scholarly journals Liver-directed lentiviral gene therapy corrects hemophilia A mice and achieves normal-range factor VIII activity in non-human primates

2021 ◽  
Author(s):  
Michela Milani ◽  
Cesare Canepari ◽  
Tongyao Liu ◽  
Mauro Biffi ◽  
Fabio Russo ◽  
...  
Keyword(s):  
Gene Therapy ◽  
Factor Viii ◽  
Neutralizing Antibodies ◽  
Hemophilia A ◽  
Coagulation Factor ◽  
Therapeutic Benefit ◽  
Clotting Factor ◽  
Normal Range ◽  
Fviii Activity ◽  
Liver Gene

Abstract Liver gene therapy with adeno-associated viral (AAV) vectors delivering a clotting factor transgene into hepatocytes has shown multi-year therapeutic benefit in adults with hemophilia. However, anti-AAV pre-existing immunity and the mostly episomal nature of AAV vectors, currently challenges application of AAV-vector mediated liver gene therapy to people with anti-AAV neutralizing antibodies and young pediatric patients. We have developed lentiviral vectors (LV), which integrate in the host cell genome, which achieve stable and efficient liver gene transfer in mice, dogs and non-human primates (NHP), by intravenous (i.v.) delivery. Here we show long-term coagulation factor VIII (FVIII) activity and restoration of hemostasis, by LV i.v. gene therapy to newborn and adult hemophilia A mice and normal-range FVIII activity in NHP, paving the way for potential clinical application.

Multiyear therapeutic benefit of AAV serotypes 2, 6, and 8 delivering factor VIII to hemophilia A mice and dogs

Blood ◽  
2006 ◽  
Vol 108 (1) ◽  
pp. 107-115 ◽  
Author(s):  
Haiyan Jiang ◽  
David Lillicrap ◽  
Susannah Patarroyo-White ◽  
Tongyao Liu ◽  
Xiaobing Qian ◽  
...  
Keyword(s):  
Factor Viii ◽  
Neutralizing Antibodies ◽  
Hemophilia A ◽  
Coagulation Factor ◽  
Canine Model ◽  
Therapeutic Benefit ◽  
Efficacy And Safety ◽  
Spontaneous Bleeding ◽  
Efficient Gene ◽  
Fviii Activity

Hemophilia A, a deficiency of functional coagulation factor VIII (FVIII), is treated via protein replacement therapy. Restoring 1% to 5% of normal blood FVIII activity prevents spontaneous bleeding, making the disease an attractive gene therapy target. Previously, we have demonstrated short-term activity of a liver-specific AAV2 vector expressing canine B-domain-deleted FVIII (cFVIII) in a hemophilia canine model. Here, we report the long-term efficacy and safety of AAV-cFVIII vectors of serotypes 2, 5, 6, and 8 in both hemophilia A mice and dogs. AAV6-cFVIII and AAV8-cFVIII restored physiologic levels of plasma FVIII activity in hemophilia A mice. The improved efficacy is attributed to more efficient gene transfer in liver compared with AAV2 and AAV5. However, supraphysiologic cFVIII levels correlated with the formation of cFVIII-neutralizing antibodies in these mice. Of importance, hemophilia A dogs that received AAV2-cFVIII, AAV6-cFVIII, and AAV8-cFVIII have persistently expressed therapeutic levels of FVIII, without antibody formation or other toxicities, for more than 3 years. However, liver transduction efficiencies are similar between AAV2, AAV6, and AAV8 serotypes in hemophilia A dogs, in contrast to mice. In summary, this is the first report demonstrating multiyear therapeutic efficacy and safety of multiple AAV-cFVIII vectors in hemophilia A dogs and provides the basis for human clinical studies. (Blood. 2006;108:107-115)

scholarly journals Eradication of neutralizing antibodies to factor VIII in canine hemophilia A after liver gene therapy

