Carrier Detection in Severe (Type III) von Willebrand Disease Using Two Intragenic Restriction Fragment Length Polymorphisms

DNA from a family with a female member affected with severe (type III) vWD was analysed using three restriction enzymes and a partial vWF cDNA probe. Two restriction fragment length polymorphisms (RFLPs) detected with the enzymes Bgl II and Xba I proved to be informative in this family. A 36.0 Kb allele, demonstrated with the enzyme Xba I was rare in the general population but very important in this family for segregation analysis of the alleles and their association with the putative defective chromosome. The propositus was homozygous for the 36.0 Kb Xba I polymorphic band and heterozygous for the Bgl II polymorphism. She was the only member of the family showing this allelic pattern. The linkage of the alleles could be determined because her mother was homozygous for the 9.0 Kb Bgl II polymorphism but heterozygous for the Xba I polymorphism. The segregation of the alleles could be traced to the proband’s son and a niece. The genotypic analysis revealed that her niece could be considered as carrying a defective gene for severe vWD.

Multicenter Comparison of von Willebrand Factor Multimer Sizing Techniques

A multicenter study of various types of von Willebrand’s disease (vWD) was conducted in order to compare the different electrophoretic techniques used to evaluate von Willebrand factor multimers in plasma. Seven laboratories participated in the blind study of eight plasma samples from two healthy subjects and six vWD types and subtypes (la, lb, IIA, IIB, IIC and IID). From the results of the multimeric analysis of these samples, it appears that the differential diagnosis of vWD types and subtypes should be first approached by using a low-resolution electrophoretic technique, where each vWF multimer appears as a single band. Low-resolution techniques differentiate type I from type II, subtype la from lb and also subtype IIA from other type II subtypes. When type II subtypes other than IIA are identified with these techniques, samples should be rerun using high resolution techniques that resolve each of the fastest migrating multimers in at least three subbands, and permit the differentiation of subtypes IIB, IIC and IID.

An Enzyme Immunoassay (ELISA) for the Quantitation of Human Factor VII

A new solid phase enzyme-linked immunosorbent assay (ELISA) was developed for the quantitation of human Factor VII antigen (F VII Ag), using a monospecific rabbit anti-F VII antiserum. Anti-F VII F(ab′)2 fragments were adsorbed to polystyrene plates. The binding of serial dilutions of control or test plasma, containing F VII, was detected by incubation with peroxidase-labeled anti- FV II IgG followed by the addition of hydrogen peroxyde and O-phenylenediamine. This ELISA is specific, sensitive (detection limit: 0.05%) and accurate (coefficient of variation: 1.5-4% for within- and 1.6-9% for between-assays). F VII coagulant activity (F VII C) and F VII Ag were determined in large populations of controls and patients. In normal plasma (n = 38), F VII Ag ranged from 83 to 117% and the correlation coefficient between F VII Ag and F VII C was 0.94. In patients with severe (F VII C inf. 1%) congenital F VII deficiency (n = 5), F VII Ag was undetectable in two cases (inf. 0.05%) and markedly reduced (0.35 to 5.6%) in the three other cases. In patients with liver cirrhosis (n = 15), F VII Ag ranged from 21 to 59% and was in good correlation with F VII C (r = 0.84). In dicoumarol treated patients (n = 15), the levels of F VII Ag ranged from 51% to 79% and a poor correlation (r = 0.52) with F VIIC was observed. In “compensated” DIC (n = 5), levels of F VII Ag varied from 60 to 186%, with significantly higher F VII C levels (from 143 to 189%). In contrast, in “decompensated” DIC (n = 7), low F VII Ag and F VII C levels were observed (from 7 to 27%). In patients with deep-vein thrombosis (n = 25), high levels of F VII Ag (from 102 to 136%) and F VII C (from 110 to 150%) were demonstrated. In surgical patients, no significant difference was observed before and one day after intervention.

