title: Abacavir induces loading of novel self-peptides into HLA-B*57: 01:  an autoimmune model for HLA-associated drug hypersensitivity.
abstract: BACKGROUND
  Abacavir drug hypersensitivity in HIV-treated patients is associated with HLA-B57:01 expression. To understand the immunochemistry of abacavir drug reactions, we investigated the effects of abacavir on HLA-B57:01 epitope-binding in vitro and the quality and quantity of self-peptides presented by HLA-B57:01 from abacavir-treated cells.
  
  
  METHODS
  An HLA-B57:01-specific epitope-binding assay was developed to test for effects of abacavir, didanosine or flucloxacillin on self-peptide binding. To examine whether abacavir alters the peptide repertoire in HLA-B57:01, a B-cell line secreting soluble human leucocyte antigen (sHLA) was cultured in the presence or absence of abacavir, peptides were eluted from purified human leucocyte antigen (HLA), and the peptide epitopes comparatively mapped by mass spectroscopy to identify drug-unique peptides.
  
  
  RESULTS
  Abacavir, but not didansosine or flucloxacillin, enhanced binding of the FITC-labeled self-peptide LF9 to HLA-B57:01 in a dose-dependent manner. Endogenous peptides isolated from abacavir-treated HLA-B57:01 B cells showed amino acid sequence differences compared with peptides from untreated cells. Novel drug-induced peptides lacked typical carboxyl (C) terminal amino acids characteristic of the HLA-B57:01 peptide motif and instead contained predominantly isoleucine or leucine residues. Drug-induced peptides bind to soluble HLA-B57:01 with high affinity that was not altered by abacavir addition.
  
  
  CONCLUSIONS
  Our results support a model of drug-induced autoimmunity in which abacavir alters the quantity and quality of self-peptide loading into HLA-B57:01. Drug-induced loading of novel self-peptides into HLA, possibly by abacavir either altering the binding cleft or modifying the peptide-loading complex, generates an array of neo-antigen peptides that drive polyclonal T-cell autoimmune responses and multiorgan systemic toxicity.
authors.affiliation: Laboratory of Immunology, Division of Therapeutic Proteins, Office of Biotechnology Products, Center for Drug Evaluation and Research, Food and Drug Administration, Bethesda, MD 20892, USA. Michael.norcross@fda.hhs.gov
authors.forename: Michael A
authors.initials: MA
authors.lastname: Norcross
authors.forename: Shen
authors.initials: S
authors.lastname: Luo
authors.forename: Li
authors.initials: L
authors.lastname: Lu
authors.forename: Michael T
authors.initials: MT
authors.lastname: Boyne
authors.forename: Mary
authors.initials: M
authors.lastname: Gomarteli
authors.forename: Aaron D
authors.initials: AD
authors.lastname: Rennels
authors.forename: Janet
authors.initials: J
authors.lastname: Woodcock
authors.forename: David H
authors.initials: DH
authors.lastname: Margulies
authors.forename: Curtis
authors.initials: C
authors.lastname: McMurtrey
authors.forename: Stephen
authors.initials: S
authors.lastname: Vernon
authors.forename: William H
authors.initials: WH
authors.lastname: Hildebrand
authors.forename: Rico
authors.initials: R
authors.lastname: Buchli
mesh_terms: D000163:Acquired Immunodeficiency Syndrome / Q000188:drug therapy / Q000276:immunology*; D019380:Anti-HIV Agents / Q000494:pharmacology*; D015551:Autoimmunity / Q000187:drug effects*; D002478:Cells, Cultured; D015224:Dideoxynucleosides / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004342:Drug Hypersensitivity / Q000276:immunology*; D015235:HLA-B Antigens / Q000276:immunology*; D006650:Histocompatibility Testing / Q000379:methods*; D006801:Humans; D018448:Models, Immunological; D010446:Peptide Fragments / Q000276:immunology*; D017634:Self Tolerance / Q000276:immunology*; D013057:Spectrum Analysis; D000099227:Abacavir
chemical_list: D019380:Anti-HIV Agents; D015224:Dideoxynucleosides; D015235:HLA-B Antigens; D010446:Peptide Fragments; D000099227:Abacavir; C484830:HLA-B*57:01 antigen