A chimeric toxin vaccine protects against primary and recurrent Clostridium difficile infection

Infect Immun. 2012 Aug;80(8):2678-88. doi: 10.1128/IAI.00215-12. Epub 2012 May 21.

Abstract

The global emergence of Clostridium difficile infection (CDI) has contributed to the recent surge in severe antibiotic-associated diarrhea and colonic inflammation. C. difficile produces two homologous glucosylating exotoxins, TcdA and TcdB, both of which are pathogenic and require neutralization to prevent disease occurrence. However, because of their large size and complex multifunctional domain structures, it has been a challenge to produce native recombinant toxins that may serve as vaccine candidates. Here, we describe a novel chimeric toxin vaccine that retains major neutralizing epitopes from both toxins and confers complete protection against primary and recurrent CDI in mice. Using a nonpathogenic Bacillus megaterium expression system, we generated glucosyltransferase-deficient holotoxins and demonstrated their loss of toxicity. The atoxic holotoxins induced potent antitoxin neutralizing antibodies showing little cross-immunogenicity or protection between TcdA and TcdB. To facilitate simultaneous protection against both toxins, we generated an active clostridial toxin chimera by switching the receptor binding domain of TcdB with that of TcdA. The toxin chimera was fully cytotoxic and showed potent proinflammatory activities. This toxicity was essentially abolished in a glucosyltransferase-deficient toxin chimera, cTxAB. Parenteral immunization of mice or hamsters with cTxAB induced rapid and potent neutralizing antibodies against both toxins. Complete and long-lasting disease protection was conferred by cTxAB vaccinations against both laboratory and hypervirulent C. difficile strains. Finally, prophylactic cTxAB vaccination prevented spore-induced disease relapse, which constitutes one of the most significant clinical issues in CDI. Thus, the rational design of recombinant chimeric toxins provides a novel approach for protecting individuals at high risk of developing CDI.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antibodies, Bacterial / biosynthesis
  • Antibodies, Bacterial / blood
  • Antibodies, Neutralizing / biosynthesis
  • Antibodies, Neutralizing / blood
  • Bacterial Proteins / immunology
  • Bacterial Toxins / genetics
  • Bacterial Toxins / immunology*
  • Bacterial Toxins / metabolism
  • Bacterial Vaccines / immunology*
  • Clostridium difficile / immunology*
  • Cricetinae
  • Enterocolitis, Pseudomembranous / prevention & control*
  • Enterotoxins / immunology
  • Immunotoxins / immunology*
  • Mice
  • Mice, Inbred BALB C
  • Mice, Inbred C57BL
  • Neutralization Tests
  • Vaccines, Attenuated / immunology
  • Vaccines, Synthetic / immunology

Substances

  • Antibodies, Bacterial
  • Antibodies, Neutralizing
  • Bacterial Proteins
  • Bacterial Toxins
  • Bacterial Vaccines
  • Enterotoxins
  • Immunotoxins
  • Vaccines, Attenuated
  • Vaccines, Synthetic
  • tcdA protein, Clostridium difficile
  • toxB protein, Clostridium difficile