Blood ◽  
2010 ◽  
Vol 116 (26) ◽  
pp. 5842-5848 ◽  
Author(s):  
Jonathan D. Finn ◽  
Margareth C. Ozelo ◽  
Denise E. Sabatino ◽  
Helen W. G. Franck ◽  
Elizabeth P. Merricks ◽  
...  
Keyword(s):  
Gene Therapy ◽  
Factor Viii ◽  
Neutralizing Antibodies ◽  
Viral Vectors ◽  
Hemophilia A ◽  
Major Complication ◽  
Complete Disappearance ◽  
Anamnestic Response ◽  
Endogenous Expression ◽  
Liver Gene

Abstract Inhibitory antibodies to factor VIII (FVIII) are a major complication in the treatment of hemophilia A, affecting approximately 20% to 30% of patients. Current treatment for inhibitors is based on long-term, daily injections of large amounts of FVIII protein. Liver-directed gene therapy has been used to induce antigen-specific tolerance, but there are no data in hemophilic animals with pre-existing inhibitors. To determine whether sustained endogenous expression of FVIII could eradicate inhibitors, we injected adeno-associated viral vectors encoding canine FVIII (cFVIII) in 2 strains of inhibitor hemophilia A dogs. In 3 dogs, a transient increase in inhibitor titers (up to 7 Bethesda Units [BU]) at 2 weeks was followed by continuous decline to complete disappearance within 4-5 weeks. Subsequently, an increase in cFVIII levels (1.5%-8%), a shortening of clotting times, and a reduction (> 90%) of bleeding episodes were observed. Immune tolerance was confirmed by lack of antibody formation after repeated challenges with cFVIII protein and normal protein half-life. A fourth dog exhibited a strong early anamnestic response (216 BU), with slow decline to 0.8 BU and cFVIII antigen detection by 18 months after vector delivery. These data suggest that liver gene therapy has the potential to eradicate inhibitors and could improve the outcomes of hemophilia A patients.

scholarly journals Ultrasound Combined with Microbubbles Mediated Factor VIII Plasmid Gene Therapy in Hemophilia a Mice

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 2039-2039
Author(s):  
Shuxian Song ◽  
James Harrang ◽  
Bryn Smith ◽  
Carol H. Miao
Keyword(s):  
Gene Expression ◽  
Gene Therapy ◽  
Gene Transfer ◽  
Factor Viii ◽  
Hemophilia A ◽  
Liver Perfusion ◽  
Transfer Efficiency ◽  
Clotting Factor ◽  
Gene Transfer Efficiency ◽  
Fviii Activity

