Antiviral activity and underlying mechanisms of baicalin against avian infectious bronchitis virus in vitro

Baicalin, a flavonoid compound extracted from the dry root of Scutellaria baicalensis Georgi, has been shown to have anti-inflammation, anti-viral, anti-bacterial, and immunomodulatory activity. However, the effect of baicalin against avian infectious bronchitis virus (IBV) remains unknown. The purpose of this study was to investigate the anti-IBV activity and underlying mechanism of baicalin in vitro. The results showed that baicalin has a direct virucidal effect but no prophylactic effect on IBV infection. The mRNA and protein of IBV N were decreased significantly when IBV-infected cells were treated with baicalin during the multiple stages of the virus replication cycle, including viral adsorption, invasion, internalization, and release. Stress granule (SG) formation resulted from the increase of G3BP1 and the phosphorylation of the PKR/eIF2α due to the treatment of IBV-infected cells with baicalin. The inhibitory activity of baicalin on IBV replication was increased when G3BP1 expression was inhibited, and the down-regulation of G3BP1 expression occurred when the expression of PKR and eIF2α was inhibited. These findings revealed that baicalin activates phosphorylation of the PKR/eIF2α pathway and induces SG formation by targeting G3BP1, initiating the antiviral response to suppress IBV replication in Vero cells. The results suggest that baicalin is a promising candidate drug to treat or prevent IBV infection.RESEARCH HIGHLIGHTS Baicalin inhibits IBV replication by reducing IBV N protein and mRNA.Baicalin disturbs multiple stages of the IBV life cycle.Baicalin activates PKR/eIF2α pathway and induces stress granule formation to exert anti-IBV response.