Search PubMed⌕ Search

Biomedical subjects

T Burnouf

Publications and source records attributed to T Burnouf.

At least 19 recordsLinked to original sources
PubMed2006

A minipool process for solvent-detergent treatment of cryoprecipitate at blood centres using a disposable bag system.

BACKGROUND AND OBJECTIVES: Single-donor or small-pool cryoprecipitates are produced by blood establishments, mostly in developing countries, for substitute therapy in haemophilia A, von Willebrand disease and fibrinogen deficiency, as well as for the manufacture of fibrin sealant. As cryoprecipitate may be contaminated with pathogenic plasma-borne viruses, there is an urgent need to develop a simple method for the viral inactivation of cryoprecipitate. MATERIALS AND METHODS: Cryoprecipitate was obtained according to standard procedures. Ten minipools of five or six donations of cryoprecipitate were prepared and subjected, in sterile closed bags, to a viral inactivation treatment using either 2% tri(n-)butyl phosphate (TnBP) for 4 h at 37 degrees C or the combination of 1% TnBP and 1% Triton X-45 for 4 h at 31 degrees C. The cryoprecipitates were subsequently extracted three times in their processing bags by mixing and decantation using 7.5% sterile ricinus oil. The TnBP-treated cryoprecipitates were further subjected to a clarifying centrifugation step at 3800 g for 30 min. The final products were dispensed into individual bags and frozen at -30 degrees C or lower. RESULTS: The cryoprecipitates treated with either 2% TnBP or 1% TnBP + 1% Triton X-45 showed excellent (> 93%) mean recovery of coagulant factor VIII (FVIII), ristocetin cofactor Von Willebrand factor (VWF:RCo), and clottable fibrinogen activity. Prothrombin time, international normalized ratio and activated partial thromboplastin time increased during solvent-detergent treatment but returned to initial values after oil extractions. The final content of TnBP and Triton X-45 was < 10 and 50 ppm, indicating excellent removal by the oil-extraction procedure. CONCLUSIONS: Viral inactivation treatment by TnBP, with or without Triton X-45, can be applied to minipools of cryoprecipitate, with good recovery of FVIII, VWF and fibrinogen. The viral inactivation and solvent-detergent removal process can be performed in a closed bag system and using simple blood establishment techniques and equipment. This technology could be considered for the improved viral safety of cryoprecipitate which is used to treat haemophilia A, von Willebrand disease or fibrinogen deficiency, or to prepare fibrin sealant.

Blood Banks↗
PubMed2004

Content and functional activity of von Willebrand factor in apheresis plasma.