Abstract Hemophilia A is a genetic bleeding disorder resulted from a deficiency of blood clotting factor VIII. In order to develop the efficient approach to gene therapy for hemophilia A, we previously explored reporter gene transfer mediated by ultrasound (US) combined with microbubbles (MBs). It was demonstrated that US/MB can significantly enhance gene transfer efficiency and serve as an efficient non-viral physical delivery strategy. In this study, we further delivered a therapeutic FVIII plasmid into the livers of hemophilia A (HA) mice. In consideration of FVIII synthesis from multiple tissues/cell lines, we first explored the distribution of gene expression using a pGL4.13 [luc2/SV40] luciferase plasmid driven by a ubiquitous promoter. One day following gene transfer, hepatocytes and endothelia cells were isolated from treated lobes by liver perfusion and centrifuge method. Evaluation of luciferase levels in two cell populations indicated that luciferase predominantly expressed in hepatocytes (5.35´104 RLU/107 cells vs. 1.46´103 RLU/107 cells in endothelia cells). Furthermore, gene transfer of pGFP (driven by a ubiquitous CMV promoter) mediated by US/MB also showed fluorescence distribution mostly in hepatocytes. These results indicate that hepatocyte is the predominant site of gene expression following US/MB mediated gene transfer into the liver. Based on these results, a hepatocyte-specific human FVIII plasmid (pBS-HCRHP-hFVIII/N6A) was used for US/MB mediated gene transfer in HA mice. In the short-term experiment, FVIII activity levels of treated HA mice ranged from 4-40% of normal FVIII activity. To follow FVIII expression for longer term, HA mice were pretreated with IL-2/IL-2 mAb (JES6-1) complexes on day −5, −4, and −3 to prevent immune response. In addition, the mice were infused with normal mouse plasma and human FVIII protein prior to gene transfer to maintain hemostasis. Subsequently, FVIII plasmids and 5 Vol% NUVOX MBs were injected into the mouse liver under simultaneous US exposure (1.1MHz transducer H158A driven by a pulse generator and high-power radio frequency amplifier capable of generating up to 1000W). Blood and liver samples were collected at serial time points after treatment to determine FVIII activity in plasma and liver damage. Following gene transfer, 10-30% of FVIII activity was achieved on day 4 and persisted in the average level of 20% by day 28. In a separate long-term follow-up experiment (n=3), 2 of 3 mice still maintained 10-30% activity after 120 days. Both transaminase levels (alanine aminotransferase and aspartate aminotransferase) and histological examination showed that the procedure of plasmid/MBs portal-vein injection and pulse-train acoustic exposure produced transiently localized liver damages however the damages were repaired and the liver recovered rapidly. Phenotypic correction of HA mice was further examined by tail clip assay. Blood loss of US/MB treated mice was significantly reduced compared with naive HA mice. Furthermore, a novel plasmid encoding a B domain-deleted FVIII variant containing mutations of 10 amino acids in the A1 domain (BDDFVIII-X10, a kind gift from Weidong Xiao) was constructed. Preliminary results from ongoing study showed that the gene transfer efficiency could be further improved with better plasmid and more efficient immune modulation. Together all the results indicate that US/MB mediated gene transfer is highly promising for efficient and safe gene therapy of hemophilia A. Disclosures No relevant conflicts of interest to declare.

scholarly journals Factor VIII Level Comparison in Patients with Severe Hemophilia a on Emicizumab with Inhibitors with One Stage, Bovine and Human Chromogenic Assays and the Factor VIII Equivalency of Emicizumab Using In Vivo Global Hemostasis Assays

Blood ◽  
2021 ◽  
Vol 138 (Supplement 1) ◽  
pp. 4234-4234
Author(s):  
Hande Kizilocak ◽  
Elizabeth Marquez-Casas ◽  
Joshua Brown ◽  
Jemily Malvar ◽  
Guy Young
Keyword(s):  
Factor Viii ◽  
Thrombin Generation ◽  
Hemophilia A ◽  
Activated Partial Thromboplastin Time ◽  
Clotting Factor ◽  
Normal Range ◽  
One Stage ◽  
Chromogenic Assay ◽  
Coagulation Defect ◽  
Fviii Activity

