Background and Aims: The emergence of drug-resistant influenza viruses has become a serious threat for human and animal populations. Glycyrrhiza glabra (Gg) is a traditional medicine clinically used for the treatment of viral respiratory infection symptoms in most countries. We evaluated the effects of the herb on influenza virus replication in human lung cultured cells (A549) following the determination of cytotoxic concentration 50 of Gg for the cell in culture.
Materials and Methods: Suspensions of influenza virus-infected A549 cells were examined for infectivity up to 48 h after the addition of Gg at various concentrations before and after adsorption of the virus. The possible anti-influenza activity of Gg was also determined using apoptosis detection.
Results: At concentrations ranging from 50 to 400 μg/ml, Gg did not cause a cytotoxic effect against the cells. The increase in viral titers before adsorption and a dose-dependent inhibitory action of Gg after virus adsorption indicated that the herb did not affect influenza virus replication in human epithelial respiratory cells. DNA fragmentation showed that Gg protected cells from influenza virus-induced apoptosis before and after adsorption of the virus.
Conclusion: The findings suggest that Gg cannot directly affect viral HA activity during virus replication. A decrease in virus titer after-treatment of the infected cells with higher concentrations of Gg may interact with cellular signaling factors either involved in viral entry or budding.