A species of gut bacteria may be responsible for preventing allergies in children.
Allergies have become much more common in industrialised countries since the mid-20th century, but it’s still not clear why.
Some evidence points to the microbiome – the community of bacteria that live inside our bodies – as a possible factor. Children whose mothers take probiotic supplements seem to have a lower risk of allergies, while those born by caesarean section, which affects the acquisition of bacteria in the gut, may have a higher risk.
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Cathryn Nagler at the University of Chicago and colleagues found in an that children with a cow’s milk allergy have markedly different bacteria in their gut than healthy children.
To see if those differences contribute to the development of allergies, they took faecal samples from babies with and without cow’s milk allergies and transplanted them into mice that lacked gut bacteria.
Mice without gut bacteria and mice that received bacteria from children with allergies had anaphylactic reactions when exposed to cow’s milk for the first time, but mice that received bacteria from healthy children did not. That tells us that a certain population of bacteria is needed to prevent allergies, says Nagler.
By combining data on the bacterial populations and patterns of gene expression in the intestine, the team discovered that one particular species, Anaerostipes caccae, appears to be a protective factor. If this species alone is transplanted into germ-free mice, they do not suffer allergic reactions to cow’s milk.
From bugs to drugs
As evidence has accumulated regarding the microbiome’s role in health, there has been growing interest in faecal transplants as experimental therapies. However, Nagler doesn’t think they are a good idea.
“I think it’s potentially dangerous,” she says. “Our focus would be to move away from any sort of faecal transplant in humans and use this a proof of concept for developing drugs based on the microbiome.”
A. caccae bacteria produce a fatty acid called butyrate, which is a crucial nutrient for establishing a healthy gut microbiome. Nagler’s startup company, ClostraBio, is developing a synthetic formulation of butyrate, which they hope to test in clinical trials in the next couple of years.
Nature Medicine
