Respiratory syncytial virus and airway microbiota -- A complex interplay and its reflection on morbidity

Abstract

The immunopathology of respiratory syncytial virus (RSV) infection, the most common cause of lower respiratory tract infections (LRTI) in the pediatric population, with severe disease being the exception. The variability of the clinical presentation is incompletely explained by host, viral and environmental factors but, in infants and young children, disease severity is certainly linked to the physiological immune immaturity. There is evidence that the maturation of the host immune response is, at least in part, promoted by the composition of the nasopharyngeal microbiome that, modulating excessive inflammation, can counteract the predisposition to develop viral respiratory infections and lower the risk of disease severity. However, interaction between the nasopharyngeal microbiota and respiratory viruses can be bidirectional. Microbial dysbiosis can drive disease pathogenesis but may also represents a reflection of the disease-induced alterations of the local milieu. Moreover, viruses like RSV, can also increase the virulence of potential pathogens in nasopharynx, which is a main reservoir of bacteria, and therefore promote their spread to the lower airways causing superinfection. Negative changes in microbial community composition in early life may constitute a heightened risk towards severe RSV respiratory infection and bacterial superinfection, whilst specific groups of microorganisms can be associated with protection. A better understanding into the potential negative and positive role of the different nasopharyngeal bacterial species in disease prevention as well as into the possible benefits of microbiome therapeutic manipulation, may improve patient outcomes.

Comments on vitamin D and sensitization, asthma treatment, and lung function development

“…Asthma is the common denominator for the first two reviews featured in this issue. Rossi et al 1 comment and analyze the complex interactions between the respiratory syncytial virus (RSV) and the airway microbiota, highlighting the fact that viruses such as the RSV might increase the virulence of bacterial pathogens in the airways, but that also a disbalance in the airway microbiota may promote more severe RSV infections. The second review by a group of South‐East Asian colleagues focusing on their regional area analyzes how the environment can contribute to our understanding of the pathogenesis of asthma with an emphasis on prevention strategies 2 .…”