Imbalance between procoagulant factors and natural coagulation inhibitors contributes to hypercoagulability in the critically ill COVID-19 patient: clinical implications.

OBJECTIVE: Coronavirus Disease-2019 (COVID-19) predisposes patients to thrombosis which underlying mechanisms are still incompletely understood. We sought to investigate the balance between procoagulant factors and natural coagulation inhibitors in the critically ill COVID-19 patient and to evaluate the usefulness of hemostasis parameters to identify patients at risk of venous thromboembolic event (VTE). PATIENTS AND METHODS: We conducted an observational study recording VTEs defined as deep vein thrombosis or pulmonary embolism using lower limb ultrasound (92% of the patients), computed tomography pulmonary angiography (6%) and both tests (2%). We developed a comprehensive analysis of hemostasis. RESULTS: Ninety-two consecutive mechanically ventilated COVID-19 patients (age, 62 years [53-69] (median [25th-75th percentiles]); M/F sex ratio, 2.5; body-mass index, 28 kg/m2 [25-32]; past hypertension (52%) and diabetes mellitus (30%)) admitted to the Intensive Care Unit (ICU) from 03/11/2020 to 5/05/2020, were included. When tested, patients were receiving prophylactic (74%) or therapeutic (26%) anticoagulation. Forty patients (43%) were diagnosed with VTE. Patients displayed inflammatory and prothrombotic profile including markedly elevated plasma fibrinogen (7.7 g/L [6.1-8.6]), D-dimer (3,360 ng/mL [1668-7575]), factor V (166 IU/dL [136-195]) and factor VIII activities (294 IU/dL [223-362]). We evidenced significant discrepant protein C anticoagulant and chromogenic activities, combined with slightly decreased protein S activity. Plasma D-dimer >3,300 ng/mL predicted VTE presence with 78% (95%-confidence interval (95% CI), 62-89) sensitivity, 69% (95% CI, 55-81) specificity, 66% (95% CI, 51-79) positive predictive value and 80% (95% CI, 65-90) negative predictive value [area under the ROC curve, 0.779 (95%CI, 0.681-0.859), p=0.0001]. CONCLUSIONS: Mechanically ventilated COVID-19 patients present with an imbalance between markedly increased factor V/VIII activity and overwhelmed protein C/S pathway. Plasma D-dimer may be a useful biomarker at the bedside for suspicion of VTE.

A Case of Acquired Hemophilia A: Usefulness of Various Methods for Judging Mixing Test Results for Monitoring the Effect of Immunosuppressive Therapy.

BACKGROUND: Measurement of FVIII inhibitor (FVIII INH) levels is important for determining the effect of immunosuppressive therapy on acquired hemophilia A (AHA). However, FVIII INH can only be measured at a limited number of laboratories, which means that there are delays in obtaining the results at many sites. METHODS: A series of mixing tests were carried out in a case of AHA, followed by comparison of various methods for judging the obtained results in association with a change of FVIII INH. The mixing test results were judged using the visual waveform pattern method and the index of circulating anticoagulant (ICA), as well as the difference between the APTT values of delayed-type and immediate-type waveforms (APTT D-I) as a numerical index. RESULTS: All examined judgment methods reflected the change in FVIII INH, but ICA and APTT D-I were particularly sensitive for capturing this. CONCLUSIONS: Our results suggest that a series of mixing tests are useful for rapid monitoring of the effect of immunosuppressive therapy on AHA.

Safety and Efficacy of B-domain Deleted Third Generation Recombinant Factor VIII (GreenGene F™) in Korean Patients with Hemophilia A: Data from a Post-marketing Surveillance Study.

