Current strategies to prevent transmission of prions by human plasma derivatives

Can the administration of platelet lysates to the brain help treat neurological disorders?

Neurodegenerative disorders of the central nervous system (CNS) and brain traumatic insults are characterized by complex overlapping pathophysiological alterations encompassing neuroinflammation, alterations of synaptic functions, oxidative stress, and progressive neurodegeneration that eventually lead to irreversible motor and cognitive dysfunctions. A single pharmacological approach is unlikely to provide a complementary set of molecular therapeutic actions suitable to resolve these complex pathologies. Recent preclinical data are providing evidence-based scientific rationales to support biotherapies based on administering neurotrophic factors and extracellular vesicles present in the lysates of human platelets collected from healthy donors to the brain. Here, we present the most recent findings on the composition of the platelet proteome that can activate complementary signaling pathways in vivo to trigger neuroprotection, synapse protection, anti-inflammation, antioxidation, and neurorestoration. We also report experimental data where the administration of human platelet lysates (HPL) was safe and resulted in beneficial neuroprotective effects in established rodent models of neurodegenerative diseases such as Parkinson's disease, Alzheimer's disease, traumatic brain injury, and stroke. Platelet-based biotherapies, prepared from collected platelet concentrates (PC), are emerging as a novel pragmatic and accessible translational therapeutic strategy for treating neurological diseases. Based on this assumption, we further elaborated on various clinical, manufacturing, and regulatory issues that need to be addressed to ensure the ethical supply, quality, and safety of HPL preparations for treating neurodegenerative and traumatic pathologies of the CNS. HPL made from PC may become a unique approach for scientifically based treatments of neurological disorders readily accessible in low-, middle-, and high-income countries.

Nanofiltration of growth media supplemented with human platelet lysates for pathogen-safe xeno-free expansion of mesenchymal stromal cells

Background aims

Human platelet lysate can replace fetal bovine serum (FBS) for xeno-free ex vivo expansion of mesenchymal stromal cells (MSCs), but pooling of platelet concentrates (PCs) increases risks of pathogen transmission. We evaluated the feasibility of performing nanofiltration of platelet lysates and determined the impact on expansion of bone marrow–derived MSCs.

Methods

Platelet lysates were prepared by freeze-thawing of pathogen-reduced (Intercept) PCs suspended in 65% storage solution (SPP+) and 35% plasma, and by serum-conversion of PCs suspended in 100% plasma. Lysates were added to the MSC growth media at 10% (v/v), filtered and subjected to cascade nanofiltration on 35- and 19-nm Planova filters. Media supplemented with 10% starting platelet lysates or FBS were used as the controls. Impacts of nanofiltration on the growth media composition, removal of platelet extracellular vesicles (PEVs) and MSC expansion were evaluated.

Results

Nanofiltration did not detrimentally affect contents of total protein and growth factors or the biochemical composition. The clearance factor of PEVs was >3 log values. Expansion, proliferation, membrane markers, differentiation potential and immunosuppressive properties of cells in nanofiltered media were consistently better than those expanded in FBS-supplemented media. Compared with FBS, chondrogenesis and osteogenesis genes were expressed more in nanofiltered media, and there were fewer senescent cells over six passages.

Conclusions

Nanofiltration of growth media supplemented with two types of platelet lysates, including one prepared from pathogen-reduced PCs, is technically feasible. These data support the possibility of developing pathogen-reduced xeno-free growth media for clinical-grade propagation of human cells.

A totally recombinant fibrin matrix for mesenchymal stem cell culture and delivery

Mesenchymal stem cells (MSCs) have been widely studied for tissue engineering and treating diseases in laboratories, clinical trials, and clinics. Fibrin matrices are often used to culture MSCs or increase the retention of MSCs at the injection site. However, fibrins made with the human plasma derived fibrinogen have high cost and risk of human pathogen transmission. In this article, we studied if fibrin matrices made with recombinant human fibrinogen, recombinant human thrombin, and recombinant human factor XIII could be used to culture and deliver MSCs. We systematically investigated the relationships between the fibrin matrix formulation, its nanostructure, and the behaviors of the cells in the matrix including the cell morphology, viability, and growth. We found that the fibrinogen concentration significantly affected the matrix structure and cell behaviors. We then used an optimized fibrin matrix to deliver human MSCs into mice subcutaneously. We found that the matrix could significantly enhance the retention of MSCs at the injection site. To our best knowledge, this is the first study on using fibrin matrices made with entirely recombinant proteins for culturing and delivering MSCs. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 3135-3142, 2018.