BACKGROUND AND OBJECTIVES: Von Willebrand Factor (VWF) is a complex high-molecular-weight (HMW) plasma glycoprotein playing a critical role in primary and secondary haemostasis. Owing to its multimeric structure and sensitivity to proteolysis, VWF can be used as a marker of the impact of collection procedures on the characteristics of plasma for transfusion and for fractionation. We studied VWF content, functional activity and HMW multimers in plasmas collected by five different automated apheresis collection procedures. MATERIALS AND METHODS: Five series of 30 plasma units were obtained from volunteer donors at two collection sites using Haemonetics PCS2 machines with Revision (Rev) F, Rev G, high-separation core (HSC), or filter core (FC) procedures, or Baxter-Fenwall Autopheresis-C (Auto-C). VWF antigen (VWF:Ag), ristocetin cofactor (VWF:RCo) activity and HMW multimers were first determined in 10 randomly selected plasma donations collected with Rev G, HSC, FC and Auto-C procedures. Then, the same analyses and the collagen binding (VWF:CB) activity were determined in the pools of 30 donations from each of the five procedures and compared with two normal plasma pools (NPP1 and NPP2). A reference plasma (RP) was used to calibrate each assay. RESULTS: There were a greater number of group O individuals in the Rev F, Rev G and FC donors than in the HSC and Auto-C donors. The mean VWF:Ag level was > 100 IU/dl, VWF:RCo activity was > 90 U/dl, the VWF:RCo/Ag ratio was close to 1, and the percentage of 11-15 mers was above 100% of RP in the 10 individual plasma units from Rev G, HSC, FC, and Auto-C and in their respective pools. The mean percentage of multimers > 15 mers, relative to RP, was significantly less in Rev G plasmas (48 +/- 17%; range 32-91%), compared with Auto-C, HSC and FC plasmas (P = 0.0211; 0.0257; and 0.0376, respectively). The VWF:CB activity of the 30-donation pools was 61 and 60 U/dl in Auto C and HSC, 50 U/dl in Rev F and FC, and 43 U/dl in the Rev G pool. The VWF:CB/Ag ratio was 0.54 (Auto-C), 0.49 (HSC), 0.46 (Rev F), 0.45 (FC) and 0.37 (Rev G), compared with 0.81and 0.92 in NPPs. The percentage of VWF multimers of 11-15 mers in apheresis plasma and NPP was normal. VWF multimers > 15 mers ranged from 38 to 64% of that of RP plasma, and was 111 and 112% in NPPs. CONCLUSIONS: The VWF:Ag, VWF:RCo activity and 11-15 mer VWF multimers were well preserved in all plasma units from each of the five apheresis procedures. The VWF:CB activity and the percentage of multimers > 15 mers in apheresis plasma was less than in normal plasma pools and differed slightly among procedures.

ABO Blood-Group System↗
PubMed2004

WHO Expert Committee on Biological Standardization.

This report presents the recommendations of a WHO Expert Committee commissioned to coordinate activities leading to the adoption of international requirements for the production and control of vaccines and other biologicals and the establishment of international biological reference materials. The report starts with a discussion of general issues brought to the Committee's attention and provides information on the status and development of reference materials for various antibodies, antigens, blood products and related substances, cytokines, growth factors, and endocrinological substances. The second part of the report, of particular relevance to manufacturers and national regulatory authorities, contains recommendations for the production and quality control of meningococcal group C conjugate vaccines, guidelines for regulatory expectations for clinical evaluation of vaccines, guidelines for the production and quality control of inactivated oral cholera vaccines and guidelines on viral inactivation and removal procedures intended to assure the viral safety of human blood plasma products.

Advisory Committees↗
PubMed2003

Chromatographic purification and properties of a therapeutic human protein C concentrate.

Protein C deficiency (inherited and acquired) has a relatively high incidence rate in the general population worldwide. For many years, protein C deficient patients have been treated with fresh frozen plasma, prothrombin complex concentrates, heparin or oral anticoagulants, which all have clinical drawbacks. We report the production process of a highly purified human protein C concentrate from 1500 l of cryo-poor plasma by a four-step chromatographic procedure. After DEAE-Sephadex adsorption, protein C was separated from clotting factors II, VII and IX by DEAE-Sepharose FF and further purified, using a new strategy, by an on-line chromatographic system combining DMAE-Fractogel and heparin-Sepharose CL-6B. In addition, the product was treated against viral risks by solvent-detergent and nanofiltration on 15-nm membranes. The protein C concentrate was essentially free of other vitamin K-dependent proteins. Proteolytic activity was undetectable. Neither activated protein C, prekallikrein activator, nor activated vitamin K-dependent clotting factors were found resulting in good stability of the protein C activity. In vitro and in vivo animal tests did not reveal any sign of potential thrombogenicity. The final freeze-dried product had a mean protein C concentration of 58 IU/ml and a mean specific activity of 215 IU/mg protein, corresponding to over 12000-fold purification from plasma. Therefore, this concentrate appears to be of potential benefit for the treatment of protein C deficiency.

Animals↗
PubMed2003

Nanofiltration of plasma-derived biopharmaceutical products.