BACKGROUND: New B-domain deleted third generation recombinant factor VIII (FVIII; GreenGene F™, beroctocog alfa) was launched in 2010. We determined safety and efficacy of GreenGene F™ during routine clinical practice in patients with hemophilia A over a period of 12 months. METHODS: From July 2010 to July 2014, a total of 136 hemophilia A patients were enrolled in a post-marketing surveillance (PMS) study. Among them, 134 patients were assessed for drug safety and 114 patients were analyzed for drug efficacy. Patients with differing hemophilia A severities and medical histories were monitored during 12 months of prophylactic and/or on-demand therapy. RESULTS: Among 134 patients evaluated, 85 (63.4%) had severe hemophilia. Ninety-two received a total of 1,266,077 units for prophylaxis, and 42 received 516,491 units for bleeding episodes. Three patients developed inhibitors. In 112 previously treated patients, one patient (0.9%) developed inhibitor after intensive FVIII treatment for surgery. Among 22 previously untreated patients, inhibitors were observed in 2 infants (9.1%). Overall, there were a total of 47 adverse events (other than inhibitors) of all types in 30 patients (22.4%), 11 in 10 patients (7.5%) of which were considered showing serious adverse events (SAEs); most of which were hemorrhages at different sites. None of the SAEs were judged as product related. An excellent/good efficacy rate of 91.3% for hemostasis and 89.4% for hemorrhage prevention was recorded. CONCLUSION: The results of this PMS study support the use of GreenGene F™ as safe and efficacious in hemorrhage prevention and treatment of hemophilia A. These results are consistent with the findings from previously published GreenGene F™ studies.

Platelet surface-associated activation and secretion-mediated inhibition of coagulation factor XII.

Coagulation factor XII (fXII) is important for arterial thrombosis, but its physiological activation mechanisms are unclear. In this study, we elucidated the role of platelets and platelet-derived material in fXII activation. FXII activation was only observed upon potent platelet stimulation (with thrombin, collagen-related peptide, or calcium ionophore, but not ADP) accompanied by phosphatidylserine exposure and was localised to the platelet surface. Platelets from three patients with grey platelet syndrome did not activate fXII, which suggests that platelet-associated fXII-activating material might be released from α-granules. FXII was preferentially bound by phosphotidylserine-positive platelets and annexin V abrogated platelet-dependent fXII activation; however, artificial phosphotidylserine/phosphatidylcholine microvesicles did not support fXII activation under the conditions herein. Confocal microscopy using DAPI as a poly-phosphate marker did not reveal poly-phosphates associated with an activated platelet surface. Experimental data for fXII activation indicates an auto-inhibition mechanism (ki/ka = 180 molecules/platelet). Unlike surface-associated fXII activation, platelet secretion inhibited activated fXII (fXIIa), particularly due to a released C1-inhibitor. Platelet surface-associated fXIIa formation triggered contact pathway-dependent clotting in recalcified plasma. Computer modelling suggests that fXIIa inactivation was greatly decreased in thrombi under high blood flow due to inhibitor washout. Combined, the surface-associated fXII activation and its inhibition in solution herein may be regarded as a flow-sensitive regulator that can shift the balance between surface-associated clotting and plasma-dependent inhibition, which may explain the role of fXII at high shear and why fXII is important for thrombosis but negligible in haemostasis.

FVIII inhibitors: pathogenesis and avoidance.

The pathogenesis of inhibitory antibodies has been the focus of major scientific interest over the last decades, and several studies on underlying immune mechanisms and risk factors for formation of these antibodies have been performed with the aim of improving the ability to both predict and prevent their appearance. It seems clear that the decisive factors for the immune response to the deficient factor are multiple and involve components of both a constitutional and therapy-related nature. A scientific concern and obstacle for research in the area of hemophilia is the relatively small cohorts available for studies and the resulting risk of confounded and biased results. Careful interpretation of data is recommended to avoid treatment decisions based on a weak scientific platform. This review will summarize current concepts of the underlying immunological mechanisms and risk factors for development of inhibitory antibodies in patients with hemophilia A and discuss how these findings may be interpreted and influence our clinical management of patients.

Computer-predicted peptides that mimic discontinuous epitopes on the A2 domain of factor VIII.

