A new paper published on 24 June in Nature Medicine pinpoints changes in the gut microbiome — the billions of bacteria that live in the human gut — associated with the development of food allergies in infants (1). The authors identified particular species of gut bacteria that protect infants from allergies. In mice, these bacteria suppress food allergies and maintain resistance to the allergy.
At present, the most effective way to fully prevent a potentially deadly allergic reaction to food is to avoid the offending ingredient entirely. Oral immunotherapy involves exposing an allergy sufferer to small, increasing amounts of the allergen and can be an effective strategy, but only in some cases.
The search for new treatments has led researchers to contemplate a link between the complex ecosystem of microorganisms living in the gut. And it seems an altered gut microbiome may play a pivotal role in the development of food allergies.
To this end, the researchers from Brigham and Women’s Hospital and Boston Children’s Hospital in the US may have identified a particular species of gut bacteria that protect infants from allergies.
To make this discovery, they collected faecal samples from 56 infants every four to six months and analyzed differences in the microbe content compared that of 98 infants without allergies.
When samples of the same faecal microbiota were transplanted into mice allergic to eggs, mice who received microbiota from healthy controls were more protected against the allergy than those who received microbiota from infants with food allergies.
Mice given an enriched oral formulation of five or six species of bacteria found in the human gut — belonging to species within the Clostridiales or the Bacteroidetes — were protected against food allergies. The bacteria, it would seem, are capable of re-establishing a tolerance to food allergens.
In addition, by looking at immunological changes, the researchers discovered that the bacteria target two important immunological pathways. This stimulates specific regulatory T cells, the cells that play a central role in the immune system to promote more tolerant responses as opposed to allergic responses. The same response was demonstrated in both the mice and infants.
The findings represent a profound shift in the approach used to develop therapeutics for food allergies, the authors report. The researchers identified microbes associated with protection and ones that are associated with food allergies.
Therefore, the protective microbes could be used as a therapeutic not only to prevent the development of food allergies but to potentially reverse existing allergies but “resetting the immune system”, says Dr Lynn Bry, director of the Massachusetts Host-Microbiome Center at the Brigham and senior co-author on the paper.
Scientists are increasingly recognising the importance of the gut microbiome. Another recent study showed changes in the microbiome with age (2). Moreover, alterations in gut bacteria are linked to diseases of the gut, as well as mood disorders, such as depression — several species of gut bacteria are missing in people with depression (3).
And many researchers have identified important links between diet, microbiota, and health. For example, disturbances in the gut microbiome are associated with a number of physical pathologies from inflammatory bowel disease to diabetes, obesity, atherosclerosis — a build-up of fatty deposits in the arteries — and even cancer.
Now, this new evidence should give some hope to allergy sufferers that a new, improved therapy is on the horizon. Unlike immunotherapy, the so-called bacteriotherapy could rewire the immune system to broadly treat food allergies rather than desensitizing an individual to a specific allergen.
(1) Abdel-Gadir, A. et al. Microbiota therapy acts via a regulatory T cell MyD88/RORγt pathway to suppress food allergy. Nature Medicine (2019). DOI: 10.1038/s41591-019-0461-z
(3) Fedor Galkin et al. Human microbiome aging clocks based on deep learning and tandem of permutation feature importance and accumulated local effects. bioRxiv (2018) DOI: 10.1101/507780
(3) Valles-Colomer, M et. The neuroactive potential of the human gut microbiota in quality of life and depression. Nature Microbiology (2019). DOI: 10.1038/s41564-018-0337-x