Abstract Introduction Emicizumab is a recombinant, humanized bispecific monoclonal antibody that mimics the function of factor VIII (FVIII) which results in a significant reduction in the annualized bleeding rate in patients with hemophilia A (HA), however, the degree with which emicizumab corrects the coagulation defect remains unclear. The objective of this study was to compare the current available laboratory methods in clinical practice; one-stage clotting factor assays (OSCA), bovine and human chromogenic FVIII activity (bovCHR and humCHR, respectively) and FVIII Equivalency of Emicizumab by Thrombin Generation (F8EmT). Aims The aim of this study is to address the differences of FVIII activity with different techniques in patients with severe HA with inhibitors on emicizumab. Materials and Methods Factor VIII levels are determined with an activated partial thromboplastin time (aPTT), OSCA using SynthASil on the ACL TOP 500 (Instrumentation Laboratory, Bedford, MA). Factor VIII activity is also determined photometrically via the Chromogenix Coatest® SP4 FVIII chromogenic assay kit (bovCHR, Diapharma Group, West Chester, OH) and the Biophen FVIII:C chromogenic assay kit (humCHR, Aniara Diagnostica, West Chester, OH). For F8EmT, linear regression was utilized to model the FVIII levels as a function of the endogenous thrombin potential (ETP) and peak thrombin values for patients with mild/moderate hemophilia. Then, we used the ETP and peak thrombin results of the severe HA patients on emicizumab with the calibration curve to calculate their F8EmT. Association between patient weight and their F8EmT were also examined and evaluated by linear regression. Results Data is presented for eight patients with severe HA with inhibitors on emicizumab in the non-bleeding state (Table-1). All patients' FVIII levels measured with OSCA are in or above the normal range (94.0-289.1). Bovine chromogenic FVIII activity is in the severe hemophilia range for five out of eight patients, for the rest it is in the moderate hemophilia range. Human chromogenic FVIII activity ranged between 12.5-49.8%. Factor VIII Equivalency of Emicizumab by Thrombin Generation is either in the mild hemophilia or normal range in all participants of the study. Conclusion One-stage clotting factor assays demonstrated falsely high results as expected since it is activated partial thromboplastin time based. Bovine chromogenic FVIII activity results were consistent with the severe HA range of the patients though a few had results slightly above that level. Previous literature has stated that the humCHR in patients on emicizumab results in FVIII levels of ∼30% when emicizumab is at its therapeutic concentration (∼50 mcg/ml). This study also demonstrated similar results with 5/8 patients having levels 30-50%. F8EMT levels were mostly consistent with the humCHR. In conclusion, understanding the degree to which emicizumab corrects the coagulation defect of is an important goal as it has clinical implications.Certainly, additional studies with higher participant numbers are needed to confirm these findings. Figure 1 Figure 1. Disclosures Young: Apcintex, BioMarin, Genentech/Roche, Grifols, Novo Nordisk, Pfizer, Rani, Sanofi Genzyme, Spark, Takeda, and UniQure: Consultancy; Genentech/Roche, Grifols, and Takeda: Research Funding.

Development of neutralizing antibodies in application of various concentrates of blood coagulation factor VIII in the treatment of hemophilia A

2021 ◽  
Author(s):  
Н.И. Зозуля
Keyword(s):  
Factor Viii ◽  
Cell Line ◽  
Neutralizing Antibodies ◽  
Hemophilia A ◽  
Chinese Hamster ◽  
Coagulation Factor ◽  
Human Cell Line ◽  
Chinese Hamster Cell ◽  
Coagulation Factor Viii ◽  
Recombinant Fviii

Серьезным осложнением, связанным с лечением гемофилии А, является развитие ингибиторов. В последние годы был проведён ряд исследований, посвящённых данной проблеме: RODIN, INSIGHT, FranceCoag, SIPPET и NuProtect. В данном обзоре суммируются основные результаты этих исследований. Согласно результатам рандомизированного исследования SIPPET, препараты плазматического фактора свертывания крови VIII (FVIII) обладают меньшей иммуногенностью, чем препараты рекомбинантного FVIII, синтезированного из клеточной линии китайских хомячков, что следует учитывать при выборе стратегии лечения. Согласно результатам исследования NuProtect, опубликованным в 2019 г., концентрат рекомбинантного FVIII, полученный из клеточной линии человека, демонстрирует профиль иммуногенности, сходный с таковым у препаратов плазматического FVIII. У ранее нелеченых пациентов с ненулевыми мутациями при применении симоктоког альфа не наблюдалось образования ингибиторов, также как и в случае применения препаратов плазматического FVIII в исследовании SIPPET. Inhibitor development is a serious complication associated with hemophilia A therapy. A number of studies have been carried out of this issue — RODIN, INSIGHT, FranceCoag, SIPPET, and NuProtect. This review summarizes the main results of these studies. According to the results of the SIPPET randomized trial, plasma-derived coagulation factor VIII (FVIII) products are less immunogenic than recombinant FVIII products synthesized from a Chinese hamster cell line; this fact should be taken into account in choosing a treatment strategy. According to the results of NuProtect study published in 2019, the concentrate of human cell line-derived recombinant FVIII demonstrates immunogenicity profi le similar to the one in plasma-derived FVIII products. Previously untreated patients with non-zero mutations receiving simoctocog alfa did not show development of inhibitors as well as in case of administration of plasma-derived FVIII products in SIPPET study.

