title: Affinity of FVIII-specific antibodies reveals major differences between neutralizing and nonneutralizing antibodies in humans.
abstract: Recently, we reported that distinct immunoglobulin (Ig) isotypes and IgG subclasses of factor VIII (FVIII)-specific antibodies are found in different cohorts of patients with hemophilia A and in healthy individuals. Prompted by these findings, we further investigated the distinguishing properties among the different populations of FVIII-specific antibodies. We hypothesized that the affinity of antibodies would discriminate between the neutralizing and nonneutralizing antibodies found in different study cohorts. To test this idea, we established a competition-based enzyme-linked immunosorbent assay technology to assess the apparent affinities for each isotype and IgG subclass of FVIII-specific antibodies without the need for antibody purification. We present a unique data set of apparent affinities of FVIII-specific antibodies found in healthy individuals, patients with congenital hemophilia A with and without FVIII inhibitors, and patients with acquired hemophilia A. Our data indicate that FVIII-specific antibodies found in patients with FVIII inhibitors have an up to 100-fold higher apparent affinity than that of antibodies found in patients without inhibitors and in healthy individuals. High-affinity FVIII-specific antibodies could be retrospectively detected in longitudinal samples of an individual patient with FVIII inhibitors 543 days before the first positive Bethesda assay. This finding suggests that these antibodies might serve as potential biomarkers for evolving FVIII inhibitor responses.
authors.affiliation: Baxter BioScience, Vienna, Austria;
authors.forename: Christoph J
authors.initials: CJ
authors.lastname: Hofbauer
authors.affiliation: Baxter BioScience, Vienna, Austria;
authors.forename: Shawn F J
authors.initials: SF
authors.lastname: Whelan
authors.affiliation: Baxter BioScience, Vienna, Austria;
authors.forename: Maria
authors.initials: M
authors.lastname: Hirschler
authors.affiliation: Baxter BioScience, Vienna, Austria;
authors.forename: Peter
authors.initials: P
authors.lastname: Allacher
authors.affiliation: Baxter BioScience, Vienna, Austria;
authors.forename: Frank M
authors.initials: FM
authors.lastname: Horling
authors.affiliation: Baxter BioScience, Vienna, Austria;
authors.forename: John-Philip
authors.initials: JP
authors.lastname: Lawo
authors.affiliation: Institute for Experimental Hematology and Transfusion Medicine, Bonn, Germany;
authors.forename: Johannes
authors.initials: J
authors.lastname: Oldenburg
authors.affiliation: Department of Hematology, Hemostasis, Oncology, and Stem Cell Transplantation, Hannover Medical School, Hannover, Germany;
authors.forename: Andreas
authors.initials: A
authors.lastname: Tiede
authors.affiliation: Department of Pediatrics, Medical University of Vienna, Vienna, Austria;
authors.forename: Christoph
authors.initials: C
authors.lastname: Male
authors.affiliation: Institute of Hematology and Transfusion Medicine, Warsaw, Poland;
authors.forename: Jerzy
authors.initials: J
authors.lastname: Windyga
authors.affiliation: Institute for Immunology and Transfusion Medicine, Greifswald Medical School, Greifswald, Germany; and.
authors.forename: Andreas
authors.initials: A
authors.lastname: Greinacher
authors.affiliation: Department of Internal Medicine I, Medical University of Vienna, Vienna, Austria.
authors.forename: Paul N
authors.initials: PN
authors.lastname: Knöbl
authors.affiliation: Baxter BioScience, Vienna, Austria;
authors.forename: Gerald
authors.initials: G
authors.lastname: Schrenk
authors.affiliation: Baxter BioScience, Vienna, Austria;
authors.forename: Jadranka
authors.initials: J
authors.lastname: Koehn
authors.affiliation: Baxter BioScience, Vienna, Austria;
authors.forename: Friedrich
authors.initials: F
authors.lastname: Scheiflinger
authors.affiliation: Baxter BioScience, Vienna, Austria;
authors.forename: Birgit M
authors.initials: BM
authors.lastname: Reipert
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D057134:Antibodies, Neutralizing / Q000276:immunology*; D000915:Antibody Affinity; D001323:Autoantibodies / Q000276:immunology*; D016022:Case-Control Studies; D005169:Factor VIII / Q000276:immunology*; D005260:Female; D006467:Hemophilia A / Q000097:blood / Q000276:immunology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D055815:Young Adult
chemical_list: D057134:Antibodies, Neutralizing; D001323:Autoantibodies; D005169:Factor VIII