This review presents the current status on the use and benefits of viral removal filtration systems--known as nanofiltration--in the manufacture of plasma-derived coagulation factor concentrates and other biopharmaceutical products from human blood origin. Nanofiltration of plasma products has been implemented at a production scale in the early 1990s to improve margin of viral safety, as a complement to the viral reduction treatments, such as solvent-detergent and heat treatments, already applied for the inactivation of human immunodeficiency virus, hepatitis B and hepatitis C virus. The main reason for the introduction of nanofiltration was the need to improve product safety against non-enveloped viruses and to provide a possible safeguard against new infectious agents potentially entering the human plasma pool. Nanofiltration has gained quick acceptance as it is a relatively simple manufacturing step that consists in filtering protein solution through membranes of a very small pore size (typically 15-40 nm) under conditions that retain viruses by a mechanism largely based on size exclusion. Recent large-scale experience throughout the world has now established that nanofiltration is a robust and reliable viral reduction technique that can be applied to essentially all plasma products. Many of the licensed plasma products are currently nanofiltered. The technology has major advantages as it is flexible and it may combine efficient and largely predictable removal of more than 4 to 6 logs of a wide range of viruses, with an absence of denaturing effect on plasma proteins. Compared with other viral reduction means, nanofiltration may be the only method to date permitting efficient removal of enveloped and non-enveloped viruses under conditions where 90-95% of protein activity is recovered. New data indicate that nanofiltration may also remove prions, opening new perspectives in the development and interest of this technique. Nanofiltration is increasingly becoming a routine step in the manufacture of biopharmaceutical products.

Blood Coagulation Factors↗
PubMed2003

Nanofiltration of single plasma donations: feasibility study.

BACKGROUND AND OBJECTIVES: Major technical developments have been made in recent years to improve the quality and safety of human plasma for transfusion and fractionation. The present study was performed to assess, for the first time, the feasibility of applying a nanofiltration process, using 75-nm and 35-nm mean pore size membranes (Planova) 75N and Planova 35N), to human plasma. MATERIALS AND METHODS: Ten apheresis plasma units were obtained from 10 plasma donors. Within 4 h of collection, plasma was subjected to leucoreduction and filtration (using 75-nm and 35-nm mean pore size membranes) at 35 degrees C, at less than 1 bar pressure. Aliquots of plasma were taken at all steps of the filtration procedure and numerous plasma quality parameters were measured. In addition, six hepatitis C virus (HCV)-positive plasma donations were experimentally subjected to the same filtration sequence and subsequently assessed by RNA polymerase chain reaction (PCR) and branched-chain DNA-quantification assays. RESULTS: Leucoreduced plasma can be reproducibly nanofiltered onto a sequence of 75-nm and 35-nm membranes, at a flow rate of 450 ml/h and a temperature of 35 +/- 0.5 degrees C. Some protein dilution, or loss, was found during filtration, but the plasma filtered through membranes with a mean pore size of 75 nm and 35 nm met in vitro specifications for use in transfusion or fractionation. There were no signs of activation of the coagulation system. HCV-positive plasma donations became negative, as judged by PCR and branched-chain DNA assay results, after filtration through the 35-nm membrane. CONCLUSIONS: It is possible to apply a 75 + 35-nm filtration process to leucoreduced human plasma. This technology may have important future benefits in improving the quality and safety of plasma, by removing blood cell debris and infectious agents.

Blood Donors↗
PubMed2001

Affinity chromatography in the industrial purification of plasma proteins for therapeutic use.

Affinity chromatography is a powerful technique for the purification of many proteins in human plasma. Applications cover the isolation of proteins for research purposes but also, to a large extent, for the production of therapeutic products. In industrial plasma fractionation, affinity chromatography has been found to be particularly advantageous for fine and rapid capture of plasma proteins from industrial plasma fractions pre-purified by ethanol fractionation or by ion-exchange chromatography. To date, affinity chromatography is being used in the production of various licensed therapeutic plasma products, such as the concentrates of Factor VIII, Factor IX, von Willebrand Factor, Protein C, Antithrombin III, and Factor XI. Most commonly used ligands are heparin, gelatin, murine antibodies, and, to a lesser extent, Cu(2+). Possible development of the use of affinity chromatography in industrial plasma fractionation should be associated to the current development of phage display and combinatorial chemistry. Both approaches may lead to the development of tailor-made synthetic ligands that would allow implementation of protein capture technology, providing improved productivity and yield for plasma products.

