A comprehensive survey concerning the Shiraz Hemophilia Society and the associated haemophilia treatment centre was undertaken in April 2002 to collect data on demographics, signs and symptoms in the southern Iranian population with haemophilia and allied disorders. The total number of patients with coagulation disorders was 367. Haemophilia A (factor [F] VIII deficiency) was found in 271, 39 had haemophilia B (FIX deficiency) and 24 had von Willebrand disease. The rare coagulation disorders (n = 33) included 11 patients with FX deficiency; 10 with FVII; six with FXIII; two with afibrinogenaemia; two with FXI; one with combined FVIII and FV; and one with combined FVII, FVIII and FIX deficiency. The prevalence was 6.64 per 100,000 inhabitants. The most common symptoms were haemarthrosis, haematomas and epistaxis. None of the patients were human immunodeficiency virus positive but 47 (15%) were hepatitis C virus positive and two (0.7%) were hepatitis B positive, so that the rate of transfusion-transmitted infections was lower compared with other populations.

BACKGROUND

Associations between common F7 haplotypes, plasma factor VII (FVII) levels, and cardiovascular risk have recently been reported in population studies involving predominantly European men.

METHODS

We assessed associations between F7 haplotypes and cardiovascular risk in two US population-based studies: a case-control study of these alleles related to a decreased risk of arterial thrombotic outcomes such as myocardial infarction (MI) in young-to-middle-aged women (n = 671), and a cohort study of cardiovascular disease risk factors in young women (n = 1040).

RESULTS

The high-expression F7 haplotype B (containing the promoter variant allele -402A) was associated with an increased FVII level among controls, but not with MI risk. Women carrying a> or =1 copy of the low FVII expression level haplotype C (containing the -401T/-323del/-122C and Gln353 alleles) had decreased FVII levels and decreased risk of MI (odds ratio 0.54, 95% CI 0.31-0.93) compared with women homozygous for the most common haplotype A. Haplotype C was also associated with a decreased body mass index (BMI) and an increased high-density lipoprotein (HDL) cholesterol level, but not with MI risk after adjustment for these metabolic risk factors. In a cohort study composed of young US women, individuals homozygous for haplotype C had a lower BMI and lower systolic blood pressure, but the association between the F7 haplotype and HDL cholesterol was not confirmed.

CONCLUSIONS

Common FVII haplotypes may contribute to the risk of MI in women, but the mechanisms appear complex. The association between F7 haplotypes and MI susceptibility may be mediated in part through an influence on atherogenic risk factors such as BMI.

BACKGROUND

According to AABB standards, fresh-frozen plasma (FFP) should be thawed at 30 to 37°C and expire after 24 hours. An increase in the aggressive management of trauma patients with thawed plasma has heightened the risk of plasma waste. One way to reduce plasma waste is to extend its shelf life, given that the full range of therapeutic efficacy is maintained. We evaluated the effect of prolonged storage at 1 to 6°C on the activity of Factor (F)V, FVII, and FVIII in plasma thawed at 37 or 45°C.

METHODS

Group O plasma from healthy donors (n=20) was divided into 10 pairs and frozen and stored at not more than -18°C. One sample from each pair was thawed at 37 or 45°C, and all were stored at 1 to 6°C. Samples were analyzed for FV, FVII, and FVIII activity on Days 0, 5, 10, 15, and 20.

RESULTS

Plasma thawing time was 17% less at 45°C than at 37°C. No differences were observed between thawing groups in coagulation activity of FV, FVII, and FVIII during the 20-day storage period (p>0.12). In both groups, the activity of FV and FVIII decreased over time but remained within a normal range at 10 days.

CONCLUSIONS

Although levels of plasma clotting factors are reduced in storage, therapeutic levels of FV and FVIII are maintained in thawed plasma stored for up to 10 days at 1 to 6°C. Thawing of FFP at 45°C decreases thawing time but does not affect the activity of FV, FVII, and FVIII.

BACKGROUND

To date, no clinical trials have characterized FFP infusion efficacy, and infusion still carries infectious risk. This single-blinded crossover study compared postinfusion kinetics of FVII in photochemically treated FFP to standard FFP.

