A Novel Deletion in the Fviii B-Domain That Reduces Transgene Size While Preserving FVIII Activity.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 3182-3182
Author(s):  
Yi-Lin Liu ◽  
Hua Zhu ◽  
Alexander Schlachterman ◽  
Heesoon Chang ◽  
Rodney M. Camire ◽  
...  
Keyword(s):  
Gene Therapy ◽  
Factor Viii ◽  
Dose Group ◽  
Hemophilia A ◽  
Specific Activity ◽  
Post Injection ◽  
Vector Genome ◽  
Fviii Activity

Abstract Hemophilia A is an inherited X-linked bleeding disorder caused by a deficiency in Factor VIII (FVIII). Clinically significant improvement of hemophilia phenotype can be achieved with low circulating factors, thus makes it a good target disease for gene therapy. Adeno-associated virus (AAV) vectors have proven successful for the delivery of the factor IX gene in humans with hemophilia B. For the treatment of hemophilia A, a problem in the packaging of the rFVIII cDNA or various B-domainless derivatives (i.e. rFVIII-SQ) in AAV vectors is the large size of the insert, which combined with required elements, can exceed the packaging capacity of AAV (~5 kb). This difficulty limits the choice of both promoter and regulatory elements when designing an expression cassette for AAV vectors. Here we developed strategies to overcome these limitations by (1) development of a novel FVIII B-domain deleted molecule (2) construction of a short liver-specific promoter. We further tested these vectors in a series of in vitro and in vivo experiments. Factor VIII-SQ is a well-characterized derivative of FVIII and has been used by several groups in a gene therapy setting; the recombinant protein is used clinically to treat hemophilia A. We have constructed a shorter version of FVIII-SQ, by deleting the entire B-domain. In addition, we have engineered this FVIII to be intracellularly processed using a PACE-furin recognition site such that the protein is secreted from cells as two chains (FVIII-RKR; fully processed heavy and light chains). This FVIII-RKR along with FVIII-SQ was transiently expressed in COS-1 cells and conditioned media was collected at 24, 48 and 72 hrs post transfection. Using a combination of ELISA and functional assays we were able to demonstrate that FVIII-RKR was efficiently secreted from these cells. The data also revealed that FVIII-RKR has a 4–8-fold increase in specific activity compared to FVIII-SQ. We further tested whether FVIII-RKR could function in an in vivo setting. Plasmid DNA (50μg) containing FVIII-RKR or FVIII-SQ with liver-specific mouse transthyretin (mTTR) promoter were introduced into hemophilia A (HA) mice hydrodynamically via tail vein. Two out of four mice in the SQ group and three out of four mice in the RKR group had significant shortening of the clotting time at days 1 and 3 post injection, indicating that this shortened version of FVIII is functional in vivo. To address FVIII long-term expression we synthesized AAV vectors and delivered to immuno-deficient HA mice through hepatic portal vein. AAV vectors containing an expression cassette of mTTR promoter and FVIII-SQ have been administered. Expression of physiological FVIII levels was observed in high dose group (4.0E+12 vector genome per animal, n=4). FVIII activity averages 1.88 U/ml by Coamatic assay or 0.81 U/ml by aPTT assay at 12 weeks post injection. In low dose group (1.0E+12 vector genome per animal, n=5) therapeutic level of FVIII is achieved, 0.59 U/ml by Coamatic assay or 0.23 U/ml by aPTT assay at 12 weeks post injection. Finally, AAV vectors with FVIII-RKR have been produced and shown to have similar packaging efficiency to AAV-FVIII-SQ. Studies are currently underway with AAV-FVIII-RKR to evaluate the ability of this vector to drive long-term expression of functional protein. In summary, we developed a novel FVIII molecule that has high specific activity and is suitable for efficiently packaging in the AAV vectors.

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.

