title: Improved cell surface display of Salmonella enterica serovar Enteritidis antigens in Escherichia coli.
abstract: BACKGROUND
  Salmonella enterica serovar Enteritidis (SE) is one of the most potent pathogenic Salmonella serotypes causing food-borne diseases in humans. We have previously reported the use of the β-autotransporter AIDA-I to express the Salmonella flagellar protein H:gm and the SE serotype-specific fimbrial protein SefA at the surface of E. coli as live bacterial vaccine vehicles. While SefA was successfully displayed at the cell surface, virtually no full-length H:gm was exposed to the medium due to extensive proteolytic cleavage of the N-terminal region. In the present study, we addressed this issue by expressing a truncated H:gm variant (H:gmd) covering only the serotype-specific central region. This protein was also expressed in fusion to SefA (H:gmdSefA) to understand if the excellent translocation properties of SefA could be used to enhance the secretion and immunogenicity.
  
  
  RESULTS
  H:gmd and H:gmdSefA were both successfully translocated to the E. coli outer membrane as full-length proteins using the AIDA-I system. Whole-cell flow cytometric analysis confirmed that both antigens were displayed and accessible from the extracellular environment. In contrast to H:gm, the H:gmd protein was not only expressed as full-length protein, but it also seemed to promote the display of the protein fusion H:gmdSefA. Moreover, the epitopes appeared to be recognized by HT-29 intestinal cells, as measured by induction of the pro-inflammatory interleukin 8.
  
  
  CONCLUSIONS
  We believe this study to be an important step towards a live bacterial vaccine against Salmonella due to the central role of the flagellar antigen H:gm and SefA in Salmonella infections and the corresponding immune responses against Salmonella.
authors.affiliation: Royal Institute of Technology (KTH), Division of Industrial Biotechnology, AlbaNova University Center, SE 10691, Stockholm, Sweden. margu@kth.se.
authors.forename: Martin
authors.initials: M
authors.lastname: Gustavsson
authors.affiliation: Institute of Biotechnology, Vietnam Academy of Science and Technology, 18-Hoang Quoc Viet, Cau Giay, Ha Noi, Vietnam. dohuyen@ibt.ac.vn.
authors.forename: Thi-Huyen
authors.initials: TH
authors.lastname: Do
authors.affiliation: Department of Microbiology, Tumor and Cell Biology, Division of Clinical Microbiology, Karolinska Institute and Karolinska University Hospital, Stockholm, Sweden. petra.luthje@karolinska.se.
authors.forename: Petra
authors.initials: P
authors.lastname: Lüthje
authors.affiliation: Institute of Biotechnology, Vietnam Academy of Science and Technology, 18-Hoang Quoc Viet, Cau Giay, Ha Noi, Vietnam. tranngoctan2003@yahoo.com.
authors.forename: Ngoc Tan
authors.initials: NT
authors.lastname: Tran
authors.affiliation: Department of Microbiology, Tumor and Cell Biology, Division of Clinical Microbiology, Karolinska Institute and Karolinska University Hospital, Stockholm, Sweden. Annelie.Brauner@ki.se.
authors.forename: Annelie
authors.initials: A
authors.lastname: Brauner
authors.affiliation: Royal Institute of Technology (KTH), Division of Industrial Biotechnology, AlbaNova University Center, SE 10691, Stockholm, Sweden. patrik@biotech.kth.se.
authors.forename: Patrik
authors.initials: P
authors.lastname: Samuelson
authors.affiliation: Institute of Biotechnology, Vietnam Academy of Science and Technology, 18-Hoang Quoc Viet, Cau Giay, Ha Noi, Vietnam. tnhai@ibt.ac.vn.
authors.forename: Nam Hai
authors.initials: NH
authors.lastname: Truong
authors.affiliation: Royal Institute of Technology (KTH), Division of Industrial Biotechnology, AlbaNova University Center, SE 10691, Stockholm, Sweden. gen@kth.se.
authors.forename: Gen
authors.initials: G
authors.lastname: Larsson
mesh_terms: D001428:Bacterial Vaccines / Q000276:immunology*; D002462:Cell Membrane / Q000378:metabolism*; D004926:Escherichia coli / Q000378:metabolism*; D006801:Humans; D012477:Salmonella enteritidis / Q000378:metabolism*
chemical_list: D001428:Bacterial Vaccines