Epitope Mapping of Factor Viii Inhibitor Antibodies of Chinese Origin
Resource
BRITISH JOURNAL OF HAEMATOLOGY v.113 n.4 pp.915-924
Journal
BRITISH JOURNAL OF HAEMATOLOGY
Journal Volume
v.113
Journal Issue
n.4
Pages
915-924
Date Issued
2001
Date
2001
Author(s)
SHEN, MING-CHING
CHEN, JEN-YANG
HUNG, MEI-HUA
LIN, SHU-WHA
Abstract
Epitopes recognized by factor VIII (FVIII) inhibitors of Chinese origin were analysed by immunoblotting with full- length recombinant FVIII(rFVIII ), thrombin-activated FVIII ( FVIIIa) and 16 FVIII fusion proteins synthesized by bacteria. Twenty-eight patients, 12 with haemophilia A and 16 with autoimmune diseases, were recruited. Antibodies from 22 patients showed reactivity with rFVIII, 20 with FVIIIa, and one reacted only with FVIII fusion proteins. Of these 22 cases, most were reactive with A2-a2 and A3-C1-C2 of FVIII( a). Of the nine cases that depicted binding to the fusion proteins, three were reactive with the A domains, three with only the B domain, and the other three with both the A and B (or C) domains. An epitope for a neutralizing antibody of a haemophilia A patient, designated TWN-112, was localized to residues 323-390, specified by FVIII fusion proteins. The same epitope also appeared on an FVIII-expression phage library screening. Immunoabsorption of antibodies from TWN- 112 with the epitope reduced the neutralizing activity of the inhibitor by 33%. The incidence of a1 of FVIII is higher , and that of a3 is lower, than previously reported. Two novel epitopes, reported for the first time in this paper, were localized on the 8B2 (amino acid residues 1022-1204) and 8A2(V) (residues 673-740) fusion proteins. These two epitopes were able to reduce inhibitory antibody activity by 24% and 25% respectively. Changes of FVIII fragment specificity were also observed in one of six patients for whom multiple samples, collected at different times, were available. Our initial finding showed that the FVIII inhibitors in these Chinese patients shared epitopes with those of patients from very different genetic backgrounds, suggesting a common mechanism for the development of FVIII inhibitors.
Subjects
factor VIII
factor VIII inhibitor
recombinant protein
haemophilia A
epitope mapping
HEMOPHILIA-A PATIENTS