Submitted to: Inflammatory Bowel Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/11/2010
Publication Date: 7/1/2011
Citation: Hamady, Z.Z., Scott, N., Farrar, M.D., Wadhwa, M., Dilger, P., Whitehead, T.R., Holland, K.T., Lodge, J.P., Carding, S.R. 2011. Treatment of colitis with a commensal gut bacterium engineered to secrete human TGF-beta1 under the control of dietary xylan. Inflammatory Bowel Diseases. 17(9):1925-1935. Interpretive Summary: Chronic disorders of the human gastrointestinal (GI) tract, for example inflammatory bowel disease (IBD) which includes the disorders Crohn’s disease and ulcerative colitis, affect a significant proportion of the population in developed countries such as the United States. Present therapies are not curative and may cause adverse side effects during treatment. Therefore, there is a need for more targeted and controlled forms of immunotherapy. Previous work has indicated that commensal bacteria that normally inhabit the GI tract might prove useful for treating certain forms of bowel disease. Therefore, a human isolate of the commensal bacterium Bacteroides ovatus was engineered in our laboratories as a probiotic for production and secretion of human transforming growth factor-beta (TGF-beta), important for the treatment of IBD, using a xylan-inducing gene system. In response to feeding xylan, mice treated with the bacterial strain had significant improvements in IBD symptoms. This novel diet-regulated, live bacterial drug delivery system may be applicable to treating various bowel disorders in humans.
Technical Abstract: Background: Growth factors have shown promise in treating inflammatory bowel disease. They are unstable when administered orally and required in higher doses with systemic administration. In consideration of these problems, we have engineered the commensal bacterium Bacteroides ovatus for the controlled in situ delivery of TGF-beta and treatment of colitis. Method: The sequence of human tgf-beta was cloned downstream the xylanase promoter in B. ovatus by homologous recombination. Resulting clones (BO-TGF) were tested for TGF-beta production in the presence and absence of polysaccharide xylan and used to treat experimental murine colitis. Clinical and pathological scores were used to assess the effectiveness of therapy. Colonic inflammatory markers were assessed by colorimetric assay and real-time polymerase chain reaction (PCR). Results: BO-TGF was able to secrete biologically active TGF-beta in-vitro and in-vivo in xylan controlled manner. Administration of xylan in drinking water to BO-BO-TGF treated mice resulted in a significant improvement of colitis, accelerating healing of damaged colonic epithelium, reducing inflammatory cells infiltration, reducing expression of pro-inflammatory cytokines, and promoting production of mucin-rich goblet cells in colonic crypts. These beneficial effects are comparable and in most cases superior to that achieved by conventional steroid therapy. Conclusion: This novel drug delivery system could be used as gene therapy in long term management of various bowel disorders.