Bacteria in Gut can Lower Peanut Allergy Risk

Bacteria can protect against peanut allergies, a new study suggests.

University of Chicago Medical Center scientists say that Clostridia in the guts can help reduce risk of allergies.

Recent research has suggested that modern living and high standards of hygiene have contributed to the growth of allergies. Food allergy rates among children living in the U.S. have increased by 50 percent between 1997 and 2011. The researchers say that these rates are co-related with rise in antimicrobial-use.

The exact cause of food allergies remains unknown.

"Environmental stimuli such as antibiotic overuse, high fat diets, caesarean birth, removal of common pathogens and even formula feeding have affected the microbiota with which we've co-evolved," said study senior author Cathryn Nagler, PhD, Bunning Food Allergy Professor at the University of Chicago. "Our results suggest this could contribute to the increasing susceptibility to food allergies."

The current study was conducted on mice models. One set of mice was raised in a germ-free environment, while the other was given antibiotics as newborns. Both sets were exposed to peanut allergens. The researchers found that both test groups displayed strong immunological response to the allergens.

The team also found that introducing Clostridia bacteria in the guts of these overtly-sensitive mice helped ease the allergic reactions.

The researchers then conducted genetic analysis and found that innate immune cells produced high levels of interleukin-22 (IL-22) in the presence of Clostridia. IL-22 is a signalling molecule that decreases the permeability of the intestinal lining.

Test mice that were given either IL-22 or the Clostridia had reduced allergen levels in the blood compared to other mice. However, when mice were given antibodies against IL-22, allergen levels shot up once again, suggesting that the signalling molecule prevents allergens from entering bloodstream.

"We've identified a bacterial population that protects against food allergen sensitization," Nagler said in a news release. "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."

Scientists have cautioned that the study did not find a cause-and-effect relationship and that future studies are required to test the idea.

The study is published in the journal Proceedings of the National Academy of Sciences.