Epitope mapping of human factor IX inhibitor antibodies.
We have determined the location of epitopes on the factor IX for three haemophilia B inhibitor antibodies (HB-1, HB-3, HB-7) and a monoclonal anti-factor IX inhibitory antibody (designated 65-10). The main binding region of HB-1, HB-3 and HB-7 was 155YVNSTEAETI164 (residues 155-164), 167NITQSTQSFN176 and 156VNSTEAETI164, respectively. The binding region of 65-10 was 168ITQSTQSFNDFTRVV182, which included the cleavage site (180R-V181) for activation by factor XIa. By neutralization experiments using two peptides, 156VNSTEAETI164 and 167NITQSTQSFN176, the degree of neutralization of anti-factor IX IgG purified by protein A was determined. Neutralization of three antibodies, HB-1, HB-3 and HB-7, in the presence of 10 mM of the peptides 156VNSTEAETI164 was 30.1%, 0% and 10.8%, respectively, and in the presence of 4 mM of 167NITQSTQSFN176 it was 0%, 13.5% and 17.3%, respectively. On the other hand, when plasmas of patients instead of purified IgG were used for neutralization, 10 mM of 156VNSTEAETI164 and 4 mM of 167NITQSTQSFN176 failed to neutralize the inhibitor in the plasmas.
Takahashi
I
I
Japanese Red Cross Aichi Blood Centre.
Mizumo
S
S
Kamiya
T
T
Takamatsu
J
J
Saito
H
H
D000595:Amino Acid Sequence; D000906:Antibodies; D004797:Enzyme-Linked Immunosorbent Assay; D018604:Epitope Mapping; D000939:Epitopes / Q000235:genetics / Q000276:immunology*; D005164:Factor IX / Q000037:antagonists & inhibitors / Q000235:genetics / Q000276:immunology*; D017353:Gene Deletion; D006455:Hemoglobins, Abnormal / Q000235:genetics / Q000276:immunology; D002836:Hemophilia B / Q000235:genetics / Q000276:immunology*; D006801:Humans; D008969:Molecular Sequence Data; D010455:Peptides / Q000494:pharmacology
D000906:Antibodies; D000939:Epitopes; D006455:Hemoglobins, Abnormal; D010455:Peptides; D005164:Factor IX