What is already known on this topic
The incidence of childhood allergies has increased in the past few decades. Although genetic factors could predispose infants to allergies, environmental factors such as antibiotic use, caesarean delivery, and dietary habits could also play a role. Most of these environmental factors have been shown to modulate the gut microbiota, but it remains unclear whether gut bacteria can cause food and respiratory allergies.

What this research adds
Researchers analyzed the gut microbiota of 30 healthy children and 90 children affected by food or respiratory allergies. Compared to controls, allergic children present specific microbial signatures in their microbiota, such as higher levels of Ruminococcus gnavus and Faecalibacterium prausnitzii, and lower abundances of Bifidobacterium longum, Bacteroides dorei, B. vulgatus and other fiber-degrading bacteria. Allergic children also have increased numbers of microbial genes involved in the production of inflammatory molecules.

Conclusions
The findings reveal alterations in the gut microbiota of allergic children, and may help to develop new strategies to prevent and treat childhood allergies.

The incidence of childhood allergies has increased in the past few decades, with food allergies increasing about 50% between 1997 and 2011 in US children. A new study reveals that specific gut microbiota signatures are associated with food or respiratory allergies in early life.

The findings, published in Nature Communications, reveal alterations in the gut microbiota of allergic children, and may help to develop new strategies to prevent and treat childhood allergies.

Although genetic factors could predispose infants to develop allergies in early life, environmental factors such as antibiotic use, caesarean delivery, and dietary habits could also play a role. Most of these environmental factors have been shown to modulate the gut microbiota, but it remains unclear whether gut bacteria can cause food and respiratory allergies.

To assess the gut microbiota of allergic children, researchers led by Danilo Ercolini and Roberto Berni Canani at the University of Naples Federico II analyzed fecal samples from 30 healthy children and 90 children affected by food or respiratory allergies.

Microbial blueprint

Compared to controls, allergic children had specific microbial signatures in their microbiota, such as higher levels of Ruminococcus gnavus and Faecalibacterium prausnitzii, and lower abundances of Bifidobacterium longum, Bacteroides dorei, B. vulgatus and other fiber-degrading bacteria, the researchers found.

Children with food allergies had lower levels of B. vulgatus and higher levels of Blautia wexlerae compared with children with respiratory allergies, whereas the latter showed increased abundances of Anaerostipes hadrus and Prevotella copri.

Over the course of 36 months, some allergic children developed immune tolerance. These children showed higher abundances of B. longum, Lachnospira pectinoschiza and A. hadrus, and lower levels of Ruthenibacterium lactatiformans and Clostridium leptum compared to children who did not acquire immune tolerance.

Allergy management

An analysis of the genome of gut microbes revealed that the microbiota of allergic children was characterized by higher inflammatory potential than that of healthy children. Indeed, in the microbiota of allergic children, the researchers found increased numbers of genes involved in the production of lipo-polysaccharides and urease

Lipo-polysaccharides are known to stimulate the production of inflammatory immune molecules, and have been associated with the onset of allergic rhinosinusitis. Ureases are involved in urea degradation and ammonia production. “An increased potential for urea degradation was suggested to promote gut microbiota dysbiosis and to exacerbate colitis in mice,” the researchers note.

The findings suggest that the production of pro-inflammatory molecules may be associated with the increased inflammation typical of allergies, the researchers add. The results could also help to develop microbiota-based strategies for allergy management.

Manipulation of the gut microbiome could be a promising approach for novel preventive and therapeutic strategies against allergy,” the authors say. “Therefore, identifying microbial signatures typical of allergic diseases and understanding the functional potential of the disrupted microbiome is of primary importance for the design of such innovative strategies.”

Avatar
Giorgia Guglielmi is a freelance science writer based in Cambridge, Massachusetts. She received a PhD in Biology from the European Molecular Biology Laboratory and a Master’s in Science Writing from the Massachusetts Institute of Technology.