Antiviral activity of epicatechin against Singapore grouper iridovirus in vitro and in vivo

As the main highly pathogenic pathogen of grouper, Singapore grouper iridovirus (SGIV) can give rise to significant economic losses in grouper aquaculture. Epicatechin (EC) belongs to flavonoids, which primarily derived from the traditional Chinese medicinal plants, green tea. In this study, the role of EC in SGIV infection was evaluated in vitro and in vivo. In the meantime, the mechanism of EC worked on SGIV was also explored, including the impact of EC on SGIV virus particles, the effects of EC on SGIV infection process, and the influence of EC on host immune response. The results showed that EC had concentration dependent antiviral effects against SGIV both in vitro and in vivo. EC could limit SGIV infection by interacting with SGIV virus particles, interfering with the invasion and replication process of SGIV infection. Moreover, EC was able to upregulate the expression of genes involved in interferon system (IFN, TRAF6, ISG15, IRF3, IRF7, TLR9, and myd88), downregulate the expression of TNF-alpha and IL1-beta related to inflammation, and inhibit the cell apoptosis induced by SGIV to exert antiviral effects. Our finding revealed that EC probably is a potential excellent anti-SGIV drug with a clear antiviral mechanism, which provides a theoretical basis for the development of environmentally friendly fishing drugs for the prevention and control of SGIV.