Respiratory syncytial virus infection results in airway hyperresponsiveness and enhanced airway sensitization to allergen.

TLDR

Viral respiratory infections may predispose to asthma, though the underlying mechanisms are unknown. The authors developed a murine RSV model to study how viral infections influence airway sensitization and altered responsiveness. Acute RSV infection provokes airway hyperresponsiveness, neutrophilic and eosinophilic inflammation, and Th‑1 cytokine production, and it amplifies allergen‑induced hyperresponsiveness with Th‑2 cytokine dominance; anti‑IL‑5 treatment reduces eosinophilic inflammation and hyperresponsiveness but not neutrophilic inflammation.

Abstract

Viral respiratory infections can predispose to the development of asthma by mechanisms that are presently undetermined. Using a murine model of respiratory syncytial virus (RSV) infection, acute infection is associated with airway hyperresponsiveness as well as enhanced responses to subsequent sensitization to allergen. We demonstrate that acute viral infection results in increased airway responsiveness to inhaled methacholine and pulmonary neutrophilic and eosinophilic inflammation. This response is associated with predominant production of Th-1-type cytokines in peribronchial lymph node cells in vitro. Mice sensitized to ovalbumin via the airways after RSV infection developed increased airway responsiveness to methacholine and pulmonary eosinophilic and neutrophilic inflammation, associated with the predominant production of Th-2-type cytokines. Treatment of the mice with anti-IL-5 antibody abolished airway hyperresponsiveness and eosinophilic but not neutrophilic inflammation in both acutely infected mice and mice sensitized after infection. We conclude that RSV infection results in airway hyperresponsiveness in the acute phase and leads to changes in immune function that can enhance the effects of airway sensitization to antigen after infection. In both situations, airway hyperresponsiveness is closely associated with pulmonary eosinophilic inflammation. This model provides a means for further analyzing the influence of viral respiratory infections on airway sensitization and the development of altered airway responsiveness.