Design of a Dual Adjuvant Multi-epitope Vaccine Candidate against Helicobacter pylori

Despite the classification of Helicobacter pylori (H. pylori) as a Class I carcinogen affecting over half the global population, no licensed vaccine exists against this pathogen, and the rise in antimicrobial resistance continues to undermine standard eradication regimens. This study designed a novel dual adjuvant multi-epitope vaccine (MEV) candidate against H. pylori. The complete proteome of H. pylori strain 26695 was used to identify unique vaccine targets. Linear B-cell epitopes as well as HTL and CTL epitopes were predicted using BepiBLAST, NetMHCIIpan-4.3, and NetMHCpan-4.1, respectively. Predicted epitopes were further screened for antigenicity, allergenicity, and toxicity using VaxiJen, AllerTOP, and ToxinPred3.0. This pipeline identified four potential vaccine targets, where two most promising B-cell epitopes, one HTL epitope, and two CTL epitopes were selected and assembled into a recombinant MEV construct using linkers. Furthermore, Rv0652 and RS09 adjuvants were linked at the N and C termini of the vaccine, respectively, using appropriate linker sequences. Physicochemical analysis of the vaccine revealed a stable 204 amino acid construct of 20.69 κDa with an instability index of 23.57, a near-neutral GRAVY of 0.017, and an acidic theoretical isoelectric point of 5.06. Molecular docking of the MEV against the TLR-4/MD-2 complex yielded a highly favorable predicted binding, primarily mediated through hydrophobic interactions at the MD-2 binding interface. In silico immune simulation demonstrated that the vaccine elicited a robust humoral response, which was largely IgG1 dominated, and a strong B-cell memory following three doses. Results show that the MEV elicited a Th1-polarized response with sustained T-cell memory and a transient CD8+ response after the primary dose as well as a cytokine milieu dominated by IFN-γ and IL-2. These findings suggest that the designed MEV is a promising prophylactic vaccine candidate against H. pylori infection; as such, recombinant expression and subsequent preclinical studies are recommended.