Respiratory Viruses, Eosinophilia and Their Roles in Childhood Asthma

Abstract

With the advent of highly sensitive and specific screening of respiratory specimens for viruses, new viruses are discovered, adding to the growing list of those associated with wheezing illness and asthma exacerbations. It is not known whether early childhood infections with these viruses cause asthma, and, if so, what exactly are the pathophysiologic mechanisms behind its development. The current consensus is that respiratory viral infection works together with allergy to produce the immune and physiologic conditions necessary for asthma diasthesis. One link between viruses and asthma may be the eosinophil, a cell that plays a prominent role in asthma and allergy, but can also be found in the body in response to viral infection. In turn, the eosinophil and its associated products may be novel therapeutic targets, or at the very least, used to elucidate the complex pathophysiologic pathways of asthma and other respiratory illnesses. Together or separately, they can be used for diagnosis, treatment and monitoring. Not only symptoms, but also the underlying disease mechanisms must be taken into consideration for the optimal care of a patient.

Innate Immune Components That Regulate the Pathogenesis and Resolution of hRSV and hMPV Infections

“…Most importantly, the presence of eosinophils cells was a parameter measured during the characterization of wheezing in patients infected with hMPV [ 186 ]. Since the hMPV infection leads to the recruitment of eosinophils to the lung, and these cells are associated with the development of wheezing and asthma, it is possible to suggest that eosinophils are the reason why these symptoms are present during a hMPV infection [ 215 ].…”

The hygiene hypothesis revisited

“…The complex interaction between viral infections and the development of asthma is detailed in several review articles [28,29]. These studies highlight both inconsistencies in the literature and the nuanced…”

Bacterial Lysate Increases the Percentage of Natural Killer T Cells in Peripheral Blood and Alleviates Asthma in Children

“…Repeated or chronic respiratory infections can damage respiratory epithelial integrity (by impairing its defensive function) and lead to eosinophil accumulation and sustained release of cysteinyl leukotrienes and other inflammatory mediators. This causes chronic inflammation and persistent respiratory airway hyperresponsiveness, promotes airway remodeling and dysfunction, enhances susceptibility to pathogens and common allergens, and promotes a continued decline in lung function in children with recurrent wheezing [6,7]. A study of asthma patients with less well-controlled asthma showed a close relationship between airway microbial infections and airway hyperresponsiveness [8].…”