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  • American Society of Hematology  (5)
  • 1
    In: Blood, American Society of Hematology, Vol. 89, No. 12 ( 1997-06-15), p. 4371-4377
    Kurzfassung: The development of inhibitory antibodies to factor VIII in patients affected by a mild form of hemophilia A (factor VIII 〈 0.05 IU/mL) is considered a rare event. In this study, we evaluated the relationship between genotype and anti-factor VIII antibody formation in a patient with mild hemophilia A. Mutation analysis showed that a missense mutation in the factor VIII gene leading to replacement of Arg593 by Cys in the A2 domain of factor VIII was associated with hemophilia A in this patient. The anti-factor VIII antibodies present in the patient's plasma were characterized using metabolically labeled factor VIII fragments expressed in insect cells. The anti-factor VIII antibodies, composed of subclasses IgG2 and IgG4, reacted with both the fragment corresponding to the factor VIII heavy chain and the A2 domain. The Arg593 → Cys substitution was introduced into the cDNA encoding the A2 domain of factor VIII and the resulting construct was expressed in insect cells. Strikingly, the metabolically labeled A2 domain carrying the Arg593 → Cys mutation was not recognized by the anti-factor VIII antibodies present in the plasma of the patient. These data indicate that the anti-factor VIII antibodies are exclusively directed against exogenous factor VIII. This strongly suggests that the Arg593 → Cys substitution results in recognition of wild-type factor VIII as nonself and is thereby related to the formation of anti-factor VIII antibodies after factor VIII replacement therapy in this particular patient.
    Materialart: Online-Ressource
    ISSN: 1528-0020 , 0006-4971
    RVK:
    RVK:
    Sprache: Englisch
    Verlag: American Society of Hematology
    Publikationsdatum: 1997
    ZDB Id: 1468538-3
    ZDB Id: 80069-7
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 2
    In: Blood, American Society of Hematology, Vol. 95, No. 2 ( 2000-01-15), p. 558-563
    Kurzfassung: A serious complication in hemophilia care is the development of factor VIII (FVIII) neutralizing antibodies (inhibitors). The authors used V gene phage display technology to define human anti-FVIII antibodies at the molecular level. The IgG4-specific, variable, heavy-chain gene repertoire of a patient with acquired hemophilia was combined with a nonimmune, variable, light-chain gene repertoire for display as single-chain variable domain antibody fragments (scFv) on filamentous phage. ScFv were selected by 4 rounds of panning on immobilized FVIII light chain. Sequence analysis revealed that isolated scFv were characterized by VH domains encoded by germline genes DP-10, DP-14, and DP-88, all belonging to the VH1 gene family. All clones displayed extensive hypermutation and were characterized by unusually long CDR3 sequences of 20 to 23 amino acids. Immunoprecipitation revealed that all scFv examined bound to the C2 domain of FVIII. Furthermore, isolated scFv competed with an inhibitory murine monoclonal antibody for binding to the C2 domain. Even though scFv bound FVIII with high affinity, they did not inhibit FVIII activity. Interestingly, the addition of scFv diminished the inhibitory potential of patient-derived antibodies with C2 domain specificity. These results suggest that the epitope of a significant portion of anti-C2 domain antibodies overlaps with that of the scFv isolated in this study.
    Materialart: Online-Ressource
    ISSN: 1528-0020 , 0006-4971
    RVK:
    RVK:
    Sprache: Englisch
    Verlag: American Society of Hematology
    Publikationsdatum: 2000
    ZDB Id: 1468538-3
    ZDB Id: 80069-7
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 3
    In: Blood, American Society of Hematology, Vol. 97, No. 4 ( 2001-02-15), p. 966-972
    Kurzfassung: A well-known complication of factor VIII replacement therapy in patients with hemophilia A is the development of inhibitory antibodies. Several studies have demonstrated the presence of a binding site for factor VIII inhibitors in the A3 domain. Six different human monoclonal single-chain variable domain antibody fragments (scFv) directed toward the A3-C1 domains of factor VIII have been isolated, using phage display technology. Sequence analysis revealed that the VH domains of 2 scFv were encoded by germline gene segments from the VH1 gene family and 4 by germline gene segments belonging to the VH3 gene family. Epitope mapping of the scFv was performed, using a series of hybrid factor VIII/factor V light chain fragments. This analysis revealed that 5 of 6 scFv were directed against a region encompassing amino acid sequence Q1778-D1840 in the A3 domain, a previously identified binding site for factor VIII inhibitors. Only 2 of 5 scFv directed against amino acid sequence Q1778-D1840 inhibited the procoagulant activity of factor VIII. Our results define the properties of human antibodies directed against region Q1778-D1840 in the A3 domain. Binding of one, noninhibitory scFv was independent of the region Q1778-D1840, suggesting the presence of an additional binding site for anti–factor VIII antibodies in the A3-C1 domains of factor VIII.
