Circulating Antibody and Memory B-Cell Responses to C. difficile Toxins A and B in Patients with C. difficile-Associated Diarrhoea, Inflammatory Bowel Disease and Cystic Fibrosis

Tanya M Monaghan,Adrian Robins,Herbert F Sewell,Yashwant R Mahida,Alan Knox,Cordula M Stover,Arun Rishi

doi:10.1371/journal.pone.0074452

Tanya M Monaghan, Adrian Robins + Show 5 more

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https://doi.org/10.1371/journal.pone.0074452

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Abstract

C. difficile infection (CDI) is rarely reported in cystic fibrosis (CF) patients despite frequent hospitalisations and antibiotic usage. Conversely, the prevalence of CDI in inflammatory bowel disease (IBD) has received increased attention. We investigated components of the IgG-specific humoral immune response to C. difficile toxins A and B in patients with C. difficile-associated diarrhoea (CDAD), IBD patients with CDI, CF patients and healthy controls. Serum anti-toxin IgG was determined by ELISA. Circulating antigen-activated B-cells were investigated using Alexa Fluor 488-labelled toxin A and assessed by flow cytometry. Following induction of differentiation of memory B-cells, toxin A- and B-specific antibody secreting cells (ASCs) were quantified using ELISpot. We present the first data showing levels of serum anti-toxin A and B antibodies were significantly higher in patients with CF (without a history of CDI) than in CDAD patients and were stably maintained over time. Notably, the CDAD patients were significantly older than the CF patients. We also show that circulating toxin A-specific memory B-cells (IgD-negative) can be detected in CDAD patients [0.92 (0.09–1.78)%], and were prominent (5.64%, 1.14%) in two CF patients who were asymptomatic carriers of C. difficile. There was correlation between toxin A- and B-specific ASCs, with significantly higher proportions of the latter seen. In some with CDAD, high serum antibody levels were seen to only one of the two toxins. Mucosal secretion of toxin-specific IgG was detected in an additional group of IBD patients with no history of CDI. We conclude that enhanced and stable humoral immune responses to toxins A and B may protect CF and some IBD patients against CDI. The impaired ability to generate strong and/or sustained toxin-specific antibody and memory B-cell responses may increase susceptibility of older patients to CDI and highlight the need to investigate the role of immune senescence in future studies.

Highlights

C. difficile infection is a significant clinical problem in patients exposed to the hospital environment
The characteristics of the subjects in the four study groups are shown in Table 1, which demonstrates that patients with C. difficile-associated diarrhoea were significantly older than those in the other three groups
In 16 of the 18 patients with cystic fibrosis, there was no history of C. difficile infection; 2 had a history of previous C. difficile infection; stool samples from a further 2 patients grew C. difficile and they were deemed to be carriers

Summary

Introduction

C. difficile infection is a significant clinical problem in patients exposed to the hospital environment. Clinical presentation in those colonised with toxigenic C. difficile can include asymptomatic carriage, mild self-limiting diarrhoea and severe life-threatening pseudomembranous colitis. Host factors that may determine the development and nature of clinical disease are not fully understood but include age, the use of proton-pump inhibitors or H2 blockers, tube feeding and the host immune response [1,3,4,5,6]. Asymptomatic carriage of C. difficile has been reported in 22-32% of such patients [10,11], but the mechanism of protection against the development of colonic disease remains to be determined

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