title: The prevalence of proteolytic antibodies against factor VIII in hemophilia A.
abstract: BACKGROUND
  Factor VIII inhibitors are IgG alloantibodies that arise during replacement therapy in 25 to 50 percent of patients with severe hemophilia A. The hydrolysis of factor VIII by anti--factor VIII antibodies has been proposed as a mechanism of inactivation of factor VIII.
  
  
  METHODS
  We purified IgG from patients with severe hemophilia A. The proteolytic activity of the antibodies was assessed by incubating the IgG with biotinylated human factor VIII and analyzing patterns of factor VIII cleavage by sodium dodecyl sulfate--polyacrylamide-gel electrophoresis and immunoblotting. The controls were normal human IgG and IgG purified from plasma of patients with hemophilia who did not have inhibitory antibodies.
  
  
  RESULTS
  Significant proteolytic activity was detected in IgG from 13 of 24 inhibitor-positive patients. No hydrolytic activity was detected in control antibodies of IgG from patients without inhibitors. The rate of hydrolysis of factor VIII by purified IgG correlated positively with the factor VIII--neutralizing activity of IgG in plasma (r2=0.67, P=0.029). Principal-component analysis of migration profiles of digestion fragments demonstrated the heterogeneity of the catalytic potential of factor VIII inhibitors among patients.
  
  
  CONCLUSIONS
  Proteolysis is a mechanism by which IgG antibodies against factor VIII can inactivate factor VIII.
authors.affiliation: INSERM Unité 430 and Université Pierre et Marie Curie, Hôpital Broussais, Paris, France.
authors.forename: Sébastien
authors.initials: S
authors.lastname: Lacroix-Desmazes
authors.forename: Jagadeesh
authors.initials: J
authors.lastname: Bayry
authors.forename: Namita
authors.initials: N
authors.lastname: Misra
authors.forename: Michael P
authors.initials: MP
authors.lastname: Horn
authors.forename: Sylvie
authors.initials: S
authors.lastname: Villard
authors.forename: Anastas
authors.initials: A
authors.lastname: Pashov
authors.forename: Natalie
authors.initials: N
authors.lastname: Stieltjes
authors.forename: Roseline
authors.initials: R
authors.lastname: d'Oiron
authors.forename: Jean-Marie
authors.initials: JM
authors.lastname: Saint-Remy
authors.forename: Johan
authors.initials: J
authors.lastname: Hoebeke
authors.forename: Michel D
authors.initials: MD
authors.lastname: Kazatchkine
authors.forename: Joseph
authors.initials: J
authors.lastname: Reinbolt
authors.forename: Dipika
authors.initials: D
authors.lastname: Mohanty
authors.forename: Srini V
authors.initials: SV
authors.lastname: Kaveri
mesh_terms: D017151:Antibodies, Catalytic / Q000097:blood* / Q000378:metabolism; D005169:Factor VIII / Q000037:antagonists & inhibitors / Q000276:immunology* / Q000378:metabolism; D006467:Hemophilia A / Q000097:blood / Q000276:immunology* / Q000378:metabolism; D006801:Humans; D006868:Hydrolysis; D007074:Immunoglobulin G / Q000097:blood* / Q000378:metabolism; D007518:Isoantibodies / Q000097:blood* / Q000378:metabolism
chemical_list: D017151:Antibodies, Catalytic; D007074:Immunoglobulin G; D007518:Isoantibodies; D005169:Factor VIII