Enhanced severity of virus associated lower respiratory tract disease in asthma patients may not be associated with delayed viral clearance and increased viral load in the upper respiratory tract

Background: Viral respiratory infections, particularly human rhinovirus (HRV) infections, are the most common cause of asthma exacerbation. HRV infections usually lead to more severe and longer duration of lower respiratory tract (LRT) symptoms in asthmatics than in otherwise healthy individuals. However, the exact mechanism by which viruses contribute to exacerbation of asthma is unknown. Objectives: The main objective of our study was to investigate the relationship of the enhanced severity of LRT symptoms to viral dynamics or cytokine responses in the upper respiratory tract (URT). Study design: Therefore, we conducted a longitudinal study in which asthmatics and healthy controls were followed during natural viral respiratory tract infections. Results: Our study confirmed that viral respiratory tract infections caused more severe problems of the LRT in asthma patients as compared to healthy controls. However, for all subjects, the severity of LRT symptoms were not related to viral load or prolonged viral shedding in the URT. In addition, we did not detect differences in proinflammatory cytokines in the URT between asthmatics and controls. Conclusion: Persistence of the virus, as well as viral load in the URT, may not be associated with the induction and/or persistence of asthmatic symptoms. (c) 2007 Elsevier B.V. All rights reserved.