Engineered ferritin nanoparticle carrying multi-epitope antigens induces specific immune protection against TiLV in tilapia.

Tilapia lake virus (TiLV) is an emerging negative sense single stranded RNA virus which exhibits high infectivity and pathogenicity toward tilapia, having resulted substantial economic losses on the aquaculture industry. To date, there isn't any effective or commercial vaccine can prevent tilapia from getting infected. In this study, we tandemly fused multiple screened tilapia epitopes to SpyTag003 (MEP) and linked ferritin to SpyCatcher 003 (SCF). Based on the SpyTag/SpyCatcher technique, the two proteins were conjugated to gain a ferritin nanocomplex (SCF-MEP). To evaluate the immunoprotective effect of the nanovaccine, tilapia were intraperitoneally injected through different treatments (PBS, SCF, MEP and SCF-MEP). 28 days after vaccination, the experimental fish were infected with live TiLV. The immune efficacy of MEP and SCF-MEP was assessed by measuring key immune parameters, including serum antibody levels and the expression levels of immune-related genes. The results demonstrated that tilapia injected with MEP and SCF-MEP exhibited significantly elevated levels of these indices relative to those injected PBS and SCF. Notably, fish immunized with the SCF-MEP nanovaccine developed a stronger and more sustained immune response than those injected with MEP antigen alone. Moreover, the SCF-MEP group had the highest relative survival rate (61.2%), which was 19.3 percentage points higher than that of the MEP group (41.9%). Overall, the strategy shows great promise for efficient vaccine delivery and provides a valuable reference for developing new vaccines against TiLV.