Clinical aspects of bronchial reactivity and cell-virus interaction

This chapter illustrates the clinical importance of virus-induced wheezing and airway hyperreactivity (referred to as infectious asthma). It reviews the evidence that is in support of the role of the immune system in provoking these illnesses, and summarizes the experimental data on the inducible expression of epithelial cell cytokines by respiratory viruses. Respiratory syncytial virus (RSV), the most common etiologic agent worldwide to induce lower respiratory tract infections in infants and young children, is linked to the development of asthma, airway hyperresponsiveness, and sensitization to environmental allergens. Massive infiltration of mononuclear cells and activation of eosinophil and basophil leukocytes correlates with the severity of acute RSV disease in both human and animal models. Inflammatory cytokines and CC chemokines with discrete target-cell selectivity for eosinophils and Th2 cells are strongly induced to express in RSV-infected respiratory epithelium. The secretion of CC chemokines, including RANTES and eotaxin by respiratory epithelial cells, in combination with Th2-derived cytokines, is the central pathogenetic event in airway mucosa inflammation, sensitization to bystander antigens, and augmentation of allergen-induced Th2 cell recruitment.