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Infect Immun. 2014 Oct;82(10):4080-91. doi: 10.1128/IAI.01950-14. Epub 2014 Jul 14.

An optimized, synthetic DNA vaccine encoding the toxin A and toxin B receptor binding domains of Clostridium difficile induces protective antibody responses in vivo.

Author information

1
Department of Microbiology and Immunology, Drexel University College of Medicine, Philadelphia, Pennsylvania, USA.
2
Division of Infectious Diseases and HIV Medicine, Department of Medicine, Drexel University College of Medicine, Philadelphia, Pennsylvania, USA.
3
Inovio Pharmaceuticals, Blue Bell, Pennsylvania, USA.
4
Department of Biochemistry, Drexel University College of Medicine, Philadelphia, Pennsylvania, USA.
5
Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts, USA.
6
Tulane National Primate Research Center and Department of Tropical Medicine, School of Public Health and Tropical Medicine, Tulane University, Covington, Louisiana, USA.
7
School of Public Health, Drexel University College of Medicine, Philadelphia, Pennsylvania, USA.
8
Department of Pathology and Laboratory Medicine, University of Pennsylvania, School of Medicine, Philadelphia, Pennsylvania, USA.
9
Department of Microbiology and Immunology, Drexel University College of Medicine, Philadelphia, Pennsylvania, USA Division of Infectious Diseases and HIV Medicine, Department of Medicine, Drexel University College of Medicine, Philadelphia, Pennsylvania, USA mkutzler@drexelmed.edu.

Abstract

Clostridium difficile-associated disease (CDAD) constitutes a large majority of nosocomial diarrhea cases in industrialized nations and is mediated by the effects of two secreted toxins, toxin A (TcdA) and toxin B (TcdB). Patients who develop strong antitoxin antibody responses can clear C. difficile infection and remain disease free. Key toxin-neutralizing epitopes have been found within the carboxy-terminal receptor binding domains (RBDs) of TcdA and TcdB, which has generated interest in developing the RBD as a viable vaccine target. While numerous platforms have been studied, very little data describes the potential of DNA vaccination against CDAD. Therefore, we created highly optimized plasmids encoding the RBDs from TcdA and TcdB in which any putative N-linked glycosylation sites were altered. Mice and nonhuman primates were immunized intramuscularly, followed by in vivo electroporation, and in these animal models, vaccination induced significant levels of both anti-RBD antibodies (blood and stool) and RBD-specific antibody-secreting cells. Further characterization revealed that sera from immunized mice and nonhuman primates could detect RBD protein from transfected cells, as well as neutralize purified toxins in an in vitro cytotoxicity assay. Mice that were immunized with plasmids or given nonhuman-primate sera were protected from a lethal challenge with purified TcdA and/or TcdB. Moreover, immunized mice were significantly protected when challenged with C. difficile spores from homologous (VPI 10463) and heterologous, epidemic (UK1) strains. These data demonstrate the robust immunogenicity and efficacy of a TcdA/B RBD-based DNA vaccine in preclinical models of acute toxin-associated and intragastric, spore-induced colonic disease.

PMID:
25024365
PMCID:
PMC4187890
DOI:
10.1128/IAI.01950-14
[Indexed for MEDLINE]
Free PMC Article

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