Animal Testing of Retroviral-Mediated Gene Therapy for Factor VIII Deficiency

1999 ◽  
Vol 82 (08) ◽  
pp. 555-561 ◽  
Author(s):  
Douglas Jolly ◽  
Judith Greengard
Keyword(s):  
Gene Therapy ◽  
Factor Viii ◽  
Hemophilia A ◽  
Joint Damage ◽  
Coagulation Factor ◽  
The United States ◽  
Severe Hemophilia ◽  
Factor Viii Gene ◽  
Bleeding Episodes

IntroductionHemophilia A results from the plasma deficiency of factor VIII, a gene carried on the X chromosome. Bleeding results from a lack of coagulation factor VIII, a large and complex protein that circulates in complex with its carrier, von Willebrand factor (vWF).1 Severe hemophilia A (<1% of normal circulating levels) is associated with a high degree of mortality, due to spontaneous and trauma-induced, life-threatening and crippling bleeding episodes.2 Current treatment in the United States consists of infusion of plasma-derived or recombinant factor VIII in response to bleeding episodes.3 Such treatment fails to prevent cumulative joint damage, a major cause of hemophilia-associated morbidity.4 Availability of prophylactic treatment, which would reduce the number and severity of bleeding episodes and, consequently, would limit such joint damage, is limited by cost and the problems associated with repeated venous access. Other problems are associated with frequent replacement treatment, including the dangers of transmission of blood-borne infections derived from plasma used as a source of factor VIII or tissue culture or formulation components. These dangers are reduced, but not eliminated, by current manufacturing techniques. Furthermore, approximately 1 in 5 patients with severe hemophilia treated with recombinant or plasma-derived factor VIII develop inhibitory humoral immune responses. In some cases, new inhibitors have developed, apparently in response to unnatural modifications introduced during manufacture or purification.5 Gene therapy could circumvent most of these difficulties. In theory, a single injection of a vector encoding the factor VIII gene could provide constant plasma levels of factor in the long term. However, long-term expression after gene transfer of a systemically expressed protein in higher mammals has seldom been described. In some cases, a vector that appeared promising in a rodent model has not worked well in larger animals, for example, due to a massive immune response not seen in the rodent.6 An excellent review of early efforts at factor VIII gene therapy appeared in an earlier volume of this series.7 A summary of results from various in vivo experiments is shown in Table 1. This chapter will focus on results pertaining to studies using vectors based on murine retroviruses, including our own work.

Codon optimization of human factor VIII cDNAs leads to high-level expression

Blood ◽  
2011 ◽  
Vol 117 (3) ◽  
pp. 798-807 ◽  
Author(s):  
Natalie J. Ward ◽  
Suzanne M. K. Buckley ◽  
Simon N. Waddington ◽  
Thierry VandenDriessche ◽  
Marinee K. L. Chuah ◽  
...  
Keyword(s):  
Gene Therapy ◽  
Factor Viii ◽  
Viral Vectors ◽  
Hemophilia A ◽  
Lentiviral Vector ◽  
Wild Type ◽  
Fviii Activity ◽  
Human Factor Viii

Abstract Gene therapy for hemophilia A would be facilitated by development of smaller expression cassettes encoding factor VIII (FVIII), which demonstrate improved biosynthesis and/or enhanced biologic properties. B domain deleted (BDD) FVIII retains full procoagulant function and is expressed at higher levels than wild-type FVIII. However, a partial BDD FVIII, leaving an N-terminal 226 amino acid stretch (N6), increases in vitro secretion of FVIII tenfold compared with BDD-FVIII. In this study, we tested various BDD constructs in the context of either wild-type or codon-optimized cDNA sequences expressed under control of the strong, ubiquitous Spleen Focus Forming Virus promoter within a self-inactivating HIV-based lentiviral vector. Transduced 293T cells in vitro demonstrated detectable FVIII activity. Hemophilic mice treated with lentiviral vectors showed expression of FVIII activity and phenotypic correction sustained over 250 days. Importantly, codon-optimized constructs achieved an unprecedented 29- to 44-fold increase in expression, yielding more than 200% normal human FVIII levels. Addition of B domain sequences to BDD-FVIII did not significantly increase in vivo expression. These significant findings demonstrate that shorter FVIII constructs that can be more easily accommodated in viral vectors can result in increased therapeutic efficacy and may deliver effective gene therapy for hemophilia A.