Homozygous Variant of Antithrombin III : AT III Fontainebleau

A qualitative defect of antithrombin III (AT III) was demonstrated in four members of a large Tunisian family by the discrepancy between a normal amount of antigen and decreased or absent heparin cofactor activity. The propositus, a 3-year-old girl, died from massive intracardiac thrombosis despite oral anticoagulant therapy. Heparin cofactor activity measured in the presence of thrombin or F. Xa was undetectable in her plasma. Anti-F. Xa activity was also absent when using low molecular weight heparin or a synthetic pentasaccharide, representing the binding site to AT III. The lack of affinity of the propositus AT III for heparin was demonstrated by two-dimensional immunoelectrophoresis and chromatography on heparin-Sepha-rose. The parents, first cousins, and the sister of the propositus also demonstrated a qualitative abnormality of AT III, with levels of heparin cofactor activity close to 50% of the normal range. Our data support the view that the abnormal protein was present at the heterozygous state in the parents and sister and at the homozygous state in the propositus. None of the affected family members had thrombotic episodes, except for the propositus. The name of AT III Fontainebleau is proposed for this variant.

Impaired Prothrombin Consumption in Bernard-Soulier Syndrome Is Corrected In Vitro by Human Factor VIII

The Bernard-Soulier syndrome (BSS) is characterized by thrombocytopenia with giant platelets, a prolonged bleeding time with defective platelet adhesion to the subendothelium related to a defect in platelet membrane glycoprotein lb (GPIb) and a decreased prothrombin consumption. The mechanism of the latter abnormality remains unknown. In this study, we showed that this defect was corrected by the addition of purified human factor VIII (FVIII) to blood from four patients with BSS. The correction of prothrombin consumption was almost complete at concentrations between 1.5 and 3 IU/ml of FVIII procoagulant activity (VIII.'C) and partially abolished by a monoclonal antibody which neutralizes VIII:C. This correction was specific for FVIII and was not observed after addition of purified human FIX. It was obtained, in the same magnitude range, with FVIII complexed to von Willebrand factor (vWF) but not with free vWF. These data provide a new insight into the knowledge of the physiological interaction between the platelet membrane and the vWF-FVIII complex facilitating plasma coagulation activation and may lead to helpful therapeutic advances.

Antibodies to Macromolecular Platelet Factor 4-Heparin Complexes in Heparin-induced Thrombocytopenia: a Study of 44 Cases

As heparin-PF4 (H-PF4) complexes are the target for antibodies associated to heparin-induced thrombocytopenia (HIT), an ELISA has been developed and optimised for testing antibodies binding to H-PF4. This test was consistently negative in 50 healthy subjects (A492 <0.3) and 35 patients with other causes of thrombocytopenia (A492 <0.5). In contrast, 43 out of 44 HIT patients showed antibodies to H-PF4 (A492 = 1.70 ± 0.81) including 5 patients with a negative platelet aggregation test. In one patient with HIT, antibodies to H-PF4 were already present at day 7, whereas platelet counts dropped ≤ 100 × 109/l only at days 11–12. Surprisingly, among 41 patients under heparin for >7 days, 5 showed antibodies to H-PF4, without HIT. These findings underline the major interest of this ELISA for the early diagnosis of HIT. We also showed that LMWH as well as other sulphated polysaccharides can bind to HIT antibodies in the presence of PF4 and that their reactivity is dependent on the molecular weight and the sulphation grade. The mechanism for HIT involves platelet PF4 receptors which bind the macromolecular H-PF4 complexes formed in the presence of a well defined heparin/PF4 ratio.

Multicenter Comparison of Five Functional and Two Immunological Assays for Protein C

Five functional assays and two immunoassays for protein C (PC) were evaluated in parallel for the same plasma samples collected from healthy subjects, patients with congenital and acquired PC deficiencies or patients with conditions associated with high PC levels. For 7 patients starting warfarin therapy and for 15 patients during stabilized warfarin therapy, there were significant between-assay differences. For these groups immunoassays gave higher values than most functional assays and the latter also gave varied results, probably depending on their respective capacity for recognizing acarboxylated PC. On the other hand, there were no significant between-assay differences nor discrepancies between PC activity and antigen levels for healthy subjects (n = 39), patients with congenital PC deficiency (n = 10), myocardial infarction (n = 25), chronic liver disease (n = 19), disseminated intravascular coagulation (n = 35), in the post-operative period (n = 20) or in women taking oral contraceptives (n = 20). This comparison of PC assays indicates that PC levels measured by different functional or immunological assays are very close in the majority of clinical conditions, but not for patients on oral anticoagulants.

