Novel Clostridium difficile Anti-Toxin (TcdA and TcdB) Humanized Monoclonal Antibodies Demonstrate In Vitro Neutralization across a Broad Spectrum of Clinical Strains and In Vivo Potency in a Hamster Spore Challenge Model

PLoS One. 2016 Jun 23;11(6):e0157970. doi: 10.1371/journal.pone.0157970. eCollection 2016.


Clostridium difficile (C. difficile) infection (CDI) is the main cause of nosocomial antibiotic-associated colitis and increased incidence of community-associated diarrhea in industrialized countries. At present, the primary treatment of CDI is antibiotic administration, which is effective but often associated with recurrence, especially in the elderly. Pathogenic strains produce enterotoxin, toxin A (TcdA), and cytotoxin, toxin B (TcdB), which are necessary for C. difficile induced diarrhea and gut pathological changes. Administration of anti-toxin antibodies provides an alternative approach to treat CDI, and has shown promising results in preclinical and clinical studies. In the current study, several humanized anti-TcdA and anti-TcdB monoclonal antibodies were generated and their protective potency was characterized in a hamster infection model. The humanized anti-TcdA (CANmAbA4) and anti-TcdB (CANmAbB4 and CANmAbB1) antibodies showed broad spectrum in vitro neutralization of toxins from clinical strains and neutralization in a mouse toxin challenge model. Moreover, co-administration of humanized antibodies (CANmAbA4 and CANmAbB4 cocktail) provided a high level of protection in a dose dependent manner (85% versus 57% survival at day 22 for 50 mg/kg and 20 mg/kg doses, respectively) in a hamster gastrointestinal infection (GI) model. This study describes the protective effects conferred by novel neutralizing anti-toxin monoclonal antibodies against C. difficile toxins and their potential as therapeutic agents in treating CDI.

MeSH terms

  • Animals
  • Antibodies, Bacterial*
  • Antibodies, Monoclonal / immunology*
  • Antibodies, Monoclonal, Humanized*
  • Antibodies, Neutralizing*
  • Antitoxins / immunology*
  • Bacterial Proteins / immunology*
  • Bacterial Toxins / immunology*
  • Clostridioides difficile / immunology
  • Clostridioides difficile / isolation & purification
  • Clostridium Infections / immunology
  • Clostridium Infections / microbiology
  • Clostridium Infections / mortality
  • Cricetinae
  • Disease Models, Animal
  • Enterotoxins / immunology*
  • Humans
  • Immunoglobulin G / immunology
  • Mice
  • Neutralization Tests*
  • Spores, Bacterial


  • Antibodies, Bacterial
  • Antibodies, Monoclonal
  • Antibodies, Monoclonal, Humanized
  • Antibodies, Neutralizing
  • Antitoxins
  • Bacterial Proteins
  • Bacterial Toxins
  • Enterotoxins
  • Immunoglobulin G
  • tcdA protein, Clostridium difficile
  • toxB protein, Clostridium difficile

Grants and funding

The authors have no support or funding to report. All authors were employees of Cangene Corporation during the execution of these experiments and are now current employees of Emergent BioSolutions dba (doing business as) Cangene Corporation. Cangene Corporation provided support in the form of salaries for all authors, 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.