Diverse Gut Bacteria in Infants Linked to Reduced Food Allergies

Laird Harrison

December 03, 2021

Infants with greater diversity of bacteria in their stools are less likely to have allergies to foods such as egg, milk, or peanuts, researchers say.

The finding could lead to new approaches to preventing immunoglobulin E-mediated food allergy (IgE-FA), according to Christine Joseph, PhD, MPH, an epidemiologist in the Henry Ford Health System in Detroit, Michigan, and colleagues.

"Bacterial colonization is a potentially modifiable factor along the causal pathway to IgE-FA," they write in  Pediatric Allergy and Immunology.

Food allergies can result when exposure to specific foods activate mast cells and basophils. The allergies may cause atopic eczema in infancy and rhinitis and asthma later in life.

In healthy infants, food proteins interact with antigen-presenting cells, but T regulatory cells suppress immune responses, preventing allergies, the researchers write.

The relationship between gut bacteria and allergy is complex. Oligosaccharides in human milk that induce the production of interleukin 10 and IgA also stimulate the growth of Bifidobacterium and Lactobacillus, according to the researchers. Clostridia activate the release of TGF-β, which helps induce T regulatory cells to suppress undesirable immune reactions. Gut bacteria also help ferment complex carbohydrates generating short-chain fatty acids, which influence B-cell and intestinal barrier function.

Previous studies have turned up associations between gut microbiota composition and food sensitivities. They have indicated that delayed colonization of bacteria in the gut may lead to irregularities in the development of gut-associated lymphoid tissues.

To understand this relationship better, Joseph and colleagues analyzed data from the Microbes, Allergy, Asthma, and Pets Research Program of the Wayne County Health Environment Allergy and Asthma Longitudinal Study birth cohort.

Researchers recruited pregnant women ages 21-45 years in metropolitan Detroit who were receiving prenatal care at Henry Ford obstetric clinics between September 2003 and November 2007. They collected infant blood samples at 6- and 12-month home visits. At a 24-month clinic visit, they collected allergen-specific serum IgE, administered skin prick allergy tests, and interviewed parents about their children's medical history, food avoidance, gastrointestinal symptoms, and reactions to food. The researchers collected stool samples at 1 month and 6 months of age.

A panel of two board-certified allergists reviewed clinical and interview data from birth through age 3-5 years to classify infants as likely or unlikely to have IgE-FA. A third allergist ruled on disagreements.

Of the 447 children with sufficient data, 44 were diagnosed with IgE-FA. Of these, 59% were allergic to one food, 30% were allergic to two foods, and 11% were allergic to three foods. The most common allergy was egg (in 73% of the allergic children), followed by peanut (59%) and milk (20%).

Among the children at 3-5 years, the stool samples of those who were allergic showed substantially less diversity of gut microbiota compared with those who were not allergic, especially to milk and peanut. The difference was statistically significant (all covariate adjusted P values for alpha metrics < .007)

Testing for specific bacteria in the 6-month-olds, the researchers found decreased abundance of 20 individual operational taxonomic units (OTUs) in the allergic children, mostly in the orders Bacteroidales and Clostridiales. On the other hand, these children had greater abundance of Bifidobacteriales.

The finding could lead to new approaches at preventing food allergies, said Vivian Hernandez-Trujillo, MD, director of allergies and immunology at Nicklaus Children's Hospital in Miami, Florida, who was not involved in the study.

"It's a little early, but certainly research needs to continue in this area because the possibility for intervention into IgE-mediated food allergy would be incredible," she told Medscape Medical News. "Studies like this give us hope that we will be able to prevent food allergies."

There is not yet enough evidence to recommend any treatment such as probiotics that might influence infants' gut microbiota, she said.

So far, the best approach to preventing peanut allergies is to begin introducing solid foods in general, and peanut products specifically, early in the infant's life, Hernandez-Trujillo said, citing Addendum Guidelines for the Prevention of Peanut Allergy in the United States: Report of the National Institute of Allergy and Infectious Diseases.

Hernandez-Trujillo reports financial relationships to DBV Technologies and Kaléo. Joseph has disclosed no relevant financial relationships.

Pediatr Allergy Immunol. Published online November 23, 2021. Abstract

Laird Harrison writes about science, health, and culture. His work has appeared in national magazines, in newspapers, on public radio, and on websites. He is at work on a novel about alternate realities in physics. Harrison teaches writing at the Writers Grotto. Visit him at lairdharrison.com or follow him on Twitter @LairdH

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