Development of antibodies (Abs) against factor VIII (FVIII) is a severe complication of haemophilia A treatment. Recent publications suggest that domain specificity of anti-FVIII antibodies, particularly during immune tolerance induction (ITI), might be related to the outcome of the treatment. Obtaining suitable tools for a fine mapping of discontinuous epitopes could thus be helpful. The aim of this study was to map discontinuous epitopes on FVIII A2 domain using a new epitope prediction functionality of the PEPOP bioinformatics tool and a peptide inhibition assay based on the Luminex technology. We predicted, selected and synthesized 40 peptides mimicking discontinuous epitopes on the A2 domain of FVIII. A new inhibition assays using Luminex technology was performed to identify peptides able to inhibit the binding of anti-A2 Abs to A2 domain. We identified two peptides (IFKKLYHVWTKEVG and LYSRRLPKGVKHFD) able to block the binding of anti-A2 allo-antibodies to this domain. The three-dimensional representation of these two peptides on the A2 domain revealed that they are localized on a limited region of A2. We also confirmed that residues 484-508 of the A2 domain define an antigenic site. We suggest that dissection of the antibody response during ITI using synthetic peptide epitopes could provide important information for the management of patients with inhibitors.

Renal thromboembolism during treatment with recombinant activated factor VII (rFVIIa) in a child with hemophilia B with factor IX inhibitors.

BACKGROUND: Serious thromboembolic events connected with rFVIIa therapy in hemophilia patients are rare. Only three cases are reported in children, all of them with hemophilia A. CASE PRESENTATION: We present unique case of patient with hemophilia B and high titer inhibitors to coagulation FIX, who developed severe renal damage due to thromboembolic event during rFVIIa therapy, associated with unsuspected renovascular anomalies. CONCLUSION: Caution is necessary if hematuria B requires administration of rFVIIa. US color doppler renal imaging before and after drug administration should be sufficient as an early warning.

Current management of hemophilia B: recommendations, complications and emerging issues.

Hemophilia B is a rare hereditary hemorrhagic disorder characterized by deficiency of the clotting factor IX (FIX). Hemophilia B patients experience mild-to-severe bleeding complications according to the degree of FIX defect. The mainstay of treatment of hemophilia B consists of replacement therapy and nowadays several plasma-derived and recombinant FIX products are commercially available. This article reviews the current management of hemophilia B patients analyzing the results of the most important clinical trials. In addition, it will focus on the more recent advances in the production of new FIX molecules aimed at the improvement of the clinical management of such patients.

The first recombinant FVIII produced in human cells--an update on its clinical development programme.

The development of inhibitors and the need for frequent venous access for FVIII injection are major challenges in current haemophilia treatment. Presently available recombinant FVIII (rFVIII) products produced in hamster cell lines are associated with inhibitor formation in up to 32% of previously untreated patients. The new human cell line-derived recombinant human FVIII (Human-cl rhFVIII) protein is the first native, unmodified truly human rFVIII product produced in a human cell line without additive animal proteins. The aim of using a human cell line for the production of rFVIII is the avoidance of non-human epitopes on rFVIII, thereby potentially reducing the rate of inhibitor development, avoiding allergic reactions and allowing personalized prophylaxis with the chance of fewer infusions. Studies to date show that prophylaxis with Human-cl rhFVIII prevents 96% of bleeding events in adults with severe haemophilia A when compared to on-demand treatment. Available pharmacokinetic data with a mean half-life of 17.1 h allow personalized prophylaxis with the chance of fewer infusions. Studies in previously treated children and adults indicate that Human-cl rhFVIII is efficacious and safe in the prevention and treatment of bleeding episodes and that none of the treated patients developed inhibitors or allergic reactions thus far.

Laboratory monitoring of the haemostatic system changes during orthotopic liver transplantation.