METHODS

Subjects donated plasma by apheresis. Half of the collected plasma was treated with the psoralen amotosalen hydrochloride (S-59) and UVA light, and half were prepared as standard plasma. Subjects received warfarin over 4 days to lower FVII levels. On Day 4, subjects received 1 L of either treated or standard FFP. After 2 weeks, subjects underwent a regimen identical to that with the other type of FFP.

RESULTS

After warfarin ingestion, the mean FVII concentration was 0.33 IU per mL. Both types of FFP exhibited comparable FVII kinetics, with a mean peak increment of 0.10 to 0.12 IU per mL occurring at the end of infusion. The effect disappeared after 8 hours.

CONCLUSIONS

Study data of warfarin-treated healthy volunteers demonstrate that psoralen plus UV-treated FFP provides an equivalent in vivo coagulation response to control plasma. A 1-L dose of FFP in adults may provide an initial increment of 0.10 IU per mL of FVII. In the absence of bleeding, FVII levels return to baseline after 8 hours.

Antiphospholipid antibodies (APLA) are associated with anti-phospholipid syndrome (APS), a thrombotic disorder, but they are also frequently detected in immune thrombocytopenic purpura (ITP), a bleeding disorder. To investigate possible differences of APLA between these two disorders, we assayed IgG and IgM APLA by ELISA in 21 patients with ITP and 33 with APS. The APLA reacting against two protein target antigens, beta(2)-glycoprotein 1 (beta2GP1) and FVII/VIIa, and four phospholipids [cardiolipin (CL), phosphatidylcholine (PC), phosphatidylserine (PS), and phosphatidylethanolamine (PE)] as well as lupus anticoagulant (LA) were analyzed. We made the following observations: (i) IgG and IgM antibodies to beta2GP1 and IgM antibodies to FVII/VIIa were more common in APS than ITP, P < 0.05, while IgG antibodies against the phospholipids (aCL, aPC, aPS, aPE) were more common in ITP than APS, P < 0.05; (ii) multiple APLA>> or =3 antigens) were more frequent in APS than ITP, P < 0.05; (iii) LA was frequently associated with APS but was absent in ITP; (iv) APLA is quite common in ITP: two-thirds were positive for at least one APLA. In summary, APLA are prevalent in ITP but their profile differs from APS. In APS, antibodies were predominantly against beta2GP1 and 80% had positive LA, while in ITP the APLA reacted most often with the phospholipids without LA. The difference in APLA may result in opposite clinical manifestations in two disorders.

Limitations of current anticoagulant therapies have led us to develop two distinct classes of exosite peptide inhibitors for the initiator of the clotting process, the tissue factor-factor VIIa (TF.FVIIa) complex (Roberge, M., Santell, L., Dennis, M. S., Eigenbrot, C., Dwyer, M. A., and Lazarus, R. A. (2001) Biochemistry 40, 9522-9531). Although both peptide classes are potent and selective inhibitors of TF.FVIIa, neither showed 100% inhibition at saturating concentrations. Crystal structures of these peptides in complex with the FVII/FVIIa protease domain revealed their distinct binding sites and close proximity to the active site. The favorable orientation of the 15-mer A-site peptide A-183 (EEWEVLCWTWETCER) suggested that a C-terminal extension into the FVIIa active site could yield a chimeric inhibitor that was not only potent and selective but complete as well. A novel two-step "protease switch" approach using substrate phage display was developed by first binding all phage containing A-183 and C-terminal extension libraries to immobilized and inactive FVIIa. Upon altering pH and adding TF to switch on FVIIa enzymatic activity, only those phage released by proteolytic cleavage within the extension were propagated. This process selected for both preferred sequence and length in the extension, leading to a 27-mer peptide A-183X (EEWEVLCWTWETCERGEGVEEELWEWR) with a C-terminal 12-mer extension containing an Arg in the P1 position. A-183X was a more potent and complete inhibitor of FX activation, having a maximal extent of inhibition of approximately 99% with an IC50 of 230 pm versus A-183 which maximally inhibited to 74% with an IC50 of 1.5 nm. A-183X also had a maximal prolongation of the prothrombin time of 7.6- versus 1.9-fold for A-183, making it a more effective anticoagulant.

