Water extract of Cinnamomum cassia Blume inhibited human respiratory syncytial virus by preventing viral attachment, internalization, and syncytium formation

Ethnopharmacological relevanceCinnamomum cassia Blume is a popular traditional Chinese herbal medicine that has been used to manage respiratory tract disease, including common cold and chronic bronchitis for thousand years. Human respiratory syncytial virus (HRSV) is one of the leading causes of severe lower respiratory tract illness worldwide. No effective therapeutic modality against HRSV infection has been proved. It is unknown whether Cinnamomum cassia is effective against HRSV.Aim of the studyThis study tested the hypothesis that Cinnamomum cassia can effectively decrease HRSV-induced plaque formation and syncytium formation in respiratory mucosal cell lines.Materials and methodsAntiviral activity of the hot water extract of Cinnamomum cassia against HRSV was tested by plaque reduction assay in both human upper (HEp-2) and low (A549) respiratory tract cell lines. Its ability to inhibit the synthesis of viral fusion (F) protein was examined by Western blot assay.ResultsCinnamomum cassia dose-dependently inhibited HRSV-induced plaque formation in both HEp-2 and A549 cell lines (p<0.0001). Cinnamomum cassia was more effective when given before viral infection (p<0.0001) mainly by inhibition of viral attachment (p<0.0001) and internalization (p<0.0001). Cinnamomum cassia could inhibit F protein production and syncytium formation to interfere with HRSV spreading.ConclusionsCinnamomum cassia prevented airway epithelia from HRSV infection through inhibiting viral attachment, internalization and syncytium formation. Cinnamomum cassia could be a candidate to develop therapeutic modalities to manage HRSV infection in the future.

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