title: Synthesis, characterization and immunological properties of Escherichia coli 0157:H7 lipopolysaccharide- diphtheria toxoid conjugate vaccine.
abstract: OBJECTIVE
  Escherichia coli O157:H7, an emerging pathogen, causes severe enteritis and the extraintestinal complication of hemolytic-uremic syndrome. The goal of this study was to evaluate the conjugate of E. coli O157: H7 lipopolysaccharide (LPS) with diphtheria toxoid (DT) as a candidate vaccine in mice model.
  
  
  METHODS
  LPS from E. coli O157:H7 was extracted by hot phenol method and then detoxified. Purified LPS was coupled to DT with adipic acid dihydrazide (ADH) as a spacer and 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDAC) as a linker. The coupling molar ratio of LPS to DT was 3:1. Clinical evaluation of E. coli O157:H7 LPS-DT conjugate was also performed.
  
  
  RESULTS
  The conjugate was devoid of endotoxin activity and indicated 0.125 U/ml of D-LPS. Mice immunization with D-LPS DT conjugate elicited fourfold higher IgG antibody in comparison to D-LPS. Also, in vivo protection of mice with conjugate provided high protection against the LD50 of E. coli O157:H7, which indicated a good correlation with the IgG titer.
  
  
  CONCLUSIONS
  Our results showed that the suggested vaccine composed of E. coli O157:H7 LPS and DT had a significant potential to protect against E. coli infections.
authors.affiliation: Young Researchers and Elite Club, Urmia Branch, Islamic Azad University, Urmia, IR Iran.
authors.forename: Shadi
authors.initials: S
authors.lastname: Rokhsartalab-Azar
authors.affiliation: Department of Microbiology, Zanjan Branch, Islamic Azad University, Zanjan, IR Iran.
authors.forename: Reza
authors.initials: R
authors.lastname: Shapouri
authors.affiliation: Biologic Research Center, Zanjan Branch, Islamic Azad University, Zanjan, IR Iran.
authors.forename: Mehdi
authors.initials: M
authors.lastname: Rahnema
authors.affiliation: Young Researchers Club, Bonab Branch, Islamic Azad University, Bonab, IR Iran.
authors.forename: Faezeh
authors.initials: F
authors.lastname: Najafzadeh
authors.affiliation: Department of Medical Biotechnology, School of Advanced Medical Sciences, Tabriz University of Medical Sciences, Tabriz, IR Iran.
authors.forename: Anvarsadat
authors.initials: A
authors.lastname: Kianmehr
keywords: Conjugate vaccine; Diphtheria toxoid (DT); Escherichia coli O157:H7; Lipopolysaccharide (LPS)