Scientific Abstract

Proposal No. IBD-0198R
Principal Investigator:  Sylvia Daunert, Pharm.D., Ph.D.
Applicant Organization:  University of Kentucky Research Foundation (Lexington, U.S.A.)
Project Title:  Non-invasive biosensors for the diagnosis and management of Crohn's disease
Period of Award:  June 1, 2007 – November 30, 2008

Studies carried out in animals and humans established that gut bacterial flora is an important determinant of bowel inflammation, especially in CD.  Overall, there is evidence that an overly aggressive immune response to commensal bacterial flora in genetically predisposed individuals contributes to the inflammatory states in IBD.  Altered bacterial homeostasis may translate to periodic clinical exacerbations of IBD.  Given that the presence of bacteria is critical in the pathogenesis of Crohn’s, we believe that bacterial load and interactions play an important role in Crohn’s disease.  A key component of bacterial behavior and colonization is communication between bacteria, which is based on a phenomenon known as quorum sensing (QS).  Quorum sensing enables bacteria to communicate with each other and control expression of certain specialized genes by producing and responding to extracellular signal molecules in proportion to cell density.  Bacteria have elaborate chemical signaling systems that enable them to communicate within and between species.  Given the interplay of bacterial flora and the status of luminal inflammation, we believe that measurement of quorum sensing signal molecules (QSMs) is an attractive tool in the assessment of the inflammatory state.  Varying levels of quorum sensing molecules may thus be an early predictor of exacerbation.  In that regard, the overall goal of this project is to clarify that quorum-sensing signal molecules are biomarkers to measure intestinal inflammatory activity, and biosensors provide a useful tool to assess the QSM levels in body fluids such as saliva and stool, thus allowing the non-invasive monitoring of inflammatory activity in CD.  To that end, we will employ genetically engineered bacterial whole-cell sensing systems capable of rapid, sensitive and quantitative detection of QSMs.  This is a novel approach to investigation of CD, in that it proposes to relate bacterial cell-to-cell communication to inflammatory bowel disease, and employ living whole-cell-based biosensors for detection of quorum sensing molecules in saliva and stool of Crohn’s disease patients.  Periodic determination of a marker may provide a tool for early identification of an exacerbation.

The proposed method based on detection of quorum sensing signal molecules in saliva and stool would provide with a non-invasive diagnostic tool for early identification of exacerbations, and offer a potential method for testing of the status of luminal inflammation.  Early identification of an exacerbation of the disease would be highly beneficial to CD patients because therapy could be given before the onset of a “flare-up.”  Furthermore, the proposed diagnostic method may lead to the development of a simple tool for home-based, self-testing of the status of the disease.  Another relevant outcome of this project is that measurement of bacterial signaling mechanisms in subjects with Crohn’s disease may allow for new understanding of the interplay of gastrointestinal bacterial flora and inflammatory bowel disease, and lead to the design and development of new therapeutic agents that target bacterial quorum sensing.