Identification of candidate antimicrobial peptides against the mandarin fish ranavirus using peptidomics analysis.

Viral diseases severely restrict the sustainable development of aquaculture, with Ranavirus exhibiting a broad host range and high pathogenicity but limited control options. Antimicrobial peptides (AMPs) are regarded as ideal antiviral candidates owing to their broad-spectrum bactericidal and antiviral properties. In this study, healthy and MRV-infected mandarin fish were used. Peptidomics analysis revealed 896 peptide fragments across skin (33), gill (289), liver (155), and head kidney (419). Based on APD, CAMPR3, and DBAASP, 58 candidate AMPs were identified and classified into α-helix (9), β-sheet (5), α-helix/β-sheet (14), and other structures (30), with evidence of tissue-specific distribution. In vivo assays demonstrated that SC1-SC4 were evaluated and found to significantly reduce viral load and tissues damage in the liver, head kidney, and spleen. The SC3 group showed a significantly lower hepatic viral load (6114.9 copies/mg), with no significant difference relative to the NC group. Molecular docking indicated a strong binding affinity to ranaviru proteins, mediated primarily by hydrophobic interactions, hydrogen bonds, and salt bridges. The binding scores of SC1-SC4 with ranaviru proteins were - 235.93, -287.61, -203.64, -188.21. Additionally, SC1 and SC3 exhibited antibacterial activities (Aeromonas hydrophila, Edwardsiella tarda, and Staphylococcus aureus). Collectively, these findings address the deficiency in systematic mining of endogenous mandarin fish AMPs against MRV, and highlight the application potential of fish-origin AMPs as novel antiviral agents for ranavirus prevention and control in aquaculture.