High-level expression and preparation of recombinant human fibrinogen as biopharmaceuticals

Fibrinogen is a large and complex glycoprotein containing two sets of each of three different chains (α, β and γ). There have been no reports of high-level expression of fibrinogen at commercial levels using mammalian cultured cells such as CHO cells because of the difficulty in highly expressing a protein with such a complex structure. We achieved high-level (1.3 g/l or higher) expression of recombinant human fibrinogen using CHO DG44 cells by optimizing the expression system and culture conditions. We also succeeded in establishing a high-recovery preparation method for recombinant fibrinogen that rarely yields degraded products. To characterize the properties of the recombinant human fibrinogen, we performed SDS-PAGE; western blotting of the α, β and γ chains using specific antibodies and scanning electron microscopy observations of fibrin fibres. We also evaluated the functional equivalence between recombinant fibrinogen and plasma fibrinogen with respect to the release of fibrinopeptides initiated by thrombin and its cross-linking properties. The basic properties of recombinant fibrinogen showed no apparent differences from those of plasma fibrinogen. Here, we report the development of methods for the culture and preparation of recombinant human fibrinogen of satisfactory quality that can be scaled up to the commercial level.

“Go no Go” in plasma fractionation in the world’s emerging economies: still a question asked 70 years after the COHN process was developed!

In the late 1980s, following the human immunodeficiency virus (HIV) epidemic and transfusion-transmitted infections from plasma-derived coagulation factor concentrates to hemophiliacs, many “advanced thinkers” claimed that plasma-derived products would be completely replaced by the year 2000 by safe recombinant products in most developed countries. However, things have not turned out that way, due to both the continual progress witnessed in plasma fractionation and viral-reduction technologies and technical difficulties still being encountered in developing more cost-effective non-immunogenic, fully active recombinant therapeutic proteins.

Accordingly, plasma fractionation remains a reasonably healthy industry worldwide, with an ever-increasing volume of plasma fractionated each year to meet the demands for safe and effective plasma-derived medicines at the global level. While high-income countries currently have generally good access to a panel of plasma-derived and recombinant products, desperate shortages of fractionated plasma products remain in developing economies, and patients still have to be treated inadequately.

The steady development of the collection of whole blood in developing economies, to gradually cover the recognized needs for red blood cell concentrates, generates an increasing volume of recovered plasma that is currently wasted. Incentives are therefore high for those countries to consider fractionating such plasma as a means of enhancing their supply of products to treat patients, thereby also decreasing the level of dependence on imported products.

Challenges of local plasma fractionation in developing economies are high, in a context where the technological and regulatory sophistication of the plasma fractionation industry is often underestimated, and the blood supply may be exposed to emerging infectious agents. In parallel, plasma product quality requirements and drivers are evolving in developed economies as is the awareness of clinicians to newer uses of products such as intravenous immunoglobulins, somewhat deviating from what currently remain the basic needs of developing countries in terms of affordable safe plasma products.

Global market trends for plasma-derived products, through plasma fractionation, are still increasing, despite increasing use of recombinant products, and attention is being focused on the five Ws of the fractionation field: which products; where; when; what and how much; and who will be the main suppliers?