Comparison of Functional Assays for Protein S: European Collaborative Study of Patients with Congenital and Acquired Deficiency

Four functional assays for protein S were evaluated by 4 different laboratories, each center using its own method. The aim of this study was to compare these different assays and to establish a relationship with results of immunological assays of total and free protein S antigen and C4bBP. The same plasma samples were distributed to each center and tested in blind. In 47 normal subjects, there was no significant difference between the 4 functional assays, with mean values ranging from 93 to 100%. These values were in good agreement with those of free and total protein S antigen. In 34 patients with a quantitative congenital deficiency of protein S the mean values of protein S activity were decreased with the 4 assays, ranging from 25 to 40%. Free protein S antigen was reduced to a similar extent, whereas total antigen was either normal or decreased. The correlation of protein S activity with free protein S antigen was satisfactory for 3 methods, with coefficients of correlation varying from 0.84 to 0.92 whereas it was only 0.70 in one lab. When total protein S antigen was reduced, protein S activity was decreased in all the patients with the 4 assays. In contrast when total protein S antigen was normal an important overlap of protein S activity between normals and patients was observed in one lab with 12 patients misclassified. In 8 patients with a functional defect, results of protein S activity differed substantially according to the assay used and about half of these patients were misclassified. In patients with inflammatory disease, protein S activity was normal with the 4 assays, in good correlation with free antigen, despite high levels of both C4bBP and total protein S antigen. In patients with oral anticoagulants, protein S activity was low with all assays. Only with one assay, protein S activity was significantly lower than free antigen, suggesting that this assay is sensitive to the hypo-carboxylated protein. Variable values of protein S activity were observed in patients with liver cirrhosis, with relatively little agreement between methods. As discordant results were obtained in some patients with dysfunctional protein S deficiency and acquired disorders, these methods do not necessarily measure the same cofactor of activated protein C. However this study indicates that all 4 functional protein S assays give similar results in normals, and almost all patients with a quantitative congenital deficiency.

Functional Analysis of the Arg91GIn Substitution in the Factor VIII Binding Domain of von Willebrand Factor Demonstrates Variable Phenotypic Expression

An Arg91Gln substitution in the mature von Willebrand factor (vWF) has been associated with defective binding of vWF to factor VIII (FVIII). We studied four families with members initially classified as having type I von Willebrand disease (vWD) who were either homozygous or heterozygous for the Arg91Gln change. The first family was the original case described by Nishino et al. (1) where three members were homozygous for the Gln91 allele. They had a low FVIII coagulant activity:vWF antigen (VIIIC:vWFAg) ratio, from 0.29 to 0.44, and the ability of their plasma vWF to bind FVIII was markedly decreased. All the heterozygous members had normal vWF and FVIII levels but the capacity of their plasma vWF to bind FVIII was reduced and intermediate between the homozygous members and normals. The affected individual from the second family was heterozygous for the Gln91 allele and demonstrated a VIIIC:vWFAg ratio of 0.98. The FVIII binding assay confirmed the heterozygous status indicating that the moderately low levels of vWF were due to reduced expression of both alleles. The propositus from the third family was also heterozygous and had below normal levels of vWF as well as a low VIIIC:vWFAg ratio of 0.34; however, FVIII binding to her plasma vWF was similar to that of the homozygous individuals suggesting that Gln91-vWF was the major circulating form. Her daughter who has type I vWD inherited the allele without the Gln91 mutation indicating that the expression of this allele was indeed impaired. The heterozygous patient in the fourth family had a vWF level of 24 U/dl but an VIIIC:vWFAg ratio greater than 2. Her plasma vWF showed normal FVIII binding implying that the Gln91 mutation was linked to a defect that repressed the expression of the allele. The Arg91Gln substitution appears to decrease but not eradicate FVIII binding suggesting a critical concentration of vWF be attained before the defect becomes phenotypically important.

