Respiratory syncytial virus induces pneumonia, cytokine response, airway obstruction, and chronic inflammatory infiltrates associated with long-term airway hyperresponsiveness in mice

Background. Respiratory syncytial virus (RSV) infection is associated with acute morbidity ( e. g., pneumonia and airway obstruction [AO]) and long-term complications ( e. g., airway hyperresponsiveness [AHR]). We present a comprehensive evaluation of the acute and chronic phases of RSV respiratory tract infection, using a mouse model. Methods. BALB/c mice were inoculated with RSV and monitored for 154 days. RSV loads and cytokines were measured in bronchoalveolar lavage (BAL) samples. Pneumonia severity was assessed using a standard histopathologic score, and pulmonary function was determined by plethysmography. Results. RSV-infected mice exhibited viral replication that peaked on day 4 - 5 and became undetectable by day 7. These mice developed acute pneumonia ( peak days, 4 - 5) and chronic pulmonary inflammatory infiltrates that lasted up to 154 days after inoculation. BAL concentrations of tumor necrosis factor-alpha, interleukin (IL) - 6, interferon - gamma, IL-4, IL-10, KC (an IL-8 homologue), MIG (CXCL9), RANTES, macrophage inflammatory protein 1alpha, and eotaxin were significantly higher in RSV-infected mice than in control mice. RSV-infected mice developed acute AO during the first week of infection that persisted for 42 days. RSV-infected mice also showed significant AHR in response to methacholine up to 154 days. Conclusion. This model provides a means to investigate the immunopathogenesis of RSV infection and its association with reactive airway disease.