Removal of transmissible spongiform encephalopathy prion from large volumes of cell culture media supplemented with fetal bovine serum by using hollow fiber anion-exchange membrane chromatography

Cases of variant Creutzfeldt-Jakob disease in people who had consumed contaminated meat products from cattle with bovine spongiform encephalopathy emphasize the need for measures aimed at preventing the transmission of the pathogenic prion protein (PrPSc) from materials derived from cattle. Highly stringent scrutiny is required for fetal bovine serum (FBS), a growth-medium supplement used in the production of parenteral vaccines and therapeutic recombinant proteins and in the ex vivo expansion of stem cells for transplantation. One such approach is the implementation of manufacturing steps dedicated to removing PrPSc from materials containing FBS. We evaluated the use of the QyuSpeed D (QSD) adsorbent hollow-fiber anion-exchange chromatographic column (Asahi Kasei Medical, Tokyo, Japan) for the removal of PrPSc from cell culture media supplemented with FBS. We first established that QSD filtration had no adverse effect on the chemical composition of various types of culture media supplemented with 10% FBS or the growth and viability characteristics of human embryonic kidney (HEK293) cells, baby hamster kidney (BHK-21) cells, African green monkey kidney (Vero) cells, and Chinese hamster ovary (CHO-k1) cells propagated in the various culture-medium filtrates. We used a 0.6-mL QSD column for removing PrPSc from up to 1000 mL of Dulbecco's modified Eagle's medium containing 10% FBS previously spiked with the 263K strain of hamster-adapted scrapie. The Western blot analysis, validated alongside an infectivity assay, revealed that the level of PrPSc in the initial 200mL flow-through was reduced by 2.5 to > 3 log10, compared with that of the starting material. These results indicate that QSD filtration removes PrPSc from cell culture media containing 10% FBS, and demonstrate the ease with which QSD filtration can be implemented in at industrial-scale to improve the safety of vaccines, therapeutic recombinant proteins, and ex vivo expanded stem cells produced using growth media supplemented with FBS.

Preparation, quality criteria, and properties of human blood platelet lysate supplements for ex vivo stem cell expansion

Most clinical applications of human multipotent mesenchymal stromal cells (MSCs) for cell therapy, tissue engineering, regenerative medicine, and treatment of immune and inflammatory diseases require a phase of isolation and ex vivo expansion allowing a clinically meaningful cell number to be reached. Conditions used for cell isolation and expansion should meet strict quality and safety requirements. This is particularly true for the growth medium used for MSC isolation and expansion. Basal growth media used for MSC expansion are supplemented with multiple nutrients and growth factors. Fetal bovine serum (FBS) has long been the gold standard medium supplement for laboratory-scale MSC culture. However, FBS has a poorly characterized composition and poses risk factors, as it may be a source of xenogenic antigens and zoonotic infections. FBS has therefore become undesirable as a growth medium supplement for isolating and expanding MSCs for human therapy protocols. In recent years, human blood materials, and most particularly lysates and releasates of platelet concentrates have emerged as efficient medium supplements for isolating and expanding MSCs from various origins. This review analyzes the advantages and limits of using human platelet materials as medium supplements for MSC isolation and expansion. We present the modes of production of allogeneic and autologous platelet concentrates, measures taken to ensure optimal pathogen safety profiles, and methods of preparing PLs for MSC expansion. We also discuss the supply of such blood preparations. Produced under optimal conditions of standardization and safety, human platelet materials can become the future 'gold standard' supplement for ex vivo production of MSCs for translational medicine and cell therapy applications.

Decontamination of prions in a plasma product manufacturing environment

BACKGROUND

The high resistance of prions to inactivating treatments requires the proper management of decontaminating procedures of equipment in contact with materials of human or animal origin destined for medical purposes. Sodium hydroxide (NaOH) is widely used today for this purpose as it inactivates a wide variety of pathogens including prions.

STUDY DESIGN AND METHODS

Several NaOH treatments were tested on prions bound to either stainless steel or chromatographic resins in industrial conditions with multiple prion strains.

RESULTS

Data show a strong correlation between inactivation results obtained by immunochemical detection of the prion protein and those obtained with infectivity assays and establish effective inactivation treatments for prions bound to stainless steel or chromatographic resins (ion exchange and affinity), including treatments with lower NaOH concentrations. Furthermore, no obvious strain-specific behavior difference was observed between experimental models.

