Structure-Based Screening of Antiviral Candidates Against Infectious Spleen and Kidney Necrosis Virus (ISKNV) Using Molecular Docking and In Vitro Evaluation

Infectious spleen and kidney necrosis virus (ISKNV) causes systemic infections and high mortality in various freshwater and marine fish species, posing a serious threat to aquaculture and ornamental fish industries. In this study, 72 antiviral compounds were screened against five ISKNV target proteins, DNA polymerase, transcription elongation factor (TFIIS), adenosine triphosphatase (ATPase), ankyrin repeat-containing protein, and major capsid protein (MCP) using molecular docking, followed by in vitro evaluation in dwarf gourami fin (DGF) cells. Fludarabine, liquiritin, and lycorine consistently ranked among the top 20 compounds across all five targets and were selected for further evaluation. Fludarabine and lycorine strongly inhibited MCP, ATPase, and DNA polymerase expression with inhibition rates exceeding 85%. Infectious viral titers were reduced by approximately 39- and 81-fold in the fludarabine- and lycorine-treated groups, respectively, compared with those in the ISKNV-infected control group. Time-course analysis revealed that both compounds suppressed extracellular viral release and delayed the progression of cytopathic effects. These results suggest that multi-target docking combined with in vitro evaluation may be a useful strategy for prioritizing antiviral candidates against ISKNV.