Rhinovirus-Induced Exacerbations of Asthma and COPD

Hershenson, Marc B.

Interferon responses, which have been shown to affect the outcome respiratory viral infections in animal models, may also be deficient in patients with asthma. How might this be the case? It is well known that many allergic asthmatics show a skewing of their T cell differentiation towards the Th2 phenotype. Since the differentiation of Th1 and Th2 T-helper cell lineages is mutually antagonistic (e.g., IL-4 blocks Th1 differentiation) [60] , allergic asthmatics with Th2 polarization may have a deficiency in their interferon response ( Figure 2 ). During induced colds, asthmatic subjects with strong peripheral blood monocytes and sputum cell interferon gamma responses showed milder cold symptoms and more rapid viral clearance [61, 62] . Also following experimental rhinovirus infection, viral clearance and airway function correlate with blood and bronchoalveolar (BAL) CD4 cell interferon gamma production [63] . Epithelial and BAL cells from asthmatic subjects show reduced type I and type III interferon responses to rhinovirus infection ex vivo [64, 65] . Together, these data suggest that asthmatics may be more susceptible for RV infection.