Scientists are targeting imbalances in intestinal bacteria, known as the microbiome, to find a new way to fight food allergies. Gut bacteria could help people reset their immune systems and avoid severe allergic reactions to food. It is what Cathryn Nagler, an immunologist at the University of Chicago, says. (1)

Microbiome and Allergies in Mice

Nagler and their team reported they supplied gut microbes from healthy, non-allergic babies and prevented severe allergic responses in allergy-prone mice. “The data are sound and very encouraging,” says pediatric allergist Jaclyn Bjelac of the Cleveland Clinic. (1)

In 2004, Nagler and her coworkers reported peanuts provoked anaphylaxis only in mice with a mutated TLR4 receptor, which sits in the membranes of immune cells. Its job is to recognize microbes. The reaction did not happen in genetically related strains but had a normal TLR4 level. However, this different reaction was eliminated when they wiped out gut bacteria populations with antibiotics. In this case, even normal mice were susceptible to food allergies. It implied that bacteria are at the root of the protection. Nagler’s lab continues to pursue which bacteria might help regulate allergic responses. (1)

Specific Bacteria in Microbiome and Allergies

Two major bacteria groups in the gut, Clostridia and Bacteroides have been the focus of the study on mice bred in a germ-free environment. Because the environment is germ-free, the mice don’t have any microbiome. Clostridia, but not Bacteroides, prevented food-allergic responses once placed in the guts of the “clean” mice. (1)

It could be related to the mice colonized with Clostridia bacteria having more regulatory T cells, which reduce immune responses. The Clostridia mice also produced more IL-22, a molecule that strengthens the intestinal lining. It led to the theory that when there are missing protective microbes, it weakens the gut barrier so food proteins can seep into the bloodstream, triggering allergic responses. (1)

The Commonality for Microbiome and Allergies

These findings work along with an observation that the typical food allergies to proteins in foods such as peanuts, eggs, milk, etc., have few biochemical things in common. All of them can stay together in the digestive tract, where food is usually broken down into small pieces and taken in as nutrients. “That seems to be what makes peanut the champion—its ability to resist degradation in the gut,” explains Nagler. (1)

Further supporting the gut bacteria and food allergies link, this finding suggests the microbiome’s impact comes early in life. By analyzing healthy baby feces and those with egg or milk allergies, the team showed that gut bacteria communities in allergic and non-allergic infants differed. (1)

Early-In-Life Ties to Microbiome and Allergies

Another study suggesting that allergy protective microbes only act early in life tested children with milk allergies from infancy to age 8. The results showed that from 2 to 6 months, certain bacteria, including Clostridia, were enriched in stool samples. These infants outgrew their allergies, which was not seen in older babies. (1)

“All of this points to the concept of a window of opportunity in terms of prevention,” says the leader of this particular study, pediatric allergist Supinda Bunyavanich of the Icahn School of Medicine at Mount Sinai in New York City. (1) 

According to Carina Venter, the microbiome is essential for preventing food allergies and inducing tolerance, a research dietician at the University of Colorado in Denver. However, she also points out “how that microbiome should look in terms of diversity and terms of specific strains; we just don’t know.” (1)

Sources:

1. https://www.scientificamerichttps://www.scientificamerican.com/article/gut-microbes-may-be-key-to-solving-food-allergies/#:~:text=Studies%20have%20further%20solidified%20the,different%20communities%20of%20gut%20bacteria.an.com/