Childhood asthma: Looking on the brighter side

http://www.eurekalert.org/pub_releases/2015-11/lm-cal112615.php

PUBLIC RELEASE: 26-NOV-2015
Childhood asthma: Looking on the brighter side
LUDWIG-MAXIMILIANS-UNIVERSITÄT MÜNCHEN

The effect of a widespread genetic variant that increases the risk for childhood asthma can be neutralized. A new study shows that young infants are particularly responsive to the positive influence of exposure to farm dust.

Asthma researchers from Ludwig-Maximilians-Universitaet (LMU) in Munich have shown, for the first time, that specific environmental influences can neutralize the effect of a prevalent genetic variant that increases risk for childhood asthma. The new study shows that carriers of this particular variant are also especially responsive to environmental factors that confer long-term protection against asthma. Bearers of the risk variant who had been exposed to airborne micro-organisms in animal sheds on farms before their first birthday were found to be significantly less likely to show symptoms of infections of the lower respiratory tract than were carriers who had had no contact with farm animals in early life. "We can conclude from this observation that these children are also less likely to develop asthma later on than carriers who did not benefit from the 'farm effect,'" says LMU's Markus Ege, Professor of Pulmonary Epidemiology at Dr. von Hauner's Children's Hospital.

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These findings argue that farm children who are regularly brought into animal sheds before they are weaned can cope more effectively with viral infections than other kids. Based on the analysis of other variables, such as the incidence of viral illnesses in older siblings, the researchers deduced that the infants are exposed to the same infection risk as children reared in non-agricultural environments. "But they react differently to infection and show no overt symptoms of acute illness," says Georg Loss. The data gathered in the course of the "Pasture" study give researchers a unique opportunity to observe the development of these children over a period of several years. As a result, they were also able to confirm that carriers of the risk variant who displayed no symptoms of infection of the lower respiratory tract during their first year of life also have a lower risk of developing asthma later on. "The protective effect of the appropriate environment is so strong that it effectively neutralizes the normally deleterious influence of the risk variant. It's as if these children didn't have the genetic variant at all," says Ege.

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