Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.21.6 (thromboplastin)
 13,278 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Antiphospholipid syndrome is characterized by the presence of high titers of anti-beta(2)-glycoprotein I (beta(2)GPI) antibodies, lupus anticoagulant associated with thromboembolic phenomena, thrombocytopenia and recurrent fetal loss. Single-chain Fv (scFv) were prepared from four anti-beta(2)GPI mAb, CAM, CAL, CAR and 2C4C2, and one anti-ssDNA. All five scFv showed the same antigen binding properties as the original mAb. Replacement of the pathogenic CAM V(H) domain with the non-pathogenic CAL V(H) or anti-ssDNA V(H) decreased the binding affinity of the scFv to beta(2)GPI and completely abrogated the anticoagulant activity. Exchanging the CAM V(H) with anti-DNA V(H) resulted in a shift from anti-beta(2)GPI to anti-ssDNA binding of the scFv. Replacement of the CAM V(L) with CAL V(L) did not affect the binding and activity. BALB/c mice were immunized with the anti-beta(2)GPI scFv, and the scFv resulting from the substitution of the heavy (H) and light (L) chains. The mice which were immunized with CAM, 2C4C2 and CAR scFv developed clinical manifestations of experimental anti-phospholipid syndrome. Elevated titers of mouse anti-cardiolipin (aCL), anti-beta(2)GPI, associated with lupus anticoagulant activity, thrombocytopenia, prolonged activated partial thromboplastin time and a high percentage of fetal resorptions were detected, in the CAM scFv group and in the scFv composed of CAM V(H) groups. High titers of aCL, anti-beta(2)GPI, anti-ss/dsDNA and anti-histone associated with lupus findings were observed in the sera of the 2C4C2 scFv-immunized mice. Immunization with CAL scFv did not lead to any clinical findings. The current study shows that scFv of pathogenic antibodies are capable of inducing the same clinical manifestations as the whole antibody molecule upon active immunization. Replacement of H/L chains point to the importance of the V(H) domains in the pathogenic potential of anti-beta(2)GPI.
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PMID:Characteristics and pathogenic role of anti-beta2-glycoprotein I single-chain Fv domains: induction of experimental antiphospholipid syndrome. 1059 Feb 57

The use of libraries of phage-displayed human single-chain antibody fragments (scFv) has become a new, powerful tool in rapidly obtaining therapeutically useful antibodies. Here, we describe the generation of human scFv and F(ab')2 directed against the gamma-carboxyglutamic acid (Gla) domain of coagulation factor IX. A large library of human scFv, displayed either on M13 phage or expressed as soluble proteins, was screened for binding to human Gla-domain peptide (Tyr1-Lys43). Among a panel of scFv that bound to the factor IX-Gla domain, six scFv clones recognized full-length factor IX and exhibited strong inhibitory activity of factor IX in vitro. After reformatting as F(ab')2, the affinity for factor IX of three selected clones was determined: 10C12 Kd = 1.6 nmol/l, 13D1 Kd = 2.9 nmol/l, and 13H6 Kd = 0.46 nmol/l. The antibodies specifically bound to factor IX and not to other coagulation factors, as assessed by enzyme-linked immunosorbent-type and human plasma clotting assays. The complementarity determining region amino acid sequences of clones 10C12 and 13D1 only differed at a single residue, whereas 13H6 showed little homology, suggesting that 13H6 binds to a different epitope within the factor IX-Gla domain. Despite the slightly lower affinity of 10C12 F(ab')2 versus 13H6 F(ab')2, 10C12 was consistently more potent than 13H6 in prolonging the activated partial thromboplastin time (APTT), in inhibiting platelet-mediated plasma clotting, and in inhibiting factor X activation by the intrinsic Xase complex. Finally, 10C12 F(ab')2 also recognized and neutralized factor IX/factor IXa of different species, as demonstrated by the specific APTT prolongation of dog, mouse, baboon and rabbit plasma. In summary, the results validate the usefulness of scFv phage-displayed libraries to rapidly generate fully human antibodies as potential new therapeutics for thrombotic disorders.
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PMID:Use of phage display for the generation of human antibodies that neutralize factor IXa function. 1069 Oct 97

