Self-assembled nanoparticle vaccine comprised of multiple epitopes provides robust protective immunity against reoviruses in fish model.

Grass carp reovirus type II (GCRV-II) has inflicted substantial economic damage to aquaculture industry due to highly contagious. To combat epidemic GCRV-II, we rational designed and constructed a multi-epitope nanoparticle vaccine (Pep-Fn) that consisted with cell penetrating peptide (CPP), epitope peptides, cell and grass carp-derived ferritin. Firstly, an anti-GCRV-II phage antibody library was constructed to screen antibodies for outer capsid proteins VP4 and VP35. Ab-1 and Ab-3 were successfully screened and demonstrated high affinity with GCRV-II particles. We further identified five potential epitopes (Pep1-Pep5) on the outer capsid protein recognized by Ab-1 and Ab-3 through protein-protein docking and alanine scanning mutagenesis. Then, a self-assembled nanoparticle displaying the Pep1-Pep5 and CPP on the surface was constructed for Pep-Fn preparation. Benefit from the nano-sized particle structure, Pep-Fn could overcome the body surface barrier and accumulate in the immune organs. Experiments demonstrated that Pep-Fn could effectively stimulate grass carp to produce anti-GCRV-II antibodies via immersion immunization and also provided protective effect against GCRV-II challenge. Collectively, our research provides a new vaccine design strategy for combating GCRV-II, and demonstrates the great potential of protein-based nanoparticle as a platform for GCRV-II vaccine development.