Rhinovirus-Induced Exacerbations of Asthma and COPD

Hershenson, Marc B.

What about viral-induced COPD exacerbations? Since COPD differs from asthma in several key respects, the pathogenesis of virus induced exacerbations may be different in this disease. COPD differs from asthma in at least the following ways. The key trigger for COPD is cigarette smoke rather than aeroallergens, air pollutants, or infection. COPD encompasses two distinct processes, chronic bronchitis, and emphysema, which result in structural changes that limit airflow. The COPD airway epithelium undergoes squamous metaplasia. In COPD, macrophages and CD8-positive cell play key roles rather than Th2 cells, eosinophils, or mast cells. COPD pathogenesis appears to be dominated by TGF-, TNF-, IL-1 , and IL-6. The lower airways of 25 to 50% of patients with COPD are colonized by bacteria, particularly Haemophilus influenzae, Streptococcus pneumonia,and Moraxella catarrhalis. [109, 110] . Finally, oxidative stress resulting either from inhaled oxidants or inflammatory cells plays a significant role. As mentioned above, about one half of COPD exacerbations are associated with viral infections, the majority of which are due to RV [22] [23] [24] [25] [26] . COPD exacerbations may also be associated with the isolation of the new bacterial strain [110] . Thus, interactions between virus, bacteria, and host may play a role in the pathogenesis of COPD exacerbations.