The prevalence of proteolytic antibodies against factor VIII in hemophilia A.
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.
Lacroix-Desmazes
Sébastien
S
INSERM Unité 430 and Université Pierre et Marie Curie, Hôpital Broussais, Paris, France.
Bayry
Jagadeesh
J
Misra
Namita
N
Horn
Michael P
MP
Villard
Sylvie
S
Pashov
Anastas
A
Stieltjes
Natalie
N
d'Oiron
Roseline
R
Saint-Remy
Jean-Marie
JM
Hoebeke
Johan
J
Kazatchkine
Michel D
MD
Reinbolt
Joseph
J
Mohanty
Dipika
D
Kaveri
Srini V
SV
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
D017151:Antibodies, Catalytic; D007074:Immunoglobulin G; D007518:Isoantibodies; D005169:Factor VIII