Tuberculosis (TB) is a serious global health issue caused by the bacteria Mycobacterium tuberculosis, which can be hard to treat due to resistance to medicines and limited effectiveness of existing vaccines. To tackle this problem, researchers created a new multi-epitope vaccine candidate called TZ1391 using circular mRNA technology. This vaccine includes several parts of the TB bacteria that can help the immune system recognize and fight the infection. Different versions of the vaccine were tested for stability and how well they can bind to immune receptors. One version, MTB-C3, was found to be the most effective, showing strong interaction with an immune receptor called TLR3 and better stability compared to others. Immune simulations suggested that TZ1391 could generate a strong and lasting immune response, making it a promising candidate for further testing against tuberculosis.
Simplified
Tuberculosis (TB), caused by Mycobacterium tuberculosis, remains a major global health burden due to latent infection, multidrug resistance, and the limited efficacy of the BCG vaccine. To address this challenge, we computationally designed and evaluated a circular mRNA-based multi-epitope vaccine candidate, TZ1391. Five experimentally validated M. tuberculosis antigens (ESAT-6, CFP-10, Ag85B, PPE18, and HspX) were used to predict immunodominant cytotoxic T lymphocyte (CTL), helper T lymphocyte (HTL), and B-cell epitopes. Three vaccine constructs (MTB-C1, MTB-C2, and MTB-C3) were assembled by integrating 20 CTL, 20 HTL, and 20 B-cell epitopes with appropriate linkers, PADRE sequence, and innate immune adjuvants. Structural modeling using AlphaFold2 and GalaxyRefine confirmed stable, native-like conformations for all constructs, with MTB-C3 showing the highest structural quality (GDT-HA = 0.8782; RMSD = 0.646 Å) and the greatest number of stabilizing disulfide bonds. Molecular docking against TLR3, TLR4, and TLR8 identified two top-performing candidates. MTB-C3 exhibited the strongest interaction with TLR3, achieving the lowest HDock score (- 480.53) and highest confidence score (0.9987), while MTB-C2 showed optimal binding to TLR4 (ClusPro score - 1488.6; confidence 0.9700). Despite favorable TLR4 engagement by MTB-C2, MTB-C3 was prioritized as the lead candidate (TZ1391) due to its superior structural stability, reduced conformational fluctuations during molecular dynamics simulations, and stronger TLR3 binding free energy (ΔG_bind = - 173.25 ± 7.9 kcal/mol). Immune simulations further predicted that TZ1391 elicits a robust Th1-biased response, characterized by sustained IgG production, strong IFN-γ and IL-2 induction, and durable immune memory. Overall, the strong TLR3-mediated interaction, combined with enhanced structural stability and favorable immunogenic profiles, establishes TZ1391 as a promising multi-epitope vaccine candidate for further experimental validation against tuberculosis.
