mphocyte proliferation assay. Spleen cells were collected from the immunized mice under aseptic conditions and adjusted to a final concentration of 10 cells/ml in complete medium(RPMI 1640 supplemented with 0.05 mM B-mercaptoethanol, 100 JI/ ml penicillin, 100 g/ml streptomycin and 10% FBS). Approximately 1 x 10 cells from each group were stimulated with the corresponding reagent(100ul saline for saline group, 500ng cordycepin for cordycepin group, 100ng vaccine for vaccine group and 100 ng HBsAg plus 500 ng cordycepin for the other 3 groups)and ConA (5 ug/ml). After 2 days of incubation(under humidified conditions of 5%CO2 and 37C) 10 ul of CCK-8 solution(Beyotime Biotechnology, China) was added 4 h before the end of the incubation period. The absorbance was measured at 450 nm using a microplate reader (Molecular Devices). The stimulation index =(test OD- blank oD)(negative OD-blank OD). An SI>2 indicated positive results IFN-y and IL-4 detection. Approximately 1 x 10 spleen cells were stimulated with the corresponding antigen for 24 h, and the supernatant was analyzed by elisa. IFN-y and IL-4 were measured using mouse-specific IL-4 and IFN-Y ELISAs(Dakew Shenzhen, China) according to the manufacturers instructions. Briefly, 100 ul/well of the diluted cytokine standard and the sample was added Thereafter, 50 ul/well of the biotinylated antibody was added and incubated for 90 min at 37oC. After washing five times, 100 ul/well of diluted streptavidin-HRP was added and incubated for 30 min at 37 C. The plate was then washed and 100 ul/well of TMB was added. After incubation in the dark for 15 min, 100 ul/well of stop solution was added, and the absorbance was measured at 450 nm15 Lymphocyte proliferation assay. Spleen cells were collected from the immunized mice under aseptic conditions and adjusted to a final concentration of 106 cells/ml in complete medium (RPMI 1640 supplemented with 0.05 mM β-mercaptoethanol, 100 UI/ml penicillin, 100 g/ml streptomycin and 10% FBS). Approximately 1 × 106 cells from each group were stimulated with the corresponding reagent (100μl saline for saline group, 500ng cordycepin for cordycepin group, 100ng vaccine for vaccine group and 100 ng HBsAg plus 500 ng cordycepin for the other 3 groups) and ConA (5 μg/ml). After 2 days of incubation (under humidified conditions of 5% CO2 and 37°C), 10 μl of CCK-8 solution (Beyotime Biotechnology, China) was added 4 h before the end of the incubation period. The absorbance was measured at 450 nm using a microplate reader (Molecular Devices). The stimulation index = (test OD- blank OD)/(negative OD-blank OD). An SI ≥ 2 indicated positive results. IFN-γ and IL-4 detection. Approximately 1 × 106 spleen cells were stimulated with the corresponding antigen for 24 h, and the supernatant was analyzed by ELISA. IFN-γ and IL-4 were measured using mouse-specific IL-4 and IFN-γ ELISAs (Dakew, Shenzhen, China) according to the manufacturer’s instructions. Briefly, 100 μl/well of the diluted cytokine standard and the sample was added. Thereafter, 50 μl/well of the biotinylated antibody was added and incubated for 90 min at 37°C. After washing five times, 100 μl/well of diluted streptavidin-HRP was added and incubated for 30 min at 37°C. The plate was then washed and 100 μl/well of TMB was added. After incubation in the dark for 15 min, 100 μl/well of stop solution was added, and the absorbance was measured at 450 nm