Factor VII is the coagulation protease responsible for starting a cascade of proteolytic events that lead to thrombin generation, fibrin deposition, and platelet activation. As such, FVII has attracted wide interest as a target for clinical anti-coagulant applications. Commensurate with the critical importance of maintaining balance between thrombosis and hemostasis and its place at the beginning of the coagulation process, FVII is subject to a variety of biological and biochemical control mechanisms, among them allosteric influences exerted by cofactors, substrates, and inhibitors. Sites on FVIIa where allosteric influences are exerted and manifested have been identified and characterized in considerable detail. In recent years, a three-dimensional context for the interpretation of these results has become available from structural studies. New X-ray structures have augmented specific aspects of our understanding, in particular the X-ray structure of a fragment of the FVII zymogen. This review summarizes general allosteric behaviors of FVIIa and recapitulates structural findings since 1996, with particular emphasis on the recently determined zymogen structure.

BACKGROUND AND OBJECTIVES: International Normalized Ratio (INR) is a world-wide routinely used factor in the monitoring of oral anticoagulation treatment (OAT). However, it was reported that other factors, e. g. factor II, may even better reflect therapeutic efficacy of OAT and, therefore, may be potentialy useful for OAT monitoring. The primary purpose of this study was to characterize the associations of INR with other vitamin K-dependent plasma proteins in a heterogenous group of individuals, including healthy donors, patients on OAT and patients not receiving OAT. The study aimed also at establishing the influence of co-morbid conditions (incl. accompanying diseases) and co-medications (incl. different intensity of OAT) on INR. DESIGN AND METHODS: Two hundred and three subjects were involved in the study. Of these, 35 were normal healthy donors (group I), 73 were patients on medication different than OAT (group II) and 95 were patients on stable oral anticoagulant (acenocoumarol) therapy lasting for at least half a year prior to the study. The values of INR and activated partial thromboplastin time (APTT) ratio, as well as activities of FII, FVII, FX, protein C, and concentration of prothrombin F1+2 fragments and fibrinogen were obtained for all subjects. In statistical evaluation, the uni- and multivariate analyses were employed and the regression equations describing the obtained associations were estimated. RESULTS: Of the studied parameters, three (factors II, VII and X) appeared as very strong modulators of INR, protein C and prothrombin fragments F1+2 had moderate influence, whereas both APTT ratio and fibrinogen had no significant impact on INR variability. Due to collinearity and low tolerance of independent variables included in the multiple regression models, we routinely employed a ridge multiple regression model which compromises the minimal number of independent variables with the maximal overall determination coefficient. The best-fitted two-component model included FII and FVII activities and explained 90% of INR variability (compared to 93% in the 5-component model including all vitamin K-dependent proteins). Neither the presence of accompanying diseases nor the use of OAT nor any other medication (acetylsalicylic acid, statins, steroids, thyroxin) biased significantly these associations. CONCLUSION: Among various vitamin K-dependent plasma proteins, the coagulation factors II, VII and X showed the most significant associations with INR. Of these variables, the two-component model, including factors II and VII, deserves special attention, as it largely explains the overall variability observed in INR estimates. The statistical power of this model is validated on virtue of the estimation that the revealed associations are rather universal and remain essentially unbiased by other compounding variables, including clinical status and medical treatment. Further, much broader population studies are needed to verify clinical usefulness of methods alternate or compounding to INR monitoring of OAT.

We have previously reported the finding of a cyclic dodecapeptide representing loop I of the second EGF-like domain of FVII, which inhibited TF-dependent FX activation (Orning et al. 1997). The biological activity was localized to the tripeptide motif, Glu-Gln-Tyr. We have now synthesized a cyclic analog of this motif, Cys-Glu-Gln-Tyr-Cys (PN7051), evaluated its anticoagulant and antithrombotic properties and performed a detailed structural characterization of the peptide. PN7051 is a dose-dependent inhibitor of TF-dependent FX activation and coagulation of plasma with IC50 values of 10+/-2 microM and 1.3+/-0.2 mM, respectively. It shows inhibitory efficacy on acute thrombus formation in an ex vivo model of human thrombosis using native blood. Fibrin deposition, platelet-fibrin adhesion, platelet-thrombus formation, and thrombin-antithrombin complex formation were all inhibited by PN7051 at IC50 values between 0.3 and 0.7 mM. The cyclic peptide is a non-competitive inhibitor of FX activation with no significant active-site effects on FXa or FVIIa, indicating it affects FVII/TF/FX complex formation and function. Studies on the structure activity relationship revealed that Gln3-Tyr4, but not Glu2 were of importance for inhibition. In line with biological results, NMR measurements of PN7051 suggested that the Gln and Tyr residues configure a structural feature that contributes to the anticoagulant activity. Modeling of the Glu99Gln100Tyr101 motif in FVII and comparison with the solution structure of PN705 I suggest that the cyclic pentapeptide exerts its antithrombotic effect by interfering with the docking of Tyr101 into a hydrophobic pocket in the catalytic domain thereby disrupting an essential interaction between the second EGF-like and the catalytic domains of FVII.

