An Immunoinformatic Approach to Designing a Multi-epitope Vaccine against Helicobacter pylori with the VacA Toxin and BabA Adhesion

Objective: Helicobacter pylori, as a carcinogen, has been related to the development of gastric cancer, particularly in developing countries. The main challenge with therapy is the recurrence of antibiotic-resistant bacteria, and vaccination is still a problem. Therefore, the objective of the current study was to rationally design a multi-epitope vaccine using two immunogenic proteins found in H. pylori. Methods: Promising epitopes for the Leb-binding adhesin A (BabA) and vacuolating cytotoxin (VacA) proteins were characterized through an immunoinformatics approach. Epitope-rich fragments were selected based on high-binding affinities with HLA classes I and II to be specifically presented to B and T lymphocytes and to selectively elicit both humoral and cellular immune responses. Results: Six constructs were planned by fusing these fragments in different arrangements with the help of GPGPG linkers. The most stable three-dimensional structure was found in Construct 6 during molecular dynamics. To improve immunogenicity and stability, an adjuvant called human β- defensin 2 (hBD-2) was joined to the N-terminus of Construct 6. Following molecular docking, the final vaccine reacted appropriately with each toll-like receptor 2 (TLR-2), TLR3, and TLR-4. The final DNA sequence was optimized for expression in E. coli K12 and in silico cloned into a pET-28a(+) plasmid. As a result of the vaccination in silico, substantial responses were developed against H. pylori. Conclusion: According to the immune response simulation, activated B and T lymphocytes and memory cell production increased. Macrophages and dendritic cells proliferated continuously, and IFN-γ and Cytokines, such as IL-2 were raised.