Fig 1.
Scanning electron microscopic analysis of (a) S. typhimurium and (b) STG. Arrows indicate trans-membrane lysis tunnels.
Fig 2.
Cell viability and pro‐ and anti‐inflammatory cytokine production of STG.
To determine cytotoxicity, murine macrophages (RAW 264.7) were exposed to PBS buffer, LPS purified from S. typhimurium, FKC, wild-type bacterial cells (ST) and NaOH-induced STG, respectively (bars). At 24 h post-exposure, macrophages were collected for analysis of cell viability using Cell counting Kit-8. Absorbance was measured at 450 nm and all experiments were performed in triplicate. Cytotoxic activity is expressed as the percentage of cell viability by the formula described in Materials and Methods. At given time post‐exposure with PBS buffer, LPS purified from S. typhimurium, FKC, ST and STG, respectively (bars), macrophages were collected for analysis of mRNA expression for pro- and anti-inflammatory cytokines and factor (TNF‐α, IL‐1β, iNOS, IL‐6 and IL‐10) using RT-qPCR. Data are representative of triplicate experiments with each sample run in triplicate. All statistical analyses were performed with one-way ANOVA using SPSS software (version 14.0) and data were expressed as mean ± standard error of the mean. *** = P < 0.001; ** = P < 0.01; * = P < 0.05 (significant difference from PBS) and ### = P < 0.001; ## = P < 0.01; # = P < 0.05 (significant difference from LPS).
Fig 3.
The levels of IgG antibody responses were determined by indirect ELISA.
(a) S. typhpimurium and (b) S. enteritidis were coated as an antigen for ELISA. Results are expressed as means ± standard errors of the means. The asterisks indicate significant differences between antibody responses of the vaccinated and non-vaccinated groups. ** = P < 0.01; * = P < 0.05.
Fig 4.
Assessment of CD4+ and CD8+ T-cells by FACS analysis.
Populations of (a) CD4+ and (b) CD8+ T-cells and (c and d) the corresponding significant analysis from vaccinated and non-vaccinated control groups one week (week 6) after the final vaccination with STG. Values are shown as means ± standard errors of the means. The asterisks indicate significant differences between T-cell populations of the vaccinated and non-vaccinated groups. ** = P < 0.01; * = P < 0.05.
Fig 5.
Serum bactericidal activities of rats vaccinated with STG against (a) S. typhpimurium or (b) S. enteritidis. Data were expressed as means ± standard errors of the means. The asterisks indicate significant differences between serum bactericidal activities of the vaccinated and non-vaccinated groups. ** = P < 0.01; * = P < 0.05.
Fig 6.
Western blot analysis of envelope proteins from (a) S. typhimurium or (b) S. enteritidis probed with PBS, FKC and STG sera. Coomassie Brilliant Blue-stained SDS-PAGE (12%) gels containing envelope proteins of S. typhimurium (ST) or S. enteritidis (SE) are in the left side of (a) and (b) panels.
Fig 7.
Protection of STG against homologous and heterologous challenges.
Bacterial loads in liver, lung, spleen and kidney homogenates after (a-d) a homologous challenge with S. typhimurium or (e-h) a heterologous challenge with S. enteritidis. Results are expressed as means ± standard errors of the means. The asterisks indicate significant differences between the bacterial clearance of the vaccinated and non-vaccinated groups. ** = P < 0.01; * = P < 0.05.