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

Susan Secore,Catherine Lancaster,Richard R Rustandi,Melanie Horton,Salvatore Vitelli,David S Thiriot,Marie-Pierre Gentile,Julie Doughtry,Matt Miezeiewski,Erica Strable,Jon H Heinrichs,Jean-Luc Bodmer,Sianny Christanti,Su Wang,Jinfu Xie,Adam Kristopeit,Bei Wang,Sheng‐Ching Wang ,Aaron R Goerke ,Julie M Skinner ,Rachel F Xoconostle

doi:10.1371/journal.pone.0170640

Susan Secore, Catherine Lancaster + Show 19 more

Open Access

https://doi.org/10.1371/journal.pone.0170640

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Journal: PloS one	Publication Date: Jan 26, 2017
Citations: 33	License type: CC BY 4.0

Affiliation: United States Military Academy, Eurofins (United States)

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.

Highlights

Clostridium difficile infections are the most widely recognized cause of hospital acquired infectious diarrhea [1]
The toxins were molecularly detoxified by introducing a series of four mutations in their glucosyltransferase domains (GTD)
The immune-reactive fragments corresponded in size to the toxins without the GTD suggesting that auto-proteolytic processing by the cysteine-protease domain (CPD) was occurring

Summary

Introduction

Clostridium difficile infections are the most widely recognized cause of hospital acquired infectious diarrhea [1]. A recent bulletin from the Centers for Disease Control and Prevention (CDC) (http://www.cdc.gov/drugresistance/ threat-report-2013) listed the current threat level from C. difficile as urgent. According to this CDC bulletin, there are 250,000 infections each year caused by this bacterium that require hospitalization or affect already hospitalized patients resulting in 14,000 deaths and at least $1 billion in excess medical costs each year. The organism is associated with persistent diarrhea primarily in individuals of advanced age with pre-existing co-morbidities, during prolonged hospitalization, and, most importantly, with the use of broad-spectrum antibiotics. Because the organism can form spores which are impervious to antibiotics, there is a significant risk of recurrence (about 30%)

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