We investigated whether the direct fXa inhibitor tick anticoagulant peptide (TAP) can be N-terminally coupled to a clot-targeting, single-chain antibody specific for fibrin (scFv(59D8)). Due to its unique position at the convergence point of the intrinsic and extrinsic pathways early in the coagulation cascade, factor Xa (fXa) represents an attractive therapeutic target. In contrast to indirect inhibitors, direct fXa inhibitors effectively inhibit clot-bound and prothrombinase-associated fXa. Targeting of direct fXa inhibitors to clots promises to enhance local anticoagulative potency and to reduce systemic anticoagulation which potentially results in less bleeding complications.TAP is a highly potent fXa inhibitor. Since its N-terminus is essential for anti-fXa activity, it was a challenging question, whether TAP will be active as a N-terminally coupled fusion molecule. Two step affinity chromatography with Ni(2+) and beta(15-22)-peptide of human fibrin results in a pure 36 kDa protein, which was tested for its targeting function and anti-fXa activity. The recombinant fusion did not destroy the function of the fusion partners. Antibody binding function was on a par with the parent molecule. TAP activity was partially reduced, arguing that a free N-terminus is not required for anti-fXa activity, but is important for maximal potency. In human whole blood clots, scFv(59D8)-TAP revealed anticoagulative properties at concentrations (200 to 500 nM) where non-targeted TAP did not reveal anticoagulative activity at all. In summary, scFv(59D8)-TAP constitutes a promising new anticoagulant with fibrin-targeted factor Xa inhibition. The production in E. coli and the established purification methods are a solid basis for a modern, large scale production at low cost and reproducible activity.
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PMID:Fibrin-targeted direct factor Xa inhibition: construction and characterization of a recombinant factor Xa inhibitor composed of an anti-fibrin single-chain antibody and tick anticoagulant peptide. 1521 44

A recombinant prodrug, single-chain urokinase-type plasminogen activator (scuPA) fused to an anti-PECAM-1 antibody single-chain variable fragment (anti-PECAM scFv/scuPA) targets endothelium and augments thrombolysis in the pulmonary vasculature.(1) To avoid premature activation and inactivation and to limit systemic toxicity, we replaced the native plasmin activation site in scFv/low-molecular-weight (lmw)-scuPA with a thrombin activation site, generating anti-PECAM scFv/uPA-T that (1) is latent and activated by thrombin instead of plasmin; (2) binds to PECAM-1; (3) does not consume plasma fibrinogen; (4) accumulates in mouse lungs after intravenous injection; and (5) resists PA inhibitor PAI-1 until activated by thrombin. In mouse models of pulmonary thrombosis caused by thromboplastin and ischemia-reperfusion (I/R), scFv/uPA-T provided more potent thromboprophylaxis and greater lung protection than plasmin-sensitive scFv/uPA. Endothelium-targeted thromboprophylaxis triggered by a prothrombotic enzyme illustrates a novel approach to time- and site-specific regulation of proteolytic reactions that can be modulated for therapeutic benefit.
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PMID:Prophylactic thrombolysis by thrombin-activated latent prourokinase targeted to PECAM-1 in the pulmonary vasculature. 1804 68

A recombinant single-chain variable antibody fragment (scFv) KM33 was previously described as a ligand that can inhibit the function of blood coagulation factor VIII (FVIII). This scFv was previously derived from an individual with anti-FVIII antibodies manifested in FVIII functional deficiency (Hemophilia A) and expressed in bacteria. In the present work, we describe an alternative approach for fast and easy production of KM33 in insect cells (Spodoptera frugiperda). The KM33 gene was codon-optimized and expressed in secreted form using a baculovirus system. The protein was isolated using metal-affinity and size-exclusion chromatography to purity of about 96% and yield of 0.4-1.2 mg per 120 mL of culture, based on several independent expression experiments. In a binding assay using surface plasmon resonance, the insect cell-derived KM33 (iKM33) was qualified as a high-affinity ligand for FVIII. Epitope specificity of iKM33 on FVIII (C1 domain) was confirmed by testing the binding with a relevant mutant of FVIII. In several FVIII functional tests (factor Xa generation, APTT clotting, thrombin generation and video microscopy clot growth assays), iKM33 strongly inhibited FVIII activity in accordance with the clinical effect of the parental antibody. Therefore, the expressed protein was concluded to be fully functional and applicable in various assays with FVIII.
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PMID:Insect cell-based expression and characterization of a single-chain variable antibody fragment directed against blood coagulation factor VIII. 2330 63