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Open Access Treg‐inducing capacity of genomic DNA of Bifidobacterium longum subsp. infantis

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Background:

Allergic and autoimmune diseases comprise a group of inflammatory disorders caused by aberrant immune responses in which CD25+ forkhead box P3‐positive regulatory T cells (Treg) cells that normally suppress inflammatory events are often poorly functioning. This has stimulated an intensive investigative effort to find ways of increasing Tregs as a method of therapy for these conditions. Commensal microbiota known to have health benefits in humans include the lactic acid‐producing, probiotic bacteria B. longum subsp. infantis and Lactobacillus rhamnosus. Mechanistically, several mechanisms have been proposed to explain how probiotics may favorably affect host immunity, including the induction of Tregs. Analysis of emerging data from several laboratories, including our own, suggest that DNA methylation may be an important determinant of immune reactivity responsible for Treg induction. Although methylated CpG moieties in normal mammalian DNA are both noninflammatory and lack immunogenicity, unmethylated CpGs, found largely in microbial DNA, are immunostimulatory and display proinflammatory properties.

Objective:

We hypothesize that microbiota with more DNA methylation may potentiate Treg induction to a greater degree than microbiota with a lower content of methylation. The purpose of the present study was to test this hypothesis by studying the methylation status of whole genomic DNA (gDNA) and the Treg-inducing capacity of purified gDNA in each of the probiotic bacteria B. longum subsp. infantis and L. rhamnosus, and a pathogenic Escherichia coli strain B.

Results:

We showed that gDNA from B. longum subsp. infantis is a potent Treg inducer that displays a dose-dependent response pattern at a dose threshold of 20 µg of gDNA. No similar Treg-inducing responses were observed with the gDNA from L. rhamnosus or E. coli. We identified a unique CpG methylated motif in the gDNA sequencing of B. longum subsp. infantis which was not found in L. rhamnosus or E. coli strain B.

Conclusion:

Although the literature indicates that both B. longum subsp. infantis and L. rhamnosus strains contribute to health, our data suggest that they do so by different mechanisms. Further, because of its small molecular size, low cost, ease of synthesis, and unique Treg-inducing feature, this methylated CpG oligodeoxynucleotide (ODN) from B. longum would offer many attractive features for an ideal novel therapeutic vaccine candidate for the treatment of immunologic diseases, such as the allergic and autoimmune disorders, in which Treg populations are diminished.

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Keywords: Bifidobacterium longum; CD4+ cells; Probiotics; Treg induction; microbial DNA

Document Type: Research Article

Affiliations: 1: From the Department of Microbiology-Immunology, Georgetown University Medical Center, Washington, D.C.; 2: Genomics and Epigenomics Shared Resource, Lombardi Comprehensive Cancer Center, Georgetown University, Washington, D.C.; 3: Department of Pediatrics, Georgetown University Medical Center, Washington, D.C.; and 4: Genomic Resource Center, University of Maryland School of Medicine, Baltimore, Maryland

Publication date: September 1, 2020

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  • Allergy and Asthma Proceedings is a peer reviewed publication dedicated to distributing timely scientific research regarding advancements in the knowledge and practice of allergy, asthma and immunology. Its primary readership consists of allergists and pulmonologists.

    The goal of the Proceedings is to publish articles with a predominantly clinical focus which directly impact quality of care for patients with allergic disease and asthma and by having the potential to directly impact the quality of patient care. AAP welcomes the submission of original works including peer-reviewed original research and clinical trial results. Additionally, as the official journal of the Eastern Allergy Conference (EAC), AAP will publish content from EAC poster sessions as well as review articles derived from EAC lectures.

    Featured topics include asthma, rhinitis, sinusitis, food allergies, allergic skin diseases, diagnostic techniques, allergens, and treatment modalities. Published material includes peer-reviewed original research, clinical trials and review articles.

    Articles marked "F" offer free full text for personal noncommercial use only.

    The journal is indexed in Thomson Reuters Web of Science and Science Citation Index Expanded, plus the National Library of Medicine's PubMed service.
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