A common group of bacteria found in the gut may protect against food allergies, a study in mice shows.
The study, reported today in the Proceedings of the National Academy of Science suggests that probiotic therapies could be developed to help prevent potentially life threatening anaphylactic reactions to foods such as peanuts.
Although causes of food allergy are unknown, efforts to reduce exposure to infection have been implicated in the rising prevalence of food allergies over a short period of time, say the study’s authors.
“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,” says the study’s senior author Professor Cathyrn Nagler from the University of Chicago.
To explore the theory that early changes in gut bacteria play a role in the development of food allergies the study authors exposed several groups of mice to peanut allergens.
The first group of mice was raised in sterile conditions and had no gut bacteria, while the second group was fed antibiotics, known to reduce levels of gut bacteria.
The researchers discovered that mice in both groups had a strong immunological response to peanuts and produced higher levels of antibodies against peanut allergens compared to mice with normal gut bacteria.
The sensitisation to food allergens could be reversed however by reintroducing a mix of Clostridia bacteria back into the mice. Another group of major intestinal bacteria, Bacteroides, did not have the same effect.
The researchers found Clostridia caused innate immune cells to produce high levels of the signalling molecule IL-22, known to decrease the permeability of the intestinal lining.
“The first step in getting sensitised 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,” says Nagler, but she cautions that more work needs to be done to prove the effect also happens in humans.
Potential role for probiotics
Allergy expert Professor Mimi Tang from the Royal Children’s Hospital and Murdoch Children’s Research Institute in Melbourne says the study is exciting because it identifies a particular bug and the mechanism by which it may protect against food allergies.
“They have identified that it might be through reduced permeability and protection against the immune system being exposed to the antigen. So all of a sudden we actually have an idea why these bugs might be helping,” says Tang, who was not involved in the study.
While it is important to keep in mind that this study was in mice, she says the results suggest there may be a potential role for probiotics in the prevention of food allergies in humans.
But not all probiotics are the same, explains Tang, who is also researching the potential of probiotic therapies to prevent allergies.
“Probiotics refer to a huge group of therapeutic bugs that have potentially beneficial effects but it is like saying antibiotics are helpful, but they are not all going to help the same disease.”
The induction of food allergy in humans is also likely to be down to a lot of factors, she says.
“It’s not just going to be one thing so just having the right bug to protect you may still not be enough. There may be other confounding things that lead to food allergy,” she says.