Viral infections and atopy in asthma pathogenesis: new rationales for asthma prevention and treatment

Viral infections can worsen episodes of allergic sensitization to allergens, putting the affected individuals, often children, at risk for developing persistent asthma during adult life. Understanding how the mechanisms mediating the antiviral response and driving allergic inflammation caused by allergens interact is crucial. This will provide insights into when and what player or molecule to target for treatment and prevention of asthma in children at the early stages of the disease. Prospective birth cohort studies tracking asthma initiation and consolidation in community cohorts have identified viral infections occurring against a background of allergic sensitization to aeroallergens as a uniquely potent risk factor for the expression of acute severe asthma-like symptoms and for the ensuing development of asthma that can persist through childhood and into adulthood. A combination of recent experimental and human studies have suggested that underlying this bipartite process are a series of interactions between antiviral and atopic inflammatory pathways that are mediated by local activation of myeloid cell populations in the airway mucosa and the parallel programming and recruitment of their replacements from bone marrow. Targeting key components of these pathways at the appropriate stages of asthma provides new opportunities for the treatment of established asthma but, more crucially, for primary and secondary prevention of asthma during childhood.