Anticoagulants↗
PubMed2001

Passive transfer of scrub typhus plasma to patients with AIDS: a descriptive clinical study.

We examined the HIV-inhibitory effects previously found to be associated with scrub typhus infection. Individual 500 ml units of plasma from donors with mild scrub typhus were safety-tested, subjected to virucidal heat treatment, and administered to 10 HIV-1-infected recipients who were not receiving antiretroviral drugs. HIV-1 copy number fell three-fold or more in two recipients, and virus burden was reduced for 8 weeks in 70% (7/10) of recipients of a single plasma infusion, compared with the mean of three pre-infusion measurements. Scrub typhus donor plasma inhibited HIV-1 in vitro compared with normal human plasma and media controls. In the clearest in vivo response, reduction in viral load was accompanied by clinical improvement, a switchback from the syncytia-inducing to the non-syncytia-inducing phenotype, and decreases in CD8 cells and IL-6 levels. Scrub typhus infections can generate heat-stable, transferable plasma factors that exert prolonged anti-HIV effects. Whether variability in the results is due to different scrub typhus infections, different HIV infections or different individual responses, is unclear.

Acquired Immunodeficiency Syndrome↗
PubMed2000

Virucidal heat-treatment of single plasma units: a potential approach for developing countries.

Since HIV first burst onto the scene of transfusion medicine, the quest for viral inactivation processes for plasma and plasma products has not ceased. Sophisticated methods for improving viral safety are currently used in the industrial world. However, in developing countries, with no facilities for treating plasma, nonviral-inactivated fresh frozen plasma [FFP] continues to be used extensively, and as screening may not be optimal (or may even be absent), FFP still contributes to the spread of HIV and other infectious viruses. The feasibility of heat-treating FFP at the liquid state, in its collection bag, was explored by testing diverse conditions of temperature and duration, in the presence of biologically compatible stabilisers. Quality of the heat-treated plasma was evaluated by haematological, biochemical and animal assays. The efficiency of the method to inactivate viruses was validated using HIV and model viruses. The selected heating conditions are 50 degrees C for 3 h. The optimized combination of stabilizers is composed of 30 mM trisodium citrate, 10 g L-1 L-lysine, 12 mM calcium gluconate and 150 g L-1 sorbitol. Plasma coagulability is appropriately preserved as shown by the KCT ratio (1.4). Recovery of biological activity of most coagulation factors is higher than 70% (including fibrinogen & von Willebrand factor). Electrophoretic and immunoblotting studies did not evidence protein aggregation and/or degradation. Viral validation studies of this procedure have shown complete inactivation of HIV (> 6.6 log) in less than 1 h of treatment. A viral reduction of at least 4 log for various model viruses, including those of hepatitis A and C viruses, suggests a potential contribution of the method to diminish the risk from various blood-borne viruses. The selected formulation appears to preserve plasma protein integrity and properties. The procedure does not require sophisticated equipment but it is mandatory to monitor it carefully to ensure quality and reproducibility. If properly controlled and standardized, this approach offers an opportunity to reduce the risk of transmission of HIV and other viruses, particularly in poor countries with a high incidence of HIV.

Developing Countries↗
PubMed2000

Reducing the risk of infection from plasma products: specific preventative strategies.