Direct Comparison of Bioengineered Factor VIII Expression Constructs: Towards an Optimal Transgene for Gene Therapy of Hemophilia A.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 5477-5477
Author(s):  
Kerry L. Titus ◽  
Paul Lee ◽  
H. Trent Spencer ◽  
Christopher Doering
Keyword(s):  
Gene Therapy ◽  
Amino Acid ◽  
Factor Viii ◽  
Hemophilia A ◽  
Double Mutation ◽  
Specific Amino Acid ◽  
Stable Transfectants ◽  
Glycosylation Sites ◽  
Fviii Activity ◽  
A2 Domain

Abstract A major obstacle for gene therapy of hemophilia A is the achievement of adequate factor VIII (fVIII) expression. Bioengineering strategies have targeted specific sequences within human fVIII that are thought to be responsible for its generally poor expression. Specific amino acid substitutions, L303E/F309S herein referred to as double mutation (DM), function to decrease fVIII binding to BiP, a resident ER chaperone, which results in increased fVIII secretion (Swaroop, Moussalli et al. 1997). Furthermore, addition of 6 N-linked glycosylation sites, designated 226/N6, located within the human B domain also increases human fVIII expression (Miao, Sirachainan et al. 2004). We previously demonstrated that porcine and certain hybrid human/porcine fVIII constructs are expressed at 10 – 14-fold greater levels than human fVIII (Doering, Healey et al. 2002; Doering, Healey et al. 2004). The aim of the current study was to directly compare various fVIII expression constructs in order to determine an optimal transgene for gene therapy applications. The following fVIII constructs were generated: human B-domain-deleted fVIII (HBDD-fVIII), HBDD-fVIII with a 14 amino acid linker between the A2 domain and the activation peptide (HSQ-fVIII), porcine fVIII containing a 24 amino acid linker (HEP-fVIII), hybrid human/porcine-fVIII which has porcine A1 and A3 domains (HP47), and modified HBDD, HSQ and HEP-fVIII constructs containing DM and/or 226/N6. Each construct was transiently transfected into BHK-M cells, and fVIII production between 48 – 72 hrs post-transfection was measured using a one-stage clotting assay. Under these conditions, the addition of the DM and 226/N6 significantly increased fVIII expression for HBDD (P = 0.003), though not for HSQ. Addition of DM or 226/N6 alone did not significantly increase the expression of either human fVIII construct, and furthermore, the addition of DM to HEP-fVIII decreased its expression 98%. HEP-fVIII was expressed at 8-fold or greater levels than any of the other human constructs. Next, ~25 stably transfected BHK-M clones were isolated following transfection with each of the fVIII expression constructs and the rate of fVIII production for each clone was determined. Several clones did not express detectable fVIII activity (<0.01 units/mL) and were excluded from the analysis. Approximately 14% of the total number of clones were excluded, ranging from 0 – 42% for the different constructs. HEP-DM-fVIII was the exception, where 82% of the clones had activity <0.01 units/mL. Mean HEP-fVIII expression was 3.93 ± 3.22 units/mL/24 hr (n = 19) (Figure 1), and HP47 was similarly expressed at 3.21 ± 2.31 units/mL/24 hr (n = 19). All of the HSQ-based constructs and HBDD-DM/226/N6 showed similar mean expression levels (0.28 ± 0.03 units/mL/24 hr) and were significantly higher than HBDD and HBDD-DM, which had a mean of 0.12 ± 0.01 units/mL. In the current study, we provide experimental evidence that the expression of HEP-fVIII and HP47 is superior to other bioengineered fVIII expression constructs, which should eliminate the expression barrier that has hampered the clinical translation of gene therapy for hemophilia A. Figure 1: Stable Transfectants Figure 1:. Stable Transfectants

scholarly journals Expression of the blood-clotting factor-VIII cDNA is repressed by a transcriptional silencer located in its coding region

