1 show similar infectivity and pathogenicity in mice.

Figure 1

a–c, BALB/c mice were intranasally inoculated with 105 PFU in 50 μL of Omicron/BA.1 (NC928), Omicron/BA.2 (NCD1288), or PBS (mock). a, Body weight changes in BALB/c mice after viral infection. Body weights of virus-infected (n =5) and mock-infected mice (n =5) were monitored daily for 10 days. Data are presented as the mean percentages of the starting weight (± s.e.m.). b, Pulmonary function analyses in infected mice (n =5). Penh and Rpef were measured by using whole-body plethysmography. Mean ± s.e.m. c, Virus replication in infected BALB/c mice. Mice (n =5) were euthanized at 2 and 5 dpi for virus titration. Virus titers in the nasal turbinates and lungs were determined by plaque assay. Vertical bars show the mean ± s.e.m. Points indicate data from individual mice. The lower limit of detection is indicated by the horizontal dashed line. Data were analyzed by using the Mann-Whitney test. d, Histopathological examination of the lungs of infected mice. Three mice per group were infected with 105 PFU of Omicron/BA.1 (NC928) or Omicron/BA.2 (NCD1288) and sacrificed at 2 or 5 dpi for histopathological examinations. Representative images of the bronchi and bronchioles/alveoli of mice infected with BA.1 or BA.2 are shown. Upper panels, hematoxylin and eosin (H&E) staining. Lower panels, in situ hybridization targeting the nucleocapsid gene of SARS-CoV-2. Scale bars, 100 μm. e, Pro-inflammatory cytokine/chemokine responses in the lungs of infected mice. BALB/c mice were intranasally inoculated with 105 PFU of Beta/B.1.351 (HP01542), BA.1 (NC928), or BA.2 (NCD1288) (infected mice, n = 4; naïve mice, n =3) at 1, 2, and 3 dpi. Vertical bars show the mean ± s.e.m. Points indicate data from individual mice. Data were analyzed by a two-way ANOVA with Tukey’s multiple comparisons test. f, g K18-hACE2 mice were intranasally inoculated with 103 PFU in 50 μL of WA1/2020 D614G or BA.2 (NCD1288). Viral titers (f) and RNA levels (g) were measured at 3 dpi (n = 7–8 per group, 2 experiments). Virus titers in the nasal turbinates and lungs were determined by plaque assay. Mean ± s.e.m. Points indicate data from individual mice. The lower limit of detection is indicated by the horizontal dashed line. Data were analyzed by Mann-Whitney test.