Peptides encrypted in the human intestinal microbial-exoproteome as novel biomarkers and immunomodulatory compounds in the gastrointestinal tract

Peptides encrypted in the intestinal microbial-exoproteome mediate the host-microbiota crosstalk, which is disrupted in inflammatory bowel disease (IBD). Here, the MAHMI database was used for the identification of 20 novel intestinal bacterial peptides. Our results revealed that serum IgA levels directed towards the peptides, but not IgG, discriminated healthy controls from IBD patients. Indeed, they also differentiated patients with ulcerative colitis from Crohns disease and, within them, patients with and without intestinal inflammation. All peptides were immunomodulatory as they changed the intestinal cytokine milieu following human lamina propria mononuclear cells culture (with/out LPS), revealing a Bifidobacterium longtun subsp. longum peptide with the highest tolerogenic properties. Therefore, bacterial peptides encrypted in the human gut metaproteome may have utility as non-invasive biomarkers to aid on IBD diagnosis and monitoring. These peptides also display immunomodulatory effects on the intestinal mucosa revealing them as novel functional compounds for non-drug therapeutic strategies in IBD.