Respiratory Viral Infections and Asthma: Is There a Link?

Erwin W. Gelfand, MD

Disclosures
In This Article

Interactions Between Viral RTI and Allergic Sensitization

To define potential mechanisms of interaction between viral RTI and allergic sensitization to inhaled allergens, a number of rodent models have been developed. The majority of these models showed increased allergic sensitization following respiratory virus infection, resulting in eosinophilic airway inflammation and AHR. In some of these models, animals were first exposed to allergen during the acute infection phase followed by subsequent allergen challenges, resulting in increased allergic sensitization with elevated serum levels of allergen-specific IgE.

In these experimental approaches, enhanced allergic sensitization was potentially due to increased allergen uptake across inflamed mucous membranes. Indeed, in both a guinea pig and a mouse model, exposure to ovalbumin aerosol caused increased levels of serum ovalbumin if administered during acute virus infection.

Schwarze and colleagues[10] reported on a murine model of RSV infection and subsequent sensitization to aerosolized ovalbumin. In this model, exposure to allergen over 10 days was begun only after the resolution of the acute (RSV) infection. This resulted in enhanced responses to allergen and, as a consequence, airway inflammation with the influx of neutrophils and eosinophils. This was associated with altered airway responsiveness to inhaled methacholine.

In contrast to many of the models discussed above, allergen-specific IgE serum levels were not higher in the group that was infected with RSV prior to allergic sensitization. This may indicate that mechanisms other than increased allergen uptake are likely responsible for the effects of RSV infection on the subsequent exposure to allergen. As demonstrated, sensitization following acute RSV infection triggers eosinophilic inflammation and associated AHR. Anti-IL-5 treatment during the allergen exposure phase prevents lung eosinophilia and the development of AHR.

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