CONCLUSION

The results generated by these investigations show that industrial NaOH decontamination regimens (in combination with the NaCl elution in the case of the chromatography process) attain substantial prion inactivation and/or removal between batches, thus providing added assurance to the biologic safety of the final plasma-derived medicinal products.

Removal of TSE agent from plasma products manufactured in the United Kingdom

BACKGROUND AND OBJECTIVES

The outbreak of vCJD in the UK leads to concern regarding the potential for human-to-human transmission of this agent. Plasma-derived products such as albumin, immunoglobulin and coagulation factors were manufactured by BPL from UK plasma up until 1999 when a switch to US plasma was made. In the current study, the capacity of various manufacturing processes that were in use both prior to and after this time to remove the TSE agent was tested.

MATERIALS AND METHODS

Small-scale models of the various product manufacturing steps were developed. Intermediates were spiked with scrapie brain extract and then further processed. Samples were assayed for the abnormal form of prion protein (PrP(SC) ) by Western blotting, and the reduction in the amount of scrapie agent determined.

RESULTS

Many of the manufacturing process steps produced significant reduction in the scrapie agent. Particularly effective were steps such as ethanol fractionation, depth filtration, ion-exchange and copper chelate affinity chromatography. Virus retentive filters, of nominal pore size 15 or 20 nm, removed >3 log. The total cumulative reduction capacity for individual products was estimated to range from 7 to 14 log. In the case of factor VIII (8Y), the total removal was limited to 3 log.

CONCLUSION

All the processes showed a substantial capacity to remove the TSE agent. However, this was more limited for the intermediate purity factor VIII 8Y which included fewer manufacturing steps.

Intravenous immunoglobulin G: trends in production methods, quality control and quality assurance

Intravenous immunoglobulin G (IVIG) is now the leading product obtained by fractionation of human plasma. It is the standard replacement therapy in primary and acquired humoral deficiency, and is also used for immunomodulatory therapy in various autoimmune disorders and transplantation. Over the last 30 years, the production processes of IVIG have evolved dramatically, gradually resulting in the development of intact IgG preparations safe to administer intravenously, with normal half-life and effector functions, prepared at increased yield, and exhibiting higher pathogen safety. This article reviews the developments that have led to modern IVIG preparations, the current methods used for plasma collection and fractionation, the safety measures implemented to minimize the risks of pathogen transmission and the major quality control tests that are available for product development and as part of mandatory batch release procedures.

Estimating the pathogen safety of manufactured human plasma products: application to fibrin sealants and to thrombin

BACKGROUND

Plasma fractionators have implemented many improvements over the past decade directed toward reducing the likelihood of pathogen transmission by purified blood products, yet little has been published attempting to assess the overall impact of these improvements on the probability of safety of the final product.

STUDY DESIGN AND METHODS

Safety margins for human immunodeficiency virus (HIV), hepatitis C virus (HCV), hepatitis B virus (HBV), hepatitis A virus (HAV), parvovirus B19, and variant form of Creutzfeldt-Jakob disease (vCJD) were calculated for the two fibrin sealants licensed in the United States and for thrombin. These products were selected because their use in a clinical setting is, in most cases, optional, and both were relatively recently approved for marketing by the US Food and Drug Administration (FDA). Moreover, thrombin and fibrinogen both undergo two dedicated virus inactivation steps and/or removal steps in accord with the recommendations of regulatory agencies worldwide. Safety margins were determined by comparing the potential maximum viral loads in contaminated units to viral clearance factors, ultimately leading to the calculation of the residual risk per vial.

RESULTS

The residual risk of pathogen transmission per vial was calculated to be less than 1 in 10(-15) for HIV, HCV, HBV, and HAV for both fibrinogen and thrombin. Owing to the greater quantities that can be present and its greater thermal stability, the calculated risk for parvovirus transmission was 1 in 500,000 vials for fibrinogen and less than 1 in 10(7) per vial for thrombin. Assuming that vCJD is found to be present in plasma donations, its risk of transmission by these purified and processed plasma derivatives would appear to be very low.

