Properties of Anti-Factor VIII Inhibitor Antibodies in Hemophilia A Patients

ABSTRACT

Blood coagulation factor VIII functions in the intrinsic pathway of blood coagulation as a cofactor by enhancing the assembly of its complex with factors IX and X on the surface of activated platelets. This requires factor VIII interaction with these two proteins, von Willebrand factor (vWF), and phospholipids on the platelet surface. Once factor VIII and factor IX are activated by proteolytic cleavage, the complex is able to activate factor X to factor Xa by proteolysis. In hemophilia A patients with severe factor VIII deficiency, about 30% respond to factor VIII infusion therapy immunologically to produce antibodies that inactivate the infused factor VIII and others that are noninhibitory. An assay that measures only the inhibitor antibodies demonstrated that the factor VIII A2, A3, and C2 domains are the most immunogenic, and domains A1 and B are poorly immunogenic or not immunogenic. The specific antibody responses to A2, A3, and C2 vary considerably among individuals, and epitopes for inhibitor antibodies have been determined for all three. The anti-C2 inhibitors prevent factor VIII binding to phospholipids and vWF, and anti-A3 inhibitors prevent binding to factor IX (IXa). An inhibitor binding site for factor X has been localized to the A1 domain acidic region, leading to inhibition of factor VIII/factor X binding by antibodies. This inhibitor mechanism is rare. Beause a second binding site for factor IX was localized to the factor VIII A2 domain, it is likely but not proven that prevention of factor IX binding to factor VIII is the inhibitor mechanism for this epitope.

