(RxWiki News) Scientists at Children's Hospital Boston and Harvard Medical School have found that the influenza virus infection in young mice protected the critters against the development of allergic asthma as adults.
This tendency was higher in adult mice catching flu, however.
The same allergy/asthma-diminishing effect was accomplished when young mice were treated with a compound isolated from the bacterium that colonizes the stomach, known for causing ulcers and increasing gastric-cancer risk.
These findings support the "hygiene hypothesis," which in part attributes the increasing rate of asthma and allergies to vaccines and antibiotics that have been successful in combatting childhood infections. Results of the study appear in the Journal of Clinical Investigation.
"We certainly don't want to give people dangerous infections to prevent asthma," said Dale Umetsu of Children's Division of Immunology and a senior author of the paper. "If we can understand how infections prevent asthma, we may be able to replicate the good parts and avoid the bad parts of infection and develop new treatments for children to prevent asthma.”
Children in developed countries suffer with allergies because they don't often come in contact with viruses and bacteria like the children in developing nations, according to the researchers.
"Our results suggest that infection with certain micro-organisms can prevent the subsequent development of asthma and allergy by expanding", said Umetsu.
The study focused on a sub-group of immune-system cells called natural killer T-cells or NKT cells, which help the immune system fight against a host allergic and asthmatic reactions. These cells are often first-responders to many infections. Influenza A infection in mice appeared to confer its benefits expanding these cells in the lung.
Previous hygiene-hypothesis studies have analyzed the adaptive immune system's role. Adaptive immune cells, such as those stimulated by flu vaccines and involved in seasonal allergies, are slow to respond but are able to develop long-term memory.
Asthma is a chronic inflammatory disease of the lungs that causes temporary constriction of the airways (specifically the bronchi) leading to obstruction of airflow and breathing difficulty, according to Joseph Madia, M.D. Symptoms include the sudden onset of wheezing, gasping for breath and chest tightness. Coughing may also be present. Asthma affects more than 300 million individuals worldwide.