Figure 1.
MVA-S(3P) immunization and SARS-CoV-2 challenge schedule in hamsters and analysis of SARS-CoV-2-specific humoral immune responses elicited by MVA-S(3P) vaccination. (A) Experiment overview. Syrian hamsters (n = 10 per group) were immunized intramuscularly (i.m.) with two doses of 1 × 108 PFU of MVA-S(3P) or MVA-WT on days 0 and 28 or one dose of 1 × 108 PFU of MVA-S(3P) on day 28 and challenged intranasally (i.n.) with 2 × 105 TCID50 of SARS-CoV-2 B.1 strain on day 56, as indicated. Blood was collected on days 0, 28, 49, and 56. On day 60 (day 4 post-challenge; 4pc), all animals per group were sacrificed and blood, lungs, and nasal washes were collected for immunological, virological, and histological analysis. (B) Titers of anti-S binding IgG antibodies determined by ELISA in serum collected on days 0, 28, 49, 56, and 60. Mean values and SEM are plotted. The dashed line represents the limit of detection. Statistical significance between groups was calculated using an unpaired non-parametric Mann-Whitney test of transformed data (**p < 0.002). (C) SARS-CoV-2 neutralizing antibody titers against Wuhan isolate D614G were determined by a live microneutralization assay (left panel) or by S-pseudotyped VSV particles (right panel). NT50 (50% neutralization) titers were assessed in serum collected on day 56. Mean NT50 values ± SEM are depicted. The dotted line indicates the limit of detection. Statistical significance between groups was calculated using an unpaired non-parametric Kruskal-Wallis test of transformed data (**p < 0.002, ****p<0.0001). (D) SARS-CoV-2 neutralizing antibody titers against SARS-CoV-2 VoC beta, gamma, delta, and omicron were determined by an S-pseudotyped VSV particle assay. NT50 titers were assessed in serum collected on day 56. Mean NT50 values ± SEM are depicted. Statistical significance between groups was calculated using an unpaired non-parametric Kruskal-Wallis test of transformed data (*p < 0.033; **p < 0.002; ***p < 0.0002; ****p<0.0001).