Figure 3.

Immunization of Mosaic RBD‐np induce Th‐1 biased cellular and humoral response in mice. A) Mice were immunized with 10 µg mosaic RBD‐np/SAS, the control group were immunized with PBS/SAS. Spleens were collected at 14 days post‐boost immunization. ELISPOT was used to determine the abundance of IFN‐γ⁺, IL‐2⁺ splenocytes (2 × 10⁵ splenocytes/well) after 24 h stimulation with peptide pool. ELISA was used to determine the level of IFN‐γ, IL‐2 in the cell supernatant after 24 h stimulation with peptide pool n = 5 mice per group. Statistical analyses were performed using two‐way ANOVA. B) Ratio of MERS‐CoV, SARS‐CoV, and SARS‐CoV‐2 RBDs binding IgG2a to IgG1 were determined by ELISA at day 21 after boost immunization and at day 4 after SARS‐CoV‐2 WT infected. n = 3 mice per group, and the serum were pooled by group. Three independent experiments were analysed. Statistical analyses were performed using two‐way ANOVA. C‐D) Draining lymph nodes were collected at day 7, day 14, day 21 and day 28 after the boost immunization. The percentages of Tfh cells C) and GC cells D) were determined by FCS. n = 3‐5 mice per group. Statistical analyses were performed using two‐way ANOVA. All results are expressed as mean ± SEM. ns, no significantly difference, ^* p < 0.05, ^**** p < 0.0001.