Multi-Immunogenic Outer Membrane Vesicles Derived from a MsbB-Deficient Salmonella enterica Serovar Typhimurium Mutant

摘要

To develop low endotoxic and multi-immunogenic outermembrane vesicles (OMVs), a deletion mutant of themsbB gene in Salmonella enterica serovar Typhimurium(S. Typhimurium) was used as a source of low endotoxicOMV, and an expression vector of the canine parvovirus(CPV) VP2 epitope fused to the bacterial OmpA proteinwas constructed and transformed into the SalmonellaAmsbB mutant. In a lethality test, BALB/c mice injectedintraperitoneally with the Salmonella AmsbB mutantsurvived for 7 days, whereas mice injected intraperitoneallywith the wild type survived for 3 days. Moreover, all miceinoculated orally with the AmsbB mutant survived for 30days, but 80% of mice inoculated orally with the wild typesurvived. The OmpA::CPV VP2 epitope fusion proteinwas expressed successfully and associated with the outermembrane and OMV fractions from the mutant S.Typhimurium transformed with the fusion protein-expressingvector. In immunogenicity tests, sera obtained from themice immunized with either the Salmonella msbB mutantor its OMVs containing the OmpA::CPV VP2 epitope showedbactericidal activities against wild-type S. Typhimuriumand contained specific antibodies to the CPV VP2 epitope.In the hemagglutination inhibition (HI) assay as ameasurement of CPV-neutralizing activity in the immunesera, there was an 8-fold increase of HI titer in the OMV-immunized group compared with the control. These resultssuggested that the CPV-neutralizing antibody responsewas raised by immunization with OMV containing theOmpA::CPV VP2 epitope, as well as the protective immuneresponse against S. Typhimurium in BALB/c mice.