Differences in MHC class I self peptide repertoires among HLA-A2 subtypes

Area of Science:

• Immunology
• Molecular Biology
• Structural Biology

Background:

• Major histocompatibility complex (MHC) class I molecules present peptides to T cells.
• Single amino acid substitutions in MHC class I can influence peptide binding specificity.

Purpose of the Study:

• To investigate the impact of single amino acid substitutions in HLA-A2 subtypes on their naturally processed peptide repertoires.
• To understand how these substitutions affect peptide binding motifs and MHC molecule conformation.

Main Methods:

• Elution and sequencing of naturally processed peptides from HLA-A2 subtypes (HLA-A*0204, -A*0206, -A*0207) and HLA-A*0201.
• Mass spectrometry to quantify self-peptide repertoires.
• Computer modeling of MHC allele conformations using energy minimization.

Main Results:

• Allele-specific peptide motifs differed substantially between HLA-A2 subtypes and HLA-A*0201, particularly at anchor residues.
• Mass spectrometry data precisely reflected these motif differences.
• Computer models suggested that substituted-residue-driven conformational changes explain the observed peptide motif variations.

Conclusions:

• Single amino acid substitutions in MHC class I molecules fine-tune self-peptide repertoires.
• These conformational changes influence peptide binding and can aid in predicting antigenic peptides.