Kurarinone Inhibits HCoV-OC43 Infection by Impairing the Virus-Induced Autophagic Flux in MRC-5 Human Lung Cells

Kurarinone is a prenylated flavonone isolated from the roots of Sophora flavescens Among its known functions, kurarinone has both anti-apoptotic and anti-inflammatory properties Coronaviruses (CoVs), including HCoV-OC43, SARS-CoV, MERS-CoV, and SARS-CoV-2, are the causative agents of respiratory virus infections that range in severity from the common cold to severe pneumonia There are currently no effective treatments for coronavirus-associated diseases In this report, we examined the anti-viral impact of kurarinone against infection with the human coronavirus, HCoV-OC43 We found that kurarinone inhibited HCoV-OC43 infection in human lung fibroblast MRC-5 cells in a dose-dependent manner with an IC(50) of 3 458 ± 0 101 μM Kurarinone inhibited the virus-induced cytopathic effect, as well as extracellular and intracellular viral RNA and viral protein expression Time-of-addition experiments suggested that kurarinone acted at an early stage of virus infection Finally, we found that HCoV-OC43 infection increased the autophagic flux in MRC-5 cells;kurarinone inhibited viral replication via its capacity to impair the virus-induced autophagic flux As such, we suggest that kurarinone may be a useful therapeutic for the treatment of diseases associated with coronavirus infection