title: Epitope analysis of anti-myeloperoxidase antibodies in patients with ANCA-associated vasculitis.
abstract: OBJECTIVE
  Increasing evidences have suggested the pathogenic role of anti-neutrophil cytoplasmic antibodies (ANCA) directing myeloperoxidase (MPO) in ANCA-associated vasculitis (AAV). The current study aimed to analyze the association between the linear epitopes of MPO-ANCA and clinicopathological features of patients with AAV.
  
  
  METHODS
  Six recombinant linear fragments, covering the whole length amino acid sequence of a single chain of MPO, were produced from E.coli. Sera from 77 patients with AAV were collected at presentation. 13 out of the 77 patients had co-existence of serum anti-GBM antibodies. Ten patients also had sequential sera during follow up. The epitope specificities were detected by enzyme-linked immunosorbent assay using the recombinant fragments as solid phase ligands.
  
  
  RESULTS
  Sera from 45 of the 77 (58.4%) patients with AAV showed a positive reaction to one or more linear fragments of the MPO chain. The Birmingham Vasculitis Activity Scores and the sera creatinine were significantly higher in patients with positive binding to the light chain fragment than that in patients without the binding. The epitopes recognized by MPO-ANCA from patients with co-existence of serum anti-GBM antibodies were mainly located in the N-terminus of the heavy chain. In 5 out of the 6 patients, whose sera in relapse recognize linear fragments, the reactivity to linear fragments in relapse was similar to that of initial onset.
  
  
  CONCLUSIONS
  The epitope specificities of MPO-ANCA were associated with disease activity and some clinicopathological features in patients with ANCA-associated vasculitis.
authors.affiliation: Renal Division, Department of Medicine, Peking University First Hospital, Peking University Institute of Nephrology, Key Laboratory of Renal Disease, Ministry of Health of China, Key Laboratory of Chronic Kidney Disease Prevention and Treatment (Peking University), Ministry of Education, Beijing, China.
authors.forename: Shen-Ju
authors.initials: SJ
authors.lastname: Gou
authors.forename: Peng-Cheng
authors.initials: PC
authors.lastname: Xu
authors.forename: Min
authors.initials: M
authors.lastname: Chen
authors.forename: Ming-Hui
authors.initials: MH
authors.lastname: Zhao
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D056648:Anti-Neutrophil Cytoplasmic Antibody-Associated Vasculitis / Q000097:blood / Q000276:immunology* / Q000473:pathology; D000906:Antibodies / Q000097:blood / Q000276:immunology*; D003429:Cross Reactions; D018604:Epitope Mapping; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010446:Peptide Fragments / Q000276:immunology; D009195:Peroxidase / Q000235:genetics / Q000276:immunology* / Q000302:isolation & purification; D011994:Recombinant Proteins / Q000235:genetics / Q000276:immunology / Q000302:isolation & purification; D012008:Recurrence; D017384:Sequence Deletion; D055815:Young Adult
chemical_list: D000906:Antibodies; D010446:Peptide Fragments; D011994:Recombinant Proteins; D009195:Peroxidase