Computational and experimental mapping of antigenic epitopes on iridovirus major capsid protein for precision vaccine design.

The major capsid protein (MCP), owing to its strong immunogenicity, has emerged as a critical target for largemouth bass ranavirus (LMBV) vaccine development. However, its key antigenic epitopes remain uncharacterized. This study integrated phage display technology with bioinformatics approaches to design a multiepitope vaccine against LMBV. By constructing a phage Ab library derived from LMBV-infected largemouth bass spleen tissues, we obtained high-affinity Abs (Ab-S1 and Ab-S2) capable of specifically binding LMBV. Through molecular docking and alanine scanning mutagenesis of MCP-Ab complexes, 6 critical antigenic epitopes (pep1-pep6) were identified. Animal experiments demonstrated that these synthetic peptides could induce robust specific Ab responses and confer effective immune protection. Notably, the multiepitope microparticle vaccine, prepared by conjugating these 6 epitopes and encapsulating them with poly(lactic-co-glycolic acid), demonstrated enhanced immunogenicity and protective efficacy, achieving an immune protection efficiency of up to 63.33% and significantly reducing viral load. This study not only establishes an efficient methodology for dominant epitope screening but also provides both theoretical foundations and practical solutions for the prevention and control of viral diseases.