Inhibitory activity of the scorpion venom peptide Ctry2459 against Tembusu virus

Tembusu virus (TMUV) causes egg-drop syndrome and neurological disease in poultry and poses a substantial threat to the waterfowl industry. Specific antiviral drugs against TMUV are currently unavailable. This study investigated the antiviral activity of the scorpion venom-derived peptide Ctry2459 against TMUV and explored its possible mechanism of action. Ctry2459 showed no cytotoxicity or hemolytic activity up to 160 µM, and showed maximal inhibition of TMUV at 20 µM. The antiviral effect occurred primarily during virus-peptide co-treatment and was associated mainly with direct virion inactivation. Although peptide exposure during the adsorption stage reduced subsequent infection, direct measurement of cell-associated viral RNA did not show significant inhibition of viral attachment, and no significant effect on entry/fusion was observed. TEM revealed virion shrinkage and structural damage upon peptide treatment. Ctry2459 also inhibited PEDV and PRRSV at higher concentrations, and MD simulations supported its interaction with the TMUV E protein. Endocytosis inhibition by chlorpromazine increased Ctry2459-associated cytotoxicity, suggesting that cellular uptake/endocytic processing may contribute to host-cell tolerance. Ctry2459 inhibits TMUV infection in vitro mainly by acting during the early stage of infection, with direct effects on viral particles representing the most strongly supported mechanism. Peptide exposure during the adsorption stage reduced subsequent infection, although direct attachment of TMUV to cells was not significantly decreased. Its activity against additional enveloped RNA viruses and its interaction with the TMUV E protein further broaden the mechanistic understanding of this peptide. These findings support further investigation of Ctry2459 as a promising antiviral peptide candidate.