Role of viruses in asthma

Abstract

Respiratory viral infections are the most important triggers of asthma exacerbations. Rhinovirus (RV), the common cold virus, is clearly the most prevalent pathogen constantly circulating in the community. This virus also stands out from other viral factors due to its large diversity (about 170 genotypes), very effective replication, a tendency to create Th2-biased inflammatory environment and association with specific risk genes in people predisposed to asthma development (CDHR3). Decreased interferon responses, disrupted airway epithelial barrier, environmental exposures (including biased airway microbiome), and nutritional deficiencies (low in vitamin D and fish oil) increase risk to RV and other virus infections. It is intensively debated whether viral illnesses actually cause asthma. Respiratory syncytial virus (RSV) is the leading causative agent of bronchiolitis, whereas RV starts to dominate after 1 year of age. Breathing difficulty induced by either of these viruses is associated with later asthma, but the risk is higher for those who suffer from severe RV-induced wheezing. The asthma development associated with these viruses has unique mechanisms, but in general, RV is a risk factor for later atopic asthma, whereas RSV is more likely associated with later non-atopic asthma. Treatments that inhibit inflammation (corticosteroids, omalizumab) effectively decrease RV-induced wheezing and asthma exacerbations. The anti-RSV monoclonal antibody, palivizumab, decreases the risk of severe RSV illness and subsequent recurrent wheeze. A better understanding of personal and environmental risk factors and inflammatory mechanisms leading to asthma is crucial in developing new strategies for the prevention and treatment of asthma.

Insights Into Type I and III Interferons in Asthma and Exacerbations

“…Respiratory syncytial virus (RSV), human metapneumovirus (hMPV), rhinovirus (RV), and human parainfluenza virus (hPIV) represent four of the leading causes of respiratory tract infections in children and can lead to chronic wheezing and other pulmonary complications (17,18). Numerous studies have linked childhood RV infection with wheeze (2,19,20). In infants, RSV is the most common cause of acute bronchiolitis and wheeze.…”

Rhinovirus Infection in Children with Acute Bronchiolitis and Its Impact on Recurrent Wheezing and Asthma Development

“…It remains to be elucidated whether RV bronchiolitis contributes to asthma development or is a marker of asthma susceptibility. In this sense, RV may be a revealing factor for those with early airway inflammation (i.e., epithelial barrier dysfunction, Th2 polarized inflammation), low IFN responses (i.e., impaired viral defense), and/or genetic variations (i.e., virus-specific risk genes, single nucleotide polymorphisms), acting as a clinically useful risk marker of asthma [ 53 ].…”

Role of SARS-CoV-2 in Asthma Exacerbations

“…Viral respiratory infections and viral colonization in the respiratory tract are the main factors associated with childhood-onset asthma (8). Rhinovirus is a nonenveloped positive-strand RNA virus from the family of Picornaviridae, and is classified into three species: RV-A, B, and C (9). Asthma exacerbations and disease severity are closely linked to RV infections.…”