Fifth Åland Island conference on von Willebrand disease.

The fifth Åland Island meeting on von Willebrand disease (VWD) was held on the Åland Islands, Finland, from 22 to 24 September 2016-90 years after the first case of VWD was diagnosed in a patient from the Åland Islands in 1926. This meeting brought together experts in the field of VWD to share knowledge and expertise on current trends and challenges in VWD. Topics included the storage and release of von Willebrand factor (VWF), epidemiology and diagnostics in VWD, treatment of VWD, angiogenesis and VWF inhibitors.

Comprehensive re-evaluation of historical von Willebrand disease diagnosis in association with whole blood platelet aggregation and function.

INTRODUCTION: Diagnosis of von Willebrand disease (VWD) is challenging, particularly for type 1. The current diagnostic guidelines emphasize simultaneous bleeding symptoms and von Willebrand factor (VWF) levels of <30-40 IU/dL. Historical diagnoses require updated evaluation. We assessed the accuracy of past VWD diagnoses in our comprehensive care center with the standardized bleeding score (BS) and central laboratory analysis, focusing on VWF-dependent platelet functions in whole blood. METHODS: Our study comprised 83 adults with prior VWD who were diagnosed a median of 20 years ago. We assessed BS, VWF antigen and activity (minimum of 3 measurements), FVIII, PFA-100® , and platelet aggregation via Multiplate® . Genetic testing was targeted to types 3, 2N, 2B, and equivocal cases. RESULTS: All 13/13 (100%) type 3 and 29/32 (90%) type 2, but only 10/38 (26%) of type 1 (overall 52/83 (63%)) patients met the current criteria for VWD. All confirmed cases had abnormal BS, impaired PFA-100® , and decreased or absent ristocetin-induced platelet aggregation (RIPA), except subtype 2B. VWF, FVIII, RIPA, and PFA correlated with BS including all study subjects. Ten of the 38 patients with previous type 1 had low VWF (35-50 IU/dL) and variable VWF-dependent platelet function. Altogether, 21/83 patients (25%) had repeatedly normal VWF:RCo (>50 IU/dL). CONCLUSION: von Willebrand disease is associated with impaired VWF-dependent whole blood platelet functions that match traditional VWF measurements. We detected normal VWF in 25% of historically diagnosed patients, mainly type 1 patients, implying that there is a need to systematically re-evaluate historical VWD diagnoses.

Phenotypic and genotypic characterization of 10 Finnish patients with von Willebrand disease type 3: discovery of two main mutations.

Severe von Willebrand's disease (VWD) type 3 is a rare autosomal-recessively inherited bleeding disorder, showing considerable genotypic heterogeneity. We investigated the phenotype in correlation with the genotype in Finnish type 3 VWD patients. Ten patients previously diagnosed with VWD type 3 treated at the Coagulation Disorder Unit in Helsinki University Hospital were re-evaluated for bleeding tendency and treatment. Phenotypic characterization included coagulation and platelet function testing confirming the diagnosis. The genotype was assessed by initial screening for the common c.2435delC mutation and subsequently if needed, by analysing all 51 coding exons of the von Willebrand factor gene. Our result confirmed the diagnosis of type 3 VWD for all 10 patients. We discovered two common mutations: nine of the 20 alleles (45%) were found to carry the c.2435delC frameshift mutation, previously described to be frequent in countries surrounding the Baltic Sea. The nonsense mutation c.4975C>T (p.R1659X) was found on 8/20 (40%) of the alleles. In addition, three novel mutations, a potential splice site mutation (c.874+2T>C) and two frameshift mutations (c.1668delC and c.2072delCCinsG) were found. Seven patients were homozygous and three compound heterozygous for the reported mutations. This study indicates that mainly two mutations (c.2435delC and p.R1659X) cause the majority of type 3 VWD in Finland. This result sets future standards for the genetic testing among the Finnish type 3 VWD population.

Identification of a VWF peptide antagonist that blocks platelet adhesion under high shear conditions by selectively inhibiting the VWF-collagen interaction.

BACKGROUND: Because the collagen-VWF-GPIb/IX/V axis plays an important role in thrombus formation, it represents a promising target for development of new antithrombotic agents. OBJECTIVES: We used phage display to identify potential small peptides that interfere with the VWF-collagen binding and might serve as lead products for the development of possible oral antithrombotic compounds. METHODS: A random linear heptamer peptide library was used to select VWF-binding peptides. RESULTS: We identified a phage clone, displaying the YDPWTPS sequence, further referred to as L7-phage, that bound to VWF in a specific and a dose-dependent manner. This L7-phage specifically inhibited the VWF-collagen interaction under both static and flow conditions. Epitope mapping using deletion mutants of VWF revealed that the L7-phage does not bind to the known collagen-binding A3 domain within VWF, but to the more carboxyterminal situated C domain. This inhibition was not due to steric hindrance of the A3 domain-collagen interaction by the L7-phage. Indeed, a tetrabranched multi-antigen peptide (MAP) presenting four copies of the peptide, but not the scrambled MAP, also inhibited VWF-collagen interaction under conditions of high shear stress at a concentration of 148 nmol L(-1). CONCLUSIONS: Based on these results, we conclude that we have identified the first peptide antagonist that binds to the VWF C domain and by this specifically inhibits the VWF binding to collagen, suppressing platelet adhesion and aggregation under high shear conditions. As a consequence, this peptide and its future derivates are potentially interesting antithrombotic agents.