Sophora alopecuroides biflavones glycoside, isolated from Sophora alopecuroides, inhibits the secretion of hepatitis B virus surface antigen through direct interaction with its antigenic loop domain.

backgroundHigh levels of circulating hepatitis B surface antigen (HBsAg) contribute to the dysfunction of the host immune response against HBV and the persistence of viral infection. This study aimed to investigate the effects and mechanisms of Sophora alopecuroides biflavones glycoside (SABG), isolated from the traditional herbal medicine Sophora alopecuroides, on HBV replication and HBsAg secretion.

methodsTo systematically evaluate the antiviral efficacy, a comprehensive set of experimental analyses was employed, including qPCR, RT-qPCR, ELISA, Western blot and particle gel assay. The DIA-based proteomic analysis, CETSA, molecular docking, and molecular dynamics simulation analyses were combined to explore the potential mechanisms.

resultsWe discovered that SABG could not only remarkably inhibit intracellular level of HBV core DNA but also significantly reduce the extracellular levels of HBV DNA, pgRNA, HBsAg and e antigen (HBeAg). Intriguingly, SABG had no impact on the intracellular levels of HBV pgRNA and core protein; instead, it caused abnormal accumulation of S protein. Further mechanistic studies revealed that SABG could bind directly to the antigenic loop (AGL) domain of HBs, thereby obstructing its post-translational cellular vesicle-based transport process. Finally, we observed a synergistic effect of SABG and lamivudine in the inhibition of intracellular level of HBV core DNA and the extracellular level of HBsAg.

conclusionOur studies reveal that SABG exhibits an antiviral activity against HBV by directly binding to the antigenic loop of surface protein, thereby impeding its secretion, which provides pharmacological evidence for the potential use of SABG as a candidate for the alternative treatment of HBV infection.