New approaches needed to treat asthma attacks, say researchers
Respiratory infections are the most common trigger of asthma attacks, and new approaches to therapy are needed, say scientists working on the EU-funded GA2LEN (Global Allergy and Asthma European Network) project, in an article in the journal Allergy. In the review paper, the researchers note that the majority of asthma attacks occur following common colds and other infections of the upper respiratory tract. In some cases, particularly among children, the common cold is the only precursor of wheezing and other symptoms. However, much less is known about these virus-induced asthma attacks than the less common allergy-induced attacks. 'Over the years, chronic asthma has become treatable,' said Dr Nikolaos Papadopoulos of the University of Athens, the lead author of the paper. 'But prevention of acute (and sometimes lethal) attacks remains very difficult - and it is these attacks that cause the pain and anxiety that make asthma so difficult to live with.' When an individual is infected with a cold or other respiratory infection, damage to the cells lining the airways triggers responses in the respiratory, immune and nervous systems. The aim of these responses is to remove the virus from the system quickly and efficiently. In people with asthma, elements of these responses are altered, leading to airway hyper-responsiveness and contributing to the development of asthmatic symptoms. 'Healthy adults have a fast and efficient mechanism to clear the invading pathogen associated with the common cold,' commented Dr Papadopoulos. 'By following infected asthmatic individuals, we may be able to identify how that mechanism differs from a non-asthmatic reaction. This would help us understand how to prevent the hyper-responsive reactions that lead to asthma attacks.' The paper also points to evidence of interactions between viral infections and air pollutants. For example, a study covering 15 European cities revealed an association between elevated NO2 levels and an increase in asthma-related admissions to hospital. The authors also highlight a study which found that children with colds who are exposed to environmental tobacco smoke are at an increased risk of wheezing and hospitalisation due to asthma. According to the scientists, although our understanding of how viruses trigger asthma attacks has increased substantially in recent years, major gaps in our knowledge still exist. 'Details studies of the molecular pathways that underlie virus-induced inflammation may help identify new therapeutic targets,' the project partners write. 'Further studies are also needed in order to differentiate between the response of normal and asthmatic individuals to viruses and to clarify the mechanisms that lead to increased severity and/or preclude resolution of infection in the latter. 'Finally, interactions between multiple triggers and their mechanisms, as well as the impact of virus-induced inflammation on subsequent tissue remodelling are only starting to be unravelled.' The GA2LEN Network of Excellence brings together 31 partners from over 20 European countries. The project aims to integrate research on asthma and allergies in Europe, and ultimately improve the well-being of patients by decreasing the burden of allergic diseases in Europe.