Figure 4.

Effect of Omicron BA.1 re-infection in 614G convalescent Syrian golden hamsters. (A) Detection of viral genome in throat swabs of 614G infected Syrian golden hamsters prior to re-challenge. The mean of each group is shown as solid line, SEM displayed as shading. Data of individual animals is depicted as dashed line. Time point of re-challenge with Omicron BA.1 (13 dpi) is indicated with a red star.(B) Relative body weight of immunologically naïve hamsters infected with Omicron and convalescent hamsters re-challenged with Omicron BA.1. The mean of each group is shown as solid line, SEM displayed as shading. Significant statistic differences were calculated with 2-way ANOVA with Dunnett’s correction for multiple comparisons. (C) Detection of viral genome in throat swabs of immunologically naïve hamsters infected with Omicron BA.1 and convalescent hamsters re-challenged with Omicron. The mean of each group is shown as solid line, SEM displayed as shading. Significant statistic differences (****p < 0.0001) were calculated with 2-way ANOVA with Dunnett’s correction for multiple comparisons. (D) Representative gross pathological lesions of animals inoculated with (I) Omicron BA.1¹ or (II) 614G convalescent and Omicron BA.1 re-challenged animals. Foci (*) of pulmonary consolidation. (E) Detection of SARS-CoV-2 genome² in respiratory tissue of infected hamsters. Significant statistic differences were calculated with unpaired t-test (*: p < 0.05). (F-I) Histopathological changes and viral antigen expression in nasal turbinates and lungs of re-challenged Syrian golden hamsters. (F) H&E staining and (G) IHC of lungs. (H) H&E staining and (I) IHC of nasal turbinates. Bars indicate 200 µm for images of the lungs and 20 µm for the nasal turbinates. ^1,2 Data shown for comparison to Omicron BA.1 inoculated hamsters are based on data shown in Figure 1 (¹) and Figure 3 (²).