Vaccine-induced immune thrombotic thrombocytopenia (VITT) is a complication of adenoviral-based vaccine against SARS-CoV-2 due to prothrombotic immunoglobulin (Ig) G antibodies to platelet factor 4 ...(PF4) and may be difficult to distinguish from heparin-induced thrombocytopenia (HIT) in patients treated with heparin.
We assessed the usefulness of competitive anti-PF4 enzyme immunoassays (EIAs) in this context.
The ability of F(ab′)2 fragments of 1E12, 1C12, and 2E1, 3 monoclonal anti-PF4 antibodies, to inhibit the binding of human VITT or HIT antibodies to PF4 was evaluated using EIAs. Alanine-scanning mutagenesis was performed to define the amino acids involved in the interactions between the monoclonal antibodies and PF4.
A strong inhibition of VITT IgG binding to PF4 was measured with 1E12 (median inhibition, 93%; n = 8), whereas it had no effect on the binding of HIT antibodies (median, 6%; n = 8). In contrast, 1C12 and 2E1 inhibited VITT (median, 74% and 76%, respectively) and HIT antibodies (median, 68% and 53%, respectively) binding to PF4. When a competitive anti-PF4 EIA was performed with 1E12 for 19 additional VITT samples, it strongly inhibited IgG binding to PF4, except for 1 patient, who had actually developed HIT according to the clinical history. Epitope mapping showed that 1E12 interacts with 5 key amino acids on PF4, of which 4 are also required for the binding of human VITT antibodies, thus explaining the competitive inhibition.
A simple competitive anti-PF4 EIA with 1E12 could help confirm VITT diagnosis and distinguish it from HIT in patients when both diagnoses are possible.
Background: The use of extending half-life (EHL) FVIII or FIX products is today a current strategy in Hemophilia A (HA) patients for improving prophylaxis and reducing the number of IV injections. Fc ...fusion technology is based on the use of the neonatal Fc receptor and endogenous Fc recycling pathway, thereby prolonging the half-life (T1/2) of rFVIII-Fc. A single dose phase 1/2 pharmacokinetic (PK) study performed in 16 severe HA patients demonstrated a prolonged T ½ of rFVIII-Fc equal to 18.8 hours (mean) compared to 12.2 hours with one conventional rFVIII (Malhangu et al. Blood 2014).
The aim of the present study was to analyze PK data collected with Elocta® in “real life” i.e. in a large cohort of patients treated in 13 different French hemophilia care centers, and results were compared to those obtained with conventional FVIII, when available. Importantly, this study was performed without any involvement of Sobi, the pharmaceutical company that provides Elocta® in France.
Patients and methods: 113 severe Hemophilia A (HA) patients with the following characteristics were included: mean age 30 years (range 3 - 70); weight 65 Kg (17-125); total FVIII-Fc dose injected 2650 IU (500-5750); FVIII-Fc IU/Kg: 41 (25 - 59); VWF Ag 98% (41-279). The FVIII recovery (R) was calculated as follows: (body weight (Kg) x observed increased in FVIII (%))/administered dose (IU/Kg). The T1/2 was calculated with the following formula: Ln2/((Ln FVIII% T1 - Ln FVIII%T2)/T2 - T1)), with T1 ≥ 4 hours and T2 ≥ 24 hours.
Results were compared to those performed with conventional FVIII (non EHL-FVIII) in 48 patients (Advate® n = 14, Refacto® n = 2, Helixate®/Kogenate®/Kovaltry® n = 29, Factane® n = 3)
Results: rFVIII-Fc activity measured by one stage clotting assay (OSA) was 20% lower than those obtained with chromogenic assay (CSA) in samples with FVIII levels higher than 20%, but this difference was lower than 10% when FVIII levels < 20%. Therefore, rFVIII-Fc recovery (R) always appeared lower when measured with OSA (Mean 2.38, range 1.33 - 5.7) than with CSA (mean 2.82, ranges 1.35 - 5.5) (p < 0.0001). No correlation was found between this recovery and age, weight, injected doses or VWF Ag levels. Mean T1/2 measured with rFVIII-Fc equaled 15 hours whatever the measurement method used (OSA or CSA), and was strongly correlated with vWFAg levels (R2 = 0.57). Using OSA, significantly lower recovery (1.86 vs. 2.49, p = 0.0002) and T1/2 values (11.75 vs. 15.13 hours, p = 0.0004) were measured in children (< 10 years, n = 19) compared to adults. Similar differences were evidenced with data obtained by CSA (recovery : 2.26 vs. 2.93, p = 0.0009 and T1/2 : 11.4 vs. 15.6 h, p = 0.004, n = 14 children < 10 years).
