Evolving concepts in how viruses impact asthma: A Work Group Report of the Microbes in Allergy Committee of the American Academy of Allergy, Asthma & Immunology

Abstract

Over the past decade, there have been substantial advances in our understanding about how viral infections regulate asthma. Important lessons have been learned from birth cohort studies examining viral infections and subsequent asthma and from understanding the relationships between host genetics and viral infections, the contributions of respiratory viral infections to patterns of immune development, the impact of environmental exposure on the severity of viral infections, and how the viral genome influences host immune responses to viral infections. Further, there has been major progress in our knowledge about how bacteria regulate host immune responses in asthma pathogenesis. In this article, we also examine the dynamics of bacterial colonization of the respiratory tract during viral upper respiratory tract infection, in addition to the relationship of the gut and respiratory microbiomes with respiratory viral infections. Finally, we focus on potential interventions that could decrease virus-induced wheezing and asthma. There are emerging therapeutic options to decrease the severity of wheezing exacerbations caused by respiratory viral infections. Primary prevention is a major goal, and a strategy toward this end is considered.

Keywords: Virus; asthma; genetics; immune; microbiome.

Figure 1.

Immune responses to virus in the allergic asthmatic host. In the healthy host, anti-viral IFN responses control and clear respiratory viral infections. In allergic asthmatics, the release of the type 2-skewing cytokines TSLP, IL-25, and IL-33 promote the induction of Th2 cytokines and the suppression of IFN responses, in addition to promoting airway hyperreactivity (AHR) and increased mucus and IgE production. Furthermore, IgE has the capacity to suppress IFN-α production by Plasmacytoid DCs (pDCs).