The Light Chain of Rat Factor VIII Confers Its Superior Cofactor Activity

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 2038-2038
Author(s):  
Qizhao Wang ◽  
Jenni Firrman ◽  
Katie A Pokiniewski ◽  
Wenjing Cao ◽  
Hongying Wei ◽  
...  
Keyword(s):  
Gene Therapy ◽  
Factor Viii ◽  
Light Chain ◽  
Hemophilia A ◽  
Specific Activity ◽  
Genetic Defect ◽  
High Dose ◽  
Coagulation Activity ◽  
Fviii Activity ◽  
Cofactor Activity

Abstract Hemophilia A is caused by genetic defect of human coagulation factor VIII (hFVIII) and patients have to take lifelong replacement therapy to prevent excessive bleedings upon hemostatic challenges. Due to the short half-life of hFVIII, replacement treatment has to be given frequently and inhibitors against infused hFVIII can be developed in about 20-30% of patients. These shortcomings have generated tremendous interest in developing HA gene therapies which is more efficient and long-lasting. However, early preclinical studies have shown FVIII activities were still limited after vector delivery. A Modified hFVIII with higher specific activity and pharmacodynamics properties is highly desirable to overcome the disadvantages of current protein replacement and gene therapy strategies. In the current study, we successfully constructed a B-domain deleted rat FVIII(rBDDF8) that contained a PACE/furin recognition site (RHQR) within a 14 amino acid linker between A2 and A3 domains. The rBDDF8 displayed significantly higher coagulation activity(~2.5-fold) than hBDDF8 after transfection into HEK 293 cells. In order to explore the mechanism for the observed superior cofactor activity, we constructed heavy chain(rHC) and light chain(rLC) of rFVIII. The rHC and rLC are able to reconstitute 5 times more FVIII activity than their human counter parts. However, when rHC is associated with human FVIII light chain (hLC), the reconstituted FVIII activity is lower that from hHC and hLC, suggesting that high coagulation activity of rFVIII is not mediated by its HC. On the contrary, when FVIII is constituted by hHC with rLC, we found that the activity is increased by 3~5-fold as against hHC and hLC. The hHC antigen level of FVIII reconstituted from hHC and rLC was 1.5-fold higher than that of hHC and hLC, suggesting that higher activity of FVIII with hHC and rLC is not through increased secretion. The specific activity deduced from activity/antigen ratio showed that FVIII with rLC is 3 times higher more than FVIII with hLC. To investigate the potential application of rFVIII in gene therapy, rBDDF8 was delivered in hemophilia A mouse model using AAV8 vectors. The high dose rBDDF8(4*1011 vg/mouse) resulted 2.5U FVIII activity at week 17, which is much higher(about 10-fold) than that of hBDDF8. When the rFVIII was delivered by dual chains strategy, i.e, administering vectors carrying only LC or HC simultaneously, it also showed 2-4 fold increased in FVIII activity. Interestingly, the combination of hHC and rLC also generated similar FVIII activity as rHC and rLC, further proving the rLC is the major contributor to the superior coagulation activity of rFVIII. Our results showed that the rFVIII has higher cofactor activity conferred by its LC. Our results suggest that rFVIII can be further exploited to make an ideal candidate for hemophilia gene therapy using AAV vectors. Disclosures No relevant conflicts of interest to declare.

RECOVERY TEST AND ITS ROLE IN ASSESSMENT OF LONG-TERM PROPHYLAXIS EFFECTIVENESS IN HEMOPHILIA A PATIENTS

2017 ◽  
Author(s):  
Т. Андреева ◽  
И. Лавриченко ◽  
В. Константинова ◽  
А. Ким ◽  
О. Крашенинникова ◽  
...  
Keyword(s):  
Factor Viii ◽  
Hemophilia A ◽  
Coagulation Factor ◽  
Recombinant Factor Viii ◽  
Coagulation Factor Viii ◽  
Recovery Test ◽  
Fviii Activity ◽  
In Vivo Recovery

