title: Monoclonal antibodies to human cartilage oligomeric matrix protein: epitope mapping and characterization of sandwich ELISA.
abstract: BACKGROUND
  Cartilage oligomeric matrix protein/thrombospondin 5 (COMP/TSP 5) is one of the most promising serologic markers with regard to an ability to prognose development of osteoarthritis (OA). Our aim was to map the epitopes of three monoclonal antibodies (mAb) to COMP and to develop and characterize a sandwich enzyme-linked immunosorbent assay (ELISA) for measuring COMP levels in human body fluids.
  
  
  METHODS
  COMP was digested with trypsin and the NH(2)-terminal sequence of the fragments recognized by each of the mAbs was determined. Steric competition among the mAbs was tested with an antibody capture assay. A sandwich ELISA was developed using unlabeled mAb 16-F12 as a capture antibody, and mAb 17-C10 labeled with biotin as the second antibody.
  
  
  RESULTS
  Epitopes of the three mAbs were mapped to three different domains within the COMP subunit (16-F12, NH(2)-terminal domain; 17-C10, EGF-like domain; 12-C4, COOH-terminal domain). These epitopes did not overlap. mAbs 17-C10 and 12-C4 yielded similar serum COMP results when used as the secondary antibodies. Serum COMP levels measured with the new sandwich ELISA using mAbs 16-F12 and 17-C10 correlated strongly with results based on an inhibition ELISA with mAb 17-C10 alone (r(2) = 0.836; P < 0.0001). We characterized the new sandwich ELISA with regards to inter- and intra-assay variability, the range of COMP levels that can be expected in human synovial fluids (SF) and sera (controls and OA and rheumatoid arthritis (RA) patients), and the day-to-day and diurnal variability of COMP levels in sera.
  
  
  CONCLUSIONS
  We have developed and characterized a sandwich ELISA for COMP that is sensitive and yields highly reproducible COMP results upon analysis of human sera and synovial fluids.
authors.affiliation: Institute of Rheumatology, Na Slupi 4, 128 50 Prague 2, Czech Republic. vili@revma.cz
authors.forename: Vladimír
authors.initials: V
authors.lastname: Vilím
authors.forename: Zdenek
authors.initials: Z
authors.lastname: Vobůrka
authors.forename: Richard
authors.initials: R
authors.lastname: Vytásek
authors.forename: Ladislav
authors.initials: L
authors.lastname: Senolt
authors.forename: Ilja
authors.initials: I
authors.lastname: Tchetverikov
authors.forename: Virginia B
authors.initials: VB
authors.lastname: Kraus
authors.forename: Karel
authors.initials: K
authors.lastname: Pavelka
mesh_terms: D000911:Antibodies, Monoclonal / Q000276:immunology*; D064236:Cartilage Oligomeric Matrix Protein; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods*; D018604:Epitope Mapping; D016326:Extracellular Matrix Proteins / Q000032:analysis / Q000276:immunology*; D006023:Glycoproteins / Q000032:analysis / Q000276:immunology*; D006801:Humans; D064235:Matrilin Proteins; D013582:Synovial Fluid / Q000737:chemistry
chemical_list: D000911:Antibodies, Monoclonal; D064236:Cartilage Oligomeric Matrix Protein; D016326:Extracellular Matrix Proteins; D006023:Glycoproteins; D064235:Matrilin Proteins; C577553:TSP5 protein, human