title: Immunogenicity of a Salmonella typhimurium aroA aroD vaccine expressing a nontoxic domain of Clostridium difficile toxin A.
abstract: The C-terminal repeat domain of Clostridium difficile toxin A harbors toxin-neutralizing epitopes and is considered to be a candidate component of a vaccine against C. difficile-associated disease (CDAD). Fourteen of the 38 C-terminal toxin A repeats (14CDTA) were cloned into pTECH-1 in frame with the immunogenic fragment C of tetanus toxin (TETC) to generate plasmid p56TETC. Expression of the TETC-14CDTA fusion protein was driven from the anaerobically inducible nirB promoter within attenuated Salmonella typhimurium BRD509 (aroA aroD). The TETC-14CDTA fusion protein was purified and shown to bind to known toxin A receptors found on the surface of rabbit erythrocytes. Intranasal (i.n.) and intragastric (i.g.) immunization with 10(7) and 10(10) CFU, respectively, of BRD509(p56TETC) generated significant (P < 0.05) anti-toxin A serum responses after a single dose. Antibody titers were elevated following a boosting dose with either live vaccine or a subcutaneous injection of 0.5 microgram of purified 14CDTA protein. Importantly, serum from mice immunized with BRD509(p56TETC) neutralized toxin A cytotoxicity. Both i.n. and i.g. immunizations also generated toxin A-specific immunoglobulin A on the pulmonary and intestinal mucosa, respectively. Intranasal vaccination induced consistently higher serum and mucosal anti-toxin A antibody responses. Significant anti-tetanus toxoid serum and mucosal antibodies were also generated by both immunization routes. The availability of live attenuated Salmonella typhi for human use may allow the development of a multivalent mucosal vaccine against CDAD, tetanus, and typhoid.
authors.affiliation: Microbial Pathogenicity Research Group, Department of Microbiology, St. Bartholomew's and the Royal London School of Medicine and Dentistry, London EC1A 7BE, United Kingdom.
authors.forename: S J
authors.initials: SJ
authors.lastname: Ward
authors.forename: G
authors.initials: G
authors.lastname: Douce
authors.forename: D
authors.initials: D
authors.lastname: Figueiredo
authors.forename: G
authors.initials: G
authors.lastname: Dougan
authors.forename: B W
authors.initials: BW
authors.lastname: Wren
mesh_terms: D000281:Administration, Intranasal; D000818:Animals; D000907:Antibodies, Bacterial / Q000096:biosynthesis / Q000097:blood; D001427:Bacterial Toxins; D001428:Bacterial Vaccines / Q000008:administration & dosage / Q000235:genetics / Q000276:immunology*; D001483:Base Sequence; D016360:Clostridioides difficile / Q000235:genetics / Q000276:immunology*; D017931:DNA Primers / Q000235:genetics; D004761:Enterocolitis, Pseudomembranous / Q000276:immunology / Q000517:prevention & control; D004768:Enterotoxins / Q000235:genetics / Q000276:immunology*; D005260:Female; D006801:Humans; D006836:Hydro-Lyases / Q000235:genetics / Q000276:immunology*; D018928:Immunity, Mucosal; D007114:Immunization; D007070:Immunoglobulin A / Q000096:biosynthesis; D051379:Mice; D008807:Mice, Inbred BALB C; D011817:Rabbits; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000276:immunology; D022562:Salmonella Vaccines; D012486:Salmonella typhimurium / Q000235:genetics / Q000276:immunology*; D014436:Typhoid-Paratyphoid Vaccines; D017778:Vaccines, Combined / Q000008:administration & dosage / Q000235:genetics / Q000276:immunology; D014614:Vaccines, Synthetic / Q000008:administration & dosage / Q000235:genetics / Q000276:immunology*
chemical_list: D000907:Antibodies, Bacterial; D001427:Bacterial Toxins; D001428:Bacterial Vaccines; D017931:DNA Primers; D004768:Enterotoxins; D007070:Immunoglobulin A; D011993:Recombinant Fusion Proteins; D022562:Salmonella Vaccines; D014436:Typhoid-Paratyphoid Vaccines; D017778:Vaccines, Combined; D014614:Vaccines, Synthetic; C087350:aroA Salmonella vaccine; C041348:tcdA protein, Clostridium difficile; D006836:Hydro-Lyases; C020000:3-dehydroquinate dehydratase