INTRODUCTION: In liver diseases, all components of the haemostatic system are changed and the degree of dysfunction is proportional to hepatocellular damage. During the liver transplantation, values of haemostatic parameters show substantial changes, while postoperatively there is a gradual normalisation of the haemostatic system function. OBJECTIVE: The aim was to monitor the changes of the haemostatic system intraoperatively and postoperatively, including the dynamics at which physiological values of parameters are reached after transplantation. METHODS: There were 17 cadaveric transplantations performed at the Clinical Centre of Vojvodina in the period from June 2008 to February 2012. The following parameters were tested: platelets, activated partial thromboplastin, prothrombin and thrombin time, fibrinogen, euglobulin clot lysis time, D-dimer, antithrombin and heparinemia.The results were presented intraoperatively in phases of transplantation, and postoperatively from day 1 to day 7, ending with postoperative day 14. RESULTS: During transplantation, the most pronounced disorders among those observed are: thrombocytopenia (96 +/- 66.1 x 10(9)/L), prolonged activated partial thromboplastin (1.80 +/- 0.8 R), prothrombin (1.59 +/- 0.4 R) and thrombin time (2.03 +/- 1.7 R), hypofibrinogenemia (2.13 +/- 0.5 g/L), hyperfibrinolysis (29 +/- 12.0 min), increase of D-dimer (1393 +/- 1220.4 ng/mL) and decrease of antithrombin (61 +/- 18.0%). Further monitoring after transplantation from postoperative day 1 revealed a gradual normalisation in the values, reaching physiological values for all parameters on postoperative day 14, except for the sustained high value of D-dimer (2606 +/-1055.1 ng/mL). Heparinemia was within the prophylactic range (0.26 +/- 0 IU/mL). CONCLUSION: Thorough monitoring of the haemostatic system parameters in liver transplantations is of great importance, as it enables the use of optimal substitution therapy during and after transplantation, as well as an adequate postoperative thromboprophylaxis. Our study has shown normalisation of investigated laboratory parameters within 7-14 days after transplantation.

Validation of 4% albumin as a diluent in the Bethesda Assay for FVIII inhibitors.

INTRODUCTION: External quality assurance programs show the Nijmegen Bethesda Assay for FVIII inhibitors improves test specificity compared to the Classic Bethesda Assay but its uptake has been slow possibly due to the cost of using FVIII deficient plasma as diluent. This study was conducted to determine if modifying the Nijmegen Bethesda assay by replacement of FVIII deficient plasma with 4% as a diluent would be suitable for for measuring FVIII inhibitors. MATERIALS AND METHODS: The titres of 59 samples from 35 patients with FVIII inhibitors were determined in parallel tests by the Nijmegen Bethesda Assay and and the modified Nijmegen assay. Method reproducibility was assessed on inhibitor-containing samples from seven individuals covering a range of titres from 1-200 Bethesda units/mL. RESULTS: The all-sample geometric mean titre was 6.73 Bethesda units/mL for the Nijmegen Bethesda Assay and 7.54 Bethesda units/mL for the modified Nijmegen assay. No sample was found where a difference in measured titre between methods would have altered clinical management. Agreement was very close in samples with titres less than 2BU/mL. Both assays gave inhibitor titres in external quality assurance samples of close to consensus values. The average between-run coefficients of variation were 8.6% for the Nijmegen Bethesda Assay and 7.9% for the modified Nijmegen assay. CONCLUSIONS: The modified Nijmegen assay using 4% albumin as the sample diluent showed good overall comparability to our existing Nijmegen Bethesda Assay and is substantially more cost-effective, making it a reasonable alternative for measuring FVIII inhibitors.

Coagulation abnormalities in the cirrhotic patient.