Collection and testing procedures of blood and plasma that are designed to exclude donations contaminated by viruses provide a solid foundation for the safety of all blood products. Plasma units may be collected from a selected donor population, contributing to the exclusion of individuals at risk of carrying infectious agents. Each blood/plasma unit is individually screened to exclude donations positive for a direct (e.g., viral antigen) or an indirect (e.g. anti-viral antibodies) viral marker. As infectious donations, if collected from donors in the testing window period, can still be introduced into manufacturing plasma pools, the production of pooled plasma products requires a specific approach that integrates additional viral reduction procedures. Prior to the large-pool processing, samples of each donation for fractionation are pooled ('mini-pool') and subjected to a nucleic acid amplification test (NAT) by, for example, the polymerase chain reaction (PCR) to detect viral genomes (in Europe: HCV RNA plasma pool testing is now mandatory). Any individual donation found PCR positive is discarded before the industrial pooling. The pool of eligible plasma donations (which may be 2000 litres or more) may be subjected to additional viral screening tests, and then undergoes a series of processing and purification steps that, for each product, comprise one or several reduction treatments to exclude HIV, HBV HCV and other viruses. Viral inactivation treatments most commonly used are solvent-detergent incubation and heat treatment in liquid phase (pasteurization). Nanofiltration (viral elimination by filtration), as well as specific forms of dry-heat treatments, have gained interest as additional viral reduction steps coupled with established methods. Viral reduction steps have specific advantages and limits that should be carefully balanced with the risks of loss of protein activity and enhancement of epitope immunogenicity. Due to the combination of these overlapping strategies, viral transmission events of HIV, HBV, and HCV by plasma products have become very rare. Nevertheless, the vulnerability of the plasma supply to new infectious agents requires continuous vigilance so that rational and appropriate scientific countermeasures against emerging infectious risks can be implemented promptly.

Biomarkers↗
PubMed2000

Evaluation of a fibrin sealant free of bovine-derived components in an experimental vas anastomosis study.

OBJECTIVES: The risk of transmission of bovine spongiform encephalopathy cannot be excluded from the use of bovine-derived products. The present study was undertaken to evaluate the performance of a new fibrin glue free of bovine-derived components in vas anastomosis and to compare this product to conventional vas anastomosis with fibrin glue. METHODS: Bilateral delayed vas anastomosis was performed in 40 Sprague-Dawley rats. All animals underwent a fibrin glue-assisted vas anastomosis with three transmural sutures tied prior to fibrin glue application. The composition and preparation of fibrin glue was similar for all vas anastomoses except the fibrinolysis inhibitor component which was aprotinin (3,000 KUI/ml) in group 1 and tranexamic acid (10 mg/ml) in group 2. The animals (20 rats in both groups) were sacrificed 7 weeks postoperatively and evaluated for gross patency, presence of sperm granuloma and tensile strength measurements at the anastomosis site. RESULTS: No difference was found between the 2 groups for all parameters evaluated whether a bovine-derived or a synthetic fibrinolysis inhibitor component was used. CONCLUSION: This study showed that tranexamic acid, a fibrinolysis inhibitor, can be substituted for conventional fibrin glue thereby avoiding the risks of bovine products.

Anastomosis, Surgical↗
PubMed2000

Purification of human ceruloplasmin as a by-product of C1-inhibitor.

Human ceruloplasmin (Cp) has been purified from cryoprecipitate-poor plasma as a by-product of the C1-inhibitor production chain. Highly purified Cp was obtained by subsequent ion-exchange chromatography on sulfate-Fractogel EMD and TMAE-Fractogel EMD. Treatments for viral safety included application of the solvent-detergent method and two nanofiltration steps using 35- and 15-nm pore size filters at the end of the process. Overall antigen yield was 95 (+/-5) %. Purified human ceruloplasmin was studied by electron spin resonance (ESR) to characterize its different types of copper complexes and to check its antioxidant properties. We distinguished three types of complexes: one type-2 Cu(II) with g// = 2.25 and A// = 180 G and two type-I Cu(II) exhibiting different narrow hyperfine splitting (A// = 72 G and A// = 90 G) with close g// (2.20 and 2.21). Purified Cp has a specific activity of 24.5+/-0.2 mU/mg of proteins. This process provides a method for Cp purification that could be easily integrated into modern plasma fractionation.