BACKGROUND

The efficacy of oral anticoagulant therapy is largely conditioned by both environmental and genetic factors.

OBJECTIVE

To attempt to define the genetic profile involved in the response to this treatment.

METHODS

We selected 100 men younger than 75 years, with non-valvular atrial fibrillation, who started anticoagulation with acenocoumarol following the same protocol: 3 mg for three consecutive days. Then, doses were individually adjusted to achieve a steady International Normalized Ratio (INR). The basal plasma level and the level after 3 days were obtained, and the INR was determined. We studied five functional polymorphisms: FVII -323 Del/Ins, CYP2C*9, VKORC1 c1173t, calumenin (CALU) R4Q and CALU a29809g. The dose required for a steady INR was also recorded.

RESULTS

Only the VKORC1 genotype had significant impact on the efficacy of therapy. Carriers of the 1173t allele were significantly more sensitive to therapy for 3 days [INR 2.07 (1.59-2.87) vs. 1.74 (1.30-2.09); P = 0.015] and they needed lower acenocoumarol doses to stabilize their INR (15.8 +/- 5.6 vs. 19.5 +/- 6.0 mg week(-1); P = 0.004). Its effect was exacerbated by combination with the CALU a29809g polymorphism. Carriers of both variants (27% of the sample) achieved the highest INR [2.26 (1.70-3.32)] and required the lowest dose (14.1 +/- 5.1 mg week(-1)). This genetic profile was particularly relevant in patients with INR>>or= 3.5 at the start of therapy (P = 0.005; odds ratio = 6.67, 95% confidence interval = 1.32-37.43).

CONCLUSIONS

Our results suggest that CALU a29809g might be a new genetic factor involved in the pharmacogenetics of anticoagulant therapy, and confirm that specific genetic profiles defined by different polymorphisms will determine the initial response and dose required to achieve a stable and safe INR.

OBJECTIVE

To study the efficacy and safety of factor VII (fVII)-verteporfin for targeted photodynamic therapy (TPT) compared with nontargeted photodynamic therapy (PDT) in a rat model of choroidal neovascularization (CNV). fVII-verteporfin binds tightly and specifically to tissue factor, which is expressed on endothelial cells of CNV but not normal vasculature.

METHODS

Multiple CNV lesions were induced by laser photocoagulation of the retina in Brown-Norway rats. After 3 weeks, the rats were injected intravenously with fVII-verteporfin (0.5 and 1.0 mg/m(2)) or Visudyne (6.0 mg/ m(2); QLT Inc., Vancouver, BC, Canada). Randomly selected lesions were treated with a 689-nm laser 30 or 60 minutes later. The lesions were evaluated by fluorescein angiography and histopathology.

RESULTS

The rats treated with Visudyne PDT showed leakage in 75% of the CNV lesions on day 7 and 100% of lesions on day 14. The rats treated with fVII-verteporfin TPT at a dose of 0.5 mg/m(2) showed leakage in 33% and 36% of the CNV lesions on days 7 and 14, respectively. When the dose was increased to 1.0 mg/m(2) for TPT, leakage was detected in 25% and 23% of the CNV lesions on days 7 and 14, respectively. No ocular side effect was detected by histopathologic evaluation.

CONCLUSIONS

The frequency of leakage in CNV lesions was significantly reduced using fVII-verteporfin TPT compared with PDT. The efficacious dose with fVII-verteporfin was approximately 10% of the dose usually used in nontargeted Visudyne PDT. Using fVII-verteporfin for TPT may improve the efficacy and safety of PDT for treating choroidal neovascularization.

