title: Direct evidence for the formation of diastereoisomeric benzylpenicilloyl haptens from benzylpenicillin and benzylpenicillenic acid in patients.
abstract: Covalent binding to proteins to form neoantigens is thought to be central to the pathogenesis of penicillin hypersensitivity reactions. We have undertaken detailed mass spectrometric studies to define the mechanism and protein chemistry of hapten formation from benzylpenicillin (BP) and its rearrangement product, benzylpenicillenic acid (PA). Mass spectrometric analysis of human serum albumin exposed to BP and PA in vitro revealed that at low concentrations (drug protein molar ratio 0.001:1) and during short time incubations BP and PA selectively target different residues, Lys199 and Lys525, respectively. Molecular modeling showed that the selectivity was a function of noncovalent interaction before covalent modification. With increased exposure to higher concentrations of BP and PA, multiple epitopes were detected on albumin, demonstrating that the multiplicity of hapten formation is a function of time and concentration. More importantly, we have demonstrated direct evidence that PA is a hapten accounting for the diastereoisomeric BP antigen formation in albumin isolated from the blood of patients receiving penicillin. Furthermore, PA was found to be more potent than BP with respect to stimulation of T cells from patients with penicillin hypersensitivity, illustrating the functional relevance of diastereoisomeric hapten formation.
authors.affiliation: Medical Research Council Centre for Drug Safety Science, Department of Pharmacology and Therapeutics, University of Liverpool, Liverpool, United Kingdom.
authors.forename: Xiaoli
authors.initials: X
authors.lastname: Meng
authors.forename: Rosalind E
authors.initials: RE
authors.lastname: Jenkins
authors.forename: Neil G
authors.initials: NG
authors.lastname: Berry
authors.forename: James L
authors.initials: JL
authors.lastname: Maggs
authors.forename: John
authors.initials: J
authors.lastname: Farrell
authors.forename: Catherine S
authors.initials: CS
authors.lastname: Lane
authors.forename: Andrew V
authors.initials: AV
authors.lastname: Stachulski
authors.forename: Neil S
authors.initials: NS
authors.lastname: French
authors.forename: Dean J
authors.initials: DJ
authors.lastname: Naisbitt
authors.forename: Munir
authors.initials: M
authors.lastname: Pirmohamed
authors.forename: B Kevin
authors.initials: BK
authors.lastname: Park
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000595:Amino Acid Sequence; D015153:Blotting, Western; D002384:Catalysis; D003198:Computer Simulation; D004342:Drug Hypersensitivity / Q000276:immunology; D000939:Epitopes / Q000276:immunology; D005260:Female; D006241:Haptens / Q000378:metabolism; D006801:Humans; D007202:Indicators and Reagents; D008213:Lymphocyte Activation / Q000187:drug effects; D008297:Male; D013058:Mass Spectrometry; D008875:Middle Aged; D010400:Penicillin G / Q000031:analogs & derivatives* / Q000737:chemistry / Q000493:pharmacokinetics*; D010406:Penicillins / Q000276:immunology; D012709:Serum Albumin / Q000378:metabolism; D013237:Stereoisomerism
chemical_list: D000939:Epitopes; D006241:Haptens; D007202:Indicators and Reagents; D010406:Penicillins; D012709:Serum Albumin; C016262:benzylpenicillenic acid; D010400:Penicillin G