A self-assembling ferritin nanoparticle vaccine based on SpyTag/SpyCatcher elicits protective immunity against largemouth bass ranavirus.

Largemouth bass ranavirus (LMBV) represents a detrimental aquaculture pathogen, with vaccination emerging as a validated countermeasure for infection control. Using immunoinformatics, this study predicted antigenic peptides from the LMBV major capsid protein. After screening for antigenicity, toxicity, and allergenicity, selected peptides were conjugated to Micropterus salmoides ferritin via the SpyTag/SpyCatcher system to produce a nanoparticle vaccine (EPI-SCF). High-resolution ultrastructural profiling via transmission electron microscopy and dynamic light scattering characterization confirmed spheroidal nanostructures (approximately 14 nm) for the engineered nanovaccine. By day 21 following inoculation, specific antibody levels in serum in the epitope-only group (EPI) peaked relative to controls, while specific antibody levels in serum in the EPI-SCF group continued to increase through day 28. At 1-week following immunization, serum levels of ACP, AKP and T-AOC in the EPI-SCF group demonstrated significant elevations (P < 0.01) relative to all other experimental groups. At 21 days following immunization, significant upregulation of immune-related genes (such as IL-6, IL-8, CD40, TGF-β, IFN-γ, IFN-α) were observed in different tissues compared with control groups (P < 0.01). Immunized cohorts showed significantly enhanced relative percent survival (RPS) at 14 days subsequent to viral infection challenge compared to controls at the same concentrations (EPI: 32.00%; EPI-SCF: 57.37%; P < 0.01). Although this study evaluated the efficacy of vaccine protection within 35 days, long-term immunity (T cell immune response) needs further verification in the future. Collectively, this study establishes a novel immunoinformatics-based strategy and provides a valuable reference framework for advancing the development of LMBV vaccines.