title: ELISA to measure neutralizing capacity of anti-C1-inhibitor antibodies in plasma of angioedema patients.
abstract: BACKGROUND
  Neutralizing autoantibodies (NAbs) against plasma serpin C1-inhibitor (C1-inh) are implicated in the rare disorder, acquired angioedema (AAE). There is insufficient understanding of the process of antibody formation and its correlation with disease progression and severity. We have developed an ELISA for detecting neutralizing capacity of anti-C1-inh positive plasma samples that can be used to study changes in NAb repertoire in patient plasma over the course of disease.
  
  
  METHODS
  The ELISA is based on the specific interaction of active C1-inh with its target protease C1s. Decrease in the amount of C1s bound to immobilized C1-inh in the presence of test samples is proportional to the neutralizing capacity of the sample. Assay specificity, intra- and inter-assay variation and assay cut-off are determined using anti-C1-inh antibodies. Assay capability is demonstrated using plasma samples from AAE patients.
  
  
  RESULTS
  The assay is specific to a neutralizing anti-C1-inh antibody and shows no interference by a non-neutralizing anti-C1-inh antibody or by the plasma matrix. Intra-assay and inter-assay variations are determined as 17 and 18% respectively. Neutralizing capacity of antibody positive AAE patient plasma samples (n=16) with IgG or IgM type antibodies is readily determined. All samples show positive neutralizing capacity.
  
  
  CONCLUSIONS
  We have developed a robust, specific and semi-quantitative assay to detect the neutralizing capacity of plasma samples containing anti-C1-inh antibodies. This assay can be an important tool for the study of clinical implications of anti-C1-inh NAbs.
authors: Department of Immunopathology, Sanquin Research and Landsteiner Laboratory Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands.
authors: Ruchira
authors: R
authors: Engel
authors: Sanquin Diagnostic Services, Amsterdam, The Netherlands.
authors: Irma
authors: I
authors: Rensink
authors: Department of Immunopathology, Sanquin Research and Landsteiner Laboratory Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands.
authors: Dorina
authors: D
authors: Roem
authors: Department of Immunopathology, Sanquin Research and Landsteiner Laboratory Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands.
authors: Mieke
authors: M
authors: Brouwer
authors: Sanquin Diagnostic Services, Amsterdam, The Netherlands.
authors: Asma
authors: A
authors: Kalei
authors: ViroPharma Inc. (part of Shire group of companies), Exton, PA, USA.
authors: Dawn
authors: D
authors: Perry
authors: Department of Immunopathology, Sanquin Research and Landsteiner Laboratory Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands; Department of Hematology, Academic Medical Center, University of Amsterdam, The Netherlands.
authors: Sacha
authors: S
authors: Zeerleder
authors: Department of Immunopathology, Sanquin Research and Landsteiner Laboratory Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands.
authors: Diana
authors: D
authors: Wouters
authors: Sanquin Diagnostic Services, Amsterdam, The Netherlands. Electronic address: d.hamann@sanquin.nl.
authors: Dörte
authors: D
authors: Hamann
mesh_terms: D000799:Angioedema / Q000097:blood* / Q000276:immunology; D057134:Antibodies, Neutralizing / Q000097:blood*; D001323:Autoantibodies / Q000097:blood*; D003174:Complement C1 Inactivator Proteins / Q000276:immunology*; D050718:Complement C1 Inhibitor Protein; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans
chemical_list: D057134:Antibodies, Neutralizing; D001323:Autoantibodies; D003174:Complement C1 Inactivator Proteins; D050718:Complement C1 Inhibitor Protein; C469952:SERPING1 protein, human
keywords: Acquired angioedema; Auto-autoantibodies; C1-inhibitor deficiency; Hereditary angioedema