Identification of efficient multi-epitope combinations against African swine fever virus based on AP205 scaffold-mediated nanodisplay technology

BACKGROUND: African swine fever virus (ASFV), characterized by its large genome and high antigenic diversity, has impeded the development of traditional vaccines. In this study, we employed the AP205 capsid protein as the scaffold to prepare ASFV multi-epitope nanoparticles via sequential steps: fusion of the scaffold gene with ASFV multi-epitope genes, followed by recombinant protein expression, purification, in vitro self-assembly, structural characterization, and immune evaluation in BALB/c mice. RESULTS: It was found that the dimeric AP205 scaffold enhanced the assembly efficiency of nanoparticles harboring epitopes of ASFV, and the recombinant proteins DB, 22C, and DE, fused with the scaffold and the epitopes, all formed virus-like particles (VLPs). Immunization experiments demonstrated that DE, which carries the linear B-cell epitopes pB438L 51-73, p72 244-262, and p54 132-180, exhibited the optimal immunological efficacy, with outstanding performance in immunoreactivity, immunogenicity, specific antibody titers, immune cell activation, and inhibition of ASFV nucleic acid replication by immune serum. The nanoparticle DF (carrying linear B-cell epitopes p17 5-34, 71-113, and p30 4-15) showed comparable or even superior efficacy in all aspects except for slightly lower antibody levels, while DB (carrying linear B-cell epitopes p17 68-86, pE248R 138-168, 158-185) and 22C (carrying linear B-cell epitopes pE120R 65-117, pE199L 175-189, pO61R 36-56) yielded moderate efficacy. CONCLUSIONS: The dimeric AP205 scaffold tolerates the insertion of exogenous antigen fragments with greater complexity and size, and its simplified fusion display strategy facilitates commercial production. The spatial structure of VLPs confers significant advantages in inducing efficient immune responses. Furthermore, the VLP structures designed and validated in this study provide valuable data for amino acid deconstruction of analogous architectures. Meanwhile, this study identified efficient and precise ASFV epitope combinations, providing informative data to support the application of ASFV multi-epitope nanoparticle vaccines.