Fig. 4

Immunization with E. coli SyBV protects against bacteria-induced lethality through suppression of systemic inflammation. a Study protocol for SyBV immunization and E. coli challenge for protecting against bacterial sepsis. b Survival curve measured for 5 days after intraperitoneal challenge with a lethal dose of E. coli (n = 10). c Body temperature was evaluated at 3 h following challenge with E. coli (n = 10). d, e The level of TNF-α (d) and IL-6 (e) in serum was quantified at 3 h after the last challenge (n = 5). fE. coli-specific IgG titers after the last immunization with OMV or SyBV (n = 5). g The level of E. coli-specific CD4⁺ T-cell-derived IFN-γ after CD4⁺ T-cells were isolated from immunized spleens (three independent samples). All data are presented as the mean ± s.e.m. ^*P < 0.05, ^**P < 0.01, ^***P < 0.001; ns, not significant by one-way or two-way ANOVA with Tukey’s post-test versus the sham group. For the survival curve, the Mantel–Cox log-rank test was used to compare with the sham group