Antiviral Activity of Eugenol Against Largemouth Bass Ranavirus Through Regulation of Autophagy and Apoptosis In Vitro and In Vivo.

Largemouth bass ranavirus (LMBV) causes high mortality rate in largemouth bass during outbreaks, resulting in huge economic losses. Eugenol (EUG) has potent antiviral activity, showing promising potential against LMBV. Thus, to investigate EUG's efficacy against LMBV, corresponding analysis was conducted in vivo and in vitro. Firstly, EUG demonstrated to be able to down-regulate both the mRNA and protein levels of the major capsid protein (MCP) in LMBV-infected cells. In addition, EUG could inhibit the expression of cleaved-caspase-3 in LMBV-infected fathead minnow (FHM) cell. On the other hand, EUG would not only directly regulate the protein kinase B (AKT)/mammalian target of rapamycin (mTOR) pathway but also affect the AMP-activated protein kinase (AMPK) pathway in FHM cells during LMBV infection. These results indicated that EUG exerts its antiviral effects by modulating both LMBV-induced apoptosis and autophagy. Notably, EUG reduced the viral load present within the tissues of LMBV-infected largemouth bass, thereby ultimately enhancing their survival rate in the culture environment by about 20%. These mechanistic assays revealed the anti-LMBV properties of EUG, which could significantly enrich the research content of plant extracts in the field of aquatic antiviral, and provide important theoretical basis for the development and application of related products.