Antioxidants↗
PubMed1999

Influence of formulation on jet nebulisation quality of alpha 1 protease inhibitor.

As foam appears during solution constitution and nebulisation of alpha 1 protease inhibitor (alpha 1 PI), we selected in a previous work, antifoams likely to be associated with an alpha 1 PI solution to be nebulised: span 65 at a 0.025% concentration and cetyl alcohol at a 0.05% concentration associated with tyloxapol at 0.025% concentration. The purpose of this study was, on the one hand to study the influence of the formulation on nebulisation quality by relating physicochemical properties and nebulisation capacity, and on the other hand, to define the alpha 1 PI that will be retained for a clinical study. The properties of the different alpha 1 PI formulations are compared: surface tension, viscosity, time required to constitute the protein solution and pH. Nebulisation quality is evaluated under different operating conditions by measuring the droplet size, the quantity of alpha 1 PI nebulised, nebulisation time and the quantity of alpha 1 PI likely to reach the lungs which was subjected to statistical analysis. The statistical analysis of results indicates that the addition of the cetyl alcohol/tyloxapol mixture improves nebulisation effectiveness by significantly increasing the quantity of drug nebulised and therefore the quantity of alpha PI likely to reach the lungs. It is this formulation that will be retained for clinical trials. We check that the nebuliser and operating conditions influence all the parameters, that is to say the respirable fraction, the quantity nebulised and the nebulisation time. Although there is no interaction between the nebuliser and the formulation, nebulisation quality is the combined result of the formulation, the nebuliser and the operating conditions.

Antifoaming Agents↗
PubMed1998

Application of bioaffinity technology in therapeutic extracorporeal plasmapheresis and large-scale fractionation of human plasma.

This paper describes the increasingly unique and powerful role that affinity chromatography is occupying both as a tool for the treatment of extracorporeal plasma exchange (to discard biological compounds with noxious metabolic or immunologic effects in patients) and as a purification tool in the production of therapeutic plasma protein derivatives. Management of both applications requires careful monitoring of the parameters applied to the plasma material, to avoid immunological stimulation or activation of the coagulation cascade. Examples of direct current applications of affinity ligands in therapeutic removal and industrial production of plasma compounds are presented.

Chromatography, Affinity↗
PubMed1998

Vasal reanastomosis using fibrin glue combined with sutures: which combination of sutures in a delayed protocol? Experimental study in rats.

OBJECTIVES: The actual number of transmural sutures needed to ensure a successful fibrin-glued vasovasostomy is a key study parameter of the few experimental works already published. The present work was done to evaluate fibrin-glued vasovasostomy in rats in combination with only 2 transmural sutures. We compared the results to our previous study in which we demonstrated the efficiency of a combination of the use of fibrin glue with 3 sutures in comparison with a conventional microsurgical technique. MATERIALS AND METHODS: Twenty Sprague-Dawley rats underwent bilateral vasectomy followed 2 weeks later by bilateral vasovasostomy using fibrin glue combined with 2 transmural sutures. Each animal was sacrificed 7 weeks postoperatively after a 3-week mating period with a Sprague-Dawley female rat, the vasal specimens were evaluated for sperm granuloma formation. Mean operative time and fertility rates were recorded. RESULTS: The combination of fibrin glue with 2 transmural sutures gave evidence of less successful performances than the combination with 3 transmural sutures and the conventional microsurgical technique for all parameters evaluated but the mean operative time. CONCLUSION: Our study underlines the need for a third transmural suture placed 120 degrees apart from the others when performing a fibrin glue delayed vasovasostomy. This allows a better vas lumen opening at the anastomotic site and therefore a more efficient vasal anastomosis in a delayed protocol.

Anastomosis, Surgical↗