Введение. Гемофилия А (ГФА) — сцепленное с Х-хромосомой рецессивное врожденное заболевание, обусловленное недостаточностью VIII фактора свертывания крови (FVIII). Главным признаком заболевания является склонность к кровотечениям. Клинические проявления ГФА, как правило, коррелируют с уровнем активности FVIII. Единственным эффективным лечением гемофилии в настоящее время является заместительная терапия препаратами дефицитного фактора. Материалы и методы. Проведен ретроспективный анализ результатов обследования 28 пациентов (14 детей в возрасте от 3 до 17 лет и 14 взрослых в возрасте от 21 до 57 лет) с тяжелой формой ГФА. Все пациенты находились на длительной профилактической терапии препаратами FVIII — как рекомбинантными, так и плазматическими. Для подбора оптимального режима профилактики пациенту с ГФА проводили тест восстановления (in vivo recovery) — определение активности FVIII в двух пробах крови; определяли также прирост показателя восстановления (incremental recovery), активированное частичное тромбопластиновое время и каолиновое время. Результаты. Проведена оценка теста восстановления фактора свертывания VIII при применении плазматических и рекомбинантного препаратов фактора VIII у пациентов с тяжелой гемофилией А; изучена корреляция теста восстановления с фармакодинамическими показателями, характеризующими состояние коагуляции. Заключение. Ввиду наличия внутрииндивидуальных и межиндивидуальных колебаний фармакокинетических показателей препаратов фактора свертывания VIII у пациентов с ГФА рекомендуется проведение теста восстановления как при назначении препарата фактора свертывания VIII, так и в процессе длительной профилактики с целью контроля за терапией и ее оптимизации в случае необходимости. Introduction. Hemophilia A (HРA) is a recessive X-linked congenital disease caused by the defi ciency of VIII coagulation factor (FVIII). Hemorrhagic tendency is the main sign of the disease. As a rule, clinical manifestations of HPA correlate with level of FVIII activity. At present time substitution therapy with medication of defi cit factor is the only eff ective treatment for hemophilia. Materials and methods. We performed a retrospective study analysis of 28 patients (14 children aged from 3 to 17 years and 14 adults aged from 21 to 57 years) examination with severe HРA. All patients received prolonged preventive therapy with recombinant factor VIII products. To select the optimal prophylaxis mode for patients with HPA we performed a recovery test (in vivo recovery), determination of FVIII activity in two blood samples, determined index of incremental recovery, activated partial thromboplastin time and kaolin time. Results. We assessed recovery test for coagulation factor VIII using plasma and recombinant factor VIII products in patients with severe haemophilia A and studied correlation of recovery test with pharmacodynamic parameters that characterized coagulation state. Conclusion. Due to intra-individual and inter-individual fl uctuations in pharmacokinetic parameters of recombinant factor VIII products in patients with HPA we recommend to perform a recovery test both at appointment of coagulation factor VIII product and also during of long-term prophylaxis for monitoring and optimization of therapy.

scholarly journals Therapeutic factor VIII levels and negligible toxicity in mouse and dog models of hemophilia A following gene therapy with high-capacity adenoviral vectors

Blood ◽  
2003 ◽  
Vol 101 (5) ◽  
pp. 1734-1743 ◽  
Author(s):  
Marinee K. L. Chuah ◽  
Gudrun Schiedner ◽  
Lieven Thorrez ◽  
Brian Brown ◽  
Marion Johnston ◽  
...  
Keyword(s):  
Gene Therapy ◽  
Factor Viii ◽  
Hemophilia A ◽  
High Capacity ◽  
Scid Mice ◽  
Therapeutic Window ◽  
Expression Levels ◽  
Cellular Immune

High-capacity adenoviral (HC-Ad) vectors expressing B-domain–deleted human or canine factor VIII from different liver-specific promoters were evaluated for gene therapy of hemophilia A. Intravenous administration of these vectors into hemophilic FVIII-deficient immunodeficient SCID mice (FVIIIKO-SCID) at a dose of 5 × 109 infectious units (IU) resulted in efficient hepatic gene delivery and long-term expression of supraphysiologic FVIII levels (exceeding 15 000 mU/mL), correcting the bleeding diathesis. Injection of only 5 × 107 IU still resulted in therapeutic FVIII levels. In immunocompetent hemophilic FVIII-deficient mice (FVIIIKO), FVIII expression levels peaked at 75 000 mU/mL but declined thereafter because of neutralizing anti-FVIII antibodies and a cellular immune response. Vector administration did not result in thrombocytopenia, anemia, or elevation of the proinflammatory cytokine interleukin-6 (IL-6) and caused no or only transient elevations in serum transaminases. Following transient in vivo depletion of macrophages before gene transfer, significantly higher and stable FVIII expression levels were observed. Injection of only 5 × 106 HC-Ad vectors after macrophage depletion resulted in long-term therapeutic FVIII levels in the FVIIIKO and FVIIIKO-SCID mice. Intravenous injection of an HC-Ad vector into a hemophilia A dog at a dose of 4.3 × 109 IU/kg led to transient therapeutic canine FVIII levels that partially corrected whole-blood clotting time. Inhibitory antibodies to canine FVIII could not be detected, and there were no signs of hepatotoxicity or of hematologic abnormalities. These results contribute to a better understanding of the safety and efficacy of HC-Ad vectors and suggest that the therapeutic window of HC-Ad vectors could be improved by minimizing the interaction between HC-Ad vectors and the innate immune system.