The effects of two cyclically administered, triphasic, combined low dosage oestrogen and progestogen oral contraceptives on haemostasis have been compared in a longitudinal study, over 6 months, in 26 healthy females aged 16-30 years. Subjects received either Logynon (ethinyl oestradiol and Levonorgestrol, n = 14) or SHD 415G (Schering U.K., n = 12), which contains a similar dosage of ethinyl oestradiol, but in combination with a new progestogen, gestodene. Both groups showed increases in biological activities of procoagulant factors fibrinogen, X and XII and decreased activity of the naturally occurring coagulation inhibitor antithrombin III (AT-III). The majority of these changes were statistically significant (P less than 0.05 to less than 0.001), apparent after one cycle and maintained over the six cycle period. FVII activity increased in both groups, achieving statistical significance (P less than 0.01) by cycle 6 in the SHD 415G group but not in the females receiving Logynon. Protein C activity remained unchanged in both groups. Between-group comparisons showed no differences in the procoagulant factor changes, but protein C was lower (P less than 0.05) in the SHD 415G group after three cycles of therapy. These findings indicate that both triphasic oral contraceptives Logynon and SHD 415G induce increases in procoagulant factor activities which are not balanced by increased biological levels of the two most important physiological coagulation inhibitors AT-III and protein C. These prothrombotic changes are not modified by the new progestogen, gestodene.

BACKGROUND

As thrombosis is an essential factor in the pathogenesis of acute myocardial infarction (AMI), the genes of proteins affecting haemostasis are good candidate genes for AMI.

METHODS

Associations of the known polymorphisms of the coagulation factor VII (FVII) gene (R353Q), the coagulation factor XIII (FXIII) gene (V34L) and the glycoprotein Ia (Gp1a) gene (C807T) with the occurrence of AMI were studied in 142 AMI survivors and 142 age- and sex-matched control subjects.

RESULTS

Among those who smoked, the L34 allele of the amino acid FXIII polymorphism was less common in the AMI patients (16%) than in the controls (27%) (P = 0.06), suggesting a possible interaction of AMI risk between the FXIII genotype and smoking status. No differences in the allele or genotype frequencies of the studied polymorphisms were seen between the whole study groups. Logistic regression analysis showed the carriers of the L34 allele of the FXIII amino acid polymorphism to have a significantly (P = 0.03) lower AMI risk compared with those homozygous for the V34 allele (odds ratio = 0.54, 95% confidence interval 0.31-0.93).

CONCLUSIONS

The L34 allele of the amino acid polymorphism of the FXIII gene is associated with a decreased risk of AMI, and this protecting association seems to be more pronounced in smokers.

In the present study the effect of oral contraceptive (OC) treatment on selected factors involved in the activation, i.e. circulating activated factor VII (cFVIIa), and in the inhibition of blood coagulation, i.e. plasma protein S activity and circulating thrombomodulin (cTM), were for the first time measured in OC users in a prospective study. Beside other coagulation variables, these parameters were measured during treatment with three low estrogen formulations containing different gestagen components (norgestimate, gestodene). During OC treatment increases in the activation markers prothrombin fragment F1 + 2 and D-Dimer were found, suggesting an increased activation of blood coagulation and fibrinolysis. Along with elevated plasma levels of FVII antigen, cFVIIa was also found increased in all three treatment groups, while inhibitory components of blood coagulation, plasma protein S activity and cTM, significantly and similarly decreased during treatment in all three treatment groups. We conclude that low dose estrogen pills induce similar changes in the plasma levels of main regulatory components of blood coagulation, despite differences in their gestagen components. Increased levels of activators and decreased activities of inhibitors may contribute to arterial and venous thrombotic complications seen in predisposed OC users.

