Design of a multi-epitope vaccine against Mycobacterium tuberculosis using reverse vaccinology and immunoreactive peptides
Mycobacterium tuberculosis infects one-fourth of the global population, and current challenges such as latent infections, multidrug-resistant strains, and the limited efficacy of the BCG vaccine emphasize the urgent need for next-generation vaccines. This study aimed to introduce novel vaccine candidates, immunoreactive epitopes, and a novel multi-epitope vaccine (MEV). New immunogenic targets were identified based on different characteristics, including subcellular localization, antigenicity, non-similarity to the host proteome, sequence conservation, prevalence, and B-cell and T-cell epitopes. In the next step, IFN-γ releasing immunoreactive epitopes with a high similarity to TCR-interacting epitopes were identified. The MEV was generated using shortlisted epitopes and the C-terminal fragment of Clostridium perfringens enterotoxin (CPE). Finally, the interactions of MEV epitopes with human MHC I and MHC II alleles were investigated. In the first step, a total of seven proteins with desired immunogenic properties were introduced as novel immunogenic targets. Comparison of surface-exposed proteins to 4718 immunoreactive linear B-cell epitopes of M. tuberculosis resulted in identification of 719 non-redundant immunoreactive epitopes. Finally, seven immunoreactive, IFN-γ releasing epitopes with significant homology to TCR binding epitopes were employed to design a MEV. This MEV showed desirable structural and immunogenic properties. Moreover, it revealed promising interactions with human MHC I and MHC II alleles in molecular docking. This study suggests PE/PPE proteins and TCR-recognized immunoreactive peptides as promising vaccine components against tuberculosis. In addition, the designed MEV with the C-terminal fragment of CPE may represent a potential candidate for future development as a mucosal vaccine against M. tuberculosis.