Common cold and asthma research takes its next steps
20 August 2008
Following his exciting work, published earlier this year, which used a mouse model to explore the role of the common cold in triggering allergic inflammation of the airways (like that seen in asthma), Professor Sebastian Johnston at Imperial College London has been further investigating how rhinovirus infection can cause a reaction within the human body that is typical of an asthma attack, and why this reaction occurs.
The research investigated responses to rhinovirus infection in ten people with asthma and 15 control volunteers without asthma. Subjects were given a standard dose of the virus and their reactions were monitored and recorded.
After administering the virus both groups had colds of similar severity, but it was found that the volunteers with asthma had a clear increase in asthma symptoms compared with the control volunteers who developed only minimal symptoms. People with asthma also experienced a reduction in lung function and increased airway sensitivity in response to the infection; however this was not seen in the control volunteers.
After further analysis, it became apparent that the reaction seen in people with asthma was related to a deficiency in anti-viral immune responses, which normally restrict the replication of a virus within the lung, thereby limiting asthma symptoms. With an impaired response the virus replicates to higher levels, meaning that airway inflammation, and therefore asthma symptoms, are increased.
Although the number of subjects in the study was small, the results mark a new stage in investigations into the causal relationship between rhinovirus infection and asthma symptoms. The model used by Professor Johnston and his colleagues can now form the basis for testing possible future treatments for the worsening of asthma symptoms and asthma attacks as a result of rhinovirus infection. Similarly, novel approaches based on inhibiting viral replication and encouraging protective immune responses may have important therapeutic potential in the treatment of virus-induced asthma attacks in the future.
Sebastian Johnston, Professor of Respiratory Medicine, says: "This study has demonstrated clear differences between the responses of asthmatic and normal subjects to rhinovirus infection both in terms of clinical symptoms and airway function.
"These observations provide compelling evidence supporting an important role for rhinovirus induced lower airway inflammation in precipitating asthma exacerbations and they identify new avenues for development of novel approaches to therapy.
"The study also showed that the reaction seen in people with asthma was related to the severity of their allergic airway inflammation before they were infected. This important finding emphasises the importance of keeping allergic airway inflammation under control by taking asthma controller medications."
Leanne Male, Assistant Director of Research at Asthma UK, says: "In conjunction with the recently developed mouse model, the results of this study can pave the way for new breakthroughs in reducing the very significant impact that viruses currently have on the lives of the 5.2 million people with asthma in the UK."
Image: Anthea Sieveking; Wellcome Images