Pinpointing the ‘Good Bacteria’ that Protect Against Food Allergies

According a study published today in Nature Medicine, food allergies are caused by an absence of certain beneficial bacterial in the human gut and restoration of these bacteria may protect children from developing food allergies—and even reverse it in those who already have it.

The study was carried out by scientists at Boston Children’s Hospital and Brigham and Women's Hospital seeking to build on the hypothesis that certain lifestyle factors can disrupt normal microbiota, depriving babies of “good” bacteria that train the immune system to recognize food as harmless.

To study the microbial population in those with food allergies, the scientists collected stool samples from 56 babies with food allergies and 98 samples from matched controls. Comparative analysis of the samples revealed that the bacteria in the feces of babies with food allergies were different than the controls.

Next the researchers needed to determine if the differences played a role in food allergy development. To do this, they transplanted fecal bacteria from both groups of babies into a strain of allergy-prone mice. The mice were sensitized to egg protein, then challenged with a large dose. The mice given fecal bacteria from food-allergic babies went into anaphylaxis, but the mice that received fecal bacteria from the control subjects did not.

To determine which bacteria might be offering protection, six bacterial species from the order Clostridiales that had previous studies had identified as potentially being protective against food allergy were selected. When these bacteria were given to mice, they were protected from allergy, while those given other common bacteria were not. Similar findings were repeated with bacteria from the order Bacteroidales.

The researchers were also able to describe the specific immunological pathway by which the bacteria act in mice. It is mediated through a protein known as MyD88, which serves as a “microbial sensor” in regulatory T cells. It appears commensal bacteria trigger the MyD88/ROR-gamma pathway, activating protection against food allergies.

The researchers believe these findings could help in development of probiotics or drugs that could be given as a preventative or treatment for food allergies.