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Neutrophil degranulation and cell lysis is associated with clinical severity in virus-induced asthma

¹ Airways Research Centre, John Hunter Hospital, Newcastle, Australia. ² Dept of Respiratory Medicine, National Heart and Lung Institute at St Marys, Imperial College School of Medicine, London, UK. ³ Institute for Molecular Genetics and Genetic Engineering, Belgrade, Yugoslavia. ⁵ Faculty of Medicine, University of Newcastle, Newcastle, Australia

CORRESPONDENCE: P.G. Gibson, Dept of Respiratory and Sleep Medicine, John Hunter Hospital, Locked Bag 1, Hunter Region Mail Centre, NSW 2310, Australia. Fax: 61 249213469

Keywords: acute asthma, induced sputum, influenza, respiratory syncytial virus, virus infection

Received: May 7, 2001
Accepted August 2, 2001

This work was funded by Asthma NSW, the National Health and Medical Research Council (Australia) and the John Hunter Hospital Charitable Trust.

Acute exacerbations of asthma are frequently caused by viral infections, but the inflammatory mechanisms in virus-induced asthma are poorly understood. The aim of the present study was to determine whether viral infection in acute asthma was associated with increased sputum neutrophil degranulation and increased cellular lysis and whether these changes are related to clinical severity.

Adults (n=49) presenting to the emergency department with acute asthma were examined for infection by means of sputum direct-fluorescence antigen detection, sputum culture, and sputum polymerase chain reaction for Mycoplasma, Chlamydia and Legionella pneumophila, and all common respiratory viruses. Subjects infected with one of these agents were classed as having an infective exacerbation. Spirometry and sputum induction were performed on presentation and 4–5 weeks later.

Thirty-seven subjects (76%) had virus infection and acute asthma. Those with virus infection had increased sputum neutrophils (p<0.05) and increased neutrophil elastase (p<0.05), this was related to increased elevated sputum lactate dehydrogenase (LDH). Subjects with noninfective asthma had an increase in the proportion of sputum eosinophils. Both groups had elevated sputum eosinophil cationic protein (ECP) concentrations. Higher levels of sputum LDH and ECP were associated with a longer hospital stay.

Virus infection and acute asthma is associated with neutrophilic inflammation, cell lysis and more severe clinical disease.