title: Epitope characterization of an anti-PIVKA-II antibody and evaluation of a fully automated chemiluminescent immunoassay for PIVKA-II.
abstract: OBJECTIVE
  Protein induced by vitamin K absence or antagonist-II (PIVKA-II) has been used as a tumor marker to aid in the diagnosis of hepatocellular carcinoma (HCC). We developed an anti-PIVKA-II monoclonal antibody, 3C10, and a fully automated quantitative immunoassay for PIVKA-II on the ARCHITECT® i-systems. The aim of this study was to characterize the epitope of 3C10 and to evaluate the reactivity to PIVKA-II of this assay.
  
  
  METHODS
  The epitope characterization was examined by using prothrombin γ-carboxyglutamic acid residues (Gla) domain polypeptides which are amino acid residues 17-27 that include four Gla residues at positions 19, 20, 25 and 26. The correlation with Picolumi PIVKA-II MONO (Eidia, Tokyo, Japan) and tube type equivalency was evaluated by using the developed fully automated quantitative immunoassay.
  
  
  RESULTS
  Peptides having glutamic acid residues (Glu) at Gla domains strongly reacted to 3C10 but lost reactivity when the Glu at positions 19 or 20 was changed to Gla. The results were equivalent with an existing in vitro diagnostics product for PIVKA-II using the MU-3 antibody. A correlation study with the Picolumi PIVKA-II MONO gave a correlation coefficient of 0.99 and a regression slope of 0.92. No difference between a plain serum tube and a rapid serum tube including thrombin (RST) was observed on ARCHITECT PIVKA-II.
  
  
  CONCLUSIONS
  The results demonstrate that this anti-PIVKA-II antibody detects equivalent epitopes with MU-3 and has equivalent reactivity to PIVKA-II as MU-3. Moreover, the ARCHITECT PIVKA-II assay has good correlation with the existing PIVKA-II product, and is applicable for use with RST.
authors: Research and Development, Abbott Japan Co., Ltd., Chiba, Japan. Electronic address: hideki.kinukawa@abbott.com.
authors: Hideki
authors: H
authors: Kinukawa
authors: Research and Development, Abbott Japan Co., Ltd., Chiba, Japan.
authors: Takuma
authors: T
authors: Shirakawa
authors: Research and Development, Abbott Japan Co., Ltd., Chiba, Japan.
authors: Toru
authors: T
authors: Yoshimura
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology*; D015415:Biomarkers / Q000097:blood; D014408:Biomarkers, Tumor / Q000097:blood / Q000276:immunology; D006528:Carcinoma, Hepatocellular / Q000097:blood / Q000175:diagnosis / Q000276:immunology; D002460:Cell Line; D000939:Epitopes / Q000276:immunology*; D018698:Glutamic Acid / Q000276:immunology; D006801:Humans; D006825:Hybridomas / Q000276:immunology; D007118:Immunoassay / Q000379:methods; D007159:Immunologic Tests / Q000379:methods; D008113:Liver Neoplasms / Q000097:blood / Q000175:diagnosis / Q000276:immunology; D051379:Mice; D011498:Protein Precursors / Q000097:blood / Q000276:immunology*; D011516:Prothrombin / Q000276:immunology*; D013917:Thrombin / Q000276:immunology
chemical_list: D000911:Antibodies, Monoclonal; D015415:Biomarkers; D014408:Biomarkers, Tumor; D000939:Epitopes; D011498:Protein Precursors; D018698:Glutamic Acid; C008208:acarboxyprothrombin; D011516:Prothrombin; D013917:Thrombin
keywords: 3C10; Chemiluminescent microparticle immunoassay; DCP; Hepatocellular carcinoma; PIVKA-II; Tumor marker