Fig. 4.

The vaccine components induce high titers of antibodies in BALB/c mice. a A schematic showing the timeline of the vaccinations in BALB/c mice. We tested the immunogenicity of the vaccine candidates by injecting 50 µL of each non-adjuvanted compound i.m. to four or five mice, according to Table 1. b–d Log10 transformations of IgG antibody titers against HA2 (b), SpyCatcher-HA2 (c) or SpyCatcher-M2e (d), as measured in ELISA wells coated with the recombinant protein indicated above each graph. Mean titers are represented by the thick line ± standard deviation; * symbolizes significant difference with p < 0.05, determined by Mann–Whitney U-test. Each dot represents a single mouse. Undetectable antibody levels were denoted with the titer 100 (dashed line)