Circulating antibody and memory B cell responses to Clostridium difficile toxins A and B

• Main Author: Monaghan, Tanya Marie
• Published: University of Nottingham 2013
• Subjects: 616.93
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.595681

In C. difficile infection (COl), the antibody-mediated immune response to secreted toxins A and B appears to be important in determining the nature of clinical disease. The aim of this study was to evaluate multiple aspects of the humoral immune response to C. difficife toxins A and B in patients with C. difficile-associated disease (COAO), among which included subjects with inflammatory bowel disease. Humoral immune measurements were also quantified for healthy controls and patients with cystic fibrosis (CF) who have been reported to rarely develop COl. Isolated peripheral blood mononuclear cells (PBMCs) were fluorescently labelled with Alexa Fluor® 488 and other B cell markers to identify transiently circulating toxin A-specific antigen-activated B cells during clinical disease by flow cytometry. PBMCs were also polyclonally stimulated in vitro for 6 days to induce proliferation and differentiation of memory B cells (MBCs) to antibody-secreting cells (ASCs). ELiSPOT assays were used to quantify toxin A- and B-specific IgG ASCs. Toxin A- and B-specific antibody levels in sera and supernatant samples of cultured PBMCS were studied by ELISA. A small proportion of toxin A-specific, antigen-activated B cells were detected in the circulation soon after COl. Differential antibody and MBC responses to C. difficile toxins A and B were detected over many months following CDl and in CF patients. The magnitude of these responses did not significantly differ between patients with single and recurrent CDAD. A greater proportion of toxin B-specific MBCs were present in the peripheral circulation in the CDAD and CF groups. No correlation was seen between the frequency of circulating toxin-specific antigen-activated or MBCs and contemporaneous serum anti-toxin IgG levels in either group. These data suggest that serum anti-toxin antibodies can underestimate the breadth of humoral immunity and strongly support the use of toxin-specific B (memory) cell analyses to complement serological studies.