title: B-Cell epitope mapping of DNA topoisomerase I defines epitopes strongly associated with pulmonary fibrosis in systemic sclerosis.
abstract: We hypothesized that B-cell epitope mapping of DNA Topoisomerase I (type-I topoisomerase, or Topo I) may define epitopes strongly associated with pulmonary interstitial fibrosis (PIF) in systemic sclerosis (SSc). B-cell epitope mapping of Topo I was performed using 63 20-mer peptides overlapping by eight residues and spanning the entire length of the Topo I sequence. These peptides, coupled to polystyrene pins, were tested for antibody binding by enzyme-linked immunosorbent assays (ELISAs) using immunoglobulin G fractions from anti-Topo I, anticentromere, anti-U3RNP-positive, and normal sera. Four major epitopes were recognized by anti-Topo I sera, but not from the control sera: WWEEERYPEGIKWKFLEHKG (205-224, epitope I), RIANFKIEPPGLFRGRGNHP (349-368, epitope II), PGHKWKEVRHDNKVTWLVSW (397-416, epitope III), and ELDGQEYVVEFDFLGKDSIR (517-536, epitope IV). Peptide-epitopes were then synthesized in their soluble forms and ELISA systems were developed. Epitopes II to IV are localized at highly exposed sites of the Topo I tertiary structure, whereas epitope I is localized at a less accessible site. In a cohort of 81 patients with SSc with clinical data on the evolution of their disease, patients with antibodies in their sera recognizing at least three of the four epitopes had 3.1 times (P = 0.02) the hazard of developing PIF compared with patients whose sera recognized no epitopes or only one or two of the four epitopes. The discrimination was much stronger than that achieved by the simple determination of Topo I antibodies by counterimmunoelectrophoresis and immunoblot (hazard ratio 1.7, P = 0.30) in the same patients. B-cell epitope mapping of the anti-Topo I response has identified four major epitopes which cumulatively show a strong association with the development of PIF in SSc.
authors.affiliation: Department of Organic Chemistry and Biochemistry, School of Natural Sciences, University of Ioannina.
authors.forename: C
authors.initials: C
authors.lastname: Rizou
authors.forename: J P
authors.initials: JP
authors.lastname: Ioannidis
authors.forename: E
authors.initials: E
authors.lastname: Panou-Pomonis
authors.forename: M
authors.initials: M
authors.lastname: Sakarellos-Daitsiotis
authors.forename: C
authors.initials: C
authors.lastname: Sakarellos
authors.forename: H M
authors.initials: HM
authors.lastname: Moutsopoulos
authors.forename: P G
authors.initials: PG
authors.lastname: Vlachoyiannopoulos
mesh_terms: D000595:Amino Acid Sequence; D000906:Antibodies / Q000494:pharmacology; D001402:B-Lymphocytes / Q000201:enzymology / Q000276:immunology*; D001667:Binding, Competitive / Q000276:immunology; D004264:DNA Topoisomerases, Type I / Q000737:chemistry / Q000276:immunology*; D004797:Enzyme-Linked Immunosorbent Assay; D018604:Epitope Mapping / Q000706:statistics & numerical data*; D000939:Epitopes; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry / Q000276:immunology; D011237:Predictive Value of Tests; D016016:Proportional Hazards Models; D017434:Protein Structure, Tertiary; D011658:Pulmonary Fibrosis / Q000276:immunology* / Q000473:pathology; D012595:Scleroderma, Systemic / Q000276:immunology* / Q000473:pathology
chemical_list: D000906:Antibodies; D000939:Epitopes; D010446:Peptide Fragments; D004264:DNA Topoisomerases, Type I