Novel Chimeric Protein Vaccines Against Clostridium difficile Infection.

Shaohui Wang,Ciaran P Kelly,Xingmin Sun,Yuanguo Wang,Ying Cai

doi:10.3389/fimmu.2018.02440

Abstract

Clostridium difficile infection (CDI) is the leading cause of world-wide nosocomial acquired diarrhea in adults. Active vaccination is generally accepted as a logical and cost-effective approach to prevent CDI. In this paper, we have generated two novel chimeric proteins; one designated Tcd169, comprised of the glucosyltransferase domain (GT), the cysteine proteinase domain (CPD), and receptor binding domain (RBD) of TcdB, and the RBD of TcdA; the other designated Tcd169FI, which contains Salmonella typhimurium flagellin (sFliC) and Tcd169. Both proteins were expressed in and purified from Bacillus megaterium. Point mutations were made in the GT (W102A, D288N) and CPD (C698) of TcdB to ensure that Tcd169 and Tcd169FI were atoxic. Immunization with Tcd169 or Tcd169Fl induced protective immunity against TcdA/TcdB challenge through intraperitoneal injection, also provided mice full protection against infection with a hyper-virulent C. difficile strain (BI/NAP1/027). In addition, inclusion of sFlic in the fusion protein (Tcd169Fl) enhanced its protective immunity against toxin challenge, reduced C. difficile numbers in feces from Tcd169Fl-immunized mice infected C. difficile. Our data show that Tcd169 and Tcd169FI fusion proteins may represent alternative vaccine candidates against CDI.

Highlights

Clostridium difficile (C. difficile) is a Gram-positive, spore-forming, toxin-producing and anaerobic bacillus that is transmitted through spore forms [1]
To ensure that Tcd169 and Tcd169FI were atoxic, point mutations were made in the glucosyltransferase domain (GT) (W102A, D288N) and cysteine proteinase domain (CPD) (C698A) of Tcd169 and mTcd169FI (Figure 1)
Recombinant Tcd169 or Tcd169Fl with a 6xHistag was expressed in Bacillus megaterium, and purified by Niaffinity chromatography followed by ion exchange purification

Summary

Introduction

Clostridium difficile (C. difficile) is a Gram-positive, spore-forming, toxin-producing and anaerobic bacillus that is transmitted through spore forms [1]. It is the most common cause of nosocomial antibiotic-associated diarrhea [2,3,4]. In the United States, C. difficile is the most common healthcare-associated pathogen [6] with approximately half a million infections and more than 29,000 deaths attributable to C. difficile per year [7]. Standard therapy relies on treatment with vancomycin, metronidazole, or fidaxomicin [9,10,11], but none of which is fully effective, with up to a 35% recurrence rate [12]. No vaccine is licensed for the prevention of CDI

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Conclusion