Figure 2
Detection of sM2-specific humoral and cell mediated immune responses. Sera were collected at days 0 (pre-immune), 7 (first immunization) and 21 (second immunization) of immunization with the 4sM2 recombinant protein. The absorbance of antibody was detected by indirect ELISA. (A) Detection of serum IgG using the sM2 protein as coating antigen. (B) Detection of serum IgG using the M2 peptide as coating antigen. (C) Detection of serum IgG1 and IgG2a antibody responses in mouse sera. (D) Detection of serum IgG using the whole inactivated virus as coating antigen. Splenocytes were harvested 10 days after the last immunization. Cells were re-stimulated in vitro with the sM2 protein or M2 peptide and cytokine forming cell spots were determined by ELISPOT assay. IFN-γ and IL-4 spot-forming cells per 5 × 105 splenocytes were determined. (E) Splenocytes producing IFN-γ stimulated with the sM2 protein and M2 peptide. (F) Splenocytes producing IL-4 stimulated with sM2 protein and M2 peptide. Bars denote mean ± standard deviations. Comparison of groups were analyzed by Student’s t-test and ANOVA; the differences were statistically significant (* P < 0.05). Abbreviations: 4sM2, recombinant multimeric sM2 protein; NC, negative control; PC, positive control.