PK parameters of FVIII-Fc were compared to those obtained with non EHL-FVIII (rFVIII or pdFVIII) in 47 patients (mean T1/2 equal to 10.0 hours; range 5.3 - 21.2), and half-lives of these two categories of products were well correlated (r2 = 0.57). However, the apparent benefit provided by FVIII-Fc was variable from one patient to another, with a mean T1/2 rFVIII-Fc / T1/2 FVIII ratio ranging from 0.6 to 2.4 (mean 1.4). Interestingly, the increase in T1/2 with FVIII-Fc was lower than 20% only in patients previously treated with BHK-derived rFVIII i.e. Helixate®/Kogenate®/ Kowaltry® (n=10). Whatever the FVIII injected (FVIII-Fc or other non EHL-FVIII), the T1/2 measured was also strongly correlated to vWF levels, which were significantly lower in patients for whom the mean T1/2 rFVIII Fc / T1/2 FVIII ratio was > 1.3 (mean 79% vs 116% in the others, p=0.017).
Conclusion: This study is the first to report PK data obtained with rFVIII-Fc (Elocta®) in a large group of HA patients. Our results confirm the benefit of rFVIII-Fc in most HA patients, adults or children, but also emphasize the impact of vWF on half-life of rFVIII-Fc or conventional non EHL-FVIII. Indeed, the benefit of rFVIII-Fc clearly appears higher in patients with lower vWF levels, with a more significant prolongation of T1/2.
No relevant conflicts of interest to declare.
The use of enhanced half‐life (EHL) FVIII has improved the quality of prophylaxis in haemophilia A, but with a benefit that may vary from one patient to another. We analysed the pharmacokinetic data ...obtained with efmoroctocog alfa (rFVIII‐Fc) in 114 patients and, in 47 cases, compared them to those previously measured with non‐EHL FVIII. The in vivo recovery (IVR) of rFVIII‐Fc measured with one stage clotting assay (OSA) and chromogenic assay (CSA) was 2.2 and 2.8 IU/mL per IU/kg, respectively. The median half‐life (T1/2) of rFVIII‐Fc was 14.5 hours whatever the FVIII:C assay used, but variable and correlated with preinfusion VWF:Ag levels (r = .76). Both IVR and T1/2 were lower in patients under 12 years old (2.4 IU/mL per IU/kg and 11.1 hours, respectively; CSA). PK study of rFVIII‐Fc vs non‐EHL FVIII showed a T1/2 ratio of 1.4 in favour of rFVIII‐Fc, regardless of the patient's age. However the relative increase in T1/2 with rFVIII‐Fc was lower than 30% in one‐third of patients evaluated, particularly when the previous FVIII administered was a BHK‐derived product. This study therefore suggests that analysis of individual PK profile in response to a specific FVIII concentrate is potentially useful before a switch in haemophilia A patients.
Introduction:
Cerebral venous thrombosis (CVT) is a rare disease with highly variable clinical presentation and outcome. Etiological assessment may be negative. The clinical and radiological ...presentation and evolution can be highly variable. The mechanisms involved in this variability remain unknown.
Objective:
The aim of this multicenter French study registered on ClinicalTrials.gov (NCT02013635) was therefore to prospectively recruit a cohort of patients with cerebral venous thrombosis (FPCCVT) in order to study thrombin generation and clot degradation, and to evaluate their influence on clinical radiological characteristics. The first part of the study was to compare our cohort with a reference cohort.
