[ Watch the Video: Pet Dogs May Shield Kids From Later Allergies ]
Brett Smith for redOrbit.com – Your Universe Online
Previous research has shown that children who grow up in a house with a dog are less likely to develop severe allergies and now a new study from an American team of researchers has found that gut bacteria may play a role in that relationship.
According to a study published Monday in the Proceedings of the National Academy of Sciences (PNAS), mice that were exposed to dust from houses where pet dogs are allowed both inside and outdoors had their community of gut microbes altered and experienced a diminished immune system reaction to common allergens.
The study team was also able to identify a specific bacterial species, Lactobacillus johnsonii, that is critical in safeguarding air passages against both allergens and viral infection.
“We set out to investigate whether being exposed to a distinct house dust microbiome associated with indoor/outdoor dogs mediated a protective effect through manipulation of the gut microbiome and, by extension, the host immune response,” said study author Susan Lynch, an associate professor of gastroenterology at the University of California, San Francisco.
“The results of our study indicate that this is likely to be one mechanism through which the environment influences immune responses in early life,” she added.
The researchers noted that while their results were obtained using tests of lab mice – the results also point to a mechanism explaining the lowered allergy risk among children raised with dogs.
Mice in the study were exposed to cockroach or protein allergens. The researchers found that the mice’ inflammatory responses in the lungs were significantly cut in mice that had been exposed to dog-associated dust, compared to both mice that were exposed to dust from dog-free homes and mice not exposed to any dust.
L. johnsonii was one species of gut bacteria that appeared to convey a lower inflammation response based on initial results. When researchers fed this species by itself to the mice, they discovered that it led to the aversion of the airway inflammation response to allergens or even respiratory syncytial virus (RSV) infection. Severe RSV infection in infants is linked with elevated risk of developing asthma.
The researchers also found that the beneficial effects were associated with lowered numbers and activity of asthma-associated immune cells.
While the level of protection afforded by L. johnsonii was still less than that provided by the full complement of microbes from dog-related dust, the finding did suggest that other, readily-available bacterial species could be used to provide full protection.
Lynch said her own work along with other recent similar studies has convinced her that “the composition and function of the gut microbiome strongly influence immune reactions and present a novel avenue for development of therapeutics for both allergic asthma and a range of other diseases.”
She added that her study points to changes in the gut microbiome having wide-reaching effects beyond the digestive tract.
The researchers had previously shown that a home with an inside-outside pet was linked to a considerably more diverse house dust microbiome that augmented species found in the gastrointestinal tract of humans.