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Tuesday, September 15, 2009
Those scientists took a bacterium called Bacteroides ovatus, which people naturally have in their gut, and genetically altered it to secrete a protein called KGF-2 when exposed to a sugar called xylan.
The point is to bump up the presence of KGF-2, which is a human growth factor that could help heal damage done by inflammatory bowel diseases.
Why not just give human growth factors directly? Because "they are unstable when administered orally and systemic administration requires high doses, increasing the risk of unwanted side effects," the researchers write in the online edition of the journal Gut.
Their study focused on mice with colitis, a type of inflammatory bowel disease. The scientists gave the genetically engineered bacteria orally to some of the mice every other day, and also laced the drinking water of some of the mice with xylan. For comparison, other mice didn't get the bacteria and/or the xylan drink.
Compared to the other mice, the mice treated with bacteria and xylan had a reduction in rectal bleeding, inflammation, and weight loss; they also had faster healing of colitis-damaged tissue and an improvement in their stool consistency.
Tests need to be done in people, and one of the researchers, Simon Carding, PhD, discussed the treatment with WebMD via email. Carding is a professor of mucosal immunology at England's University of East Anglia Medical School and the director of integrated biology of the gastrointestinal tract research program at the Institute of Food Research in Norwich, England.
Carding writes that the bacteria used "are present in the gut of everyone, so patients will be taking something that they already have and the treatment should be well tolerated. The outstanding questions concern formulation and dosing protocols, which we plan to address as part of our phase of studies."
It might be possible to do a short, one-time bacteria dosing regimen that would establish a permanent colony of the genetically engineered bacteria. Another option would be to establish a temporary colony, repeating those treatments when the disease flares up.
Carding says natural sources of xylan -- tree bark, rice husks, and oat kernels -- aren't commonly found in the diet, so patients would need to supplement their diets with xylan, such as in a drink.
"Animals tolerate high concentrations of xylan [in] their drinking water very well and have never exhibited any adverse signs from excessive xylan consumption," Carding writes.
Carding notes that the bacteria strategy could be used to treat various gut diseases, including delivering agents to interfere with the formation of new blood vessels that feed intestinal tumors and delivering vaccine antigens to build the gut's immunity against viruses, bad bacteria, and infection.