The clotting process is a dynamic array of multiple processes which can be described in four phases: platelet plug initiation and formation, clotting process propagation by the coagulation cascade, clotting termination by antithrombotic mechanisms and clot removal by fibrinolysis. The liver plays a central role in each of these phases of clotting process, as it synthesizes the majority of coagulation factors and proteins involved in fibrinolysis as well as thrombopoeitin, which is responsible for platelet production from megakaryocytes. Many pathological processes associated with cirrhosis, such as portal hypertension and endothelial dysfunction, as well as co-morbid conditions, may also alter the coagulation process. Consequently, patients with liver disease have a disturbed balance of procoagulant and anti-coagulant factors which deviates from the normal coagulation cascade. This situation poses an additional problem in the diagnostic and therapeutic approach to this group of patients, since traditional coagulation test may not be reliable for assessing bleeding or thrombotic risk and traditional transfusional strategies may not be applicable in cirrhotic patients. In this article, we review the pathophysiological bases of coagulation abnormalities, in cirrhotic patients, the diagnostic therapeutic strategies to be followed and its impact on the clinical outcome in the cirrhotic patient.

Perioperative haemostatic management of haemophilic mice using normal mouse plasma.

Intense haemostatic interventions are required to avoid bleeding complications when surgical procedures are performed on haemophilia patients. The objective of this study was to establish an appropriate protocol for perioperative haemostatic management of haemophilic mice. We assessed the prophylactic haemostatic effects of normal mouse plasma (NMP) on haemophilia B (HB) mice for both a skin flap procedure and a laparotomy. When 500 µL of NMP was administered to the mice, plasma factor IX (FIX:C) levels peaked at 15.1% immediately after intravenous (IV) administration, at 6.1% 2 h after intraperitoneal (IP) administration and at 2.7% 6 h after subcutaneous administration. Administering 500 µL of NMP via IP or IV 30 min in advance enabled the skin flap procedure to be performed safely without any complications. After the laparotomy procedure, several mice in the IP administration group exhibited lethal bleeding, but all mice survived in the IV administration group. Anti-mouse FIX inhibitors did not develop, even after repetitive administrations of NMP. However, human FIX concentrates, especially plasma-derived concentrates, elicited the anti-human FIX inhibitors. The results show that administering 500 µL of NMP via IV or IP 30 min in advance enables surgical procedures to be safely performed on HB mice, and that IV administration is more desirable than IP if the procedure requires opening of the abdominal wall.

Intensity of factor VIII treatment and inhibitor development in children with severe hemophilia A: the RODIN study.

The objective of this study was to examine the association of the intensity of treatment, ranging from high-dose intensive factor VIII (FVIII) treatment to prophylactic treatment, with the inhibitor incidence among previously untreated patients with severe hemophilia A. This cohort study aimed to include consecutive patients with a FVIII activity < 0.01 IU/mL, born between 2000 and 2010, and observed during their first 75 FVIII exposure days. Intensive FVIII treatment of hemorrhages or surgery at the start of treatment was associated with an increased inhibitor risk (adjusted hazard ratio [aHR], 2.0; 95% confidence interval [CI], 1.3-3.0). High-dose FVIII treatment was associated with a higher inhibitor risk than low-dose FVIII treatment (aHR, 2.3; 95% CI, 1.0-4.8). Prophylaxis was only associated with a decreased overall inhibitor incidence after 20 exposure days of FVIII. The association with prophylaxis was more pronounced in patients with low-risk F8 genotypes than in patients with high-risk F8 genotypes (aHR, 0.61, 95% CI, 0.19-2.0 and aHR, 0.85, 95% CI, 0.51-1.4, respectively). In conclusion, our findings suggest that in previously untreated patients with severe hemophilia A, high-dosed intensive FVIII treatment increases inhibitor risk and prophylactic FVIII treatment decreases inhibitor risk, especially in patients with low-risk F8 mutations.

Residues of the 39-loop restrict the plasma inhibitor specificity of factor IXa.