Aurin Tricarboxylic Acid Inhibits Platelet Adhesion to Collagen by Binding to the 509-695 Disulphide Loop of von Willebrand Factor and Competing with Glycoprotein Ib

Aurin tricarboxylic acid (ATA) is known to inhibit ristocetin-induced platelet agglutination but not arachidonic acid-, epinephrine- or ADP-induced aggregation. Its capacity to abolish human von Willebrand factor (vWF)-platelet interactions was further investigated by measurement of platelet adhesion to collagen, platelet agglutination tests and binding studies. In flowing blood using parallel-plate perfusion chambers and human collagen, ATA inhibited platelet adhesion to completion in a dose-dependent manner only at the highest shear rate tested (2,600 s–1). It was without effect at 100 and 650 s–1. ATA completely abolished vWF-dependent platelet agglutination induced by ristocetin, botrocetin and asialo-vWF, respectively. 125I-vWF binding to ristocetin- and botrocetin-treated platelets, to heparin and to sulfatides as well as 125I-botrocetin binding to vWF was competitively inhibited by ATA. By contrast, binding of 125I-vWF to collagen was not affected. To further localize the domain of vWF interacting with ATA, experiments of inhibition of binding of selected 125I-monoclonal antibodies (MoAbs) to immobilized vWF by ATA were performed. Our data led to the conclusion that: 1) the interaction of ATA with vWF involves sequences of the A1 disulphide loop of vWF (residues 509–695) and close epitopes which interact with GPIb and 2) the inhibition of platelet adhesion by ATA occurs only at a high shear rate where vWF is known to play a key role. Thus ATA, which blocks the vWF/GPIb pathway by interfering with vWF and not with platelets, is a potential tool in preventing the early stages of thrombosis.

Processing and Characterization of Recombinant von Willebrand Factor Expressed in Different Cell Types Using a Vaccinia Virus Vector

The cloning of the cDNA encoding von Willebrand factor (vWF) has revealed that it is synthesized as a large precursor (pre-pro-vWF) molecule and it is now clear that the prosequence or vWAgll is responsible for the intracellular multimerization of vWF. We have cloned the complete vWF cDNA and expressed it using a recombinant vaccinia virus as vector. We have characterized the structure and function of the recombinant vWF (rvWF) secreted from five different cell types: baby hamster kidney (BHK), Chinese hamster ovary (CHO), human fibroblasts (143B), mouse fibroblasts (L) and primary embryonic chicken cells. Forty-eight hours after infection, the quantity of vWF antigen found in the cell supernatant varied from 3 to 12 U/dl depending on the cell type. By SDS-agarose gel electrophoresis, the percentage of high molecular weight forms of vWF varied from 39 to 49% relative to normal plasma for BHK, CHO, 143B and chicken cells but was less than 10% for L cells. In all cell types, the two anodic subbands of each multimer were missing. The two cathodic subbands were easily detected only in BHK and L cells. By SDS-PAGE of reduced samples, pro-vWF was present in similar quantity to the fully processed vWF subunit in L cells, present in moderate amounts in BHK and CHO and in very low amounts in 143B and chicken cells. rvWF from all cells bound to collagen and to platelets in the presence of ristocetin, the latter showing a high correlation between binding efficiency and degree of multimerization. rvWF from all cells was also shown to bind to purified FVIII and in this case binding appeared to be independent of the degree of multimerization. We conclude that whereas vWF is naturally synthesized only by endothelial cells and megakaryocytes, it can be expressed in a biologically active form from various other cell types.

