Development of a Novel Vaccine Containing Binary Toxin for the Prevention of Clostridium difficile Disease with Enhanced Efficacy against NAP1 Strains

PLoS One. 2017 Jan 26;12(1):e0170640. doi: 10.1371/journal.pone.0170640. eCollection 2017.

Abstract

Clostridium difficile infections (CDI) are a leading cause of nosocomial diarrhea in the developed world. The main virulence factors of the bacterium are the large clostridial toxins (LCTs), TcdA and TcdB, which are largely responsible for the symptoms of the disease. Recent outbreaks of CDI have been associated with the emergence of hypervirulent strains, such as NAP1/BI/027, many strains of which also produce a third toxin, binary toxin (CDTa and CDTb). These hypervirulent strains have been associated with increased morbidity and higher mortality. Here we present pre-clinical data describing a novel tetravalent vaccine composed of attenuated forms of TcdA, TcdB and binary toxin components CDTa and CDTb. We demonstrate, using the Syrian golden hamster model of CDI, that the inclusion of binary toxin components CDTa and CDTb significantly improves the efficacy of the vaccine against challenge with NAP1 strains in comparison to vaccines containing only TcdA and TcdB antigens, while providing comparable efficacy against challenge with the prototypic, non-epidemic strain VPI10463. This combination vaccine elicits high neutralizing antibody titers against TcdA, TcdB and binary toxin in both hamsters and rhesus macaques. Finally we present data that binary toxin alone can act as a virulence factor in animal models. Taken together, these data strongly support the inclusion of binary toxin in a vaccine against CDI to provide enhanced protection from epidemic strains of C. difficile.

MeSH terms

  • Animals
  • Bacterial Toxins / genetics*
  • Bacterial Toxins / toxicity
  • Bacterial Vaccines / administration & dosage*
  • Bacterial Vaccines / genetics
  • Clostridioides difficile / drug effects
  • Clostridioides difficile / pathogenicity
  • Clostridium Infections / genetics
  • Clostridium Infections / microbiology
  • Clostridium Infections / prevention & control*
  • Cricetinae
  • Disease Models, Animal
  • Enterotoxins / genetics*
  • Enterotoxins / toxicity
  • Humans
  • Macaca mulatta / microbiology
  • Mesocricetus / microbiology

Substances

  • Bacterial Toxins
  • Bacterial Vaccines
  • Enterotoxins
  • tcdA protein, Clostridium difficile

Grants and funding

The research was fully funded by Merck and Co., Inc. The funder provided support in the form of salaries for authors SS, SW, JD, JX, RRR, MH, RX, BW, CL, AK, SCW, SC, SV, MPG, AG, JS, ES, DST, JLB, and JHH, but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific roles of these authors are articulated in the ‘author contributions’ section.