Assay of factor VIII antigen (VIII:CAg) in 294 haemophilia A patients by a new commercial ELISA using monoclonal antibodies

Therapeutic levels of FVIII following a single peripheral vein administration of rAAV vector encoding a novel human factor VIII variant

Recombinant adeno-associated virus (rAAV) vectors encoding human factor VIII (hFVIII) were systematically evaluated for hemophilia A (HA) gene therapy. A 5.7-kb rAAV-expression cassette (rAAV-HLP-codop-hFVIII-N6) containing a codon-optimized hFVIII cDNA in which a 226 amino acid (aa) B-domain spacer replaced the entire B domain and a hybrid liver-specific promoter (HLP) mediated 10-fold higher hFVIII levels in mice compared with non-codon-optimized variants. A further twofold improvement in potency was achieved by replacing the 226-aa N6 spacer with a novel 17-aa peptide (V3) in which 6 glycosylation triplets from the B domain were juxtaposed. The resulting 5.2-kb rAAV-HLP-codop-hFVIII-V3 cassette was more efficiently packaged within AAV virions and mediated supraphysiologic hFVIII expression (732 ± 162% of normal) in HA knock-out mice following administration of 2 × 10(12) vector genomes/kg, a vector dose shown to be safe in subjects with hemophilia B. Stable hFVIII expression at 15 ± 4% of normal was observed at this dose in a nonhuman primate. hFVIII expression above 100% was observed in 3 macaques that received a higher dose of either this vector or the N6 variant. These animals developed neutralizing anti-FVIII antibodies that were abrogated with transient immunosuppression. Therefore, rAAV-HLP-codop-hFVIII-V3 substantially improves the prospects of effective HA gene therapy.

Quality control of recovered plasma for fractionation: an extensive Italian study

BACKGROUND

This study was aimed at obtaining significant information on the quality of whole-blood plasma (WBP) delivered to a private pharmaceutical company by the blood transfusion centers (BTCs) of 10 Italian regions.

STUDY DESIGN AND METHODS

A statistical sampling plan of plasma units took into account the contribution each selected blood transfusion center, belonging to the 10 regions, made to the plasma pool annually delivered to the pharmaceutical company. A total of 1787 plasma units were selected for coagulation Factor VIII (FVIII:C) and Factor VIII antigen (FVIII:Ag) analysis.

RESULTS

The FVIII:C mean value was 0.99 IU per mL; it was significantly lower in O units (0.86 IU/mL) than in non-O units (1.08 IU/mL). The mean value of FVIII:Ag was 0.90 IU per mL; it was significantly lower in O units (0.78 IU/mL) than in non-O units (0.99 IU/mL). In units with a FVIII:C level of less than 0.70 IU per mL, the FVIII:Ag mean value (0.62 IU/mL) was higher in comparison to the FVIII:C mean value (0.57 IU/mL). Instead, in the units with a FVIII:C level of at least 0.70 IU per mL, the mean level of FVIII:C (1.08 IU/mL) was higher than that of FVIII:Ag (0.96 IU/mL).

CONCLUSIONS

The mean value of FVIII:C (0.99 IU/mL) in whole-blood plasma produced by the 10 Italian regions is higher than that reported in other studies. A total of 83.1 percent of units have a FVIII:C level of at least 0.70 IU per mL. The mean level of FVIII:Ag is lower than that of FVIII:C. FVIII:Ag is higher in those units with a FVIII:C level of less than 0.70 IU per mL, while it gradually decreases as FVIII:C exceeds 0.70 IU per mL, thus showing a greater resistance to handling of plasma in the production steps mostly affecting FVIII:C stability.

A solvent/detergent-treated and 15-nm filtered factor VIII: a new safety standard for plasma-derived coagulation factor concentrates

BACKGROUND

Since the early 1990 s the Committee for Proprietary Medicinal Products has set the mandatory requirement that all manufacturing processes for blood products include two virus removal/inactivation steps that are complementary in their action.

OBJECTIVES

The objective was to develop a manufacturing process for factor VIII (FVIII) including two complementary steps of viral inactivation/elimination.

METHODS

A 35-15 nm nanofiltration step was added to a former FVIII manufacturing process that included solvent/detergent (S/D) treatment to generate a new FVIII concentrate called Factane. The impact of nanofiltration on the structural and functional characteristics of FVIII, as well as virus/transmissible spongiform encephalopathy reduction factors were assessed.

