Inflammatory Bowel Disease (IBD) is an auto-inflammatory disorder characterized by unregulated intestinal inflammation. Current therapies are unable to treat all patients afflicted with the condition and are often accompanied by undesirable side effects. Therefore, an urgent demand exists for the development of novel therapies.
Parasitic nematodes actively secrete products modulating the host’s immune system which enables them to persist and reproduce for long periods of time. Parasite driven immunomodulation has been shown to ameliorate murine experimental gut inflammation and clinical IBD in humans. Cystatin secreted by the filarial nematode Acanthocheilonema viteae (AvCys) has strong anti-inflammatory properties when in contact with immune cells, predominantly targeting macrophages. A novel treatment for IBD was developed utilizing a probiotic bacterium, Escherichia coli Nissle 1917 (EcN), genetically modified as a carrier for AvCys to allow for the site-directed, prolonged secretion of the immunomodulator in the gut.
The transgenic probiotic EcN-AvCys was applied in a murine model of acute colitis, where it significantly suppressed the intestinal expression of chemoattractants, infiltration of inflammatory cells and T-cell cytokine responses, leading to drastically lowered inflammatory scores. To assess the anti-inflammatory activity of EcN-AvCys in a genetically diverse, outbred model equipped with a gastrointestinal tract highly similar to that of humans, high doses were repeatedly applied to piglets suffering from post-weaning intestinal malfunction. The treatment significantly reduced post-weaning gut inflammation and, importantly, was safe in terms of body weight development and immune function. Furthermore, EcN-AvCys treatment significantly improved colon epithelial barrier functions. Similarly, short-term exposure of porcine colon tissue and human intestinal epithelial cells to EcN-AvCys supernatants improved transepithelial resistance.
To analyse the mechanistic basis for the anti-inflammatory action of EcN-AvCys, the phenotype of porcine monocytes was investigated after incubation with EcN or EcN-AvCys cell culture media supernatants, or recombinant AvCys. While recombinant AvCys had very little effect on the expression of monocyte markers related to phenotypic specialization and function, EcN and EcN-AvCys supernatants induced the indiscriminate early expression of M1 associated markers, as well as regulatory IL-10.
To test the hypothesis that AvCys may interfere with pro-inflammatory macrophage functions by interfering with the inflammasome and thus activation of the pro-inflammatory cytokine IL-1ß, monocytes and macrophages where exposed to supernatants of the transgenic and control probiotic and IL-1ß secretion was determined. However, EcN-AvCys supernatant supported rather than suppressed the secretion of IL-1ß in response to inflammasome induction in monocytes.
Thus additional research is required to determine the mechanistic basis for the documented anti-inflammatory activity of EcN-AvCys in murine and porcine gut inflammation models and further evaluate its applicability as a treatment for human IBD.
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