Naturally occurring parainfluenza virus 3 infection in adults induces mild exacerbation of asthma associated with increased sputum concentrations of cysteinyl leukotrienes.

BACKGROUND

Viral respiratory tract infections represent the most frequent cause of asthma exacerbation in both children and adults, but the precise mechanism of such exacerbation remains unknown.

OBJECTIVES

To determine the critical mediator of naturally occurring parainfluenza virus (PIV) 3-induced mild asthma exacerbations in adults.

METHODS

The study subjects were 19 adult asthmatics with mild asthma exacerbation (peak expiratory flow = 60-80% of predicted before bronchodilator use and >80% of predicted after initial bronchodilator treatment). Differential cell counts and concentrations of inflammatory markers including eosinophil cationic protein (ECP), cysteinyl leukotrienes (cysLTs), interleukin (IL)-5, IL-10 and IL-12 were measured in the induced sputum obtained from adults with PIV3- (n = 9) and non-cold-induced (n = 10) exacerbation of asthma during both acute and convalescent phases.

RESULTS

PIV3 infection was confirmed by the presence of viral RNA in nasopharyngeal aspirates. Mild exacerbation of asthma was not associated with significant changes in sputum differential cell counts. Concentrations of sputum ECP and cytokines were comparable between PIV3 and non-cold-induced patients. In contrast, PIV3 infection was associated with a significant increase in sputum cysLTs during the acute phase of mild asthma exacerbation.

CONCLUSIONS

Our results identified cysLTs as a critical mediator of PIV3-induced acute asthma exacerbation.