What is IBD?
Inflammatory bowel disease (IBD) is a group of autoimmune diseases characterized by inflammation in the intestines. One of the two existing subtypes of IBD is Crohn's disease (CD), distinguished by interspersed areas of inflammation. The incidence of IBD is on the rise, and Canada has among the highest prevalence globally. As of 2018, 270 000 Canadians are affected by IBD, and this number is expected to rise to 403 000 by the year 2030 (Kaplan et al., 2019). The direct cost of caring for individuals with IBD, which reached $1.28 billion in 2018, places a significant strain on the Canadian healthcare system (Kuenzig et al., 2019).
How is our therapeutic unique?
Having surveyed current therapeutic strategies, we believe that an effective approach would require a mechanism that is intrinsic to the bacteria. Colicins are a family of bacteriocins produced by certain E. coli to inhibit the growth of closely related strains. Specific colicins have been found to target a pathogenic group deemed adherent-invasive E. coli (AIEC). AIEC has been shown to be implicated in the development of IBD through biofilm formation on the lining of the intestinal wall. This is due to the pathogenic bacteria’s ability to invade the intestinal epithelia and interact with the immune cell-rich mucosa therein. Additionally, AIEC is able to induce inflammation and exacerbate symptoms in IBD patients by surviving and replicating intensively inside macrophages and inducing inflammatory cytokines such as TNF-α. We believe that taking advantage of the natural survival mechanism of colicin production will allow us to selectively eliminate AIEC bacteria and treat IBD.
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In this project, we propose the construction of a genetic circuit that can simultaneously detect the inflammation marker nitric oxide, and a pathogen-specific quorum sensing factor named autoinducer-3. Upon activation, the genetic circuit expresses colicin E1 and E9, two bacteriocins that can selectively eliminate the AIEC. We designed detailed experimental workflows for circuit construction through Gibson assembly and for functional verification. A mathematical model was also established to predict the outcomes of our design. The following diagram shows a preliminary version of our circuit design. During our engineering iteration process, we have made significant changes to the design to address to improve its functionality and to address some of the challenges that had surfaced. We hope our project can make a meaningful contribution to IBD patients in the near future.