    Materialart: Online-Ressource
    ISSN: 1528-0020 , 0006-4971
    RVK:
    RVK:
    Sprache: Englisch
    Verlag: American Society of Hematology
    Publikationsdatum: 2001
    ZDB Id: 1468538-3
    ZDB Id: 80069-7
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 4
    In: Blood, American Society of Hematology, Vol. 96, No. 2 ( 2000-07-15), p. 540-545
    Kurzfassung: One of the major binding sites for factor VIII inhibitors is located within the A2 domain. In this study, phage display technology was used to isolate 2 human monoclonal antibodies, termed VK34 and VK41, directed toward the heavy chain of factor VIII. The VHdomain of a single-chain variable domain antibody fragment (scFv) VK34 is encoded by germline gene segment DP-10. Epitope-mapping studies revealed that scFv VK34 is directed against amino acid residues Arg484–Ile508 , a previously identified binding site for factor VIII inhibitors in the A2 domain. ScFv VK34 inhibited factor VIII activity with a titer of 280 BU/mg. The VH domain of VK41 was encoded by germline gene segment DP-47. A phage corresponding to VK41 competed with a monoclonal antibody for binding to amino acid residues Asp712–Ala736 in the acidic region adjacent to the A2 domain. Reactivity of VK41 with a factor VIII variant in which we replaced amino acid residues Asp712–Ala736for the corresponding region of heparin cofactor II was strongly reduced. In addition, substitution of Tyr718719723 for Phe abrogated binding of VK41 to factor VIII. ScFv VK41 did not inhibit factor VIII activity. This study not only defines the primary structure of human anti-factor VIII antibodies reactive with the A2 domain, it also describes an antibody with an epitope not previously identified in the antibody repertoire of hemophilia patients with an inhibitor.
    Materialart: Online-Ressource
    ISSN: 1528-0020 , 0006-4971
    RVK:
    RVK:
    Sprache: Englisch
    Verlag: American Society of Hematology
    Publikationsdatum: 2000
    ZDB Id: 1468538-3
    ZDB Id: 80069-7
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 5
    In: Blood, American Society of Hematology, Vol. 96, No. 2 ( 2000-07-15), p. 540-545
    Kurzfassung: One of the major binding sites for factor VIII inhibitors is located within the A2 domain. In this study, phage display technology was used to isolate 2 human monoclonal antibodies, termed VK34 and VK41, directed toward the heavy chain of factor VIII. The VHdomain of a single-chain variable domain antibody fragment (scFv) VK34 is encoded by germline gene segment DP-10. Epitope-mapping studies revealed that scFv VK34 is directed against amino acid residues Arg484–Ile508 , a previously identified binding site for factor VIII inhibitors in the A2 domain. ScFv VK34 inhibited factor VIII activity with a titer of 280 BU/mg. The VH domain of VK41 was encoded by germline gene segment DP-47. A phage corresponding to VK41 competed with a monoclonal antibody for binding to amino acid residues Asp712–Ala736 in the acidic region adjacent to the A2 domain. Reactivity of VK41 with a factor VIII variant in which we replaced amino acid residues Asp712–Ala736for the corresponding region of heparin cofactor II was strongly reduced. In addition, substitution of Tyr718719723 for Phe abrogated binding of VK41 to factor VIII. ScFv VK41 did not inhibit factor VIII activity. This study not only defines the primary structure of human anti-factor VIII antibodies reactive with the A2 domain, it also describes an antibody with an epitope not previously identified in the antibody repertoire of hemophilia patients with an inhibitor.
    Materialart: Online-Ressource
    ISSN: 1528-0020 , 0006-4971
    RVK:
    RVK:
    Sprache: Englisch
    Verlag: American Society of Hematology
    Publikationsdatum: 2000
    ZDB Id: 1468538-3
    ZDB Id: 80069-7
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
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