Recombinant activated factor VIIa (rFVIIa) is a well-established treatment for bleeding episodes in patients with congenital or acquired haemophilia A or B with inhibitors to factors VIII and IX and patients with FVII deficiency. The aim of this trial was to demonstrate bioequivalence between the currently marketed (rFVIIa/NovoSeven) and a new rFVIIa formulation (VII25) stable at up to 25 degrees C. Furthermore, short-term safety and tolerability of VII25 and pharmacokinetics of both formulations were investigated. In this single-centre, randomized, double-blind, two-way cross-over trial, healthy male subjects received one intravenous bolus injection of rFVIIa and one of VII25, both at 90 microg kg(-1), in a randomized order 2-3 weeks apart. Mean VII25/rFVIIa ratio for area under the plasma activity-time curve from time 0 to last quantifiable activity (primary bioequivalence endpoint), was 0.93, 90% confidence interval (CI) (0.89-0.96), within the predefined bioequivalence range (0.80-1.25). Secondary pharmacokinetic parameters were comparable between formulations. No serious adverse events were observed. Six mild or moderate treatment-emergent adverse events were reported in five subjects. Coagulation-related parameter profiles were similar between rFVIIa and VII25. No clinically abnormal changes were observed for laboratory parameters and no subjects developed FVIIa antibodies. This trial demonstrated bioequivalence between the currently available rFVIIa and VII25 stable at up to 25 degrees C. VII25's 'user-friendly' formulation removes the inconvenience of storing/transporting at 2-8 degrees C, and as the drug substance is the same, the activity and safety established for rFVIIa is maintained.

In three Italian patients, two point mutations and a short deletion were found in the intron 7 of factor VII gene, clustered in the donor splice site and located in the first of several repeats. The mutation 9726+5G->>A, the most frequent cause of symptomatic factor VII deficiency in Italy, as well as the deletion (9729del4) gave rise in expression studies to abnormally spliced transcripts, which were exclusively produced from the cryptic site in the second repeat. The insertion in the mature mRNA of the first intronic repeat caused (9726+5G->>A) a reading frameshift, abolishing most of the factor VII catalytic domain, or produced (9729del4), an altered factor with 11 additional residues, the activity of which was not detectable in the cell medium after mutagenesis and expression studies. Studies of factor VII ectopic mRNA from leukocytes and expression studies indicated that the deleted gene produced 30% of normally spliced transcript. Differently, the 9726+5G->>A mutation permitted a very low level (0.2% to 1%) of correct splicing to occur, which could be of great importance to prevent the onset, in the homozygous patients, of most of the life-threatening bleeding symptoms. The 9726+7A->>G mutation was found to be a rare and functionally silent polymorphism. These findings, which provide further evidence of the interplay of sequence and position in the 5' splice site selection, throw light on the heterogeneous molecular bases and clinical phenotypes of FVII deficiency.

Factor VII-activating protease (FSAP) is a serine protease in plasma that has a role in coagulation and fibrinolysis. FVII could be activated by purified FSAP in a tissue factor independent manner and pro-urokinase has been demonstrated to be a substrate for purified FSAP in-vitro. However, the physiological role of FSAP in haemostasis remains unclear. More recently FSAP is suggested to be involved in inflammation. It modulates vascular permeability directly and indirectly by the generation of bradykinin. Furthermore, FSAP is activated by dead cells induced by the inflammatory response and subsequently removes nucleosomes from apoptotic cells. FSAP activation can be detected in sepsis patients as well. However, whether FSAP activation upon inflammation is beneficial or detrimental remains an open question. In this review the structure, activation mechanisms and the possible role of FSAP in inflammation are discussed.

Factor VII (FVII) is the plasma serine protease zymogen which, on binding to its cellular receptor tissue factor (TF), initiates blood coagulation. A 47-year-old man with no clinical bleeding tendency was found to have undetectable plasma FVII activity when tested in a one-stage assay using rabbit brain TF, but 0.3 U/mL using recombinant human TF and 1.04 U/mL FVII antigen. Variant FVII purified from his plasma showed an identical migration on sodium dodecyl sulfate-polyacrylamide gel electrophoresis to wild-type zymogen. By enzyme kinetic analysis the Km of the variant using FX as a substrate was 12-fold higher than that of normal FVII. Also, the variant FVII was unable to compete with wild-type FVII for limited rabbit TF binding sites. A ligand blot procedure was used to directly demonstrate reduced binding of recombinant human TF to the variant FVII compared with normal FVII. Genetic analysis of leukocyte DNA showed a G to A mutation in the propositus' gene at codon 304 that results in the substitution of a glutamine for an arginine residue in the catalytic domain of the protease. We conclude that this region of the FVII molecule is important for its function.

