Household Dogs Protect Against Asthma Infection

Man’s best friend may be his best bet to evade asthma and allergies. That is the conclusion of a new study from Tufts University School of Medicine, where researchers have determined that a pet dog allowed indoors can reduce a young child’s risk of developing certain respiratory complications. The findings hint at new public health recommendations for at-risk individuals.
Children’s risk for developing allergies and asthma is reduced when they are exposed in early infancy to a dog in the household, and now researchers have discovered a reason why.

Exposure of mice to dust from houses where canine pets are permitted both indoors and outdoors can reshape the community of microbes that live in the mouse gut — collectively known as the gastrointestinal microbiome — and also diminish immune system reactivity to common allergens, according to a new study by researchers led by Susan Lynch, PhD, associate professor with the Division of Gastroenterology at UC San Francisco, and Nicholas Lukacs, PhD, professor with the Department of Pathology at the University of Michigan.

According to lead researcher Susan Lynch, the team “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." In other words, Lynch and her colleagues wanted to know whether sharing an environment with a dog diminishes your disposition to allergies and respiratory complications by reshaping your gut bacteria.

To investigate, the team designed an experiment with mice. Half of the subjects were exposed to dust from homes with dogs, and the rest were not. All subjects were then exposed to protein and cockroach allergens.

In their study, the scientists exposed mice to cockroach or protein allergens. They discovered that asthma-associated inflammatory responses in the lungs were greatly reduced in mice previously exposed to dog-associated dust, in comparison to mice that were exposed to dust from homes without pets or mice not exposed to any dust.

Among the bacterial species in the gut microbiome of these protected mice, the researchers homed in on one, Lactobacillus johnsonii. When they fed it alone to mice, they found it could prevent airway inflammation due to allergens or even respiratory syncytial virus (RSV) infection. Severe RSV infection in infancy is associated with elevated asthma risk.

The researchers showed in this experiment that protection of the lungs’ airways was associated with reduced numbers and activity of asthma-associated immune cells.

The team is confident that the new findings will contribute to the continued search for anti-allergenic agents and treatment options. Although the results are so far limited to mice, human trials are already underway. "The results of our study indicate that this is likely to be one mechanism through which the environment influences immune responses in early life, and it is something we are currently examining using human samples in a large multi-institutional collaborative study funded by the NIAID," Lynch said in a press release. "Gut microbiome manipulation represents a promising new therapeutic strategy to protect individuals against both pulmonary infection and allergic airway disease."

source :
http://www.medicaldaily.com/household-dog-protects-children-against-allergies-asthma-reshaped-gut-microbiome-lowers-risk-265173
http://www.ucsf.edu/news/2013/12/110746/research-shows-how-household-dogs-protect-against-asthma-and-infection