The Aesthetics of Domain Order: Next-Generation mRNA Tuberculosis Vaccine Engineered by AlphaFold3 and Immunoinformatics
##1. Limitations of BCG and the Necessity of Multi-Epitope (MEVC) Design The only currently available tuberculosis vaccine, BCG, shows markedly reduced efficacy in preventing pulmonary TB in adults and lacks flexibility to address antigenic variation. To overcome these shortcomings, the research team adopted a Multi-Epitope Vaccine Construct (MEVC) strategy that combines the key Mycobacterium tuberculosis antigens PPE68, IrtA, and PE9. This approach does not merely mix antigens; it employs an advanced bio‑IT design to identify the optimal sequence arrangement that maximizes immune responses and directs precise attacks by the immune system.
##2. Dramatic Differences in Immunogenicity According to Antigen Domain Arrangement The central finding of the study is that the order of antigen arrangement, rather than the antigen identities themselves, determines immunogenic potency. Immunoinformatics analysis revealed that the optimized sequence Pattern 3 (PPE68‑IrtA‑PE9) achieved the highest antigenicity score of 0.6122 and an overwhelming B‑cell epitope proportion of 0.865. This suggests that the physical positioning of domains dictates the three‑dimensional exposure of the protein, thereby fundamentally altering the efficiency with which immune cells recognize the antigens.
##3. Molecular Docking Simulations Demonstrate Strong Binding to TLR Receptors Structural prediction with AlphaFold3 followed by molecular docking supports the functional viability of the designed vaccine. Pattern 3 exhibited highly favorable binding free energies of –12.2 kcal/mol with TLR4/MD‑2 and –10.4 kcal/mol with TLR2, indicating very stable interactions. Notably, a total of 21 hydrogen bonds were formed with the receptors, providing a mechanistic basis for the expectation that in vivo administration will elicit robust T‑cell responses and IFN‑γ secretion, thereby establishing a solid immune barrier at the molecular level.
##4. mRNA Stability Optimization: Secondary Structure Design for Manufacturing Efficiency Equally important to vaccine efficacy is the stability of expression within cells. The team employed codon optimization to engineer the mRNA secondary structure, achieving an exceptionally low free energy of ΔG = –2217.20 kcal/mol, which maximizes thermodynamic stability. This robust mRNA architecture minimizes degradation during delivery, enhances protein expression efficiency, and provides a critical technical advantage by ensuring both manufacturing process stability and distribution convenience at the scale‑up stage.
Tuberculosis (TB), caused by Mycobacterium tuberculosis, remains a major global health challenge due to the limited efficacy of the Bacillus Calmette-Guérin (BCG) vaccine. Using an immunoinformatics-driven strategy, we designed and evaluated three distinct multi-epitope vaccine constructs (MEVCs) derived from PPE68, IrtA, and PE9, which were subsequently developed into an mRNA vaccine construct. T-cell and B-cell epitopes were predicted using IEDB tools and BepiPred-3.0, and the designed constructs were systematically evaluated for antigenicity, allergenicity, toxicity, and physicochemical characteristics. Structural modeling with AlphaFold3, followed by epitope mapping and molecular docking with TLR2 and TLR4/MD-2, identified Pattern 3 (PPE68-IrtA-PE9) as the most promising construct. It exhibited the highest antigenicity score (0.6122), a high abundance of B-cell epitopes (0.865), and demonstrated predicted binding to the TLR4/MD-2 complex (ΔG = - 12.2 kcal/mol), forming 12 hydrogen bonds and engaging both receptor components, as well as to TLR2 (ΔG = - 10.4 kcal/mol) with nine hydrogen bonds. In silico immune simulations of Pattern 3 predicted strong T-cell responses, elevated IFN-γ levels, and high IgG1, IgG2, and IgM titers, while the codon-optimized mRNA exhibited a stable secondary structure (ΔG = - 2,217.20 kcal/mol). These results suggest that antigen domain arrangement may influence predicted immunogenicity and structural stability, and exhibit a favorable in silico safety profile, supporting PPE68-IrtA-PE9 as a promising mRNA vaccine design for further experimental evaluation.
This study provides molecular‑structural evidence that the arrangement order of antigen domains is a pivotal determinant of vaccine immunogenicity. By integrating high‑precision structural predictions from AlphaFold3 with artificial immune simulations, the work establishes a new benchmark for Structure‑Based Vaccine Design, enabling the prediction and optimization of vaccine efficacy prior to experimental testing—a contribution of considerable scholarly significance.