The hyaluronic acid binding serine protease (PHBSP), an enzyme with the ability to activate the coagulation factor FVII and the plasminogen activator precursors and to inactivate factor VIII and factor V, could be isolated from human plasma in the presence of 6M urea as a single-chain zymogen, whereas under native conditions only its activated two-chain form was obtained. The total yield of proenzyme (proPHBSP) was 5-6 mg/l, corresponding to a concentration of at least 80-100nM in plasma. Upon removal of urea, even in the absence of charged surfaces a rapid development of amidolytic activity was observed that correlated with the appearance of the two-chain enzyme. The highest activation rate was observed at pH 6. ProPHBSP processing was concentration-dependent following a second order kinetic and was accelerated by catalytic amounts of active PHBSP, indicating an intermolecular autocatalytic activation. Charged macromolecules like poly-L-lysine, heparin, and dextran sulfate strongly accelerated the autoactivation, suggesting that in vivo proPHBSP activation might be a surface-bound process. The intrinsic activity of the proenzyme was determined to be 0.25-0.3%, most likely due to traces of PHBSP. The presence of physiological concentrations of known plasma inhibitors of PHBSP, like alpha2 antiplasmin and C1 esterase inhibitor, but not antithrombin III/heparin, slowed down zymogen processing. Our in vitro data suggest that the autoactivation of proPHBSP during plasma fractionation is induced by the removal of inhibitors of PHBSP and is accelerated by charged surfaces of the chromatographic resins.

BACKGROUND

Human prothrombin complex concentrates (PCCs) are used for prevention and treatment of bleeding episodes in patients under warfarin therapy. PCCs contain human factor (F) II, FVII, FIX, FX, protein C and protein S. The concentrations of these coagulation factors contained in PCCs are variable and do not reflect entirely the capacity of these drugs to correct hemostasis. Furthermore, commercially available PCCs do not have exactly the same composition, though they are all labelled and prescribed in units per kg of FIX (10-40 IU of FIX/kg). As the final product generated by PCCs is thrombin, a thrombin generation (TG) test could theoretically be used for monitoring the hemostatic correction.

METHODS

TG was measured in platelet free plasma in the presence of tissue factor 5 pm and phospholipids 4 microM with a final concentration of PCC of 0-0.1-0.2-0.3-0.4-0.5-0.75-1 IU ml(-1). The activity of vitamin K-dependent coagulation factors (i.e. FII, FVII, FIX, FX, protein C and protein S) were determined for each concentration of two different PCCs available on the French market.

CONCLUSIONS

Our results showed that the addition of two different PCCs dose-dependently increased the TG capacity in patients with INR of 2-2.5-3-4 and >7 (n = 15 subjects) that reached the normal values. We also found a significant correlation between endogenous thrombin potential (ETP) and INR (Pearson test, P < 0.0001). The two PCCs improved the TG parameters differently with increasing concentrations. The difference in the correction of TG capacity observed between the two drugs could be explained by a variable increase in FX, FVII and protein C with similar doses. These results strongly suggest that TG assay could be used for monitoring the clinical efficacy of PCC and for optimizing the therapeutic regimen towards a more individualized therapy involving the type of the bleeding complications, the level of inhibition of the coagulation system and the molecule content of the PCC.

During the haemostatic response, the formation of a primary platelet plug limits bleeding and provides a surface for clotting factors to assemble and become activated. The initial platelet plug is stabilized by fibrin monomers, covalently cross-linked by FXIII, forming a platelets-fibrin thrombus. Defects in platelets as well as inherited deficiencies of coagulation factors including fibrinogen, FII, FV, FV + FVIII, FVII, FX, FXI and FXIII deficiencies, generally lead to lifelong bleeding disorders, whose severity of bleeding symptoms is heterogeneous in platelets abnormalities but generally inversely proportional to the degree of the factor deficiency in rare bleeding disorders (RBDs). The prevalence of platelet defects among the general population has not been established, whereas for RBDs it ranges from approximately 1 in 2 million to 1 in 500,000, being higher in countries where consanguineous marriages are diffused. As a consequence of the rarity of these deficiencies, the type and severity of bleeding symptoms, the underlying molecular defects, and the actual management of bleeding episodes are not well established. In this review the main features, diagnosis, available treatment options and treatment complications of the platelet disorders, caused by abnormalities in platelet receptors for adhesive proteins, platelet receptors for soluble agonists, platelet granules, signal transduction pathways, or procoagulant phospholipids will be discussed by Dr Cattaneo, whereas fibrinogen deficiency and FXIII deficiency will be described by Dr Inbal and Dr de Moerloose, respectively. Finally, the update of the Rare Bleeding Disorders Database will be presented by Dr Spreafico.

