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Infection and Immunity, May 1999, p. 2145-2152, Vol. 67, No. 5
Microbial Pathogenicity Research Group,
Department of Microbiology, St. Bartholomew's and the Royal London
School of Medicine and Dentistry, London EC1A
7BE,1 and Department of Biochemistry,
Imperial College of Science, Technology and Medicine, London SW7
2AY,2 United Kingdom
Received 6 August 1998/Returned for modification 1 October
1998/Accepted 3 February 1999
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 107 and 1010 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 µg 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.
0019-9567/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Immunogenicity of a Salmonella typhimurium
aroA aroD Vaccine Expressing a Nontoxic Domain of
Clostridium difficile Toxin A



*
Corresponding author. Mailing address: Microbial
Pathogenicity Research Group, Department of Microbiology, St.
Bartholomew's and the Royal London School of Medicine and Dentistry,
West Smithfield, London EC1A 7BE, United Kingdom. Phone: 0171 6018411. Fax: 0171 6018409. E-mail: b.w.wren{at}mds.qmw.ac.uk.
Present address: Medeva Development, Vaccine Research Unit,
Department of Biochemistry, Imperial College of Science, Technology and
Medicine, London SW7 2AY, United Kingdom.
Present address: Laboratorio Especial de Microbiologia, Instituto
Butantan, São Paulo, SP 05503-900, Brazil.
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