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.

Mild Hemophilia A Caused by Increased Rate of Factor VIII A2 Subunit Dissociation: Evidence for Nonproteolytic Inactivation of Factor VIIIa In Vivo

Blood ◽  
1999 ◽  
Vol 93 (1) ◽  
pp. 176-183 ◽  
Author(s):  
S.W. Pipe ◽  
A.N. Eickhorst ◽  
S.H. McKinley ◽  
E.L. Saenko ◽  
R.J. Kaufman
Keyword(s):  
Factor Viii ◽  
Missense Mutation ◽  
Time Course ◽  
Hemophilia A ◽  
Specific Activity ◽  
Metabolic Labeling ◽  
Two Stage ◽  
One Stage ◽  
Thrombin Cleavage

Abstract Approximately 5% of hemophilia A patients have normal amounts of a dysfunctional factor VIII (FVIII) protein and are termed cross-reacting material (CRM)-positive. FVIII is a heterodimer (domain structure A1-A2-B/A3-C1-C2) that requires thrombin cleavage to elicit procoagulant activity. Thrombin-activated FVIII is a heterotrimer with the A2 subunit (amino acid residues 373 to 740) in a weak ionic interaction with the A1 and A3-C1-C2 subunits. Dissociation of the A2 subunit correlates with inactivation of FVIII. Recently, a phenotype of CRM-positive hemophilia A patients has been characterized whose plasma displays a discrepancy between their FVIII activities, where the one-stage clotting assay displays greater activity than the two-stage clotting assay. One example is a missense mutation whereARG531 has been substituted by HIS531. An FVIII cDNA construct was prepared containing theARG531HIS mutation and the protein was expressed in COS-1 monkey cells by transient DNA transfection. Metabolic labeling with [35S]-methionine demonstrated that ARG531HIS was synthesized at an equal rate compared with FVIII wild-type (WT) but had slightly reduced antigen in the conditioned medium, suggesting a modest secretion defect. A time course of structural cleavage of ARG531HISdemonstrated identical thrombin cleavage sites and rates of proteolysis as FVIII WT. Similar to the patient phenotypes,ARG531HIS had discrepant activity as measured by a one-stage activated partial thromboplastin time (aPTT) clotting assay (36% ± 9.6% of FVIII WT) and a variation of the two-stage assay using a chromogenic substrate (COAMATIC; 19% ± 6.9% of FVIII WT). Partially purified FVIII WT and ARG531HISproteins were subjected to functional activation by incubation with thrombin. ARG531HIS demonstrated significantly reduced peak activity and was completely inactivated after 30 seconds, whereas FVIII WT retained activity until 2.5 minutes after activation. Because the ARG531HIS missense mutation predicts a charge change to the A2 subunit, we hypothesized that theARG531HIS A2 subunit could be subject to more rapid dissociation from the heterotrimer. The rate of A2 dissociation, using an optical biosensor, was determined to be fourfold faster forARG531HIS compared with FVIII WT. Because the two-stage assay involves a preincubation phase before assay measurement, an increased rate of A2 dissociation would result in an increased rate of inactivation and reduced specific activity.

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

In Vivo Selection Of Genetically Manipulated Hematopoietic Stem Cells For Platelet Gene Therapy Of Hemophilia A

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 2329-2329
Author(s):  
Qizhen Shi ◽  
Jocelyn A. Schroeder ◽  
David A. Wilcox ◽  
Robert R. Montgomery ◽  
Yingyu Chen
Keyword(s):  
Gene Therapy ◽  
Hemophilia A ◽  
Genetically Modified ◽  
Conditioning Regimen ◽  
Selective Treatment ◽  
Hematopoietic Stem ◽  
In Vivo Selection ◽  
Fviii Activity ◽  
Selection Of

