Identification of the predominant antigenic epitopes in intestinal flora in IBD

The normal intestinal flora is required for the development of intestinal inflammation in animal models of inflammatory bowel disease (IBD). In humans, several studies indicated a potential association of Escherichia coli (E. coli) with IBD. In addition, we have shown that T-cell clones of IBD patients cross react toward different enteric bacterial species and thus likely respond to conserved bacterial antigens. Therefore, we hypothesized that highly conserved E. coli proteins might be a reasonable candidate to screen for abnormal T-cell responses in IBD. We used high-throughput techniques for cloning, expression, and purification under native conditions of a set of 271 conserved proteins of E. coli, of which 196 were used for whole blood stimulations to assess peripheral T helper (T(H))-cell responses. In addition, because of the association of an adherent-invasive E. coli with Crohn's disease (CD), we included 13 pathogenicity factors of E. coli in the study. We observed that pools of these conserved E. coli proteins less frequently induced interferon-gamma (IFNgamma) production in peripheral T(H) cells in patients with CD and ankylosing spondylitis (AS) compared with healthy controls. In addition, lower percentage of patients with CD and AS responded toward single proteins. The reason for the decreased frequency of an in vitro T(H)-cell IFNgamma response toward E. coli proteins in peripheral blood of CD and AS patients, e.g., increased suppression needs to be clarified.