BACKGROUND

Photochemical treatment (PCT) with amotosalen HCl (S-59) was developed to inactivate pathogens and white blood cells in plasma (PCT-FFP) used for transfusion support.

METHODS

An open-label, multicenter trial was conducted in patients with congenital coagulation factor deficiencies (factors [F]I, FII, FV, FVII, FX, FXI, and FXIII and protein C) to measure the kinetics of specific coagulation factors, hemostatic efficacy, and safety of PCT-FFP. Posttransfusion prothrombin time (PT), partial thromboplastin time (PTT), and clinical hemostasis were evaluated before and after PCT-FFP transfusions.

RESULTS

Thirty-four patients received 107 transfusions of PCT-FFP for kinetic studies or therapeutic indications (mean dose, 12.8 +/- 8.5 mL/kg). Incremental factor recoveries ranged from 0.9 to 2.4 IU per dL per IU per kg (FII, FV, FVII, FX, FXI, and protein C). Mean pretransfusion PT (20.7 +/- 22.2 sec) corrected after PCT-FFP (13.8 +/- 2.4 sec, p < 0.001). Mean pretransfusion PTT (51.2 +/- 29.3 sec) corrected after PCT-FFP (32.0 +/- 5.1 sec, p < 0.001). Thirteen patients required 77 transfusions for therapeutic indications. PCT-FFP provided effective hemostasis and was well tolerated.

CONCLUSIONS

Replacement coagulation factors in PCT-FFP exhibited kinetics and therapeutic efficacy consistent with conventional FFP.

Substitutive therapy has significantly ameliorated the quality of life of patients with coagulation factor deficiencies. However, there are some limitations that support research towards alternative therapeutic approaches. Here we focus on the rescue of coagulation factor biosynthesis by targeting the RNA processing and translation, which would permit restoration of the altered gene expression while maintaining the gene regulation in the physiological tissues. The essential prerequisite of the three reported RNA-based correction approaches (i-iii), which rely on mutation types and are applicable even to large size mRNAs, is the presence in cells of the precursor (pre-mRNA) or mature mRNA forms. (i) In the F7 gene, modification of the small nuclear RNA U1 (U1 snRNA), the key component of the spliceosomal U1 ribonucleoprotein, re-directs correct usage of a mutated exon-intron junction, triggering synthesis of correct mRNA and secretion of functional factor (F)VII. (ii) Spliceosome-mediated RNA trans-splicing (SMaRT) between mutated and engineered pre-mRNAs produces normal FVIII mRNA and secretion of functional protein. (iii) Aminoglycoside drugs induce ribosome readthrough and suppress premature translation termination caused by nonsense mutations in FVII, VIII and IX. The rescued expression levels ranged from very low (aminoglycosides) to moderate (U1 snRNA and SMaRT), which could result in amelioration of the disease phenotypes. These findings prompt further studies aimed at demonstrating the clinical translatability of RNA-based strategies, which might open new avenues in the treatment of coagulation factor deficiencies.

Tissue factor (TF) is a 48-kD transmembrane glycoprotein that triggers the extrinsic pathway of blood coagulation by interacting with the plasma coagulation factor VII (FVII). TF is also a true receptor in that a cellular signal is generated when activated FVII (FVIIa) binds to TF. For both of these functions, the cellular surface distribution of TF is important, since FVII is primarily available on the apical side of vascular endothelial cells and on the basolateral side of epithelial cells lining the internal and external surfaces. We show that in endothelial cells, TF (both antigen and procoagulant activity) is sorted to the apical surface, whereas in wild-type and stably transfected Madin-Darby canine kidney epithelial cells (MDCK), which form tight junctions and express TF constitutively, TF antigen is on the basolateral surface. No significant clotting activity is detectable on this surface. Truncated TF (cytoplasmic tail residues 246 to 263 deleted) is sorted as wild-type in MDCK cells.