HLA-A*02:01 Presents Penicillin-Modified Cysteinylated Peptides for T Cell Recognition.

Area of Science:

• Immunology
• Allergy Research
• Drug Hypersensitivity Mechanisms

Background:

• Immune-mediated hypersensitivity reactions to beta-lactam antibiotics are a significant clinical issue.
• Drug-specific T cells are implicated, likely through recognition of modified self-peptides (haptenation).
• Understanding drug-TCR-pHLA interactions is key to elucidating hypersensitivity mechanisms.

Purpose of the Study:

• To identify benzylpenicillin (BP)-modified peptide ligands presented by HLA-A*02:01.
• To characterize the T cell receptor (TCR) repertoire in penicillin-induced hypersensitivity.
• To determine if a dominant TCR clonotype recognizes haptenated HLA peptides.

Main Methods:

• Immunopeptidomics to identify BP-modified HLA-A*02:01 ligands.
• Single-cell sequencing of CD8+ T cells expanded with BP to analyze the drug-reactive TCR repertoire.
• Reporter cell line assay to assess the reactivity of a dominant TCR clonotype.

Main Results:

• Benzylpenicillin preferentially modifies cysteine residues over lysine residues within the HLA-A*02:01 immunopeptidome.
• A novel mechanism involving cysteine-drug conjugate formation and disulphide-mediated peptide modification was identified.
• A BP-specific TCR recognized a reduction-sensitive epitope, indicative of a BP-cysteine adduct linked via disulphide bond.

Conclusions:

• Cysteine-penicillin adducts can be presented by HLA ligands.
• These modified ligands have the potential to induce T cell-mediated allergic reactions.
• The findings offer new insights into the molecular mechanisms of beta-lactam hypersensitivity.