Fig. 8: Immunization with NDV and MVA viral vectors encoding SARS-CoV-2 S protein protects hamsters against SARS-CoV-2 direct contact transmission.

A Design of the study. Six- to eight-week-old female Golden Syrian hamsters were used. Four naïve hamsters per group were cohoused with challenged hamsters from vaccination groups 1-6 groups at day 1 post-challenge, forming the recipient groups (RGs). Throat swabs were collected at days 3 and 5 post-challenge. Hamsters from each RG were euthanized at day 5 post-challenge to harvest lungs lobes (upper right lung lobe and lower right lung lobe) and nasal turbinates. B Body weight change of recipient hamsters. Body weight was monitored for 5 days post-challenge. C Genomic viral RNA copies in throat swabs of recipient hamsters. Throat swabs of RGs were collected in 200 μL of PBS at days 3 and 5 post-challenge and SARS-CoV-2 N genomic copies detected by RT-qPCR. The geometric mean with geometric SD of values from triplicates of each sample for each group are represented. The dotted line represents the LOD, and the dashed line represents the LOQ. Two-way ANOVA followed by Tukey’s multiple comparisons test: ***p < 0.0002; ****p < 0.0001. D Viral load in the nasal turbinates of recipient hamsters. Nasal turbinates were collected from RG 1-6 and the healthy control group at day 5 post-challenge and homogenized in 0.5 ml of PBS. Viral titers were measured by plaque assay on Vero-E6 cells. The geometric mean with geometric SD of values (PFUs/mL) of each sample for each group are represented. The dotted line represents the LOD. Ordinary one-way ANOVA of transformed data followed by Tukey’s multiple comparison test: **p < 0.002; ***p < 0.0002; ****p < 0.0001. E Viral load in the lungs of recipient hamsters. The upper and lower right lung lobes were collected at day 5 post-challenge and homogenized in 1 mL of PBS. Viral titers were measured by plaque assay on Vero-E6 cells. The geometric mean with geometric SD of values (PFUs/mL) of each sample for each group are represented. The dotted line represents the LOD. Ordinary one-way ANOVA of transformed data followed by Tukey’s multiple comparison test: *p < 0.033; **p < 0.002; ***p < 0.0002; ****p < 0.0001. F Pathology analyses of the left lung lobes of recipient hamsters. Left lung lobes from RGs collected at day 5 post-challenge were fixed in 4% paraformaldehyde, cut into 5 µm sections and stained with H&E. The slides were evaluated by a pathologist who was blinded to the group information. The scoring system is shown in Supplementary Table 1. Mean and SD of cumulative histopathological lesion scores are represented. The dotted line represents the LOD. Unpaired nonparametric Kruskal-Wallis test: *p < 0.033; **p < 0.002; ***p < 0.0002.