Temporal transcriptomic analysis of scale drop disease virus in Asian seabass kidney cells reveals host immune and signaling changes.

Scale drop disease virus (SDDV), member of the genus Megalocytivirus within the family Iridoviridae, has emerged as a major viral threat in Asian seabass (ASB) (Lates calcarifer) aquaculture, causing severe mortality and significant economic impact. Progress in understanding SDDV pathogenesis remains limited by the lack of permissive in vitro models and comprehensive molecular investigations. In this study, we characterized host transcriptional responses to SDDV infection using a permissive ASB kidney (ASBK) cell system. Time-resolved RNA sequencing was performed at 8, 24 and 72 h post-infection to resolve the temporal dynamics of host gene regulation. Integrated analysis combining differential expression, protein-protein interaction (PPI) mapping, temporal clustering, and weighted gene co-expression network analysis (WGCNA) revealed distinct host responses across pathways and time. SDDV infection induced dynamic remodeling of immune signaling pathways, viral entry-associated processes, intracellular communication networks, programmed cell death pathways, and key signaling cascades. Early infection was characterized by rapid activation of innate immune sensing and signaling, whereas later stages were marked by immune modulation and cellular reprogramming. Together, this study establishes ASBK-1 cells as a robust platform for mechanistic studies of SDDV and elucidates the time-dependent host molecular networks during SDDV infection, thereby advancing our understanding of host-virus interactions in Asian seabass.