Targeting the pan-viral host protein HSPA8 with oxymatrine as a novel therapy against duck hepatitis a virus infection.

Duck hepatitis A virus type 3 (DHAV-3) has emerged as a dominant pathogen responsible for duck viral hepatitis, leading to significant economic losses in the duck industry. Given that current control strategies, primarily reliant on vaccination, often face limitations, this study investigates a host-directed therapeutic (HDT) strategy focused on targeting host factors essential for DHAV-3 replication. We identified the heat shock protein family A member 8 (HSPA8) as a key interactor of the viral structural protein VP0 through GST pull-down and mass spectrometry. Functional assays confirmed that HSPA8 significantly promotes DHAV-3 replication; its overexpression enhanced viral yield, while its inhibition suppressed it. Building on these findings, we explored oxymatrine (OMT), a natural compound derived from Sophora flavescens (Kushen), and found that it effectively downregulates HSPA8 expression, thereby inhibiting viral replication in vitro. In a duckling model, OMT treatment provided significant protection, dose-dependently improving survival rates, reducing viral loads, and alleviating DHAV-3-induced liver injury and apoptosis. Transcriptomic profiling revealed that OMT mitigates liver damage through dual mechanisms: by suppressing the overactivated RIG-I-like receptor signaling pathway and inhibiting the apoptosis pathway. Our work establishes HSPA8 as a promising pan-picornaviral target and identifies OMT as a novel and effective HDT candidate against DHAV-3 infection.