2003; baxter - Supplements - Haematologica

24J. Voorberg et al.ABFigure 4. (A) Deduced amino acid sequences of variable heavy chain domains of DP-5 (1-24) encoded human anti-C2 antibodies.FR, framework region; CDR, complementary-determining region; H1, H2 and H3, antigen binding loops defined based onstructural homology of immunoglobulins. 22 Dashes indicate sequence identity to germline gene segments. Lower case lettersindicate amino acid substitutions originating from the PCR primer. The crystal structure of a complex of BO2C11 in contactwith the C2 domain has been resolved. 34 Residues in BO2C11 in contact with the C2 domain are underlined. Aspartic acid 52and 99 are indicated by an arrow. (B) Three-dimensional model of a complex between BO2C11 and the C2 domain of factorVIII. At the left, part of the VH domain (residues 1-113) of BO2C11 is depicted, the C2 domain is positioned at the right. Thelight chain of BO2C11 is not included in this figure. Multiple contacts exist between BO2C11 and the C2 domain. 34 Loop I representcontacts between residues Met 2199 /Phe 2200 of the C2 domain with residues Ser 50 /Ile 59 of BO2C11. Loop II representscontacts between Leu 2251/2252 of C2 with residues Val 2 /Tyr 98 of BO2C11. Residues Arg 2215 and Arg 2220 (red) of C2 that interactwith negatively charged residues Asp 52 and Asp 99 (blue) in BO2C11 are highlighted.with factor VIII co-factor activity. We have previouslyshown that the non-inhibitory singlechain variable domain antibody fragment EL-14can partially neutralize factor VIII inhibitors inan in vitro assay. 18 Further study is required toestablish whether the concept of masking antigenicsites on factor VIII by antibody-derivedreagents can be translated into a new therapeuticoption for treatment of patients withinhibitors.AcknowledgementsParts of our studies are supported by a grant fromthe Netherlands Organization of Science (NWOgrant 902-26-204). We thank Dr. Sander Meijerand Gunny van Stempvoort for help with the preparationof Figure 4B.References1. Tuddenham EGD, Mannucci PM. The hemophilias—from royal genes to gene therapy. N Engl J Med 2001;344: 1773-9.2. Lenting PJ, van Mourik JA, Mertens K. The life cycle ofcoagulation factor VIII in view of its structure and function.Blood 1998; 92:3983-96.3. Mertens K, Celie PH, Kolkman JA, Lenting PJ. FactorVIII-factor IX interactions: molecular sites involved inenzyme-cofactor complex assembly. Thromb Haemost1999; 82:209-17.4. Lollar P. Characterization of factor VIII B-cell inhibitoryepitopes. Thromb Haemost 1999; 82:505-8.5. Fijnvandraat K, Celie PH, Turenhout EA, ten Cate JW,van Mourik JA, Mertens K, et al. A human allo-antibodyinterferes with binding of factor IXa to the factorVIII light chain. Blood 1998; 91:3701-9.6. Zhong D, Saenko EL, Shima M, Felch M, Scandella D.Some human inhibitor antibodies interfere with factorVIII binding to factor IX. Blood 1998; 92:136-42.7. enting PJ, van de Loo JW, Donath MJ, van Mourik JA,haematologica vol. 88(supplement n. 12):september 2003