Chemically induced Salmonella enteritidis ghosts as a novel vaccine candidate against virulent challenge in a rat model

Salmonella enteritidis ghosts (SEGs), non-living empty bacterial cell envelopes were generated by using the minimum inhibitory concentration (MIC) of sodium hydroxide (NaOH) and investigated as a vaccine candidate in rats. To determine the immunogenicity and protective efficacy of SEG vaccine, rats were divided into four groups: group A (non-vaccinated control), group B (orally vaccinated), group C (intramuscularly vaccinated) and group D (intramuscularly vaccinated with complete Freund's adjuvant). Vaccination of rats with SEGs induced significant immune responses before and after virulent challenge. Rats vaccinated with SEGs showed significant increases in serum IgG antibodies after challenging with virulent S. enteritidis on week 8 and week 10 (P<0.01). During the vaccination period, groups B, C and D showed significantly higher serum bactericidal activity (SBA) compared to group A (P<0.01). Most importantly, bacterial loads in vaccinated groups were significantly lower than in the non-vaccinated group (P<0.01). In conclusion, these results show that the chemically induced SEGs as a vaccine candidate against virulent challenge.