Abstract Our previous studies have demonstrated that targeting FVIII expression to platelets (2bF8) by lentiviral (LV) gene delivery to hematopoietic stem cells (HSCs) corrects bleeding diathesis in hemophilia A mice with or without inhibitors. Although the bleeding diathesis is improved in transduced recipients, the transduction efficiency using our current 2bF8 LV, is only about 10%, resulting a median level of platelet-FVIII (Plt-F8) of 1.5 mU/108 platelets even thought a myeloablative conditioning regimen was employed. It has been shown in clinical trials that efficient stem cell gene transfer and myeloablation is not required when there is a powerful selective advantage to the genetically modified cells. We hypothesize that incorporating a drug-resistance gene into the 2bF8 LV construct will allow for in vivo selection of 2bF8 LV-transduced cells which will result in the increase of therapeutic levels of Plt-F8 for hemophilia A gene therapy and reduce the potential for genotoxicity. To address our hypothesis, we constructed a new lentiviral vector, pWPT-2bF8/MGMT, which harbors dual genes, the 2bF8 gene and a drug-resistance gene, the MGMTP140K cassette. To explore the feasibility of the MGMT-based in vivo selection system, HSCs from FVIIInull mice were transduced with 2bF8/MGMT LV at an MOI (multiplicity of infectious) of 1, which is 1/10 of the MOI used for our regular 2bF8 LV transduction, and transplanted into littermates pre-conditioned with a non-myeloablative regimen, 660 cGy total body irradiation (TBI). We chose a low MOI because one of the goals of using the MGMT selection system is to reduce the potential for genotoxicity. After bone marrow (BM) reconstitution, the recipients were treated with O6-benzylguanine (BG) followed by 1, 3-bis-2 chloroethyl-1-nitrosourea (BCNU) monthly for 3 or 4 times. As determined by a chromogenic assay on platelet lysates, functional Plt-F8 expression in recipients was only 0.22 ± 0.15 mU/108 platelets before the drug treatment, but remarkably increased to 4.33 ± 5.48 mU/108 platelets (n = 16) after BG/BCNU drug-selective treatments. The levels of Plt-F8 in the untreated transduced control group remained low over the study period. FVIII activity was not detected in the plasma in any of the recipients even with Plt-F8 as high as 22 mU/108 platelets. The average copy number of 2bF8/MGMT proviral DNA per cell was determined by quantitative real-time PCR. 2bF8 proviral DNA was barely detectable (0.01 ± 0.02 copies/cell) in recipients before drug-selective treatment, but it increased to 0.42 ± 0.15 copies/cell after BG/BCNU treatments, confirming that 2bF8/MGMT genetically modified cells were effectively enriched in vivo after drug-selective treatment. When the tail clip survival test was used to assess phenotypic correction of the FVIIInull coagulation defect, 15 of 16 treated animals survived the tail clip challenge; in contrast, none of the untransduced FVIIInull control mice survived. When ROTEM analysis was used to determine the whole blood clotting time (CT), the CT was shortened from 3043 ± 728 seconds (n = 7) to 931± 273 seconds (n = 6) (P < 0.0001) in treated transduced recipients when compared to FVIIInull mice. There was no significant difference between wild type (722 ± 270 seconds, n = 7) and treated recipients. To ensure sustained Plt-F8 expression in BG/BCNU treated transduced recipients, some primary recipients were sacrificed 9 months after transplantation and BM mononuclear cells were transplanted into secondary recipients. Platelet lysate FVIII activity assays showed that the levels of Plt-F8 in secondary recipients were similar to those in primary recipients, confirming that long-term repopulating HSCs were successfully genetically modified by 2bF8/MGMT LV. When a low intensity pre-conditioning regimen of 440 cGy TBI was used, the levels of Plt-F8 increased from 0.06 ± 0.12 mU/108 platelets to 1.86 ± 2.06 mU/108 platelets after BG/BCNU drug-selective treatment. It is notable that no anti-FVIII inhibitory antibodies were detected in the treated recipients even after rhFVIII challenge, indicating that immune tolerance was induced in the treated animals. In contrast, all FVIIInull mice under the same challenge developed various levels of inhibitors. Taken together, we have established a powerful in vivo selective system that allows us to enrich 2bF8 LV-transduced cells and to enhance platelet-FVIII expression for hemophilia A gene therapy. Disclosures: No relevant conflicts of interest to declare.