RESULTS

Using an innovative approach, FVIII was successfully nanofiltered at 35-15 nm, while the biological properties of the active substance were unmodified. FVIII coagulant and antigen content for Factane and previous S/D-treated FVIII (FVIII-LFB, commercialized as Facteur VIII-LFB) were comparable. The FVIII one-stage chromogenic and coagulant/antigen ratios confirmed that nanofiltered FVIII was not activated. After nanofiltration, the copurified von Willebrand factor (vWF) was reduced but vWF/FVIII binding properties were unaffected. Phospholipid binding and thrombin proteolysis studies displayed no differences between Factane and FVIII-LFB. The rate of factor Xa generation was slightly lower for Factane when compared to FVIII-LFB. Viral validation studies with different viruses showed no detectable virus in the filtrate.

CONCLUSIONS

Nanofiltration of FVIII at 15 nm is feasible despite the large molecular weight of FVIII and vWF. Nanofiltration has been proven to be highly effective at removing infectious agents while preserving the structural and functional integrity of FVIII.

In vitro kinetics of factor VIII activity in patients with mild haemophilia A and a discrepancy between one-stage and two-stage factor VIII assay results

In some mild haemophilia A patients (discrepant haemophilia), factor VIII coagulant activity (FVIII:C) levels, by one-stage assay are more than double than those by two-stage assay. This may be due to the longer incubation times (10-12 min) in the two-stage assay. This study aimed to determine the time course of the activation phase of the two-stage assay, using both classical coagulation and chromogenic detection methods. In both systems, for equivalent patients (equivalent FVIII:C levels by one-stage and two-stage assays, n = 6, all different mutations), similar FVIII:C results were obtained with short- or long-incubation times. In contrast, plasma from discrepant patients (n = 8, five different mutations) showed higher FVIII:C at shorter incubation times than after longer incubation times. In the chromogenic assay, FVIII:C levels were higher after incubation for 2 min (23-56%, mean 41%) than after 10 min (19-41%, mean 29%). In the classical coagulation assay, FVIII:C levels were higher at shorter incubation times (21-64%, mean 37%) than with the longer incubation times usually used (13-29%, mean 23%). These time-course experiments have verified that the longer incubation time used in the two-stage assay is at least partly responsible for the lower FVIII:C measured by that assay in discrepant haemophilia.

Screening for peptide affinity ligands on CIM monoliths

Screening of peptide ligands for affinity chromatography usually involves incubation with the target protein in a batch system. In an additional step, peptides with fast binding kinetics have to be selected in respect to satisfactory performance under flow conditions on a support ensuring optimal three-dimensional presentation of the peptide. We have developed a rapid screening system based on peptide synthesis and screening on CIM((R)) disks. The disk size was minimized to fit into microplates usually applied for solid-phase extraction. In combination with a vacuum manifold, semi-automated peptide synthesis and screening for binding to a target protein under simulated chromatography conditions are possible. Various analytical methods can be applied for parallel and automated determination of the quantity, integrity, or activity of the target protein in the flow through or bound to the affinity support. This system also allows parallel screening for suitable chromatographic conditions like running buffer, washing, and elution conditions.

The canine factor VIII 3'-untranslated region and a concatemeric hepatocyte nuclear factor 1 regulatory element enhance factor VIII transgene expression in vivo

If gene therapy is to be an effective treatment modality for hemophilia A, therapeutic levels and tissue-restricted expression of factor VIII (FVIII) must be achieved through optimization of transgene expression. To this end, we incorporated three types of sequence elements into a canine B domain-deleted FVIII transgene cassette and individually evaluated their effect on FVIII transgene expression. Functional FVIII activity was initially assessed in vitro and hydrodynamic injection of the different transgene constructs into mice was subsequently used as a model to compare in vivo expression of the various modified transgenes. Our results demonstrate that in vitro transgene expression is, in these studies, not a good predictor of in vivo transgene performance. In vivo analysis of a hybrid tissue-restricted promoter element, consisting of a concatemer of five hepatocyte nuclear factor 1 (HNF-1) consensus-binding motifs juxtaposed to the human FVIII proximal promoter, indicates that it is as efficient at mediating expression of the FVIII protein as the cytomegalovirus promoter. Addition of the full-length canine FVIII 3'-UTR also enhances transgene expression of FVIII in vivo. Sequence analysis of the canine FVIII 3'-UTR and human FVIII 3'-UTR indicates that the former lacks instability sequences and may therefore be more effective in stabilizing FVIII mRNA. Subsequent inclusion of FVIII introns 16 and 17 into the natural locations of the transgene disrupted mRNA processing and abolished expression of the FVIII protein. Introduction of intron 17 proximal to the FVIII cDNA did not enhance in vivo expression of canine FVIII from the transgene.