Abnormality of the N-Terminal Portion of von Willebrand Factor in Type IIA and IIC von Willebrand Disease

We have established a new analytical method which allows the characterization of von Willebrand factor (vWF) degradation fragments in minute amounts (10 μ1) of plasma, without the need for immunopurification of vWF. Plasma vWF was hydrolysed by S aureus V-8 protease (V-8 protease) and the cleaved fragments separated by SDS-agarose gel electrophoresis followed by staining with 125I-labeled polyclonal or monoclonal antibodies against vWF and autoradiography. Quantification of the amount of each product was estimated by counting the incorporated radioactivity following excision. V-8 protease limitedly hydrolysed vWF in normal as well as type I von Willebrand disease (vWD) plasma and produced two distinct fragments with identical electrophoretic and antigenic characteristics to those produced from purified vWF, i.e. a C-terminal SpII and a series of N-terminal Spill fragments (SpIIIa, b and c). The method was applied to further characterize the molecular abnormalities of vWF in eighteen patients with type II vWD. In seven individuals with type IIA and five patients with type IIC, Spill appeared significantly modified as compared to normal. In type IIA, there was a marked decrease or absence of SpIIIa and an increase of SpIIIb and c. In type IIC, SpIIIb was lacking. In three patients with type IIB and in three patients with type IID, there was no significant modification of Spill. In all cases, SpII was apparently not modified. In conclusion, the molecular abnormality of vWF in type IIA and IIC vWD appears to reside in Spill, the N-terminal portion of the vWF-subunit (residues 1 to 1,365).

Haemophilia A in a Female: Study of a Family Using Intragenic and Extragenic Restriction Site Polymorphisms

Restriction fragment length polymorphisms(RFLPs) were studied in a large Algerian family which includes 6 haemophiliacs and a previously described case of female haemophilia A. The female propositus is 66 years old with a normal karyotype. Her parents are first cousins. Her 3 sons are haemophiliacs and her 3 daughters with affected children are obligate carriers. The proband has an excessive bleeding tendency and markedly reduced levels of F. VIII (VIII C 0.03 U/ml, VIII Ag 0.01 U/ml) with elevated vWF Ag (2.30 U/ml), similar to the levels observed in affected males from the family. Four RFLPs can be identified by Southern blotting after digesting genomic DNA with the restriction enzymes Bcl I, Bgl I, Kpn I/Xba I and Taq I and hybridization with a 647 bp Stu I/Sca I F. VIII genomic probe, a 1.8 Kb EcoRI F. VIII cDNA probe, a 1.0 Kb EcoRI/Sst I fragment of intron 22 and the extragenic probe ST 14, respectively. With these four RFLPS, the propositus was found to be homozygous for the alleles segregating in this family with the abnormal X-chromosome. The carrier status was proven in a granddaughter and excluded in another. In conclusion, this RFLP linkage analysis is another argument to suggest that the propositus, a rare case of female haemophilia, is homozygous for the abnormal gene.

Purification and Further Characterization of Antithrombin III Milano: Lack of Reactivity with Thrombin

The functional abnormality of Antithrombin III “Milano”, a previously described variant with monomeric and dimeric forms of abnormal AT III, has been further characterized. Affinity chromatography on heparin-Sepharose led to the separation and purification of two distinct tractions: fraction I is identical to normal AT III; fraction II (abnormal AT III) reproduces the abnormalities of the AT III “Milano”, i.e. lack of thrombin inhibition, incieased mobility by two-dimensional immunoclectrophoresis in the absence of heparin and migration as two bands with molecular weights of 60 K and 120 K by sodium dodecyl sulfate polyaeiylamide gel electrophoresis (SDS-PAGE). The interaction of both fiactions with purified u-thrombin was studied by the formation of complexes as well as by affinity chromatography on thrombin Seplmiose. No thrombin-AT III complexes could be demonstrated with either the monomeric or dimeric forms of purified variant AT III at both concentrations of thrombin used. Similarly, no binding to thrombin-Sepharose was observed, thus indicating that the molecular defect of AT III Milano is related to its absence of reactivity with thrombin.

