Asthmatics naturally deficient in antiviral immunity

Asthmatics produce lower levels of a type of immune cell protein needed to fight off infection from colds and other viruses, scientists have discovered.

The finding reported in the latest issue of the Journal of Experimental Medicine, helps to explain why asthmatics are more susceptible to respiratory virus infections -- the cause of the vast majority of acute asthma attacks in both adults and children.

The researchers, from Imperial College London and University of Southampton, found that asthmatics produce lower levels of interferon beta than healthy people.

Professor Sebastian Johnston, from Imperial College London, and St Mary's Hospital, and one of the report authors, comments: "The discovery that asthmatics produce lower levels of interferons when they encounter respiratory viruses could help in the development of new treatments for asthma attacks. By giving interferons to asthma sufferers it may be possible to prevent or treat the asthma attacks, stopping sufferers from becoming hospitalised through illness."

Professor Stephen Holgate, from the University of Southampton and one of the report authors adds: "We are all very excited about this discovery because it identifies a new way of treating and preventing bad attacks of asthma associated with the common cold.'"

The team examined the interferon responses of cells taken from the lungs of healthy and asthmatic volunteers, measuring how effectively a cold virus (Rhinovirus) was able to replicate in them. Rhinoviruses are the major trigger of acute asthma exacerbations and asthma sufferers are more susceptible to them.

They found that the replication levels of rhinovirus-infected cells was increased 50-fold in the asthmatic group compared with the healthy control group, who were almost completely protected from infection of their lung cells. The asthmatic cells displayed very deficient interferon responses, and the researchers found that replacing the interferon protected these cells from infection, making them behave like normal cells again.

The team now believe this discovery could lead to a potential new treatment for asthma attacks by using a device similar to an asthma inhaler to top up the levels of interferons in the lungs.