Carrier detection and prenatal diagnosis in haemophilia in India: realities and challenges

Organizing services for haemophilia in developing countries with few resources is a formidable task. There is wide variation in haemophilia care and management between developing and developed countries. The management of a genetic disorder such as haemophilia becomes difficult in developing countries where scanty resources are allocated mainly to nutrition and infectious diseases as a first priority. In a country such as India, with one billion people and with a wide diversity in cultural, educational and financial conditions, educating people about such diseases is difficult and will take a long time to have an effect on attitudes. Meanwhile, attempts are being made at several centres in India to develop carrier detection and prenatal diagnosis for this disease. Counselling a carrier for detection of her carrier status remains problematic in India because marriages are still largely arranged by the parents of prospective brides and bridegrooms. Hence, the very idea of communicating the carrier status to the bridegrooms' families may lead to cancellation of the marriages, and concealing the carrier status is associated with guilt both for the bride's parents as well as the bride. Prenatal diagnosis and carrier detection in India therefore must be discussed in this context.

Quantification of plasma-derived blood coagulation factor VIII by real-time biosensor measurements

Plasma-derived blood coagulation factor VIII was analyzed in real time using biosensor technology. Monoclonal antibodies directed against the heavy and against the light chain of factor VIII were immobilized on different carboxymethyl dextran surfaces. Different factor VIII concentrations were injected over the antibody surfaces in parallel and response levels were determined from the dissociation phase at a fixed time after sample injection. Serial dilutions of plasma-derived factor VIII with known concentrations determined by a commercial FVIIIC:Ag ELISA were used as standards. A quantification limit of 0.9 I.U./ml with antibody 530p and 1.5 I.U./ml with antibody 531p was calculated. Intra-assay precision expressed as percent coefficient of variation was below 10% for concentrations above 0.6 I.U./ml. Inter-assay precision for antibody 530p was below 20% for concentrations higher than 0.6 I.U./ml. For 531p, inter-assay precision was below 10% for concentrations higher than 2 I.U./ml. A sensor chip lifetime in respect to regeneration of at least 100 cycles for both antibodies was found. The small sample requirement of 35 microl allows fast analysis of different FVIII products and the use of two monoclonal antibodies directed against two different FVIII domains provides additional information about the integrity of the FVIII molecule.

Advances toward gene therapy for hemophilia at the millennium

Hemophilia A and hemophilia B are both X chromosome-linked recessive bleeding disorders that affect about 1 in 5000 males and result from a deficiency in the coagulation factors VIII and IX, respectively. Severely affected individuals require frequent administration of factor VIII or factor IX preparations derived from human plasma, and more recently, from recombinant DNA technology. Although these preparations have greatly reduced the contamination with blood-borne pathogens, there still exist significant limitations with protein replacement therapy. As we elucidate more about the expression, structure, and function of these coagulation factors new avenues will open for the development of novel genetically improved coagulation factors. Several aspects of the hemophilias A and B make these diseases attractive candidates for gene therapy. These advantages include the following: (1) these proteins are readily delivered into the circulation from a variety of different cell types; (2) low levels of expression would significantly improve the management of bleeding episodes in these patients; (3) it is unlikely that regulated expression of these proteins will be required; and (4) there are excellent animal models for these diseases. Although progress with gene transfer of factor IX has proceeded at a greater rate than factor VIII, success with both molecules has demonstrated partial persistent correction in mouse and canine models of hemophilia A and B. The information gained from these animal studies has provided new insights into gene therapeutic approaches for genetic diseases. In addition, several gene therapy clinical studies for the treatment of hemophilia A and B were initiated in 1999.