Human rhinoviruses, allergy, and asthma: a clinical approach.

The prevalence of allergic diseases is increasing in Lithuania as in the world. The prevalence of allergic sensitization is often higher than 50% of the population. The "hygiene hypothesis" proposed that reduced immune-stimulation by infections may have resulted in the more widespread clinical expression of atopic disease. However, it alone does not provide an adequate explanation for the observed increase of allergic diseases. Human rhinovirus infections are the major infections with a worldwide distribution. Viral infections of the respiratory tract are the most common triggers of acute asthma exacerbations. These exacerbations are poorly responsive to current asthma therapies and new approaches to therapy are needed. The aim of this review is to present the current knowledge and clinical implications of human rhinovirus infection in allergy and asthma development and needs for further research. Recent evidence has shown that the immune responses to human rhinoviruses differ between asthmatic and nonasthmatic subjects. Novel insights into the mechanisms of virus-induced asthma exacerbations support the possibility that viral infections may be involved in the epithelial cells damage, inflammation, and airway hyperresponsiveness as well as in profibrotic response and induction of airway remodeling. The data of original investigations support the concept that the immune stimulation by rhinovirus infections contributes to the development of asthma, when an atopic host is infected with human rhinoviruses. Early rhinoviral wheezing is the predictor of subsequent asthma development in high-risk children. Synergistic effect of allergic sensitization, allergen exposure, and viral infection was suggested in the increased risk of hospitalization for asthma in both children and adults. Timing of allergen exposure may be important in a synergistic outcome. The increased susceptibility to rhinovirus infections was identified in atopic asthma. This review also presents the current options on the treatment and prevention of virus-induced asthma. Further studies are needed in order to differentiate between the response to viruses of healthy and atopic or nonatopic asthmatic children and adults. New research data may lead to novel strategies in treatment and prevention of asthma exacerbations as well as prevention of asthma induction.