Picornavirus-Induced Airway Mucosa Immune Profile in Asymptomatic Neonates.

Background. Bacterial airway colonization is known to alter the airway mucosa immune response in neonates whereas the impact of viruses is unknown. The objective was therefore to examine the effect of respiratory viruses on the immune signature in the airways of asymptomatic neonates. Methods. Nasal aspirates from 571 asymptomatic 1-month-old neonates from the Copenhagen Prospective Studies on Asthma in Childhood 2010 birth cohort were investigated for respiratory viruses. Simultaneously, unstimulated airway mucosal lining fluid was obtained and quantified for levels of 20 immune mediators related to type 1, type 2, type 17, and regulatory immune paths. The association between immune mediator levels and viruses was tested by conventional statistics and partial least square discriminant analysis. Results. Picornaviruses were detected in 58 neonates (10.2%) and other viruses in 10 (1.8%). A general up-regulation of immune mediators was found in the neonates with picornavirus (P < .0001; partial least square discriminant analysis). The association was pronounced for type 1– and type 2–related markers and was unaffected by comprehensive confounder adjustment. Detection of picornavirus and bacteria was associated with an additive general up-regulating effect. Conclusions. Asymptomatic presence of picornavirus in the neonatal airway is a potent activator of the topical immune response. This is relevant to understanding the immune potentiating effect of early life exposure to viruses

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

The immunopathology of respiratory syncytial virus (RSV) infection varies considerably, severe disease occurring only in a minority of the affected children. The variability of the clinical presentation is in part explained by viral and environmental factors but, in infants and young children, disease severity is certainly linked to the physiologic immaturity of the innate and adaptive immune system. There is evidence that the maturation of the host immune response is positively influenced by the composition of the nasopharyngeal microbiome that, promoting an efficient reaction, 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 since microbial dysbiosis may also represent 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, a main reservoir of bacteria, and therefore promote their spread to the lower airways causing superinfection. Moreover, if negative changes in microbial community composition in early life may constitute a heightened risk toward severe RSV respiratory infection, on the contrary specific groups of microorganisms seem to be associated with protection. A better understanding into the potential negative and positive role of the different nasopharyngeal bacterial species on RSV infection may improve primary prevention and possibly care of this highly contagious disorder