No F8 genetic abnormality is detected in approximately 1% to 2% of patients with severe hemophilia A (HA) using conventional genetic approaches. In these patients, deep intronic variation or F8 ...disrupting genomic rearrangement could be causal.
The study aimed to identify the causal variation in families with a history of severe HA for whom genetic investigations failed.
We performed whole F8 gene sequencing in 8 propositi. Genomic rearrangements were confirmed by Sanger sequencing of breakpoint junctions and/or quantitative polymerase chain reaction.
A structural variant disrupting F8 was found in each propositus, so that all the 815 families with a history of severe HA registered in our laboratory received a conclusive genetic diagnosis. These structural variants consisted of 3 balanced inversions, 3 large insertions of gained regions, and 1 retrotransposition of a mobile element. The 3 inversions were 105 Mb, 1.97 Mb, and 0.362 Mb in size. Among the insertions of gained regions, one corresponded to the insertion of a 34 kb gained region from chromosome 6q27 in F8 intron 6, another was the insertion of a 447 kb duplicated region from chromosome 9p22.1 in F8 intron 14, and the last one was the insertion of an Xq28 349 kb gained in F8 intron 5.
All the genetically unsolved cases of severe HA in this cohort were due to structural variants disrupting F8. This study highlights the effectiveness of whole F8 sequencing to improve the molecular diagnosis of HA when the conventional approach fails.
Adeno-associated virus (AAV)-mediated gene therapy may provide durable protection from bleeding events and reduce treatment burden for people with hemophilia A (HA). However, pre-existing immunity ...against AAV may limit transduction efficiency and hence treatment success. Global data on the prevalence of AAV serotypes are limited. In this global, prospective, noninterventional study, we determined the prevalence of pre-existing immunity against AAV2, AAV5, AAV6, AAV8, and AAVrh10 among people ≥12 years of age with HA and residual FVIII levels ≤2 IU/dL. Antibodies against each serotype were detected using validated, electrochemiluminescent-based enzyme-linked immunosorbent assays. To evaluate changes in antibody titers over time, 20% of participants were retested at 3 and 6 months. In total, 546 participants with HA were enrolled at 19 sites in 9 countries. Mean (standard deviation) age at enrollment was 36.0 (14.87) years, including 12.5% younger than 18 years, and 20.0% 50 years of age and older. On day 1, global seroprevalence was 58.5% for AAV2, 34.8% for AAV5, 48.7% for AAV6, 45.6% for AAV8, and 46.0% for AAVrh10. Considerable geographic variability was observed in the prevalence of pre-existing antibodies against each serotype, but AAV5 consistently had the lowest seroprevalence across the countries studied. AAV5 seropositivity rates were 51.8% in South Africa (
= 56), 46.2% in Russia (
= 91), 40% in Italy (
= 20), 37.2% in France (
= 86), 26.8% in the United States (
= 71), 26.9% in Brazil (
= 26), 28.1% in Germany (
= 89), 29.8% in Japan (
= 84), and 5.9% in the United Kingdom (
= 17). For all serotypes, seropositivity tended to increase with age. Serostatus and antibody titer were generally stable over the 6-month sampling period. As clinical trials of AAV-mediated gene therapies progress, data on the natural prevalence of antibodies against various AAV serotypes may become increasingly important.
Introduction
Data on failure to identify the molecular mechanism underlying FXI deficiency by Sanger analysis and the contribution of gene segment deletions are almost inexistent.
Aims and methods
...Prospective and retrospective analysis was conducted on FXI‐deficient patients’ DNA via Next Generation Sequencing (NGS), or Sanger sequencing and Multiplex Probe Ligation‐dependent Assay (MLPA) to detect cryptic causative gene variants or gene segment deletions.