Development And Application Of A Minimal-Adenoviral Vector System For Gene Therapy Of Hemophilia A

1999 ◽  
Vol 82 (08) ◽  
pp. 562-571 ◽  
Author(s):  
Steven Josephs ◽  
Jiemin Zhou ◽  
Xiangming Fang ◽  
Ramón Alemany ◽  
Cristina Balagué ◽  
...  
Keyword(s):  
Gene Therapy ◽  
Factor Viii ◽  
Human Factor ◽  
Hemophilia A ◽  
Vector System ◽  
High Level Expression ◽  
Viral Particles ◽  
Human Factor Viii ◽  
High Level

IntroductionHemophilia A and B are the most common bleeding disorders caused by deficiencies of clotting factors VIII and IX, respectively, both of which are X-linked with a recessive heredity.1 Replacement of the deficient factors with frequent intravenous injections of plasma concentrates or recombinant proteins is the standard treatment for these diseases.2 Great efforts have been made for nearly a decade toward developing experimental gene therapy for these diseases and aiming at the development of a medical intervention that is more effective and convenient than the currently available replacement therapies.3 Hemophilia is a suitable clinical model for the development of gene therapy products and has a number of advantages: 1) there is a simple and well defined cause-and-effect relationship between the protein deficiencies and bleeding symptoms; 2) tissue-specific expression and precise regulation of the transgenes are not necessary; 3) well characterized animal models are available for preclinical studies; 4) an unequivocal endpoint for product efficacy can be assessed in clinical trials; and 5) even 1% to 5% of the normal physiological levels of the proteins is therapeutic.For gene therapy of hemophilia, the most challenging hurdle, with respect to the long-term expression of the deficient proteins at adequate levels, is the development of a suitable gene delivery system. Technologies have been evolving from ex vivo to in vivo approaches, from initial use of retroviral vector to recent application of adenviral (Ad) or adeno-associated virus (AAV) vector, demonstrating progress from early results of transient low-level expression to more sustained high-level expression.3 For hemophilia A treatment, Ad vectors are particularly useful, since the liver naturally produces factor VIII, and following intravenous (i.v.) injection, Ad vectors concentrate in the liver. This makes the gene transduction efficiency to liver very high. Adenovirus vectors have been developed for gene therapy due to their high titer, broad infectivity, potential for large payload, and in vivo gene delivery capacity.4 Although the immunogenicity and cytotoxicity associated with the early-generation Ad vectors have been a concern with respect to their clinical application, newly developed vectors, in which the viral coding sequences have been deleted, have significantly reduced the side effects associated with the vectors. The “gutless” Ad vector, or so called helper-dependent, large-capacity, or mini- Ad vectors are the representative examples of these new-generation Ad vectors.5-15 The mini-Ad vector system described in this report was developed based on two major research findings. First, an Ad- SV40 hybrid virus discovered during attempts to grow human Ad in non-permissive monkey COS-7 cells.16 The hybrid virus had a genome structure in which only both ends of the Ad sequences were retained and almost all coding sequences of the Ad genome were replaced by symmetric, tandemly repeated SV40 genomes. The hybrid viruses replicated and were packaged in the presence of a wild-type Ad as a helper. This finding implied that total replacement of the Ad genome was possible to form a mini-Ad vector as long as proper helper function and selective pressure was provided. Secondly, it was discovered that Ad packaging can be attenuated by deleting portions of the packaging signal.17 This finding provided a means to put selective pressure on the helper Ad (referred to as ancillary Ad) by specifically limiting its packaging process and allowing a preferential packaging of the mini-Ad. The system, therefore, is designed to have three main components: the mini-Ad vector, the E1-deleted ancillary Ad, and a production cell line that provides AdE1 complementation.Based on the mini-Ad vector system, MiniAdFVIII was developed. The MiniAdFVIII vector carries a 27 kb expression cassette, in which the full-length human factor VIII cDNA is flanked by a human albumin promoter and cognate genomic sequences. Infection of MiniAdFVIII in vitro showed that the vector mediated expression of functional human factor VIII at levels of 100-200 ng/106 cells per 24 hours in HepG2 and 293 cells. With single-dose intravenous injection of 1011 viral particles in hemophilic mice, MiniAdFVIII produced a sustained high-level expression of human factor VIII (at 100-800 ng/ml for up to 369 days) that corrected the factor VIII-deficient phenotype. Safety studies of MiniAdFVIII showed that there were no significant toxicities in mice and dogs after a single intravenous dose of up to 3×1011 and 6×1012 viral particles, respectively. In this report, other studies for developing the MiniAdFVIII vector with a site-specific integration capability and the development of a human factor VIII-tolerized mouse model for preclinical studies of MiniAdFVIII are described.

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