Respiratory syncytial virus increases eosinophil extracellular traps in a murine model of asthma

BACKGROUND: Respiratory viral infections are the leading cause of asthma exacerbations. Eosinophil activation results in the formation of eosinophil extracellular traps (EETs), which release web-like structures of DNA and proteins that bind, disarm and extracellularly kill pathogens. OBJECTIVE: We investigated whether the respiratory syncytial virus (RSV) in vitro could induce EETs in bronchoalveolar lavage fluid eosinophils in a murine model of asthma. METHODS: BALB/cJ mice (6–8 weeks old) were sensitized with 2 subcutaneous injections of ovalbumin (20 μg) on days 0 and 7, followed by three intranasal challenges with ovalbumin (100 μg) on days 14, 15, and 16 of the protocol. The control group received Dulbecco's phosphate-buffered saline. Bronchoalveolar lavage fluid eosinophils of ovalbumin group or control group were stimulated with RSV (10(3) PFU/mL) in vitro for 3 hours. After that, culture supernatant was collected to perform the analyses proposed in this study. RESULTS: We verified an increase in extracellular DNA concentration in bronchoalveolar lavage fluid eosinophils from ovalbumin group stimulated with RSV (10(3) PFU/mL) in vitro, which was confirmed by confocal microscopy. We demonstrated that most cells are negative for annexin V and propidium iodide in all groups evaluated. Also, RSV in vitro decreased interferon-ɣ in culture supernatant when compared to the ovalbumin group. CONCLUSION: In this study, we demonstrated for the first time that RSV in vitro induces EETs formation in eosinophils from asthmatic mice.