Can flu infections prevent asthma?
By ANITuesday, December 14, 2010
WASHINGTON - In a new study, scientists found that the influenza virus infection in young mice protected the mice as adults against the development of allergic asthma.
The same protective effect was achieved by treating young mice with compound isolated from the bacterium Helicobacter pylori (H. pylori), a bacterium that colonizes the stomach and is best known for causing ulcers and increasing the risk of gastric cancers.
The findings provide a potential immunological mechanism in support of the “hygiene hypothesis,” an idea that attributes the increasing rate of asthma and allergies to the successful reduction of childhood infections with vaccines and antibiotics, say researchers at Children’s Hospital Boston.
“Some infections appear to result in important protective effects against asthma. But we certainly don’t want to give people dangerous infections to prevent asthma. So 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,” said Dale Umetsu of Children’s Division of Immunology and a senior author of the paper.
In mice, influenza A infection appeared to confer its benefits by expanding an immature cell type in the lung known as natural killer T (NKT) cells, part of the innate immune system. . The same beneficial NKT cells in the lung could be expanded by several NKT-stimulating molecules known as glycolipids, including one isolated from H. pylori.
Previous studies examining the hygiene hypothesis have focused on the adaptive immune system, which features immune cells that are slow to respond but are able to develop long-term memory, such as those stimulated by each year’s flu vaccine or those involved in seasonal allergies.
In contrast, the new paper examined the innate immune system, which responds rapidly to infections and shapes adaptive immune responses. The study specifically focuses on NKT cells, one of the first responders to many infections.
The findings are published online in the Journal of Clinical Investigation. (ANI)
