title: Towards an attenuated enterohemorrhagic Escherichia coli O157:H7 vaccine characterized by a deleted ler gene and containing apathogenic Shiga toxins.
abstract: The aim of this study was to develop a candidate vaccine against enterohemorrhagic Escherichia coli O157:H7. A ler deletion mutant derived from wild-type EHEC O157:H7 86-24 was constructed by use of suicide vector pCVD442. The bacteriophage encoding Shiga toxin (Stx) was excised by serial passage to produce a ler/stx deletion mutant, F25. Stx1 and Stx2 mutants were constructed by site-directed mutagenesis within the active center and membrane-spanning region of the toxin A subunit. Mutants stx1 and stx2 were then introduced into F25 to construct live attenuated candidate vaccine F105. The cytotoxicity of F25 was inactivated and that of F105 was significantly reduced in comparison with wild-type E. coli strain EDL933. Mice injected with candidate vaccine strains F25 and F105 gained weight and showed no clinical signs of disease. F25 and F105 reduced the colonization of wild-type O157:H7 in mouse intestine. Immunized pregnant mice were able to protect their suckling newborns from intragastric challenge with wild-type O157:H7. Immunized mice were protected against infection with wild-type O157:H7 and exhibited normal weight gain. Such attenuated vaccine strains may therefore have potential use as oral vaccines against O157:H7.
authors.affiliation: Institute of Veterinary Science, The Academy of Military Medical Sciences, 1068 Qinglong Road, Changchun 130062, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Liu
authors.forename: Yang
authors.initials: Y
authors.lastname: Sun
authors.forename: Shuzhang
authors.initials: S
authors.lastname: Feng
authors.forename: Lingwei
authors.initials: L
authors.lastname: Zhu
authors.forename: Xuejun
authors.initials: X
authors.lastname: Guo
authors.forename: Chong
authors.initials: C
authors.lastname: Qi
mesh_terms: D000818:Animals; D004927:Escherichia coli Infections / Q000517:prevention & control*; D019453:Escherichia coli O157 / Q000235:genetics / Q000276:immunology*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000276:immunology; D022361:Escherichia coli Vaccines / Q000096:biosynthesis / Q000235:genetics* / Q000276:immunology; D005260:Female; D051379:Mice; D008807:Mice, Inbred BALB C; D016297:Mutagenesis, Site-Directed; D011247:Pregnancy; D017384:Sequence Deletion; D022603:Shiga Toxins / Q000235:genetics* / Q000276:immunology; D015534:Trans-Activators / Q000235:genetics / Q000276:immunology; D014613:Vaccines, Attenuated / Q000096:biosynthesis / Q000235:genetics / Q000276:immunology
chemical_list: D029968:Escherichia coli Proteins; D022361:Escherichia coli Vaccines; C465556:Ler protein, E coli; D022603:Shiga Toxins; D015534:Trans-Activators; D014613:Vaccines, Attenuated