Scale drop disease virus (SDDV) triggering ferroptosis both in vivo and in vitro facilitates virus infection via targeting transferrin receptor 1 (TfR1)

Scale drop disease virus (SDDV) is a distinct member in genus Megalocytivirus of family Iridoviridae, garnering increasing attention due to its significant threat to teleost. Ferroptosis is a new type of cell death discovered recently and involved in various viral infections. Knowledges on SDDV induced ferroptosis remains unclear. Here, we demonstrated that SDDV infection triggers ferroptosis, as evidenced by hallmark features such as iron overload, massive lipid peroxides accumulation, glutathione depletion and glutathione peroxidase 4 downregulation. SDDV-infected MFF-1 cells exhibited increased reactive oxygen species production and mitochondrial shrinkage. Treatment with Ferrostatin-1, a potent ferroptosis inhibitor, significantly attenuated SDDV replication in MFF-1 cells and could improve the survival of mandarin fish upon SDDV challenge. Treatment with an iron chelator mitigated ferroptosis and reduced the mortality of mandarin fish following SDDV infection, suggesting that SDDV-induced ferroptosis is iron-dependent. Finally, we demonstrated that SDDV infection could upregulate the expression of transferrin receptor protein 1 (TfR1), a critical iron transporter, to disrupt cellular iron homeostasis, induce ferroptosis, and then facilitate viral infection. Collectively, our findings provide compelling evidence that SDDV infection induces ferroptosis by targeting TfR1 to facilitate virus infection. Inhibiting ferroptosis represents a promising immunotherapeutic strategy for combating SDDV infection in aquaculture.