Molecular Insights into Tumor Immunogenicity.

Area of Science:

• Immunology
• Structural Biology
• Computational Biology

Background:

• Tumor immunogenicity relies on peptide interactions with HLA molecules and T-cell receptors (TCRs).
• Not all HLA-binding peptides trigger T-cell responses, indicating a need to differentiate immunogenic epitopes from non-immunogenic binders.

Purpose of the Study:

• To identify molecular features distinguishing immunogenic T-cell epitopes from non-immunogenic HLA binders.
• To provide structural insights into TCR-peptide-HLA interactions for improved neoantigen prediction and immunotherapy design.

Main Methods:

• Analysis of two nonamer peptide datasets (38 T-cell epitopes, 144 non-epitopes) using sequence logo models.
• Molecular dynamics (MD) simulations of TCR-peptide-HLA complexes to assess interaction stability and dynamics.
• Comparative analysis of amino acid preferences at central peptide positions (p4-p8).

Main Results:

• Sequence logos showed distinct amino acid preferences at central positions (p4-p8) for T-cell epitopes, absent in non-epitopes.
• MD simulations revealed the T-cell epitope formed a more stable and flexible TCR complex, supporting an induced-fit mechanism.
• The immunogenic epitope established broader, longer-lasting hydrogen and π interactions at p4-p8, unlike the non-epitope which engaged the TCR at fewer positions.

Conclusions:

• The central region of a peptide plays a critical role in TCR engagement and immune recognition.
• Structural insights gained can enhance neoantigen prediction, cancer vaccine design, and TCR-based immunotherapies.