August 26, 2014
Common Gut Bacteria May One Day Help Protect Against Food Allergies
April Flowers for redOrbit.com - Your Universe Online
There has been a great deal of research into food allergies lately — ranging from the effect of race on food allergies to how tap water might be linked to the development of allergies. The latest study, from the University of Chicago, shows that the presence of a common gut bacteria, Clostridia, may help protect against food allergies.
The findings, published in Proceedings of the National Academy of Sciences, show that by inducing immune responses designed to prevent food allergies from entering the food stream, Clostridia is able to minimize allergen exposure and prevent sensitization in mice. Sensitization is a necessary step in the development of food allergies. The researchers hope that their results will lead toward probiotic therapies for food allergies, which so far, have been untreatable.
Food allergies are an immune system response to certain foods that can sometimes be deadly. Scientists do not know the cause of these allergies, but some studies have indicated that part of the cause might be modern hygienic and dietary practices – specifically by the way they disturb the body's natural bacterial composition. Food allergy rates among children have risen significantly in recent years, approximately 50 percent between 1997 and 2011. Other studies have revealed a link between antibiotic and antimicrobial use and the rise of food allergies, as well.
"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 Cathryn Nagler, PhD, Bunning Food Allergy Professor at the University of Chicago, in a recent statement. "Our results suggest this could contribute to the increasing susceptibility to food allergies."
Nagler and her colleagues used food allergen responses in mice to test the effect of gut bacteria on food allergies. A group of germ-free mice that were born and raised in sterile conditions (thus having no resident microorganisms), and a group of mice treated with antibiotics as newborns to reduce gut bacteria were both exposed to peanut allergens. Strong immunological responses were seen in both groups of mice. These responses produced significantly higher levels of antibodies against the allergens than mice with normal gut bacteria.
The team was then able to reverse the sensitization to the allergens by reintroducing a mix of Clostridia bacteria into the mice. Introducing another major gut bacteria, Bacteroides, was unsuccessful in reversing the sensitization. This suggests that Clostridia has a unique, protective role in the body's fight against food allergens.
The team continued their investigation, trying to discover the mechanism by which Clostridia's protective role was affected. They studied the cellular and molecular responses that occur in the gut, using genetic analysis to discover Clostridia causes innate immune cells to produce high levels of a signaling molecule known to decrease the permeability of the intestinal lining known as interleukin-22 (IL-22).
"We've identified a bacterial population that protects against food allergen sensitization," Nagler said. "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." Nagler cautions that people with food allergies should not get their hopes up yet. The study findings are most likely applicable at a population level, not an individual one yet.
Factors such as genetics have a great effect on an individual's chances of developing a food allergy, as well as how those allergies manifest. The identification of a bacteria-induced barrier-protective response, however, represents a sea change in the understanding of how to prevent sensitization to food. Common in the human gut, Clostridia provides a clear target for potential therapies to prevent or treat food allergies. The researchers are continuing their work by developing and testing compositions to be used for probiotic therapy, for which they have filed a provisional patent.
"It's exciting because we know what the bacteria are; we have a way to intervene," Nagler said. "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."
"Food allergies affect 15 million Americans, including one in 13 children, who live with this potentially life-threatening disease that currently has no cure," said Mary Jane Marchisotto, senior vice president of research at Food Allergy Research & Education. "We have been pleased to support the research that has been conducted by Dr. Nagler and her colleagues at the University of Chicago."