Fig 1: SARS-CoV-2 Spike-specific T-cell immune response in ZSVG-02-O-vaccinated mice received 2 doses of ZSVG-02-O with a 14-day interval.BALB/c mice (n = 6/group) were immunized with two doses of 3 μg, 10 μg and 30 μg ZSVG-02-O, 2 weeks apart, by intramuscular injection. Splenocytes were collected 4 weeks post second immunization and stimulated with the indicated proteins of different variants for 48 h at concentration of 1 μg/mL (A)-(H) The proportions of IFN-γ/CD69+ CD4+ and CD8+ T cells from ZSVG-02-O immunized mice stimulated with spike proteins or WT nucleocapsid protein. (I)-(J) ELISpot assay for IL-2 (I) and IL-5 (J) in splenocytes stimulated with Omicron Spike protein. Data are shown as mean ± SD, and analyzed by one-way ANOVA test (*P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001). WT, ancestral strain. SFC, spot forming cells. Saline is used as placebo.