385 Gluten-Degrading Microbes in Saliva: Novel Therapeutic Perspectives for Celiac Disease

Thursday, March 22, 2012: 2 p.m. - 3:15 p.m.
Presentation Type: Poster Session
N. TIAN1, G. WEI1, M. ZAMAKHCHARI1, D. SCHUPPAN2, F.G. OPPENHEIM1, and E. HELMERHORST1, 1Goldman School of Dental Medicine, Boston University, Boston, MA, 2Division of Gastroenterology, Beth Israel Deaconess Medical Center, Harvard Medical School, Harvard University, Boston, MA
Introduction: Celiac disease is a T cell mediated-inflammatory enteropathy caused by dietary gluten. Certain immunogenic domains in gluten are completely resistant to the major human digestive enzymes. Deamidation of gluten by transglutaminase-2 in the lamina propria greatly enhances their binding to antigen presenting cells, provoking an inflammatory immune response in susceptible individuals. One therapeutic strategy focuses on enzymes that degrade gluten into non-immunogenic peptides. We recently discovered that the oral microbiome is a novel and rich source of such enzymes. Objectives: 1) isolate the gluten-degrading oral microorganisms, 2) determine enzymatic cleavage site specificities, 3) investigate the effect of gluten degradation on transglutaminase recognition. Methods: Gluten degrading microbes were isolated from human saliva and supragingival plaque on gluten agar plates. Degradation of gliadins, representing the most immunogenic fraction of gluten was tested by zymography, SDS-PAGE, or RP-HPLC. Enzymatic cleavage site specificities were determined with gliadin-derived synthetic tripeptides. Recognition of gliadin peptides in the degradation mixture by human recombinant transglutaminas-2 was measured by crosslinking to monodansylcadaverine. Results: Selected oral microorganisms, identified as Rothia species, effectively hydrolyzed the gluten-derived synthetic peptides after YPQ and LPY. They greatly degraded gliadin in gel and in solution after 2-hours, and cleaved immunogenic gliadin peptide domains 26-mer and 33-mer into smaller fragments after 30-minutes and 8-hours respectively. A perfect correlation was observed between degradation and loss of cross-linking, showing 50% reductions after 10.5 and 10.2-minutes, respectively, for 26-mer and 4.9 and 4.3-hours, respectively, for 33-mer. Conclusion: While the human digestive enzymes are unable to cleave immunogenic gluten peptides implicated in celiac disease, such activities are present in the oral microbiome. Enzymatic abolishment of transglutaminase-mediated deamidation is a first indication for gluten epitope neutralization. The Rothia enzymes open promising new avenues in the search for novel therapies to neutralize the deleterious effects of gluten in celiac disease patients.
This abstract is based on research that was funded entirely or partially by an outside source: NIH grants DE18132, AI087803, DE05672 and DE07652

Keywords: Enzymes, Immunology, Microbiology, Saliva and celiac disease