LvHcS52, a Litopenaeus vannamei hemocyanin-derived peptide, restricts WSSV infection by promoting phagocytosis and activating the STAT signaling pathway.

Shrimp hemocyanin plays multifunctional roles in immunity, both in its native form and as proteolytic fragments generated during infection. Here, we characterize LvHcS52, a hemocyanin-derived peptide identified in the serum of white spot syndrome virus (WSSV)-infected Litopenaeus vannamei. Through molecular weight analysis, N-terminal and de novo sequencing, and bioinformatic prediction, we define LvHcS52 as a 55-amino acid fragment (residues 526-580 of hemocyanin; accession CAA57880) with a molecular mass of 5824.09 Da, structurally featuring one α-helix and two β-strands. Both recombinant and synthetic LvHcS52 significantly inhibited WSSV gene expression (ie1 and vp28), reduced viral loads, and improved shrimp survival. Mechanistically, LvHcS52 binds the WSSV envelope protein VP28 and host β-integrin on hemocytes, promoting viral phagocytosis. Moreover, it also activates the STAT signaling pathway and upregulates anti-lipopolysaccharide factors (ALFs) to restrict viral replication. Our findings underscore the immunological versatility of hemocyanin and illustrate how invertebrates maximize limited immune components to mount effective antiviral responses. This study provides new insights into crustacean innate immunity and opens avenues for developing peptide-based antiviral strategies in aquaculture.