Flu symptoms dampened by clue to inflammation
28 July 2008
A new discovery could lead to treatments to prevent lung inflammation caused by flu infection. The study, led by researchers from Imperial College London, reveals how the activity of immune cells in the lung is normally kept under control. An exaggerated immune response can make flu symptoms worse. The research is published in Nature Immunology.
Symptoms of influenza including breathlessness, weight loss and fever can be made worse by the immune system’s response to infection. The virus is often cleared from the body by the time flu symptoms appear but because the immune system continues to try to eradicate the virus, symptoms persist. This prolonged immune response causes the lungs to become inflamed, clogging the airways and making it difficult to breathe. A similar immune overreaction also occurs in asthma and some inflammatory conditions of the gut.
Lead author Professor Tracy Hussell of the the National Heart and Lung Institute at Imperial College London, explained:
“The immune system is sophisticated and much of the time it does a fantastic job of fighting infection, but it has the ability to cause a lot of damage when it overreacts.’’ Our new research is still in its early stages, but these findings suggest that it could be possible to prevent the immune system going into overdrive, and limit the unnecessary damage this can cause.”
The study reveals that the activity of immune cells in the lung is normally kept under control by a receptor known as CD200R. This receptor works in partnership with a second molecule called CD200 to limit the immune response and switch off inflammation. The influenza virus prevents CD200R from binding to CD200 and so the lungs become inflamed.
To assess whether CD200R could be used to reduce inflammation, mice infected with influenza were given either a mimic of CD200 or an antibody to stimulate production of CD200R.
The results were encouraging:
‘‘Our research is still in its early stages, but these findings suggest that it could be possible to prevent the immune system going into overdrive, and limit the unnecessary damage this can cause, ” said Professor Hussell.
The results showed that the mice that received treatment had less weight loss and less inflammation in their airways and lung tissue than mice that did not. The influenza virus was still cleared from the lungs within seven days meaning the immune system’s ability to fight the virus was not compromised.
Following these results in mice, the researchers hope that a therapy that targets the CD200R receptor to prevent immune overreaction could be developed for people. They believe this would quickly reduce symptoms and reduce the damage that the immune system can cause to the lungs.
Researcher Dr Robert Snelgrove, a Sir Henry Wellcome Postdoctoral Fellow at Imperial College London, added:
“Although flu is just an inconvenience for some people, it can be dangerous and even fatal in the very young and elderly. We hope our research could ultimately help to develop treatments which fight the effects of this lethal virus.”
In addition to the possible applications for treating influenza, the researchers hope their findings could lead to new treatments for other conditions where excessive immunity can be a problem, including other infectious diseases, autoimmune diseases and allergy.
The research was funded by the Medical Research Council, the US National Institutes of Health, the Wellcome Trust, and the European Union.
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