Phylogeny-guided multi-epitope vaccine design targeting conserved and divergent regions of Brucella OMP2, OMP25, and OMP31: an immunoinformatics study.

Brucella is a zoonotic intracellular bacterial pathogen. Currently, no human vaccines for brucellosis are approved, and only animal vaccines are available. Despite the widespread use of live attenuated vaccines, several drawbacks have prompted investigation into outer membrane proteins (OMPs) as potential vaccine candidates. This study employs immunoinformatics to design a multi-epitope vaccine targeting conserved regions of the OMP2a, OMP2b, OMP1, OMP25, and OMP31 antigens against four common Brucella species. Helper T-lymphocyte (HTL), Cytotoxic T-lymphocyte (CTL), and B-cell epitopes of OMP31, OMP25, OMP2a, and OMP10 were predicted and analyzed. The selected epitopes form a multi-epitope design featuring a flexible linker, “GGSSGG,” which connects the epitopes. This construct was fused to the Cholera Toxin B subunit (CtxB) at the N-terminus as an adjuvant, while a His-tag at the C-terminus facilitates purification. The tertiary structure of the multi-epitope was then modeled and refined. The 3D structure and its sequence were evaluated for physicochemical properties, structural features, in silico cloning, B epitope prediction, immune response simulation, and molecular docking with toll-like receptors (TLRs). The stability of the construct-TLR interactions was assessed through molecular dynamics (MD) simulations. The final vaccine construct demonstrated antigenicity and non-allergenicity, along with satisfactory physicochemical properties, as it binds to TLR2/4 receptors and induces an in-silico immune response. MD simulations confirmed the stability of the docked complexes. While this multi-epitope vaccine candidate shows promise in eliciting various immune responses against brucellosis in silico, it is crucial to validate its efficacy through laboratory and animal model testing.