The structural basis for the increased immunogenicity of two HIV-reverse transcriptase peptide variant/class I major...

Area of Science:

• Immunology
• Structural Biology
• Vaccine Development

Background:

• Designing altered peptide ligands for class I major histocompatibility complexes (MHC) is crucial for therapeutic and prophylactic strategies.
• Previous studies demonstrated enhanced in vitro immunogenicity of two human immunodeficiency virus (HIV)-reverse transcriptase (RT) peptide variants (I1Y and I1F) compared to the wild-type peptide.

Purpose of the Study:

• To elucidate the structural basis for the increased cell surface stability of I1Y and I1F peptide variants compared to the wild-type RT peptide.
• To understand the differential T cell recognition and immunological activities between the I1Y and I1F peptide variants.

Main Methods:

• X-ray crystallography was employed to determine the structures of class I MHC-peptide complexes with I1Y and I1F variants.
• Structural comparisons and modeling of T cell receptor (TCR) interactions were performed.

Main Results:

• The increased cell surface half-life of the peptide-class I complex is attributed to pi-pi stacking interactions between Trp-167 of HLA-A2.1 and the aromatic P1 residues of I1F and I1Y.
• Subtle steric and polar property changes in I1Y affect TCR engagement.
• Water-mediated hydrogen bonds between P1-Tyr and P4-Glu residues enhance the rigidity of critical TCR-engaging peptide side chains.

Conclusions:

• The I1Y and I1F peptide variants exhibit distinct immunological activities due to structural differences influencing TCR interactions.
• These findings support the candidacy of these altered peptides for the development of novel HIV vaccines due to their enhanced immunogenicity and stability.