title: Immunisation of mares with binding domains of toxins A and B of Clostridium difficile elicits serum and colostral antibodies that block toxin binding.
abstract: BACKGROUND
  Enterocolitis caused by Clostridium difficile (C. difficile) is a serious, sometimes fatal, disease of neonatal foals and older horses. Toxins A and B (TcdA and B) produced by C. difficile are important virulence factors. Immunisation of mares with receptor binding domains of toxins may prevent or reduce the severity of C. difficile colitis in foals.
  
  
  OBJECTIVE
  To determine whether antibodies generated in the pregnant mare to the binding regions of TcdA and B will neutralise TcdA and B toxicity.
  
  
  METHODS
  Sequences encoding the binding domains of each toxin were isolated by PCR amplification from C. difficile JF09, a foal isolate, and cloned and expressed into pET15b. Thirteen mares were immunised twice 2 weeks apart with 200 μg of each recombinant protein with Quil A 2 months prior to foaling. Antibodies were assayed in the sera and colostrum by ELISA and for ability to block the cytopathic activity of each of toxin for equine endothelial cells.
  
  
  RESULTS
  All mares produced strong serum antibody responses to the binding domain of each toxin. A high level of toxin-specific antibodies was also detected in colostrum and in most foal sera 2 days after suckling. Diluted sera and colostrum premixed with either TcdA or B had no effect on the morphology of equine endothelial cells. Application of the same concentration of toxins alone or premixed with nonimmune mare/foal serum or colostrum led to an unambiguous cytopathic effect that ranged from complete degradation to varying degrees of cell rounding.
  
  
  CONCLUSIONS
  Immunisation of pregnant mares with recombinant binding domains of TcdA and B of C. difficile resulted in the production of specific antibodies in serum and colostrum that blocked the cytopathic activity of toxins.
  
  
  CONCLUSIONS
  Results of studies support the feasibility of a prepartum vaccine against C. difficile enterocolitis in foals.
authors.affiliation: Gluck Equine Research Center, University of Kentucky, USA.
authors.forename: S
authors.initials: S
authors.lastname: Artiushin
authors.forename: J F
authors.initials: JF
authors.lastname: Timoney
authors.forename: M
authors.initials: M
authors.lastname: Fettinger
authors.forename: L
authors.initials: L
authors.lastname: Fallon
authors.forename: R
authors.initials: R
authors.lastname: Rathgeber
mesh_terms: D000818:Animals; D000907:Antibodies, Bacterial / Q000737:chemistry* / Q000378:metabolism; D001427:Bacterial Toxins / Q000276:immunology*; D016360:Clostridioides difficile / Q000378:metabolism*; D003126:Colostrum / Q000737:chemistry*; D004761:Enterocolitis, Pseudomembranous / Q000382:microbiology / Q000517:prevention & control / Q000662:veterinary; D004768:Enterotoxins / Q000276:immunology*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D005260:Female; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology; D006734:Horse Diseases / Q000517:prevention & control*; D006736:Horses; D018832:Molecular Chaperones; D011247:Pregnancy; D011485:Protein Binding; D017434:Protein Structure, Tertiary
chemical_list: D000907:Antibodies, Bacterial; D001427:Bacterial Toxins; C488583:Clostridium difficile lethal toxin B; D004768:Enterotoxins; D018832:Molecular Chaperones; C041348:tcdA protein, Clostridium difficile