CONCLUSIONS

The pathogen safety initiatives implemented by plasma fractionators over the past 10 to 20 years have resulted in products with excellent pathogen safety profiles. Of the agents examined, parvovirus continues to have the lowest calculated margin of safety. Despite this, parvovirus transmissions should be rare. Manufacturers are encouraged to continue exploring processes to further enlarge parvovirus safety margins and to continue exploring ways of eliminating prions.

The variant Creutzfeldt-Jakob Disease: Risk, uncertainty or safety in the use of blood and blood derivatives?

It has been long since French physician Jean-Baptiste Denys carried out the first successful blood transfusion to a human being. Using bird feathers as canules, sheep blood was transfused to a young man. The patient died soon after Denys' treatment and Denys was accused of murder. In the XXI century, known as the biotechnology century, we face new challenges in Medicine. New emerging and reemerging diseases, such as Creutzfeldt-Jakob disease (CJD) or "mad cow disease" and its human variant (vCJD), challenge the biosafety aspects of a widely extended and extremely useful technique, that is, the perfusion of blood, of its derived components and of other pharmacological products obtained from plasma. To face these new challenges we need innovative prevention strategies.

Safety procedures of coagulation factors

Abstract  Two main types of safety procedures must be applied to biological products, including plasma derivatives: (i) preventive procedures and (ii) elimination procedures.Prevention includes epidemiological control of donor populations; checks on each donor’s health condition; analysis of each donation for the main pathogens using serological methods; additional analysis of all plasma for human immunodeficiency virus (HIV), hepatitis B virus (HBV), hepatitis C virus (HCV), hepatitis A virus (HAV) and the B19 virus, using nucleic acid amplification techniques (NAT). A 60 days or longer inventory hold of all plasma donations is applied, to allow additional time to discard previous donations from potential seroconverting or otherwise rejectable donors.Elimination procedures minimize the low residual risk of transmitting pathogens, including unknown or previously undetected ones. Since the introduction 20 years ago of solvent‐detergent treatment, very effective against enveloped viruses (HIV, HBV, HCV, West Nile virus, SARS, avian influenza virus etc), there have been no known cases of transmission of this type of pathogens by products manufactured according to this procedure. Other inactivation procedures such as pasteurization, dry‐heat or nanofiltration may prove equally effective. In addition, dry‐heat treatment and nanofiltration are capable of effectively eliminating non‐enveloped viruses (HAV, B19 virus). Recent studies show that the B19 virus is much more sensitive to heat (in lyophilized state or by pasteurization) and acid pH than previously thought.Although there is no evidence for the transmission of classic transmissible spongiform encephalopathies (TSEs) through blood or blood‐products transfusion, four possible cases have been reported in the United Kingdom involving transmission by non‐leukoreduced blood components of the agent that causes variant Creutzfeldt‐Jakob Disease (vCJD), a disease linked to the outbreak of bovine spongiform encephalopathy (BSE) which took place in that country. However, there are no cases of human TSE (classic or variant) transmission by plasma‐derived products. Analytical methods capable of detecting the vCJD agent in patients’ brains (where high titres are found) and other tissues (such as the spleen, appendix and lymph nodes, where much lower concentrations are found) are unable to detect the agent in blood or plasma from patients with vCJD, even in the clinical phase of the disease. Experiments by Grifols and other groups show that the capacity of the production processes to eliminate vCJD agent models is many orders of magnitude greater than the maximum expected load of the agent. In this regard, the efficacy of precipitation, affinity chromatography, depth filtration and nanofiltration are particularly notable.

A new liquid intravenous immunoglobulin with three dedicated virus reduction steps: virus and prion reduction capacity

BACKGROUND AND OBJECTIVES

A new 10% liquid human intravenous immunoglobulin (US trade name: Gammagard Liquid; European trade name: KIOVIG) manufactured by a process with three dedicated pathogen inactivation/removal steps (solvent/detergent treatment, 35-nm nanofiltration and low pH/elevated temperature incubation) was developed. The ability of the manufacturing process to inactivate/remove viruses and prions was investigated.

MATERIALS AND METHODS

Virus and prion removal capacities were assessed with down-scale spiking experiments, validated for equivalence to the large-scale process.