Factor VIII - factor IX - factor X - phospholipids - inhibitor antibodies

REFERENCES

• 1 Kane W H, Davie E W. Blood coagulation factors V and VIII: Structural and functional similarities and their relationship to hemorrhagic and thrombotic disorders.  Blood . 1988;  71 539-555
• 2 Muntean W, Leschnik B. Factor VIII influences binding of factor IX and factor X to intact human platelets.  Thromb Res . 1989;  55 537-548
• 3 Gilbert G E, Drinkwater D. Specific membrane binding of factor VIII is mediated by O-phospho-L-serine, a moiety of phosphatidylserine.  Biochemistry . 1993;  32 9577-9585
• 4 Saenko E L, Scandella D, Yakhyaev A V, Greco N J. Activation of factor VIII by thrombin increases its affinity for binding to synthetic phospholipid membranes and activated platelets.  J Biol Chem . 1998;  273 27918-27926
• 5 Toole J J, Pittman D D, Orr E C. A large region (≈95 kDa) of human factor VIII is dispensable for in vitro procoagulant activity.  Proc Natl Acad Sci USA . 1986;  83 5939-5942
• 6 Lapan K, Fay P J. Localization of a factor X interactive site in the A1 subunit of factor VIIIa.  J Biol Chem . 1997;  272 2082-2088
• 7 Fay P J, Haidaris P J, Huggins C F. Role of the COOH-terminal acidic region of A1 subunit in A2 subunit retention in human factor VIIIa.  J Biol Chem . 1993;  268 17861-17866
• 8 Fay P J, Beattie T, Huggins C F, Regan L M. Factor VIIIa A2 subunit residues 558-565 represent a factor IXa interactive site.  J Biol Chem . 1994;  269 20522-20527
• 9 Fay P J, Koshibu K. The A2 subunit of factor VIIIa modulates the active site of factor IXa.  J Biol Chem . 1998;  273 19049-19054
• 10 Lenting P J, van de Loo H P J-W, Donath M-JSH, van Mourik A J, Mertens K. The sequence Glu1811-Lys1818 of human blood coagulation factor VIII comprises a binding site for activated factor IX.  J Biol Chem . 1996;  271 1935-1940
• 11 Wise R J, Dorner A J, Krane M, Pittman D D, Kaufman R J. The role of von Willebrand factor multimers and propeptide cleavage in binding and stabilization of factor VIII.  J Biol Chem . 1991;  266 21948-21955
• 12 Saenko E L, Scandella D. A mechanism for inhibition of factor VIII binding to phospholipid by von Willebrand factor.  J Biol Chem . 1995;  270 13826-13833
• 13 Nesheim M, Pittman D D, Giles A R. The effect of plasma von Willebrand factor on the binding of human factor VIII to thrombin-activated human platelets.  J Biol Chem . 1991;  266 17815-17826
• 14 Foster P A, Fulcher C A, Houghten R A, Zimmerman T S. Synthetic factor VIII peptides with amino acid sequences contained within the C2 domain of factor VIII inhibit factor VIII binding to phosphatidylserine.  Blood . 1990;  75 1999-2004
• 15 Li X, Gabriel D A. The physical exchange of factor VIII (FACTOR VIII) between von Willebrand factor and activated platelets and the effect of the B-domain on platelet binding.  Biochemistry . 1997;  36 10760-10767
• 16 Leyte A, Verbeet M Ph, Brodniewicz-Proba T, van Mourik A J, Mertens K. The interaction between human blood-coagulation factor VIII and von Willebrand factor; characterization of a high-affinity binding site on factor VIII.  Biochem J . 1989;  257 679-683
• 17 Foster P A, Fulcher C A, Houghten R A, Zimmerman T S. A synthetic factor VIII peptide of eight amino acid residues (1677-1684) contains the binding region of an anti-factor VIII antibody which inhibits the binding of factor VIII to von Willebrand factor.  Thromb Haemost . 1990;  63 403-406
• 18 Saenko E L, Shima M, Rajalakshmi K J, Scandella D. A role for the C2 domain of factor VIII in binding to von Willebrand factor.  J Biol Chem . 1994;  269 11601-11605
• 19 Scandella D, Mattingly M, Prescott R. A recombinant factor VIII A2 domain polypeptide quantitatively neutralizes human inhibitor antibodies which bind to A2.  Blood . 1993;  82 1767-1775
• 20 Prescott R, Nakai H, Saenko E L. The inhibitor antibody response is more complex in hemophilia A patients than in most nonhemophiliacs with factor VIII autoantibodies.  Blood . 1997;  89 3663-3671
• 21 Foster P A, Fulcher C A, Houghten R A, de Graaf Mahoney S, Zimmerman T S. Localization of the binding regions of a murine monoclonal anti-factor VIII antibody and a human anti-factor VIII alloantibody, both of which inhibit factor VIII procoagulant activity, to amino acid residues threonine³⁵¹ serine³⁶⁵ of the factor VIII heavy chain.  J Clin Invest . 1988;  82 123-128
• 22 Foster P A, Fulcher C A, Houghten R A, de Graaf Mahoney S, Zimmerman T S. A murine monoclonal anti-factor VIII inhibitory antibody and two human factor VIII inhibitors bind to different areas within a twenty amino acid segment of the acidic region of factor VIII heavy chain.  Blood Coagul Fibrinolysis . 1990;  1 9-15
• 23 Lubin I M, Healey J F, Scandella D, Runge M S, Lollar P. Elimination of a major inhibitor epitope in factor VIII.  J Biol Chem . 1994;  269 8639-8641
• 24 Healey J F, Lubin I M, Scandella D, Lollar P. Residues 484-509 contain a major determinant of the inhibitory epitope in the A2 domain of human factor VIII.  J Biol Chem . 1994;  270 14505-14509
• 25 Lubin I M, Healey J F, Barrow R T, Scandella D, Lollar P. Analysis of the human factor VIII A2 inhibitor epitope by alanine scanning mutagenesis.  J Biol Chem . 1997;  272 30191-30195
• 26 Lollar P, Parker E T, Curtis J E. Inhibition of human factor VIIIa by human anti-A2 subunit antibodies.  J Clin Invest . 1994;  93 2497-2504
• 27 Arai M, Scandella D, Hoyer L W. Molecular basis of factor VIII inhibition by human antibodies. Antibodies that bind to the factor VIII light chain prevent the interaction of factor VIII with phospholipid.  J Clin Invest . 1978;  83 1989-1984
• 28 Scandella D, Gilbert G E, Shima M. Some factor VIII inhibitor antibodies recognize a common epitope corresponding to C2 domain amino acids 2248-2312 which overlap a phospholipid binding site.  Blood . 1995;  86 1811-1819
• 29 Healey J F, Barrow R T, Tamim H M. Residues Glu2181-Val2243 contain a major determinant of the inhibitory epitope in the C2 domain of human factor VIII.  Blood . 1998;  92 3701-3709
• 30 Eaton D L, Vehar G A. Factor VIII structure and proteolytic processing. In: Coller BS, ed. Progress in Hemostasis and Thrombosis, New York: Grune & Stratton; 1986: 47-70
• 31 Shima M, Scandella D, Yoshioka A. A factor VIII neutralizing monoclonal antibody and a human inhibitor alloantibody recognizing epitopes in the C2 domain inhibit factor VIII binding to von Willebrand factor and to phosphatidylserine.  Thromb Haemost . 1993;  69 240-246
• 32 Berntorp E, Ekman M, Gunnarsson M, Nilsson I M. Variation in factor VIII inhibitor reactivity with different commercial factor VIII preparations.  Haemophilia . 1996;  2 95-99
• 33 Fijnvandraat K, Peters M, Ten Cate W J. Inter-individual variation in half-life of infused recombinant factor VIII is related to pre-infusion von Willebrand factor antigen levels.  Blood . 1995;  91 474-476
• 34 Foster P A, Fulcher C A, Houghten R A, Zimmerman T S. An immunogenic region within residues Val1670-Glu1684 of the factor VIII light chain induces antibodies which inhibit binding of factor VIII to von Willebrand factor.  J Biol Chem . 1988;  263 5230-5234
• 35 Saenko E L, Shima M, Gilbert G E, Scandella D. Slowed release of thrombin-cleaved factor VIII from von Willebrand factor by a monoclonal and a human antibody is a novel mechanism for factor VIII inhibition.  J Biol Chem . 1996;  271 27424-27431
• 36 Fijnvandraat K, Celie P HN, Turenhout E AM. A human alloantibody interferes with binding of factor IXa to the factor VIII light chain.  Blood . 1998;  91 2347-2352
• 37 Zhong D, Saenko E L, Felch M, Scandella D. Some human inhibitor antibodies interfere with factor VIII binding to factor IX.  Blood . 1998;  92 136-142
• 38 McMillan C W, Shapiro S S, Whitehurst D. The natural history of factor VIII:C inhibitors in patients with hemophilia A: A national cooperative study. II. Observations on the initial development of factor VIII:C inhibitors.  Blood . 1988;  71 344-348
• 39 Thompson A R, Murphy M EP, Liu M L. Loss of tolerance to exogenous and endogenous factor VIII in a mild hemophilia A patient with an Arg⁵⁹³ to Cys mutation.  Blood . 1997;  90 1902-1910
• 40 Fijnvandraat K, Turenhout E AM, van den Brink N E. The missense mutation Arg593 → Cys is related to antibody formation in a patient with mild hemophilia A.  Blood . 1997;  89 4371-4377
• 41 Sawamoto Y, Prescott R, Zhong D. Dominant C2 domain epitope specificity of inhibitor antibodies elicited by a heat pasteurized product, factor VIII CPS-P, in previously treated hemophilia A patients without inhibitors.  Thromb Haemost . 1998;  79 62-68