Oxidative Stress and Cardiovascular Risk in Type 1 Diabetes Mellitus: Insights From the DCCT/EDIC Study

Background

Hyperglycemia leading to increased oxidative stress is implicated in the increased risk for the development of macrovascular and microvascular complications in patients with type 1 diabetes mellitus.

Methods and Results

A random subcohort of 349 participants was selected from the DCCT / EDIC (Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications) cohort. This included 320 controls and 29 cardiovascular disease cases that were augmented with 98 additional known cases to yield a case cohort of 447 participants (320 controls, 127 cases). Biosamples from DCCT baseline, year 1, and closeout of DCCT , and 1 to 2 years post‐ DCCT ( EDIC years 1 and 2) were measured for markers of oxidative stress, including plasma myeloperoxidase, paraoxonase activity, urinary F 2α isoprostanes, and its metabolite, 2,3 dinor‐8 iso prostaglandin F 2α . Following adjustment for glycated hemoblobin and weighting the observations inversely proportional to the sampling selection probabilities, higher paraoxonase activity, reflective of antioxidant activity, and 2,3 dinor‐8 iso prostaglandin F 2α , an oxidative marker, were significantly associated with lower risk of cardiovascular disease (−4.5% risk for 10% higher paraoxonase, P <0.003; −5.3% risk for 10% higher 2,3 dinor‐8 iso prostaglandin F 2α , P =0.0092). In contrast, the oxidative markers myeloperoxidase and F 2α isoprostanes were not significantly associated with cardiovascular disease after adjustment for glycated hemoblobin. There were no significant differences between DCCT intensive and conventional treatment groups in the change in all biomarkers across time segments.

Conclusions

Heightened antioxidant activity (rather than diminished oxidative stress markers) is associated with lower cardiovascular disease risk in type 1 diabetes mellitus, but these biomarkers did not change over time with intensification of glycemic control.

Clinical Trial Registration

URL : https://www.clinicaltrials.gov . Unique identifiers: NCT 00360815 and NCT 00360893.

Frequent infection of wild boar with atypical porcine pestivirus (APPV)

The recently identified atypical porcine pestivirus (APPV) was demonstrated to be the causative agent of the neurological disorder "congenital tremor" in newborn piglets. Despite its relevance and wide distribution in domestic pigs, so far nothing is known about the situation in wild boar, representing an important wild animal reservoir for the related classical swine fever virus. In this study, 456 wild boar serum samples obtained from northern Germany were investigated for the presence of APPV genomes and virus-specific antibodies. Results of real-time RT-PCR analyses revealed a genome detection rate of 19%. Subsequent genetic characterization of APPV (n = 12) from different hunting areas demonstrated close genetic relationship and, with exception of APPV from one location, displayed less than 3.3% differences in the analysed partial NS3 encoding region. Furthermore, indirect E^rns ELISA revealed an antibody detection rate of approx. 52%, being in line with the high number of viremic wild boar. Analysis of fifteen wild boar samples from the Republic of Serbia by E^rns antibody ELISA provided evidence that APPV is also abundant in wild boar populations outside Germany. High number of genome and seropositive animals suggest that wild boar may serve as an important virus reservoir for APPV.

MEDUSA: A Fuzzy Expert System for Medical Diagnosis of Acute Abdominal Pain

Even today, the diagnosis of acute abdominal pain represents a serious clinical problem. The medical knowledge in this field is characterized by uncertainty, imprecision and vagueness. This situation lends itself especially to be solved by the application of fuzzy logic. A fuzzy logic-based expert system for diagnostic decision support is presented (MEDUSA). The representation and application of uncertain and imprecise knowledge is realized by fuzzy sets and fuzzy relations. The hybrid concept of the system enables the integration of rulebased, heuristic and casebased reasoning on the basis of imprecise information. The central idea of the integration is to use casebased reasoning for the management of special cases, and rulebased reasoning for the representation of normal cases. The heuristic principle is ideally suited for making uncertain, hypothetical inferences on the basis of fuzzy data and fuzzy relations.