HOUSTON – The specific bacterial composition of infants’ gut biomes may be key to their developing or not developing allergic disease in early childhood, supporting what researchers called “a gut-airway axis” for allergic disease.
In preliminary, unpublished findings, Susan V. Lynch, Ph.D., of the department of medicine at the University of California, San Francisco, and her colleagues looked at stool samples from 298 infants aged between 0 and 11 months. They measured gut bacterial diversity, distribution, and richness at 1, 3, 6, 9, and 12 months. Gut bacteria diversified rapidly and steadily during this time, the researchers found.
"The dramatic diversification that occurs during the first year of life is the peak period of plasticity of microbial accumulation," Dr. Lynch said at the annual meeting of the American Academy of Allergy, Asthma, and Immunology. The composition of the gut microbiomes was significantly related to the age of the infants.
Denise Fulton/Frontline Medical News
Infants' gut composition was affected by the presence or absence of furred pets, particularly dogs.
Dr. Lynch's group found that in infants less than 6 months of age gut biomes were dominated by Bifidobacteriaceae (70 infants), Enterobacteriaceae (49), or codominated by both (11). Gut composition related to the types of microbial exposures in the home and was affected by the presence or absence of furred pets, particularly dogs, Dr. Lynch said.
Infants without pets in the home were most likely to have a codominated biome, with a relative risk of multiple sensitization of 2.94 when compared with infants with a Bifidobacteriaeae biome and 2.06 compared with those with a Enterobacteriaceae-dominated biome.
“We asked is there a clinical correlate? Yes. That codominated community runs the highest risk of allergic disease development at age 2, having a significantly increased risk ratio, compared with either of the singly dominated communities,” Dr. Lynch said.
Moreover, the different bacterial profiles were responsible for observed differences in gut function. “We find very dramatic differences in carbohydrate and fatty acid metabolism in these communities for which atopy risk is highest,” Dr. Lynch said. “Perhaps the foundation for atopic development in childhood is associated with a compositionally distinct and highly dysfunctional neonatal gut.”
The potential for intervention is highest in the first year of life when the microbiome is most plastic, Dr. Lynch said; however, she declined to speculate what such interventions might amount to, noting that it was too early.
At the same talk, Dr. Erika Von Mutius, medical director of the asthma and allergy clinic at the University of Munich in Germany, described her work with children growing up on European farms, whom decades worth of studies have shown to have both higher diversity and frequency of microbial exposure and also lower risk of asthma and allergies than children raised in non-farm environments.
Dr. Von Mutius reported that her research group is beginning to pinpoint the protective microbes detected in these children’s’ environments and also their respiratory tracts.
A handful of organisms appear to work in concert as a microbial cocktail that predicts lower asthma and allergy rates. “What we’re seeing here is not the needle in the haystack, it’s not the one thing that will protect [from disease]. The question is, is the more the better, or is it like a soup, in which certain components are more important?’ We think it’s more like a soup,” she said.
The way in which these microbes work in the body to become protective is unknown, said Dr. Von Mutius, whose current research is looking at nose and throat samples from children. Dr. Von Mutius and her colleagues found more than fourfold more microbial diversity in farm children’s noses than their throats, though, she said, they did not yet understand why.
“The more diversity in the nose, the less asthma these children had,” she said, adding that it remained to be learned “whether you can do something in the nose to affect asthma” or whether lower respiratory and/or gut processes were key to mediating asthma risk. Dr. Lynch has received support or other funding from Second Genome, Janssen, Regeneron, and KaloBios. Dr. Von Mutius has received fees or support from ALK, Nestle, Airsonett, Protectimmun, and Novartis.