Asthma diagnosis and treatmentThe role of rhinovirus in asthma exacerbations
Section snippets
What role does RV play in asthma exacerbations?
Asthma exacerbations are most commonly precipitated by viral URIs, particularly with RV,2 and often occur despite concurrent use of appropriate controller medications. Detecting respiratory viruses—in particular, RV—by culture methodology alone has been insensitive and has previously underestimated the role of respiratory viruses in asthma exacerbations, especially in adults. Viral detection rates in asthma exacerbations have significantly increased with the use of sensitive methods and have
What are the virologic features of RVs?
The genera RV and Enterovirus are classified within the family Picornaviridae. There are more than 100 serotypes of RV; this explains, in part, the lack of an effective vaccine against the major etiologic agent causing the common cold. RV is a small, single-stranded RNA virus whose capsid contains 4 proteins (Fig 1). Three of these proteins, VP1, VP2, and VP3, are located on the surface of the capsid and are responsible for its antigenic diversity; the fourth, VP4, is located inside the virus
Are RV infections limited to the upper airway?
An infection with RV leads to symptoms of the common cold, which is primarily an upper airway illness. Because RV is primarily an infection of the upper airway, early research efforts were directed toward determining whether (a) RV infections could infect the lower airways directly and provoke asthma, (b) their actions on asthma occurred via indirect mechanisms due to the upper airway infection only, or (c) a combination of the 2 methods is responsible. Insight into these questions could
What are the effects of RV infection on the mechanisms of airway physiology in asthma?
Multiple studies demonstrate the adverse effects of RV on airway physiology in asthma. In school-age children, symptoms of either upper or lower respiratory tract infection were shown to last a week, and during these infectious episodes, the peak flow rates fell for a median duration of 2 weeks.2 In another study, asthmatic subjects were experimentally inoculated with RV-16 and found to demonstrate modest changes in increased airway hyperresponsiveness, airway obstruction, and inflammation.15
How does RV modulate inflammatory mediators of epithelial cells contributing to asthma exacerbations?
Epithelial cells are the principal targets of RV infections, allow viral replication, and likely initiate immune responses (Fig 3).20, 21 Papadopoulos et al10 found local induction of proinflammatory mediators that could provide a mechanism to explain how lower airway infection can lead to inflammation and asthma. RV infection resulted in an increase in mRNA expression and subsequent translation of IL-6, IL-8, and IL-16. This also occurred with RANTES, a C-C chemokine with chemoattractant
What are the risk factors for wheezing with a cold?
Various risk factors increase the susceptibility of subjects for more severe lower respiratory complications from an RV infection, such as wheezing, bronchitis, and pneumonia (Table I). These include having low neutralizing antibody titers to RV, being an infant, being elderly, having chronic lung disease, being a smoker, and being an individual with existing asthma.22
In addition, subjects who are low producers of IFN-γ in response to RV and are atopic appear to be more at risk for wheezing or
Summary
The importance of RV in asthma exacerbations is established in both adults and children. The complex mechanisms by which their interaction provokes asthma are becoming better understood. RV appears to have a direct and negative impact on the lower airways and causes an increase in obstructive airway symptoms and physiology. This effect on airway function is felt to occur as the virus upregulates proinflammatory cytokines and predisposes the asthmatic patient to more severe respiratory
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