Epitope mapping of human factor IX inhibitor antibodies |
| |
Authors: | Isao Takahashi Shinichi Mizumo Tadashi Kamiya Junki Takamatsu Hidehiko Saito |
| |
Institution: | Japanese Red Cross Aichi Blood Centre, Minamiyamaguchi, Seto, Aichi;Aichi Blood Disease Research Foundation, Machikika, Moriyama, Nagoya;First Department of Internal Medicine, Nagoya University School of Medicine, Tsuruma, Showa, Nagoya, Japan |
| |
Abstract: | Summary. 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 10m m of the peptides 156VNSTEAETI164 was 30.1%, 0% and 10.8%, respectively, and in the presence of 4 m m 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 m m of 156VNSTEAETI164 and 4 m m of 167NITQSTQSFN176 failed to neutralize the inhibitor in the plasmas. |
| |
Keywords: | factor IX inhibitor epitope mapping peptide neutralization |
|
|