Results
Sanger analysis or NGS enabled us to identify six severe and one partial (median activity 41 IU/dl) FXI deficient index cases with deletions encompassing exons 11–15, the whole gene, or both. After Sanger sequencing, retrospective evaluation using MLPA detected seven additional deletion cases in apparently homozygous cases in non‐consanguineous families, or in previously unsolved FXI‐deficiency cases. Among the 504 index cases with a complete genetic investigation (Sanger/MLPA, or NGS), 23 remained unsolved (no abnormality found n = 14 or rare intronic variants currently under investigation, n = 9). In the 481 solved cases (95% efficiency), we identified F11 gene‐deleted patients (14 cases; 2.9%). Among these, whole gene deletion accounted for four heterozygous cases, exons 11–15 deletion for five heterozygous and three homozygous ones, while compound heterozygous deletion and isolated exon 12 deletion accounted for one case each.
Conclusion
Given the high incidence of deletions in our population (2.9%), MLPA (or NGS with a reliable bioinformatic pipeline) should be systematically performed for unsolved FXI deficiencies or apparently homozygous cases in non‐consanguineous families.
Eftrenonacog-alfa is a recombinant factor IX-Fc fusion protein increasingly prescribed in hemophilia B patients. We aimed to assess its pharmacodynamics (PD) in real-life setting via FIX activity ...measurement and thrombin generation assay (TGA).
Sixty samples from 15 severe hemophilia B treated patients were collected at different time points. FIX activity was measured using product-specific one-stage clotting assay (reference method) and two chromogenic assays (CSA) (Biophen FIX and Rox FIX). TGA was triggered with 1 pM tissue factor. Five parameters were analyzed: lag time (LT), time to peak (TTP), peak height (PH), endogenous thrombin potential (ETP), and velocity. PD models were built to characterize their relationships with FIX activity, using mixed effects models.
Mean trough FIX level was estimated at 4.64 (±1.50) IU/dl with a recovery at 0.78 (±0.16) IU/dl per 1 IU/kg injected dose. FIX activity ranged between 1 and 86 IU/dl with 21.5 IU/dl median value. Biophen FIX and Rox FIX allowed reliable measurements except in samples with FIX <20 IU/dl in which values were underestimated (delta >30%). PD models revealed that velocity was the most sensitive TGA parameter to FIX activity followed by PH, ETP, TTP and finally LT. Following FIX activity peak after eftrenonacog-alfa injection, velocity decreased first, followed by PH then ETP.
Both CSA failed to accurately measure FIX in severe hemophilia B patients receiving eftrenonacog-alfa throughout the measuring range. TGA could be an additional valuable tool to evaluate hemostasis balance in treated patients.
•FIX activity measurement in eftrenonacog-α spiked sample varied according to reagent.•We reported the first PD study of eftrenonacog-α in substituted severe hemophiliacs.•Chromogenic assays failed to accurately measure low FIX activity (<20 IU/dl).•TGA could be a valuable tool to evaluate hemostasis balance in treated patients.
In the present study, we have analyzed the T cell receptor (TCR) repertoires of CD4+ T cells isolated from peripheral blood of 10 inhibitor-positive patients with severe hemophilia A. The ...distribution of complementarity determining region (CDR3) lengths of the beta chain of the TCRs was analyzed by spectratyping prior to and following in vitro stimulation of the cells with human factor VIII (FVIII). The repertoires of CD4+ T cells of patients were perturbed when compared to those of healthy blood donors. The perturbations of T cell repertoires were heterogeneous among patients with respect to the number and the nature of V-beta (BV) families that exhibited expansion following incubation with FVIII. Some patients showed alterations in one or two BV families, others exhibited more perturbed repertoires affecting 5 to 8 of the 14 BV families tested. Alterations of BV2, BV5 and/or BV9 were consistently found after incubation of CD4+ T cells in the presence of FVIII in 80% of the patients. These findings indicate that the presence of FVIII inhibitors in patients with severe hemophilia A is associated with measurable perturbations of the CD4+ T cell repertoire that results from oligoclonal expansion of FVIII-specific cells and may be relevant for the design of strategies aimed at modulating the anti-FVIII immune responses by T cell-targeted therapy
To evaluate the applicability and compliance with guidelines for early initiation of long-term prophylaxis in infants with severe hemophilia A and to identify factors associated with guideline ...compliance.
