title: Reduction of the inhibitory antibody response to human factor VIII in hemophilia A mice by mutagenesis of the A2 domain B-cell epitope.
abstract: Approximately 25% of patients with hemophilia A develop inhibitory antibodies after treatment with factor VIII. Most of the inhibitory activity is directed against epitopes in the A2 and C2 domains. Anti-A2 inhibitory antibodies recognize a 25-residue segment bounded by R484-I508. Several antigenic residues in this segment have been identified, including R484, R489, and P492. The immunogenicity of purified recombinant B domain-deleted (BDD) human factor VIII molecules containing mutations at R484A/R489A or R484A/R489A/P492A was studied in hemophilia A mice. Inhibitory antibody titers in mice receiving the R484A/R489A/P492A mutant, but not the R484A/R489A mutant, were significantly lower than in mice receiving control human BDD factor VIII. The specific coagulant activity and the in vivo clearance and hemostatic efficacy in hemophilia A mice of the R484A/R489A/P492A mutant were indistinguishable from human BDD factor VIII. Thus, the inhibitory antibody response to human factor VIII can be reduced by mutagenesis of a B-cell epitope without apparent loss of function, suggesting that this approach may be useful for developing a safer form of factor VIII in patients with hemophilia A.
authors.affiliation: Winship Cancer Institute, Emory University, Atlanta, GA 30322, USA.
authors.forename: Ernest T
authors.initials: ET
authors.lastname: Parker
authors.forename: John F
authors.initials: JF
authors.lastname: Healey
authors.forename: Rachel T
authors.initials: RT
authors.lastname: Barrow
authors.forename: Heather N
authors.initials: HN
authors.lastname: Craddock
authors.forename: Pete
authors.initials: P
authors.lastname: Lollar
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D000917:Antibody Formation / Q000235:genetics; D001402:B-Lymphocytes / Q000276:immunology*; D001777:Blood Coagulation; D000939:Epitopes / Q000235:genetics / Q000276:immunology; D005169:Factor VIII / Q000235:genetics* / Q000276:immunology*; D006467:Hemophilia A / Q000097:blood / Q000235:genetics* / Q000276:immunology*; D006801:Humans; D051379:Mice; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D011994:Recombinant Proteins / Q000276:immunology; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013552:Swine
chemical_list: D000939:Epitopes; D011994:Recombinant Proteins; D005169:Factor VIII