Immunoreactive cell wall proteins of Clostridium difficile identified by human sera

1 Centre for Molecular Microbiology and Infection, Division of Cell and Molecular Biology, Imperial College, London SW7 2AZ, UK 2 Centre for Food Safety, School of Agriculture, Food Science and Veterinary Medicine, University College Dublin, Belfield, Dublin 4, Ireland 3 Department of Medicine for the Older Person, Mater Misericordiae University Hospital, Dublin 7, Ireland Correspondence Neil F. Fairweather n.fairweather{at}imperial.ac.uk Received 24 July 2007 Accepted 19 October 2007 Clostridium difficile is a leading cause of nosocomial infection in the developed world, causing antibiotic-associated disease in susceptible populations. The identity of immunogenic proteins is important in understanding the pathogenesis of disease and in the design of vaccines. This study analysed the sera of six patients infected during a hospital outbreak of a C. difficile ribotype 017 strain. Using a proteomics-based approach, cell wall proteins were separated by two-dimensional PAGE, and immunoreactive proteins were revealed by reaction with patient sera. The identity of immunoreactive proteins was established by MS. Forty-two different proteins were identified in total. All patient sera reacted with at least one component of the surface-layer protein (SLP), four reacted with both components (high- and low-molecular-mass SLPs), and five reacted with one other cell wall protein, suggesting that these are immunodominant antigens. The role of these proteins as potential vaccine candidates and their roles in pathogenesis deserve further study. Abbreviations: 2DE, two-dimensional PAGE; CDAD, Clostridium difficile -associated disease; ECL, enhanced chemiluminescence; HRP, horseradish peroxidase; IPG, immobilized pH gradient; MALDI, matrix-associated laser desorption/ionization; MS/MS, tandem mass spectrometry; SLP, surface-layer protein. The complete dataset of immunoreactive proteins identified in this study is available as supplementary data with the online version of this paper.