Abstract: 【Objective】 The study was aimed to design a multi-epitope vaccine against Swine acute diarrhea syndrome coronavirus (SADS-CoV) S, M and E proteins.【Method】 IEDB server was used to predict the MHC class Ⅰ molecular binding epitopes of SADS-CoV S protein, M protein and E proteins of T lymphocytes.T lymphocyte MHC class Ⅱ molecule binding epitopes were predicted by NetMHCIIpan 4.0 Serve.Immunomedicine Group and IEDB server were used to predicted B lymphocyte epitopes.The overlapping epitope regions were selected as the dominant epitopes from the prediction results of each server, and the highly conservative and non-sensitizing dominant epitope regions were selected by using IEDB and AllerTOP v 2.0 servers, which were connected in series into a multi epitope vaccine through a flexible linker.The antigenicity, physicochemical properties, N-glycosylation sites, secondary and tertiary structures of the constructed multi-epitope vaccine were evaluated.The binding capacity of multi-epitope vaccines to immune receptors was evaluated by molecular docking and silico cloning was carried out.【Result】 The results showed that the multi-epitope vaccine constructed with highly conservative and non-sensitizing dominant epitopes had a relative molecular weight of 35.30 ku.It was a stable hydrophilic protein with good antigenicity.There was one N-glycosylation site, and the alpha helix, beta sheet, random coil and beta turn were 22.11%, 20.35%, 50.88% and 6.67% in the secondary structure, respectively.Ramachandran mapping of tertiary structure found that the residue base in the dominant region accounted for 90.00%.After refinement, the residue base in the dominant region increased to 91.92%.Mapping of prominent epitopes of tertiary structure also proved that the multi-epitope vaccine had good immunogenicity, and molecular docking showed that the multi epitope vaccine had high affinity with TLR3.Finally, codon optimization, reverse translation and silico cloning ensure the efficient and stable expression of the designed multi epitope vaccine in E.coli K12 expression system.【Conclusion】 The constructed multi-epitope vaccine might effectively express and induce strong T-cell and B-cell immune responses.This study provided a new method for the design of SADS-CoV multi-epitope vaccine, and provided theoretical basis and data support for the research and development of SADS-CoV multi-epitope vaccine.

Key words: Swine acute diarrhea syndrome coronavirus (SADS-CoV); structural protein; immunoinformatics method; T lymphocyte epitope; B lymphocyte epitope; multi-epitope vaccine