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

摘要

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