The two plasma inhibitors, protein Z-dependent protease inhibitor (ZPI) and tissue factor pathway inhibitor (TFPI), effectively inhibit the activity of activated factor X (FXa); however, neither inhibitor exhibits any reactivity with the homologous protease activated factor IX (FIXa). In this study, we investigated the molecular basis for the lack of reactivity of FIXa with these plasma inhibitors and discovered that unique structural features within residues of the 39-loop are responsible for restricting the inhibitor specificity of FIXa. This loop in FXa is highly acidic and contains three Glu residues at positions 36, 37, and 39. On the other hand, the loop is shorter by one residue in FIXa (residue 37 is missing), and it contains a Lys and an Asp at positions 36 and 39, respectively. We discovered that replacing residues of the 39-loop (residues 31-41) of FIXa with corresponding residues of FXa renders the FIXa chimera susceptible to inactivation by both ZPI and TFPI. Thus, the inactivation rate of the FIXa chimera by ZPI in the presence of protein Z (PZ), negatively charged membrane vesicles, and calcium ions approached the same diffusion-limited rate (>10(7) m(-1) s(-1)) that has been observed for the PZ-dependent inhibition of FXa by ZPI. Interestingly, sequence alignments indicated that, similar to FXa, residue 36 is a Glu in both mouse and bovine FIXa and that both proteases are also susceptible to inhibition by the PZ-ZPI complex. These results suggest that structural features within residues of the 39-loop contribute to the resistance of FIXa to inhibition by plasma inhibitors ZPI and TFPI.

New fundamentals in hemostasis.

Hemostasis encompasses the tightly regulated processes of blood clotting, platelet activation, and vascular repair. After wounding, the hemostatic system engages a plethora of vascular and extravascular receptors that act in concert with blood components to seal off the damage inflicted to the vasculature and the surrounding tissue. The first important component that contributes to hemostasis is the coagulation system, while the second important component starts with platelet activation, which not only contributes to the hemostatic plug, but also accelerates the coagulation system. Eventually, coagulation and platelet activation are switched off by blood-borne inhibitors and proteolytic feedback loops. This review summarizes new concepts of activation of proteases that regulate coagulation and anticoagulation, to give rise to transient thrombin generation and fibrin clot formation. It further speculates on the (patho)physiological roles of intra- and extravascular receptors that operate in response to these proteases. Furthermore, this review provides a new framework for understanding how signaling and adhesive interactions between endothelial cells, leukocytes, and platelets can regulate thrombus formation and modulate the coagulation process. Now that the key molecular players of coagulation and platelet activation have become clear, and their complex interactions with the vessel wall have been mapped out, we can also better speculate on the causes of thrombosis-related angiopathies.

Factor VIIa binding to endothelial cell protein C receptor: differences between mouse and human systems.

Recent in vitro studies have shown that the zymogen and activated form of factor (F)VII bind to endothelial cell protein C receptor (EPCR). At present, there is no evidence that FVIIa binds to EPCR on vascular endothelium in vivo in the presence of circulating protein C, a primary ligand for EPCR. The present study was carried out to investigate the interaction of murine and human ligands with murine EPCR both in vivo and in vitro . Measurement of endogenous plasma levels of FVII in wild-type, EPCR-deficient and EPCR-over expressing mice showed slightly lower levels of FVII in EPCR-over expressing mice. However, infusion of high concentrations of competing ligands, either human APCi or FVIIai, to EPCR-over expressing mice failed to increase plasma levels of mouse FVII whereas they increased the plasma levels of protein C by two- to three-fold. Examining the association of exogenously administered mouse FVIIa or human FVIIa by immunohistochemistry revealed that human, but not murine FVIIa, binds to the murine endothelium in an EPCR-dependent manner. In vitro binding studies performed using surface plasmon resonance and endothelial cells revealed that murine FVIIa binds murine EPCR negligibly. Human FVIIa binding to EPCR, particularly to mouse EPCR, is markedly enhanced by availability of Mg2+ ions. In summary, our data show that murine FVIIa binds poorly to murine EPCR, whereas human FVIIa binds efficiently to both murine and human EPCR. Our data suggest that one should consider the use of human FVIIa in mouse models to investigate the significance of FVIIa and EPCR interaction.