Are we there yet? understanding interactions between respiratory viral infections, atopy, and the microbiome

Atopic disease has become an increasingly prevalent condition worldwide and a significant health concern. Similarly, due to concerns about morbidity associated with respiratory viral illness in early childhood, there has been increased exploration of the relationship between atopy and viral illnesses. Historically, studies have focused on early-life respiratory infections driving the development of atopy or post-viral airway disease, with respiratory syncytial virus (RSV) infection driving post-viral disease in those without atopy, while human rhinovirus (hRV) leading to asthma in those with pre-existing atopy. The impact of atopy on the antiviral immune response remains debated, with some studies suggesting it provides a protective role, while others suggest it impairs the immune response. Beyond the respiratory tract, the gut microbiome increasingly is recognized as a potential modulator of both local and distant immune responses, a relationship associated with lung function termed the gut-lung axis. As we continue to elucidate the biochemical mechanisms underlying these pathways in mouse models, it will be important to identify analogous human pathways. This review explores what is currently known about the relationship between atopy and respiratory viral infections focusing on knowledge about how viral infections drive atopy and, reciprocally, how atopy modulates respiratory viral induced disease. Moreover, we review published information on analogous human pathways. Utilizing this information will help us with better disease management and potential development of targeted therapeutics.