Immunological Evaluation of a Synthetic Clostridium difficile Oligosaccharide Conjugate Vaccine Candidate and Identification of a Minimal Epitope

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• 作者：Christopher E. Martin ; Felix Broecker ; Matthias A. Oberli ; Julia Komor ; Jochen Mattner ; Chakkumkal Anish ; Peter H. Seeberger
• 刊名：The Journal of the American Chemical Society
• 出版年：2013
• 出版时间：July 3, 2013
• 年：2013
• 卷：135
• 期：26
• 页码：9713-9722
• 全文大小：528K
• 年卷期：v.135,no.26(July 3, 2013)
• ISSN：1520-5126

文摘

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鈫?)-Glc as a minimal epitope. A CRM₁₉₇-Rha-(1鈫?)-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鈫?)-Glc disaccharide are promising novel vaccine candidates against C. difficile that are currently in preclinical evaluation.