As someone who almost shuffled off this mortal coil after downing a satay, I'm always hopeful when potential breakthroughs for the treatment of food allergies arise. The latest cause for hope, which could one day let food allergy sufferers order in restaurants without worrying about potentially life-threatening ingredients hidden within, comes from scientists at the University of Chicago Medicine (UCM), who have found that a common gut bacteria protects against food allergies in mice.
Although the causes of food allergies – and the reason they have become more prevalent in recent years – remain unknown, there are many theories. One leading theory is that modern hygiene, diet and use of antibiotics and antimicrobials act to disturb the body's natural bacterial composition.
To test this theory, researchers at UCM exposed two groups of mice to peanut allergens. One group was born and raised in sterile conditions to have no resident microorganisms, while the other mice were treated with antibiotics as newborns (which significantly reduces gut bacteria). Compared to mice with normal gut bacteria, both groups displayed a strong immunological response by producing significantly higher levels of antibodies against the peanut allergens.
Now the good news. The researchers found that the sensitivity to food allergens could be reversed in both groups of mice through the reintroduction of a mix of Clostridia bacteria. This group of bacteria, which is common in humans, appeared to have a unique, protective role against food allergens as the reintroduction of another major group of intestinal bacteria known as Bacteroides had no effect on food allergen sensitivity.
Using genetic analysis to delve deeper, the team found that Clostridia prompted innate immune cells to produce high levels of interleukin-22 (IL-22), which is a signaling molecule known to decrease permeability of the intestinal lining. When antibiotic-treated mice given either IL-22 or colonized with Clostridia were exposed to peanut allergens, both exhibited reduced allergen levels in their blood compared to the control group.
Additionally, after the mice were given antibodies that neutralized IL-22, allergen levels increased significantly, which the team says indicates that Clostridia-induced IL-22 prevents allergens from entering the blood stream.
"We've identified a bacterial population that protects against food allergen sensitization," says Cathryn Nagler, PhD, Bunning Food Allergy Professor at the University of Chicago and senior author of the study. "The first step in getting sensitized to a food allergen is for it to get into your blood and be presented to your immune system. The presence of these bacteria regulates that process."
But with the various factors believed to contribute to the development of food allergies not well understood, Nagler cautions that the findings may not apply to all individuals. However, the team believes that Clostridia bacteria represents an attractive target for the development of probiotic therapies to prevent and treat food allergies. They have already filed a provisional patent for the approach are working to develop and test compositions that could be used for such a therapy.
"It's exciting because we know what the bacteria are; we have a way to intervene," Nagler says. "There are of course no guarantees, but this is absolutely testable as a therapeutic against a disease for which there's nothing. As a mom, I can imagine how frightening it must be to worry every time your child takes a bite of food."
The team's study was supported by Food Allergy Research & Education (FARE) and the University of Chicago Digestive Diseases Research Core Center and is published in the Proceedings of the National Academy of Sciences.
Source: University of Chicago Medicine