Blood ◽  
1995 ◽  
Vol 85 (9) ◽  
pp. 2447-2454 ◽  
Author(s):  
RC Hoeben ◽  
FJ Fallaux ◽  
SJ Cramer ◽  
DJ van den Wollenberg ◽  
H van Ormondt ◽  
...  
Keyword(s):  
Gene Therapy ◽  
Factor Viii ◽  
Hemophilia A ◽  
Recombinant Dna ◽  
Transcription Unit ◽  
Current Treatment ◽  
Clotting Factor ◽  
Large Animal ◽  
Coding Region ◽  
Large Animal Models

Hemophilia A is caused by a deficiency of factor-VIII procoagulant (fVIII) activity. The current treatment by frequent infusions of plasma-derived fVIII concentrates is very effective but has the risk of transmittance of blood-borne viruses (human immunodeficiency virus [HIV], hepatitis viruses). Use of recombinant DNA-derived fVIII as well as gene therapy could make hemophilia treatment independent of blood-derived products. So far, the problematic production of the fVIII protein and the low titers of the fVIII retrovirus stocks have prevented preclinical trials of gene therapy for hemophilia A in large-animal models. We have initiated a study of the mechanisms that oppose efficient fVIII synthesis. We have established that fVIII cDNA contains sequences that dominantly inhibit its own expression from retroviral as well as from plasmid vectors. The inhibition is not caused by instability of the fVIII mRNA (t1/2, > or = 6 hours) but rather to repression at the level of transcription. A 305-bp fragment is identified that is involved in but not sufficient for repression. This fragment does not overlap the region recently identified by Lynch et al (Hum Gene Ther 4:259, 1993) as a dominant inhibitor of RNA accumulation. The repression is mediated by a cellular factor (or factors) and is independent of the orientation of the element in the transcription unit, giving the repressor element the hallmarks of a transcriptional silencer.

Peptide Multimers for Binding of Factor VIII Inhibitors.

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 1224-1224
Author(s):  
Christoph Kessel ◽  
Wolfhart Kreuz ◽  
Katharina Klich ◽  
Frank Vorpahl ◽  
Karin Becker-Peters ◽  
...  
Keyword(s):  
Factor Viii ◽  
Neutralizing Antibodies ◽  
High Titer ◽  
Coagulation Factor ◽  
Peptide Ligands ◽  
Therapeutic Approaches ◽  
Random Peptide ◽  
Fviii Activity ◽  
Specific Igg

Abstract Hemophilia A is an X-chromosome linked bleeding disorder resulting from the absence or nonfunctional expression of coagulation factor VIII (FVIII). About 30% of severe hemophiliacs develop neutralizing antibodies (inhibitors) to FVIII upon treatment with exogenous factor preparations. Specificity of these antibodies is often restricted to functional determinants in the A2 and C2 domain. Phage displayed random peptide libraries were screened with various plasma samples of high titer inhibitor patients and inhibitor specific peptide ligands were selected. In silco mapping of consensus amino acid motifs among peptides revealed conformational epitopes in A2 and C2. Selected ligands partially restored FVIII activity. Equimolar combination of these ligands enhanced blocking of inhibitors in autologous and heterologous patients’ plasma. Peptide ligands were fused to the C-terminal multimerization domain of the C4bp alpha-chain and expressed as multimers in 293T cells. Peptide multimers revealed improved binding of anti-FVIII IgG and prolonged in vitro half-life in comparison to single synthetic peptides. Selected peptide ligands were combined in heteromultimers by co-transfection of respective vectors, resulting in molecules binding both A2- and C2- specific IgG and blocking up to 100% of antibody binding to FVIII. Those molecules could provide a basis for the generation of novel peptide-based therapeutic approaches.

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