Bioinformatics analysis of the antigenic epitopes of L7/L12 protein in the B- and T-cells active against Brucella melitensis.

The objective is to analyse the physicochemical properties, spatial structure and protein-protein interactions (PPIs) of L7/L12 protein using bioinformatics methods and predict their B- and T-cell epitopes to lay a theoretical foundation for developing a novel multiepitope vaccine (MEV). The National Center for Biotechnology Information (NCBI) database was searched for the amino acid sequences of L7/L12 from Brucella melitensis. In addition, the online softwares, ProtParam and ProtScale, were used to predict the physicochemical properties: NetPhos3.1 and CD-search to predict the phosphorylation sites and conserved domains; SOMPA and SWISS-MODEL to predict the secondary and tertiary structures; the STRING database to analyse the PPIs; and the IEDB, ABCpred, SVMTrip and SYFPEITHI databases to predict the B- and T-cell epitopes. L7/L12 was docked to Toll-like receptor 4 (TLR4), B-cell receptor (BCR), Major histocompatibility complex I-T cell receptor (MHC I-TCR) and MHC II-TCR complexes, respectively, and the binding ability of L7/L12 to the targeted receptors was tested. L7/L12, consisting of 124 amino acids, was determined to be a stable, intracellular, hydrophilic protein containing 6 phosphorylation sites and ribosomal protein-related conserved domains. α-helices accounted for 70.16 %, β-turns for 2.42 %, extended strands for 8.87 % and irregular coils for 18.55 % of the secondary structure. The PPIs indicated that L7/L12 was involved in the constitution of ribosomes and regulating the accuracy of the translation process. Three B-cells, two cytotoxic T lymphocytes and three helper T lymphocyte epitopes were finally screened by comparing multiple databases. L7/L12 binds to TLR4, BCR, MHC I-TCR and MHC II-TCR complexes and forms stable hydrogen bonds, respectively. L7/L12, which governs the translation curate of proteins, possesses several potentially advantageous epitopes, laying a theoretical foundation for designing MEVs.