The Antiviral Efficacy of Andrographolide Against Grass Carp Reovirus In Vitro and In Vivo

Grass carp reovirus (GCRV), which causes hemorrhagic disease in grass carp ( Ctenopharyngodon idella ), poses a significant threat to grass carp aquaculture. To develop effective treatments against GCRV infection, this study evaluated the antiviral efficacy of natural compounds derived from Chinese herbs on GCRV-infected grass carp kidney cells (CIK). Among the various compounds examined, in CIK cells, Andrographolide (Andro) at 25 mg/L exhibited the highest inhibition rates against GCRV-I and GCRV-II infections (83.27% and 87.40%, respectively). In vitro experiments showed that Andro significantly reduced the cytopathic effect, alleviated the apoptosis of GCRV-I-infected cells, inhibited the increase of mitochondrial membrane potential, and blocked CIK cell adsorption of GCRV-I and GCRV-II. Addition time studies revealed that Andro chiefly wielded its antiviral impact in the initial phase of viral replication (0–4 h). In vivo studies demonstrated that in both prevention and treatment experiments, 50 mg/kg Andro in the feed increased the survival rates of grass carp infected with GCRV-Ⅱ by 46.66% and 40%, respectively. Moreover, this compound significantly reduced the viral loads and upregulated antiviral gene expression in various organs, indicating its potential for immune modulation. In conclusion, Andro displayed significant antiviral properties that are effective to both prevent and treat GCRV infections, thus holding promise as a novel therapeutic agent for this virus.