Immunological evaluation of a synthetic Clostridium difficile oligosaccharide conjugate vaccine candidate and identification of a minimal epitope

J Am Chem Soc. 2013 Jul 3;135(26):9713-22. doi: 10.1021/ja401410y. Epub 2013 Jun 24.

Abstract

Clostridium difficile is the cause of emerging nosocomial infections that result in abundant morbidity and mortality worldwide. Thus, the development of a vaccine to kill the bacteria to prevent this disease is highly desirable. Several recently identified bacterial surface glycans, such as PS-I and PS-II, are promising vaccine candidates to preclude C. difficile infection. To circumvent difficulties with the generation of natural PS-I due to its low expression levels in bacterial cultures, improved chemical synthesis protocols for the pentasaccharide repeating unit of PS-I and oligosaccharide substructures were utilized to produce large quantities of well-defined PS-I related glycans. The analysis of stool and serum samples obtained from C. difficile patients using glycan microarrays of synthetic oligosaccharide epitopes revealed humoral immune responses to the PS-I related glycan epitopes. Two different vaccine candidates were evaluated in the mouse model. A synthetic PS-I repeating unit CRM197 conjugate was immunogenic in mice and induced immunoglobulin class switching as well as affinity maturation. Microarray screening employing PS-I repeating unit substructures revealed the disaccharide Rha-(1→3)-Glc as a minimal epitope. A CRM197-Rha-(1→3)-Glc disaccharide conjugate was able to elicit antibodies recognizing the C. difficile PS-I pentasaccharide. We herein demonstrate that glycan microarrays exposing defined oligosaccharide epitopes help to determine the minimal immunogenic epitopes of complex oligosaccharide antigens. The synthetic PS-I pentasaccharide repeating unit as well as the Rha-(1→3)-Glc disaccharide are promising novel vaccine candidates against C. difficile that are currently in preclinical evaluation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Vaccines / chemistry
  • Bacterial Vaccines / immunology*
  • Carbohydrate Conformation
  • Clostridioides difficile / chemistry*
  • Clostridioides difficile / immunology
  • Enterocolitis, Pseudomembranous / immunology
  • Enterocolitis, Pseudomembranous / therapy*
  • Epitopes / immunology*
  • Molecular Sequence Data
  • Oligosaccharides / chemistry
  • Oligosaccharides / immunology*
  • Vaccines, Synthetic / chemistry
  • Vaccines, Synthetic / immunology*

Substances

  • Bacterial Vaccines
  • Epitopes
  • Oligosaccharides
  • Vaccines, Synthetic