Identifying Cytokine Motif-Containing, Immunomodulatory Bacterial Proteins in Human Gut Microbiome.

Accumulating evidence emphasizes the importance of microbiota-immune interactions in health and disease development, and identified bacteria-derived small-molecule metabolites as well as macromolecules such as peptides and proteins as promising therapeutic approaches. Here, we identify cytokine motif-containing, immunomodulatory bacterial proteins (CMCPs) as a special category of bacterial proteins in both bacterial genomes and gut metagenomes using Hidden Markov Models (HMMs). We further find eight colorectal cancer‑associated CMCPs differentially enriched in patients or healthy controls. Engineered E. coli Nissle 1917 (EcN) expressing selected CMCPs administered to Apcmin/+ mice selectively colonize intestinal tumors, deliver functional CMCPs in situ, and elicit significant antitumor immune responses while reducing tumor burden. In vitro, purified CMCPs modulate mouse splenic T cells, bone marrow‑derived macrophages and dendritic cells. Our findings indicate that bacterially encoded CMCPs can directly modulate tumor immunity and serve as microbiota‑derived proteins as candidate immunomodulators, which can further be applied in microbiome-mediated immune therapies for CRC.