According to a recent study, published in the Journal of Nature Medicine, loss of beneficial bacteria in the human gut acts as a switch that makes children susceptible to food allergies. As per a recent estimate, the number of Americans who suffer from food allergy has risen sharply over the last decade to as many 32 million. About 8 percent of children in the U.S are affected. For the study, the researchers studied gut bacteria in babies with and without food allergies.
The researchers collected stool samples from 56 food-allergic people and 98 matched controls. The changes in bacterial content of the samples were analysed by Gerber and his colleagues at Brigham and Women's Hospital. The work revealed that the bacteria in the feces of babies with food allergies were different from those of controls.
However, to find out whether those bacterial differences played a role in their food allergies, the team transplanted fecal bacteria from the babies into a special strain of allergy-prone mice. The mice were then fed with small doses of chicken egg protein to sensitise their immune systems to this allergen. Eventually, they were then challenged with a large dose.
"The fecal bacteria from food-allergic subjects did not protect against food allergy, whereas the bacteria from control subjects did," Chatila says.
"If you give them the right bacteria, the Clostridia, they're completely resistant to food allergy," said Talal Chatila, MD, director of the Food Allergy Program at Boston Children's and a senior author on the paper.
As per the findings of the study, one of the senior authors on the study believes that the study proves that the loss of protective gut bacteria is a critical factor in food allergy.
"At the very least it is a fundamental mechanism. And more likely, in my mind, it is the fundamental mechanism on which other things can be layered," he said.
While previous studies have suggested that certain bacteria can protect against food allergies, Chatila and his colleagues go a step further, describing the specific immunological pathway by which the bacteria act in mice. It begins with a protein, known as MyD88, that serves as a "microbial sensor" in the immune system's regulatory T cells.
"You need the bacteria to give particular signals that are picked up by nascent regulatory T cells in the gut," Chatila explains.
Those signals trigger a chain reaction that changes the gut regulatory T cells into a specific type, known as ROR-gamma regulatory T cells that protect against food allergies.
The researchers believe that their findings will eventually lead to new treatments that prevent the development of food allergies in new-borns at risk. The treatments might take the form of probiotics -- mixes of beneficial bacteria -- or drugs that prime the immune system in the same way.