title: Effect of in situ expression of human interleukin-6 on antibody responses against Salmonella typhimurium antigens.
abstract: In an attempt to trigger increased mucosal secretory immune responses against bacterial surface antigens, we constructed an optimized human interleukin (hIL)-6-secreting Salmonella typhimurium strain (X4064(pCH1A+pYL3E)), utilizing the hemolysin (Hly) exporter for secretory delivery of a functional hIL-6-hemolysin fusion protein (hIL-6-HlyA(s)). Through stable introduction of a second hIL-6-HlyA(s) expression plasmid (pYL3E) in the previously described X4064(pCH1A) strain, hIL-6-HlyA(s) secretion efficiencies were increased by at least 10-fold. As pCH1A in the parental strain, pYL3E was stable in vitro in the absence of antibiotic selection and in vivo neither did plasmids interfere in their stabilities. Increased hIL-6-HlyA(s) expression did not adversely interfere with bacterial growth. Comparative immunization experiments in mice with oral application of the different hIL-6-secreting strains revealed that increased in situ hIL-6-production influenced systemic antibody responses against Salmonella antigens but had no marked effect on mucosal responses. In mice immunized with X4064(pCH1A+pYL3E) significantly higher sera IgG and IgA titers for lipopolysaccharide (LPS) were found compared to mice immunized with X4064(pCH1A) and a hIL-6-negative control strain. Higher sera antibody titers were accompanied by increased numbers of IgG- and IgA-specific antibody-secreting cells in spleens and Peyer's patches, respectively. These data suggest that systemic antibody responses against Salmonella LPS are largely effected by IL-6 and, moreover, the amount and the cellular location of recombinantly expressed IL-6 appears to be crucial for enhancement of immune responses.
authors.affiliation: Chirurgische Universitätsklinik, Chirurgische Forschung, Freiburg i. Br., Germany.
authors.forename: Yuanyi
authors.initials: Y
authors.lastname: Li
authors.forename: Kerstin
authors.initials: K
authors.lastname: Reichenstein
authors.forename: Ramona
authors.initials: R
authors.lastname: Ullrich
authors.forename: Tobias
authors.initials: T
authors.lastname: Danner
authors.forename: Bernd Ulrich
authors.initials: BU
authors.lastname: von Specht
authors.forename: Heinz P
authors.initials: HP
authors.lastname: Hahn
mesh_terms: D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood*; D000942:Antigens, Bacterial / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D006460:Hemolysin Proteins / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D006801:Humans; D018928:Immunity, Mucosal; D015850:Interleukin-6 / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D008070:Lipopolysaccharides / Q000276:immunology; D051379:Mice; D010581:Peyer's Patches / Q000276:immunology; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D012481:Salmonella Infections, Animal / Q000276:immunology; D022562:Salmonella Vaccines / Q000008:administration & dosage / Q000235:genetics / Q000276:immunology*; D012486:Salmonella typhimurium / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D013154:Spleen / Q000276:immunology
chemical_list: D000907:Antibodies, Bacterial; D000942:Antigens, Bacterial; D006460:Hemolysin Proteins; D015850:Interleukin-6; D008070:Lipopolysaccharides; D011993:Recombinant Fusion Proteins; D022562:Salmonella Vaccines