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Recombinant VWF (recombinant + vwf)
Selected AbstractsThe 80th anniversary of von Willebrand's disease: history, management and researchHAEMOPHILIA, Issue 6 2006A. B. FEDERICI Summary., The history of von Willebrand's disease (VWD) is fascinating because it demonstrates how good clinical observations, genetic studies and biochemical skills can improve basic understanding of a disease and its management. The continuous efforts of scientists and clinicians during the last 80 years have significantly improved the knowledge of von Willebrand factor (VWF) structure and function and the management of VWD. Diagnosis of phenotype and genotype is now available in many countries and treatment is becoming more specific according to the VWD type. Any therapeutic agents must correct the dual defect of haemostasis, i.e. the abnormal platelet adhesion due to reduced and/or dysfunctional and low levels of factor VIII (FVIII) associated with VWF defects. Desmopressin (DDAVP) is the treatment of choice for type 1 VWD because it induces release of VWF from cellular compartments. Plasma virally inactivated VWF concentrates containing FVIII are effective and safe in patients unresponsive to DDAVP. There are advanced plans to develop a recombinant VWF but this product will require the concomitant administration of FVIII for the control of acute bleeds. Basic research studies on cellular biology, biochemistry and immunology have confirmed the role of VWF as a crucial participant in both haemostasis and thrombosis as its main biological activity is to support platelet adhesion,aggregation in the circulation. Retrospective and prospective clinical research studies, including bleeding history and laboratory markers for diagnosis as well as the use of DDAVP and VWF concentrates to manage or prevent bleeds in patients with VWD have been essential to provide general guidelines for VWD management. The large number of publications quoting VWD and VWF emphasizes the important role of VWF in medicine. [source] Purified A2 domain of von Willebrand factor binds to the active conformation of von Willebrand factor and blocks the interaction with platelet glycoprotein Ib,JOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 7 2007C. MARTIN Summary.,Background:,von Willebrand factor (VWF) does not interact with circulating platelets unless it is induced to expose the binding site for platelet glycoprotein (GP)Ib, in the A1 domain by high shear stress, immobilization, and/or a modulator. Previous studies have implied indirectly that the A2 domain may be involved in regulating A1,GPIb, binding. Objective and methods:,Because the relationship between the A1 and A2 domains has not been defined, we have investigated the effect of the A2 domain on the binding activity of the A1 domain using recombinant A domain polypeptides, multimeric VWF, and monoclonal antibodies (mAb). Results:,The A2 domain polypeptide bound specifically to the immobilized A1 domain polypeptide or full-length VWF, with half-maximal binding being obtained at 60 or 168 nm, respectively. This A1,A2 interaction was inhibited by mAb against the A2 or A1 domain and by the A1 domain polypeptide. The A2 domain polypeptide effectively blocked GPIb,-mediated platelet adhesion under high flow conditions. The A2 domain polypeptide specifically recognizes the GPIb,-binding conformation in the A1 domain, as it only interacted with VWF activated by the modulator ristocetin or immobilized VWF. Furthermore, in contrast to plasma VWF, the ultra-large (UL)VWF multimers or a recombinant VWF,A1A2A3 polypeptide containing a gain-of-function mutation (R1308 L) of type 2B von Willebrand disease bound to the A2 domain polypeptide without the need for ristocetin. Conclusions:,The recombinant A2 domain polypeptide specifically binds to the active conformation of the A1 domain in VWF and effectively blocks the interaction with platelet GPIb, under high-flow conditions. [source] Expression studies on a novel type 2B variant of the von Willebrand factor gene (R1308L) characterized by defective collagen bindingJOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 12 2005L. BARONCIANI Summary., A novel mutation, R1308L (3923G > T) was present in the heterozygous state in five members of a family with type 2B von Willebrand disease (VWD) characterized by a full set of von Willebrand factor (VWF) multimers in plasma and by the absence of thrombocytopenia before and after desmopressin (DDAVP). The defect (R1308L) was located at the same amino acid position of one of the most common mutations associated with type 2B VWD (R1308C), which is characterized by the loss of high molecular weight VWF multimers (HMWM) in plasma and the occurrence of thrombocytopenia. To understand the mechanisms of this defect, the novel (R1308L) and ,common' (R1308C) mutations were expressed in COS-7 cells, either alone or, to mimic the patients' heterozygous state, together with wild-type VWF. R1308L recombinant VWF (rVWF) had a higher affinity for the platelet glycoprotein Ib, (GPIb,) receptor than wild-type rVWF, R1308C rVWF showing an even higher affinity. A novel finding was that both mutant rVWFs showed a similarly reduced binding to collagen type I and type III in comparison with wild-type rVWF. The latter finding suggests a more important role than recognized so far for the VWF A1 domain in VWF binding to collagen, which may contribute to the in vivo hemostatic defect associated with type 2B VWD. [source] Cysteine-mutations in von Willebrand factor associated with increased clearanceJOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 10 2005C. J. VAN SCHOOTEN Summary.,Background:,von Willebrand disease (VWD) is a bleeding disorder caused by the decrease of functional von Willebrand factor (VWF). Low levels of VWF can result from decreased synthesis, impaired secretion, increased clearance or combinations thereof. Several mutations lead to impaired synthesis or secretion of VWF, however, little is known about the survival of VWF in the circulation. Objectives:,To evaluate the effect of several VWF mutations on VWF clearance. Patients/methods:,The effect of three cysteine-mutations (C1130F, C1149R or C2671Y) on the in vivo survival of VWF was studied in patients carrying these mutations and in a VWF-deficient mice model. Results:,In patients carrying these mutations, we observed increased propeptide/mature VWF ratios and rapid disappearance of VWF from the circulation after desmopressin treatment. Detailed analysis of in vivo clearance of recombinant VWF in a VWF-deficient mice model revealed a fourfold increased clearance rate of the mutants. The mutations C1130F, C1149R and C2671Y are each associated with reduced survival of VWF in the circulation. Detailed analysis of the recombinant mutant VWF demonstrated that increased clearance was not due to increased proteolysis by ADAMTS-13. We did not identify functional or structural characteristics that the mutant proteins have in common and could be associated with the phenomenon of increased clearance. Conclusions:,Cysteine-mutations in VWF may result in reduced in vivo survival. The observation that various mutations are associated with increased in vivo clearance may have major implications for the therapeutic strategies that rely on the rise of endogenous VWF after desmopressin administration. [source] | ||||||||||