Baicalin Inhibits the Infection of CEK Cells by IBV.

Baicalin possesses anti-inflammatory, antiviral, and immunomodulatory effects. However, the antiviral effect of baicalin against infectious bronchitis virus (IBV) has not been well-studied. In this study, chicken embryo kidney (CEK) cells were used as a model to investigate the antiviral effects of baicalin against the IBV Hebei QX strain. Virus TCID, the MNTC of baicalin on CEK cells, CPE observation, CCK-8 assay for viral inhibition rate, and qPCR for viral load were performed to evaluate the antiviral effect of baicalin and determine its optimal mechanism of action. Additionally, to explore the molecular mechanism of baicalin's inhibition of IBV infection, we adopted real-time quantitative PCR (qRT-PCR) to assess its impact on the nuclear factor-kappa B (NF-κB) and melanoma differentiation-associated gene 5/interferon regulatory factor 7 (MDA5/IRF7) signaling pathways. The results showed that baicalin exhibited a maximum inhibition rate of 68.37% when acting through direct virucidal effects, which was 14.07% higher than the inhibition rate observed under the adsorption-blocking method (54.30%). Under the replication-blocking method, baicalin achieved a maximum inhibition rate of 56.31%, which showed no significant difference from the ribavirin group, but was 2.01% higher than the adsorption-blocking method. These findings suggest that baicalin significantly inhibits IBV replication, with direct virucidal activity as the primary antiviral mechanism. qRT-PCR analysis revealed that baicalin downregulated the expression of NF-κB signaling molecules, suppressed the expression of cytokines such as TRAF6, TAB1, IL-1β, IL-6, and TNF-α, and promoted the relative expression of IL-10. Furthermore, baicalin upregulated the MDA5/IRF7 pathway, enhancing the expression of cytokines IFN-α and IFN-β. These findings provide a theoretical foundation and new insights for the prevention and treatment of IBV in poultry.