Multi-tope subunit vaccine for human anthrax through pan-genome-based reverse vaccinology approach.

Anthrax is a zoonotic disease caused by Bacillus anthracis and poses a serious threat to public health. Frequent anthrax outbreaks in wild animals and livestock in the tropical regions lead to mortality and substantial economic losses. Farm workers, veterinarians, and individuals in close contact with infected animals are at risk of contracting the infection. In this study, a multi-tope vaccine for humans was designed through a pan-genome-based reverse vaccinology approach. We predicted twelve proteins that can elicit both B-cell and T-cell-mediated immunity, from which we identified eighteen surface-exposed immunodominant epitopes. Among these, seven epitopes that showed epitope-HLA binding in 97.67% of the global population, with regional coverage of 99.23% in North America and 98.24% in Europe, were used to design a multi-tope subunit vaccine. The designed multi-tope vaccine exhibited strong interactions with MHC class I (-46.4 kcal/mol), MHC class II (-80.19 kcal/mol), TLR4 (-62.33 kcal/mol), and B-cell receptors (-40.62 kcal/mol). Normal mode analysis revealed structural stability of the vaccine-receptor complex with an eigenvalue of 5.734505 × 10⁻⁶. MD simulation showed stable RMSD with an average deviation of 1.39 nm, low RMSF, and consistent solvent exposure. The in silico immune simulation generated robust primary and secondary immune responses, characterized by elevated levels of IgG1 and IFN-γ. Recurring IL-2 surges indicated T-cell proliferation and memory formation. No long-lasting increase in pro-inflammatory cytokines was observed, indicating that the vaccine is safe, immunogenic, and less reactogenic. Collectively, the proposed multi-tope subunit vaccine can serve as a potential candidate for human anthrax.