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Asthma exacerbations are most commonly triggered by viruses, particularly rhinovirus. There is currently no biomarker that can be used to predict that a virus has triggered an exacerbation.
This group studied bronchial epithelial cells (BECs) obtained by bronchoscopy from 10 healthy controls and 10 patients with asthma who had never received inhaled corticosteroids. The epithelial cells were cultured and exposed to rhinovirus 16. The supernatants were measured for various cytokines including interferon-γ-induced protein 10 (IP-10) by FACs analysis.
There was a significant increase in IP-10, RANTES, interleukin (IL)-6, IL-8 and tumour necrosis factor α from baseline, which peaked at 48 h after infection. There was no significant difference between patients with asthma and controls. Pretreatment of the BECs with dexamethasone did not significantly reduce the release of IP-10. Rhinovirus replication was significantly greater in BECs of subjects with asthma than controls, and there was a positive correlation between IP-10 release and viral concentrations.
The authors went on to investigate whether acute virus-induced asthma could be differentiated form non-infective acute asthma. These patients were not steroid naïve. They found that patients with acute virus-induced asthma had significantly increased IP-10 levels compared with those with non-viral acute asthma. Viral infections were also found to be associated with lower forced expiratory volume in 1 s. Individuals with acute rhinoviral infection specifically had significantly increased IP-10 levels, and a level of 168–1916 pg/ml increased the likelihood of rhinoviral infection more than twofold.
It appears that rhinoviral infection initiates an inflammatory response with marked release of IP-10, and this correlates with rhinovirus replication. The authors conclude that IP-10 may therefore be a useful clinical marker to identify rhinovirus-induced asthma and may be a potential therapeutic target for the future.
Wark PAB, Bucchieri F, Johnston SL, et al. IFN-γ-induced protein 10 is a novel biomarker of rhinovirus-induced asthma exacerbations. J Allergy Clin Immunol 2007;120:586–93