title: Mechanisms of protection against Clostridium difficile infection by the monoclonal antitoxin antibodies actoxumab and bezlotoxumab.
abstract: Clostridium difficile infection (CDI) represents the most prevalent cause of antibiotic-associated gastrointestinal infections in health care facilities in the developed world. Disease symptoms are caused by the two homologous exotoxins, TcdA and TcdB. Standard therapy for CDI involves administration of antibiotics that are associated with a high rate of disease recurrence, highlighting the need for novel treatment paradigms that target the toxins rather than the organism itself. A combination of human monoclonal antibodies, actoxumab and bezlotoxumab, directed against TcdA and TcdB, respectively, has been shown to decrease the rate of recurrence in patients treated with standard-of-care antibiotics. However, the exact mechanism of antibody-mediated protection is poorly understood. In this study, we show that the antitoxin antibodies are protective in multiple murine models of CDI, including systemic and local (gut) toxin challenge models, as well as primary and recurrent models of infection in mice. Systemically administered actoxumab-bezlotoxumab prevents both the damage to the gut wall and the inflammatory response, which are associated with C. difficile in these models, including in mice challenged with a strain of the hypervirulent ribotype 027. Furthermore, mutant antibodies (N297Q) that do not bind to Fcγ receptors provide a level of protection similar to that of wild-type antibodies, demonstrating that the mechanism of protection is through direct neutralization of the toxins and does not involve host effector functions. These data provide a mechanistic basis for the prevention of recurrent disease observed in CDI patients in clinical trials.
authors.affiliation: Department of Microbial Pathogenesis, University of Maryland Dental School, Baltimore, Maryland, USA.
authors.forename: Zhiyong
authors.initials: Z
authors.lastname: Yang
authors.affiliation: Department of Microbial Pathogenesis, University of Maryland Dental School, Baltimore, Maryland, USA.
authors.forename: Jeremy
authors.initials: J
authors.lastname: Ramsey
authors.affiliation: Department of Microbial Pathogenesis, University of Maryland Dental School, Baltimore, Maryland, USA.
authors.forename: Therwa
authors.initials: T
authors.lastname: Hamza
authors.affiliation: Department of Microbial Pathogenesis, University of Maryland Dental School, Baltimore, Maryland, USA.
authors.forename: Yongrong
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Microbial Pathogenesis, University of Maryland Dental School, Baltimore, Maryland, USA.
authors.forename: Shan
authors.initials: S
authors.lastname: Li
authors.affiliation: Department of Pathology and Laboratory Medicine, VAMHCS, University of Maryland School of Medicine, Baltimore, Maryland, USA.
authors.forename: Harris G
authors.initials: HG
authors.lastname: Yfantis
authors.affiliation: Department of Pathology and Laboratory Medicine, VAMHCS, University of Maryland School of Medicine, Baltimore, Maryland, USA.
authors.forename: Dong
authors.initials: D
authors.lastname: Lee
authors.affiliation: Merck & Co., Inc., Kenilworth, New Jersey, USA.
authors.forename: Lorraine D
authors.initials: LD
authors.lastname: Hernandez
authors.affiliation: Merck & Co., Inc., Palo Alto, California, USA.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Seghezzi
authors.affiliation: Merck & Co., Inc., Palo Alto, California, USA.
authors.forename: Jamie M
authors.initials: JM
authors.lastname: Furneisen
authors.affiliation: Merck & Co., Inc., Palo Alto, California, USA.
authors.forename: Nicole M
authors.initials: NM
authors.lastname: Davis
authors.affiliation: Merck & Co., Inc., Kenilworth, New Jersey, USA alex_therien@merck.com hfeng@umaryland.edu.
authors.forename: Alex G
authors.initials: AG
authors.lastname: Therien
authors.affiliation: Department of Microbial Pathogenesis, University of Maryland Dental School, Baltimore, Maryland, USA alex_therien@merck.com hfeng@umaryland.edu.
authors.forename: Hanping
authors.initials: H
authors.lastname: Feng
mesh_terms: D000818:Animals; D000907:Antibodies, Bacterial / Q000276:immunology* / Q000627:therapeutic use; D000911:Antibodies, Monoclonal / Q000235:genetics / Q000276:immunology* / Q000627:therapeutic use; D057134:Antibodies, Neutralizing / Q000276:immunology / Q000627:therapeutic use; D000992:Antitoxins / Q000276:immunology* / Q000627:therapeutic use; D001426:Bacterial Proteins / Q000276:immunology*; D001427:Bacterial Toxins / Q000276:immunology*; D002522:Chlorocebus aethiops; D016360:Clostridioides difficile / Q000276:immunology*; D004195:Disease Models, Animal; D004761:Enterocolitis, Pseudomembranous / Q000276:immunology / Q000517:prevention & control*; D004768:Enterotoxins / Q000276:immunology*; D051379:Mice; D008810:Mice, Inbred C57BL; D009154:Mutation; D017452:Receptors, IgG / Q000276:immunology; D012008:Recurrence; D014709:Vero Cells
chemical_list: D000907:Antibodies, Bacterial; D000911:Antibodies, Monoclonal; D057134:Antibodies, Neutralizing; D000992:Antitoxins; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D004768:Enterotoxins; D017452:Receptors, IgG; C041348:tcdA protein, Clostridium difficile; C031815:toxB protein, Clostridium difficile