This real-world, prospective, multicenter, population-based FranceCoag study included almost all French boys with severe hemophilia A, born between 2000 and 2009 (ie, after guideline implementation).
We included 333 boys in the study cohort. The cumulative incidence of long-term prophylaxis use was 61.2% at 3 years of age vs 9.5% in a historical cohort of 39 boys born in 1996 (ie, before guideline implementation). The guidelines were not applicable in 23.1% of patients due to an early intracranial bleeding or inhibitor development. Long-term prophylaxis was delayed in 10.8% of patients. In the multivariate analysis, 2 variables were significantly associated with “timely long-term prophylaxis” as compared with “delayed long-term prophylaxis”: hemophilia treating center location in the southern regions of France (OR 23.6, 95% CI 1.9-286.7, P = .013 vs Paris area) and older age at long-term prophylaxis indication (OR 7.2 for each additional year, 95% CI 1.2-43.2, P = .031). Long-term prophylaxis anticipation was observed in 39.0% of patients. Earlier birth year (OR 0.5, 95% CI 0.3-0.8, P = .010 for birth years 2005-2009 vs 2000-2004) and age at first factor replacement (OR 1.9 for each additional year, 95% CI 1.2-3.0, P = .005) were significantly associated with “long-term prophylaxis guideline compliance” vs “long-term prophylaxis anticipation.”
This study suggests that long-term prophylaxis guidelines are associated with increased long-term prophylaxis use. However, early initiation of long-term prophylaxis remains a challenge.
Introduction
Health of people with severe haemophilia (PwSH) improves thanks to the advancements in haemophilia care, giving them more opportunities in occupational integration. However, there is ...little literature on the occupational integration of PwSH.
Objectives
The main objective of our study was to assess the occupational integration of PwSH and to compare it with that of the general population. The secondary objective was to study the association between individual characteristics (sociodemographic, clinical and psycho‐behavioural) and occupational integration of PwSH.
Methods
A multicentre, non‐interventional, cross‐sectional study was conducted in 2018–2020 on PwSH, aged over 18 and under 65 years and included in the FranceCoag registry. Measurements included indicators of occupational integration, sociodemographic, clinical and psycho‐behavioural characteristics. The indicators of occupational integration were compared with those of the general population, using indirect standardization. The data of the general population were available from the National Institute of Statistics and Economic Studies (INSEE). Determinants of occupational integration were explored using structural equation modelling.
Results
Of 1262 eligible people, 588 were included. PwSH had a lower employment rate than the general population (standardized ratio, .85; 95% CI, .77–.94). There were more PwSH at tertiary education level than expected (standardized ratio, 1.38; 95% CI, 1.17–1.61). HIV infection, poor physical health and mental health concerns were associated with a higher risk of unemployment in PwSH.
Conclusion
Employment rate of PwSH is lower than that of the general population despite their higher education level. Target interventions focusing on determinants of difficult occupational integration could be helpful for PwSH.
Hemophilia A is an X chromosome-linked recessive disorder resulting in defective or deficient factor VIII (FVIII) molecules, which, in its severe form, is a life-threatening and crippling hemorrhagic ...disease. Infusion of homologous FVIII to patients with severe hemophilia A results, in 25% of patients, in the emergence of alloantibodies against FVIII (inhibitors)( ref. 1) that inhibit FVIII procoagulant activity by steric hindrance of the interaction of FVIII either with stabilizing molecules, with molecules essential for its activity or with activating molecules. Here, we report on the proteolysis of FVIII by alloantibodies of two patients with severe hemophilia A, demonstrating a previously unknown mechanism by which FVIII inhibitors may prevent the pro-coagulant function of FVIII. The kinetic parameters of FVIII hydrolysis indicate a functional role for the catalytic immune response in the inactivation of FVIII in vivo. The characterization of alloantibodies against FVIII as site-specific proteases may provide new approaches to the treatment of FVIII inhibitors.
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