Inflammatory diseases at both mucosal and non-mucosal sites are responsible for disease in millions of people worldwide. We found that a single oral dose of a common probiotic bacteria, Bacillus subtilis protects mice from intestinal inflammation caused by infection with an enteric pathogen, Citrobacter rodentium. B. subtilis is effective if administered as many as 3 days after C. rodentium, a time at which the pathogen has already induced early inflammatory processes. These findings suggest that B. subtilis may not only prevent inflammation, but more importantly, attenuate it. We have identified and purified a molecule, exopolysaccharide (EPS) from B. subtilis that when introduced by itself in a single intraperitoneal injection, prevents colitis induced by enteric pathogens. EPS binds F4/80+CD11b+ macrophages, and we have data indicating that protection by EPS is mediated by M2 macrophages in a TLR4-dependent manner. Further, we found that a 2nd (TLR2-dependent) cell type is required for protection by EPS. We hypothesize that EPS induces the generation of M2 macrophages which secrete cytokines that either render inflammatory T cells non-responsive, or induce development of regulatory T cells. Here, we will establish if M2 macrophages mediate protection and if EPS stimulates these cells via TLR4 signaling. Further, we will test if M2 macrophages secrete anti-inflammatory cytokines and if they inactivate T cells or induce regulatory T cells. Finally, we will use three disease models (food allergy, autoimmunity and inflammatory bowel disease) to test if EPS is effective in acute and/or chronic inflammatory diseases. We have preliminary data indicating that B. subtilis and EPS can protect from food allergy which affects millions of people. Experiments proposed in this grant will enhance our molecular understanding of how probiotic molecules function to treat and/or prevent disease, and lead to the rational application of small therapeutic probiotic molecules to humans.

Public Health Relevance

We investigate a means of protecting against inflammation such as occurs in food allergy, autoimmunity, inflammatory bowel disease, and infection by enteric pathogens. A single dose of spores or purified exopolysaccharide from a commensal-like (beneficial) bacterium prevents inflammatory disease, and the experiments are designed to determine the mechanism by which this protection occurs. The findings will be extended to several models human inflammatory diseases. We investigate which cells are responsible for protection, and the mechanism by which they prevent inflammation.

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
Research Project (R01)
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Gastrointestinal Mucosal Pathobiology Study Section (GMPB)
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Rothermel, Annette L
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Loyola University Chicago
Schools of Medicine
United States
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Swartzendruber, Julie A; Incrocci, Ryan W; Wolf, Samantha A et al. (2018) Bacillus subtilis exopolysaccharide prevents allergic eosinophilia. Allergy :
Paynich, Mallory L; Jones-Burrage, Sara E; Knight, Katherine L (2017) Exopolysaccharide from Bacillus subtilis Induces Anti-Inflammatory M2 Macrophages That Prevent T Cell-Mediated Disease. J Immunol 198:2689-2698