Molecular Insights into Tumor Immunogenicity.

Tumor immunogenicity depends on the ability of peptides to form stable and specific interactions with both HLA molecules and T-cell receptors (TCRs). While HLA binding is essential, not all HLA-binding peptides elicit T-cell responses. This study investigates the molecular features distinguishing immunogenic T-cell epitopes from non-immunogenic HLA binders. Two datasets of nonamer peptides-38 T-cell epitopes and 144 non-epitopes-were compiled and analyzed using sequence logo models and molecular dynamics (MD) simulations of TCR-peptide-HLA complexes. A comparative logo analysis revealed strong amino acid preferences at central positions (p4-p8) in T-cell epitopes and absences in non-epitopes. A representative epitope-non-epitope pair was selected for structural modeling and 100 ns MD simulations. The T-cell epitope formed a more stable complex with the TCR and exhibited greater flexibility, supporting an induced-fit recognition mechanism. It also established a broader and longer-lasting network of hydrogen bonds and π interactions across the residues at positions p4-p8. In contrast, the non-epitope engaged TCR at only two positions. These findings highlight the critical role of the peptide's central region in TCR engagement and provide structural insights useful for neoantigen prediction, vaccine design, and TCR-based immunotherapies.