Manipulation of the gut microbiota holds great promise for the treatment of inflammatory and allergic diseases1,2. Although numerous probiotic microorganisms have been identified3, there remains a compelling need to discover organisms that elicit more robust therapeutic responses, are compatible with the host, and can affect a specific arm of the host immune system in a well-controlled, physiological manner. Here we use a rational approach to isolate CD4+FOXP3+ regulatory T (Treg)-cell-inducing bacterial strains from the human indigenous microbiota. Starting with a healthy human faecal sample, a sequence of selection steps was applied to obtain mice colonized with human microbiota enriched in Treg-cell-inducing species. From these mice, we isolated and selected 17 strains of bacteria on the basis of their high potency in enhancing Treg cell abundance and inducing important anti-inflammatory molecules—including interleukin-10 (IL-) and inducible T-cell co-stimulator (ICOS)—in Treg cells upon inoculation into germ-free mice. Genome sequencing revealed that the 17 strains fall within clusters IV, XIVa and XVIII of Clostridia, which lack prominent toxins and virulence factors. The 17 strains act as a community to provide bacterial antigens and a TGF-β-rich environment to help expansion and differentiation of Treg cells. Oral administration of the combination of 17 strains to adult mice attenuated disease in models of colitis and allergic diarrhoea. Use of the isolated strains may allow for tailored therapeutic manipulation of human immune disorders.
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This work was supported by JSPS NEXT program, Grant in Aid for Scientific Research on Innovative Areas ‘Genome Science’ from the Ministry of Education, Culture, Sports, Science and Technology of Japan (No.221S0002), the global COE project of ‘Genome Information Big Bang’ and the Waksman Foundation of Japan Inc. We thank M. Suyama, K. Furuya, C. Yoshino, H. Inaba, E. Iioka, Y. Takayama, M. Kiuchi, Y. Hattori, N. Fukuda and A. Nakano for technical assistance, and P. D. Burrows for review of the manuscript.
This file contains meta 16S rRNA gene analysis for the series of gnotobiotic mice. The numbers of detected reads, the closest species, and % similarities with the closest species for each OTU in each exGF mouse are shown.
This file contains putative toxins and virulence factors found in 17 strains. BLASTP search of gene products predicted from genomes was performed using virulence factor databases (VFDB and MvirDB) with the e-value cut off of 1.0e-10, the identity >30% and the length coverage >60%. Note that several strains possess genes encoding putative hyaluronidase, sialidase, fibronectin-binding proteins, and flagella-related proteins but with low similarity to genes of pathogenic Clostridia species, and most of these genes are also encoded by other commensal Clostridia species.
About this article
Nature Reviews Immunology (2019)