title: A novel Salmonella strain inactivated by a regulated autolysis system and expressing the B subunit of Shiga toxin 2e efficiently elicits immune responses and confers protection against virulent Stx2e-producing Escherichia coli.
abstract: BACKGROUND
  Salmonella Typhimurium (S. Typhimurium) inactivated by a regulated autolysis system was genetically engineered to express the homo-pentameric B subunit of Shiga toxin 2e (Stx2eB) on its surface. To prepare a strain able to yield autolyzed Salmonella bearing Stx2eB, the plasmid pJHL184 harboring stx2eBgene was transformed into the attenuated S. Typhimurium strain, JOL1454. Stx2eB subcloned into the antigen delivery cassette of the plasmid was expressed as fusion protein with the outer membrane protein RESULTS: The expression of Stx2eB fused to the signal peptide in JOL1454 was validated by immunoblot analysis. To determine the immunogenicity of JOL1454, female BALB/c mice were intramuscularly injected with 1 × 108CFU of the inactivated cells at weeks 0 and 2. Significantly elevated levels of IgG and IgA specific to Stx2eB was observed at weeks 4 and 6 post-immunization (PI) (P <0.05). Proportion of CD3+CD4+T lymphocyte subpopulation was also significantly augmented in in vivo stimulated splenocytes relative to that in the control group. The increased titers of IgG1 and IgG2a, and of immunomodulatory cytokines indicated that the immunization elicited Th1 and Th2 immune responses. Further, immunomodulatory cytokine genes (IL-6, IL-17A, IL21 and JOL1454) efficiently upregulated in naïve porcine peripheral blood mononuclear cells (PBMCs) pulsed with JOL1454. At week 6 PI, following the challenge with a virulent Stx2e-producing Escherichia coli in the mice, all immunized mice survived whereas approximately 30% of the mice in the control group died.
  
  
  CONCLUSIONS
  JOL1454 provided superior immunogenicity and effective protection against challenge with a sublethal dose, which demonstrates its potential as a candidate vaccine against edema disease.
authors.affiliation: College of Veterinary Medicine, Chonbuk National University, Iksan campus, Gobong-ro 79, Iksan, 54596, Republic of Korea.
authors.forename: Gayeon
authors.initials: G
authors.lastname: Won
authors.affiliation: College of Veterinary Medicine, Chonbuk National University, Iksan campus, Gobong-ro 79, Iksan, 54596, Republic of Korea.
authors.forename: Tae Hoon
authors.initials: TH
authors.lastname: Kim
authors.affiliation: College of Veterinary Medicine, Chonbuk National University, Iksan campus, Gobong-ro 79, Iksan, 54596, Republic of Korea. johnhlee@jbnu.ac.kr.
authors.forename: John Hwa
authors.initials: JH
authors.lastname: Lee
mesh_terms: D000818:Animals; D049109:Cell Proliferation; D016207:Cytokines / Q000096:biosynthesis; D004926:Escherichia coli / Q000276:immunology*; D004927:Escherichia coli Infections / Q000276:immunology / Q000517:prevention & control*; D022361:Escherichia coli Vaccines / Q000235:genetics / Q000276:immunology*; D005260:Female; D007111:Immunity, Cellular; D056724:Immunity, Humoral; D051379:Mice; D008807:Mice, Inbred BALB C; D012486:Salmonella typhimurium / Q000235:genetics / Q000276:immunology*; D022641:Shiga Toxin 2 / Q000235:genetics / Q000276:immunology*; D013552:Swine; D013601:T-Lymphocytes / Q000276:immunology; D014614:Vaccines, Synthetic / Q000276:immunology
chemical_list: D016207:Cytokines; D022361:Escherichia coli Vaccines; D022641:Shiga Toxin 2; D014614:Vaccines, Synthetic
keywords: Bacterial ghost; Edema disease; Salmonella typhimurium; Shiga toxin