Figure 3.

Prime-boost vaccination of HD-Ad-FS protected hACE2 mice from SARS-CoV-2 VOCs in the lungs. (A) Schematic timeline of prime-boost hACE2 experiment. The mice were intranasally administered with a prime-boost regimen of HD-Ad-FS or HD-Ad-control (5x10⁹ + 5x10⁹ vp, three-week interval). Three weeks after the boost dose, the mice were intranasally challenged with a SARS-CoV-2 variant (Beta, Delta, or Omicron) at 1x10⁵ TCID₅₀. Animal samples were harvested at 4 dpi. (B) Body weight was recorded at 0 (pre-challenge) and 4 dpi after challenge. (C) SARS-CoV-2 variant RNA levels in the lungs were measured with RT-qPCR. (D) The titers of infectious SARS-CoV-2 variant in the lungs were determined with TCID₅₀ assays. (E, F) The titers of FS-specific IgG in sera (E) and BALs (F) were determined with ELISA. The starting dilution factors were 1:25 and 1:5 for sera and BALs, respectively (G) The titers of FS-specific sIgA in BALs were measured with ELISA. The starting dilution factor was 1:1. (H, I) Neutralizing activities in sera (H) and BALs (I) against SARS-CoV-2 variants were determined with neutralization assays. Dots represent individual mice (n=4, 5, or 6). For (C-F, H, I), the horizontal dotted lines represent the LOD of the assays. For (B), statistical analyses were performed by two-way ANOVA. Error bars represent mean ± s.e.m. For (C-I), statistical analyses were performed by Mann-Whitney test, two-tailed. Error bars represent geometric mean with geometric SD. *p<0.05, **p<0.01, and ns, not significant. Data represent one independent animal experiment with indicated biological replicates.