Methods:
This prospective, multicenter, French study was conducted from July 2011 to September 2016. Consecutive patients (aged >15 years) referred to the stroke units of 21 French centers and who had a diagnosis of symptomatic CVT were included. All patients gave their written informed consent. The diagnosis of CVT had to be confirmed by imaging. Clinical, radiological, biological, and etiological characteristics were recorded at baseline, at acute phase, at 3 months and at last follow-up visit. Thrombophilia screening and the choice of treatment were performed by the attending physician. All data were compared with data from the International Study on CVT published by Ferro et al.
Results:
Two hundred thirty-one patients were included: 117 (50.6%) had isolated intracranial hypertension, 96 (41.5%) had focal syndrome. During hospitalization, 229 (99.1%) patients received anticoagulant treatment. Median length of hospital stay was 10 days. Five patients died during hospitalization (2.2%). At 3 months, 216 patients (97.0%) had follow-up with neurological data based on an outpatient visit. The mean duration of antithrombotic treatment was 9 months, and the mean time to last follow-up was 10.5 months. At the end of follow-up, eight patients had died, and 26 patients were lost to follow-up. At least one risk factor was identified in 200 patients.
Conclusions:
We demonstrated that the FPCCVT cohort had radiological, biological, and etiological characteristics similar to the historical ISCVT cohort. Nevertheless, the initial clinical presentation was less severe in our study probably due to an improvement in diagnostic methods between the two studies.
Replacement therapy with plasma‐derived or recombinant FVIII and FIX (pdFVIII/pdFIX or rFVIII/rFIX) concentrates is the standard of treatment in patients with haemophilia A and B, respectively. ...Measurement of factor VIII (FVIII:C) or factor IX (FIX:C) levels can be done by one‐stage clotting assay (OSA) or chromogenic substrate assay (CSA). The French study group on the Biology of Hemorrhagic Diseases (a collaborative group of the GFHT and MHEMO network) presents a literature review and proposals for the monitoring of FVIII:C and FIX:C levels in treated haemophilia A and B patients, respectively. The use of CSA is recommended for the monitoring of patients treated with pdFVIII or rFVIII including extended half‐life (EHL) rFVIII. Except for rFVIII‐Fc, great caution is required when measuring FVIII:C levels by OSA in patients substituted by EHL‐rFVIII. The OSA is recommended for the monitoring of patients treated with pdFIX or rFIX. Large discordances in the FIX:C levels measured for extended half‐life rFIX (EHL‐rFIX), depending on the method and reagents used, must lead to great attention when OSA is used for measuring FIX:C levels in patients substituted by EHL‐rFIX. Data of most of recent studies, obtained with spiked plasmas, deserve to be confirmed in plasma samples of treated patients.
•JAK2V617F mutation contributes to hemorrhagic lesions and to mortality in an experimental model of cerebral venous thrombosis.•JAK2V617F mutation exacerbates thromboinflammatory response during ...cerebral venous thrombosis.
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Cerebral venous sinus thrombosis (CVST) is an uncommon venous thromboembolic event accounting for <1% of strokes resulting in brain parenchymal injuries. JAK2V617F mutation, the most frequent driving mutation of myeloproliferative neoplasms, has been reported to be associated with worse clinical outcomes in patients with CVST. We investigated whether hematopoietic JAK2V617F expression predisposes to specific pathophysiological processes and/or worse prognosis after CVST. Using an in vivo mouse model of CVST, we analyzed clinical, biological, and imaging outcomes in mice with hematopoietic-restricted Jak2V617F expression, compared with wild-type Jak2 mice. In parallel, we studied a human cohort of JAK2V617F-positive or -negative CVST. Early after CVST, mice with hematopoietic Jak2V617F expression had increased adhesion of platelets and neutrophils in cerebral veins located in the vicinity of CVST. On day 1, Jak2V617F mice had a worse outcome characterized by significantly more frequent and severe intracranial hemorrhages (ICHs) and higher mortality rates. Peripheral neutrophil activation was enhanced, as indicated by higher circulating platelet–neutrophil aggregates, upregulated CD11b expression, and higher myeloperoxydase plasma level. Concurrently, immunohistological and brain homogenate analysis showed higher neutrophil infiltration and increased blood-brain barrier disruption. Similarly, patients with JAK2V617F-positive CVST tended to present higher thrombotic burden and had significantly higher systemic immune-inflammation index, a systemic thromboinflammatory marker, than patients who were JAK2V617F-negative. In mice with CVST, our study corroborates that Jak2V617F mutation leads to a specific pattern including increased thrombotic burden, ICH, and mortality. The exacerbated thromboinflammatory response, observed both in mice and patients positive for JAK2V617F, could contribute to hemorrhagic complications.
