Targeting HSP90ab1: curcumin and silybin inhibit NNV infection in sea perch (Lateolabrax japonicus) via receptor blockade and immune enhancement.

Nervous necrosis virus (NNV), a member of the family Nodaviridae, is a devastating pathogen in global aquaculture, yet effective preventive and therapeutic strategies remain limited. This study aimed to identify natural compounds that inhibit NNV infection by targeting the host receptor Lateolabrax japonicus heat shock protein 90 alpha family class B1 (LjHSP90ab1). Herein, we identified curcumin and silybin as potent inhibitors of LjHSP90ab1. Molecular docking predicted that curcumin and silybin bind to the N-terminal and C-terminal domains of LjHSP90ab1, respectively, and fluorescence spectroscopy confirmed their direct binding to the protein. These interactions disrupted the binding of NNV capsid protein (CP) to LjHSP90ab1, blocking viral entry. In vitro assays showed that both compounds significantly suppressed NNV proliferation, and their combination exhibited synergistic efficacy. Furthermore, both compounds upregulated the expression of critical antiviral genes, including interferon (IFN), interferon-stimulated gene 15 (ISG15), virus inhibitory protein, endoplasmic reticulum-associated, interferon-inducible (Viperin), and myxovirus resistance (Mx). In vivo, bath treatment with curcumin, silybin, or their combination significantly improved survival rates of NNV-infected L. japonicus from 25.93% (infected control) to 48.15%, 40.74%, and 51.85%, respectively, and reduced viral load and tissue damage. Collectively, our findings demonstrated that curcumin and silybin exert dual antiviral effects by blocking viral entry via LjHSP90ab1 targeting and enhancing host immunity, highlighting their potential as environmentally friendly agents for NNV control in aquaculture.