RESULTS

Lipid-enveloped viruses were completely inactivated/removed by each of the three dedicated virus clearance steps, and for human immunodeficiency virus 1 (HIV-1) and pseudorabies virus (PRV), also by the upstream cold ethanol fractionation step. Relevant non-enveloped viruses [i.e. hepatitis A virus (HAV) and parvovirus B19 (B19V)] were effectively removed by nanofiltration and the cold ethanol fractionation step, and partial inactivation of non-enveloped viruses was achieved by low pH incubation. Overall log reduction factors were > 20.0 for HIV-1, > 18.1 for bovine viral diarrhoea virus, > 16.3 for West Nile virus, > 10.0 for influenza A virus subtype H5N1, > 21.8 for PRV, 12.0 for HAV, > 12.1 for encephalomyocarditis virus, 10.6 for B19V and 10.3 for mice minute virus. Prions (Western blot assay) were completely removed (> or = 3.2 mean log reduction) by a step of the cold ethanol fractionation process.

CONCLUSIONS

Introducing three dedicated virus-clearance steps in the manufacturing process of immunoglobulins from human plasma provides high margins of safety.

[Plasma fractionation in the world: current status]

From 22 to 25 million liters of plasma are fractionated yearly in about 70 fractionation plants, either private or government-owned, mainly located in industrialized countries, and with a capacity ranging from 50000 to three million liters. In an increasingly global environment, the plasma industry has recently gone through a major consolidation phase that has seen mergers and acquisitions, and has led to the closure of a number of small plants in Europe. Currently, some fifteen countries are involved into contract plasma fractionation programs to ensure a supply of plasma-derived medicinal products. The majority of the plasma for fractionation is obtained by automated plasmapheresis, the remaining (recovered plasma) being prepared from whole blood as a by-product of red cell production. Plasma for fractionation should be produced, and controlled following well established procedures to meet the strict quality requirements set by regulatory authorities and fractionators. The plasma fractionation technology still relies heavily on the cold ethanol fractionation process, but has been improved by the introduction of modern chromatographic purification methods, and efficient viral inactivation and removal treatments, ensuring quality and safety to a large portfolio of fractionated plasma products. The safety of these products with regards to the risk of transmission of variant Creutzfeldt-Jakob disease seems to be provided, based on current scientific data, by extensive removal of the infectious agent during certain fractionation steps. The leading plasma product is now the intravenous immunoglobulin G, which has replaced factor VIII and albumin in this role. The supply of plasma products (most specifically coagulation products and immunoglobulin) at an affordable price and in sufficient quantity remains an issue; the problem is particularly acute in developing countries, as the switch to recombinant factor VIII in rich countries has not solved the supply issue and has even led to an increase of the mean price of plasma-derived factor VIII to the developing world. In the last few years, the plasma fractionation industry has improved greatly, and should remain essential in the years to come for the procurement of many essential medicines.

Manufacture of plasma-derived products in France and measures to prevent the risk of vCJD transmission: Precautionary measures and efficacy of manufacturing processes in prion removal

The emergence of the variant Creutzfeldt-Jakob disease in the mid 1990s soon raised concerns about its possible transmission through the use of blood and plasma-derived medicinal products. A risk analysis approach was initiated by health authorities, based on updated scientific knowledge and precautionary measures were implemented in France and other countries for the management of this new possible risk. Assessment of the vCJD risk is based on epidemiology and estimates of the number of potential cases in the future, on blood infectivity data from models of transmissible spongiform encephalopathies and on data from studies of the capacity of manufacturing processes to remove the agent, should it be present in the plasma of infected donors. The transmission of vCJD by non leukocyte-depleted labile blood components has recently been confirmed. There have been no reports of cases associated with the use of plasma-derived products and the scientific data, and risk analyses for those plasma products, which are of the greatest therapeutic interest, support their safety with respect to this transmission risk. The precautionary measures applied in France and the data contributing to the risk assessment of plasma products are reviewed and updated in the present paper. The uncertainties, which remain, are also addressed and discussed, as well as the ongoing research and developments in this area.