The role of defensins in virus-induced asthma.

Respiratory viruses appear to play a central role in asthma pathogenesis. In addition to a major role in triggering asthma exacerbations, viral infections early in life may play a role in disease development. Although defensins were initially identified as antimicrobial peptides, recent studies have demonstrated that they have a much broader range of actions that are of relevance to virally induced asthma. Defensins are not only induced during viral infections, they exert direct antiviral actions against some enveloped viruses, and also can impair viral infection of cells. In addition, defensins modulate the activity of several cell types that contribute to innate immunity, including mast cells, epithelial cells, natural killer cells, and dendritic cells. They also have the capacity to modulate adaptive immunity and to contribute to airway remodeling. In this article, recent advances in these areas are reviewed in the context of the potential role of defensins in virus-induced asthma.