Aesculus hippocastanum L. seed extract shows virucidal and antiviral activities against respiratory syncytial virus (RSV) and reduces lung inflammation in vivo.

Respiratory syncytial virus (RSV) is a leading cause of lower respiratory tract disease and bronchiolitis in children worldwide. No vaccine or specific, effective treatment is currently available. β-escin is one of the main bioactive constituents of Aesculus hippocastanum L. (Hippocastanaceae) seed extract (AH), and both β-escin and AH have demonstrated a beneficial role in clinical therapy because of their anti-edematous, anti-inflammatory and antioxidative effects. Besides, we have reported that β-escin and AH show virucidal, antiviral and immunomodulatory activities against the enveloped viruses HSV-1, VSV and Dengue virus in vitro. In this study, we demonstrate that β-escin and AH have virucidal and antiviral activities against RSV, as well as NF-κB, AP-1 and cytokine modulating activities in RSV infected epithelial and macrophage cell lines in vitro. Besides, in a murine model of pulmonary RSV infection, AH treatment improves the course of acute disease, evidenced by decreased weight loss, reduced RSV lung titers, and attenuated airway inflammation. In contrast, even though β-escin showed, similarly to AH, antiviral and immunomodulatory properties in vitro, it neither reduces viral titers nor attenuates lung injury in vivo. Thus, our data demonstrate that AH restrains RSV disease through antiviral and immunomodulatory effect.