Laboratories of Hematology of Centre Hospitalier Universitaire, Grenoble, France. pmossuz@chu-grenoble.fr
BACKGROUND AND OBJECTIVES: The diagnosis of polycythemia vera (PV) is based on clinical and ...biological criteria defined by either the Polycythemia Vera Study Group (PVSG) or the World Health Organization (WHO). Both the PVSG and WHO PV criteria have proved helpful and are extensively used, yet diagnostic strategies and scheduling of biological investigations vary. We assessed the value of measuring serum erythropoietin (Epo) as a first intention diagnostic test in patients with absolute erythrocytosis (AE). DESIGN AND METHODS: Serum and bone marrow (BM) samples of 241 patients with a suspicion of erythrocytosis were collected in 8 hospital centers. One hundred and ninety had an absolute erythrocytosis (116 had PV, 66 had secondary erythrocytosis and 4 had idiopathic erythrocytosis). Serum Epo was assayed (ELISA) in 186. Statistical analysis (ROC curves) was used to define serum Epo thresholds that were specific for PV and secondary erythrocytosis and to analyze the diagnostic value of a low or high serum Epo level. RESULTS: A large majority of PV patients (87% or 101/116) had a serum Epo level below the normal range in healthy patients (3.3 IU/L), giving this value a specificity of 97% with a 97.8% positive predictive value for the diagnosis of PV. Statistical analysis (ROC curves) defined two thresholds allowing a specific and direct diagnosis of 65.6% (65/99) of untreated PV (Epo
Cerebral venous sinus thrombosis (CVST) is a rare disease with highly variable clinical presentation and outcomes. Clinical studies suggest a role of inflammation and coagulation in CVST outcomes. ...The aim of this study was to investigate the association of inflammation and hypercoagulability biomarkers with CVST clinical manifestations and prognosis.
This prospective multicenter study was conducted from July 2011 to September 2016. Consecutive patients referred to 21 French stroke units and who had a diagnosis of symptomatic CVST were included. High-sensitivity C-reactive protein (hs-CRP), neutrophil-to-lymphocyte ratio (NLR), D-dimer, and thrombin generation using calibrated automated thrombogram system were measured at different time points until 1 month after anticoagulant therapy discontinuation.
Two hundred thirty-one patients were included. Eight patients died, of whom 5 during hospitalization. The day 0 hs-CRP levels, NLR, and D-dimer were higher in patients with initial consciousness disturbance than in those without (hs-CRP: 10.2 mg/L 3.6-25.5 vs 23.7 mg/L 4.8-60.0, respectively; NLR: 3.51 2.15-5.88 vs 4.78 3.10-9.59, respectively; D-dimer: 950 μg/L 520-2075 vs 1220 μg/L 950-2445, respectively). Patients with ischemic parenchymal lesions (n = 31) had a higher endogenous thrombin potential5pM than those with hemorrhagic parenchymal lesions (n = 31): 2025 nM min (1646-2441) vs 1629 nM min (1371-2090), respectively (P = .0082). Using unadjusted logistic regression with values >75th percentile, day 0 hs-CRP levels of >29.7 mg/L (odds ratio, 10.76 1.55-140.4; P = .037) and day 5 D-dimer levels of >1060 mg/L (odds ratio, 14.63 2.28-179.9; P = .010) were associated with death occurrence.
Two widely available biomarkers measured upon admission, especially hs-CRP, could help predict bad prognosis in CVST in addition to patient characteristics. These results need to be validated in other cohorts.
•There are several clinical presentations of cerebral venous sinus thrombosis (CVST).•Association between inflammation and CVST severity has been observed.•D-dimer and C-reactive protein predicted bad prognosis in CVST.•Elevated endogenous thrombin potential on admission was associated with ischemic parenchymal lesions.
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