Figure 2.

Cross-reacting M2e-specific antibody responses induced by H5N1-M2e vaccination. Mice were vaccinated three times with tetrameric H5N1-M2e peptide mixed with FA (H5N1−M2e+FA) or SAS (H5N1−M2e+SAS). Mice vaccinated with PBS, FA, or SAS were used as control. Mice sera were sampled 21 days after priming and the first booster vaccination and 10 days after the second booster vaccination for the ELISA detection. The end point titer of each sample was determined as the highest dilution that yielded an OD₄₅₀ nm absorbance higher than the blank OD₄₅₀ nm absorbance plus 2 SD. The data are shown as the geometric mean of 10 mice per group with its corresponding SD on a log₁₀ scale. (A) H7N9-M2e tetrameric peptide was used as coating antigen in the ELISA. (B) H5N1-M2e tetrameric peptide was used as coating antigen in the ELISA. (C) HK/156-M2e tetrameric peptide was used as coating antigen in the ELISA. The detection limits (1:100 and 1:20) are indicated by the dotted line. *, **, and *** indicate significant differences (P < 0.05) between the H5N1-M2e and HK/156 M2e cross-reactive antibody titers detected on 21 days after priming, 21 days after first booster and 10 days after second booster H5N1−M2e+FA vaccinations, respectively. Experiments were repeated five times.