Persistence of rhinovirus RNA and IP-10 gene expression after acute asthma.

BACKGROUND AND OBJECTIVE: Viral nucleic acid may be detected for up to 6 months after an acute asthma deterioration, but the pattern and consequences of viral persistence after acute asthma are incompletely understood. This study investigates the frequency of viral persistence after acute asthma, assesses viral infectivity and determines the host inflammatory responses to viral persistence. METHODS: Adults and children presenting to hospital with acute asthma and a confirmed respiratory virus infection were studied acutely and at recovery 4-6 weeks later by clinical evaluation and induced sputum for viral and inflammatory mediator detection. RESULTS: Viral RNA was detected during both acute asthma and recovery visits in 17 subjects (viral persistence), whereas in 22 subjects viral RNA had cleared by recovery (viral clearance). The following viruses were detected at recovery: human rhinovirus: 16; respiratory syncytial virus: 2; influenza: 2. In subjects with viral persistence, eight isolates were different to the virus detected at Visit 1. Forty-four per cent of the human rhinovirus isolates were infective at recovery. Asthma and infection severity were similar in the viral clearance and viral persistence groups. Viral persistence was associated with elevated IL-10 mRNA and inducible protein-10 gene expression. CONCLUSIONS: Respiratory viral detection after acute asthma is common, and most often persistence is with non-infective human rhinovirus. There is a host inflammatory response with an altered cytokine environment, and the viral RNA can be source of persistent infection. These effects may have longer-term consequences in asthma.