Monitoring plasma processing steps with a sensitive Western blot assay for the detection of the prion protein

Development of an Absolute Quantification Method for hERG Using PRM with Single Isotopologue in-Sample Calibration

The human ether-à-go-go-related gene (KCNH2)-encoded protein hERG constitutes the α subunit of the Kv11.1 channel and contributes to the I kr current, which plays an important role in the cardiac action potential. Genetically and xenobiotically triggered malfunctions of hERG can cause arrhythmia. The expression of hERG in various study systems was assessed mainly as the fold change relative to the corresponding control. Here, we developed a simple and sensitive quantitation method using targeted mass spectrometry, i.e., the parallel reaction monitoring approach, to measure the absolute quantity of hERG in copy number. Such measurements do not require controls, and the obtained values can be compared with similar results for any other protein. To effectively avoid matrix effects, we used the heavy-match-light (HML) in-sample calibration approach that requires only a single isotopologue to achieve copy-number quantitation. No significant difference was observed in the results obtained by HML and by the classic standard addition in-sample calibration approach. Using four proteotypic peptides, we quantified the average number of copies of hERG in the HEK293T heterologous expression system as 3.6 ± 0.5 × 106 copies/cell, i.e., 1 million copies/cell for the fully assembled Kv11.1 channel.

Upregulation of Long Noncoding RNA FGD5-AS1 Ameliorates Myocardial Ischemia/Reperfusion Injury via MicroRNA-106a-5p and MicroRNA-106b-5p

ABSTRACT

Long noncoding RNAs have been known to play key roles in myocardial ischemia/reperfusion injury. This study was conducted to investigate whether upregulation of FGD5-AS1 can improve hypoxia/reoxygenation (H/R) injury of cardiomyocytes and its underlying mechanisms. Pc-FGD5-AS1 was used to overexpress FGD5-AS1 in cardiomyocytes. Cholecystokinin octapeptide and flow cytometry assays were performed to detect the effect of FGD5-AS1 on myocardial cell H/R injury. Quantitative real-time polymerase chain reaction and luciferase reporter assay were performed to assess the relationship between FGD5-AS1 and microRNA-106a-5p (miR-106a-5p) or miR-106b-5p. In patients with acute myocardial infarction and in H/R cardiomyocytes and ischemia/reperfusion myocardium, the expression levels of FGD5-AS1 were reduced, whereas the expression levels of miR-106a-5p and miR-106b-5p were increased. Overexpression of FGD5-AS1 increased the viability of H/R-treated cardiomyocytes and reduced the levels of apoptosis and creatine kinase-MB. In addition, FGD5-AS1 could bind to miR-106a-5p or miR-106b-5p and showed a mutual inhibitory effect between them. Furthermore, overexpression of miR-106a-5p or miR-106b-5p inhibited the expression of SMAD5. FGD5-AS1 upregulated the expression of SMAD5. In conclusion, FGD5-AS1 may be a potential therapeutic target for myocardial H/R injury, and its cardioprotective effect may be realized by reducing inflammatory response and cell apoptosis.

A Novel, Reliable and Highly Versatile Method to Evaluate Different Prion Decontamination Procedures

Transmissible spongiform encephalopathies (TSEs) are a group of invariably fatal neurodegenerative disorders. The causal agent is an aberrantly folded isoform (PrP^Sc or prion) of the endogenous prion protein (PrP^C) which is neurotoxic and amyloidogenic and induces misfolding of its physiological counterpart. The intrinsic physical characteristics of these infectious proteinaceous pathogens makes them highly resistant to the vast majority of physicochemical decontamination procedures used typically for standard disinfection. This means prions are highly persistent in contaminated tissues, the environment (surfaces) and, of great concern, on medical and surgical instruments. Traditionally, decontamination procedures for prions are tested on natural isolates coming from the brain of infected individuals with an associated high heterogeneity resulting in highly variable results. Using our novel ability to produce highly infectious recombinant prions in vitro we adapted the system to enable recovery of infectious prions from contaminated materials. This method is easy to perform and, importantly, results in highly reproducible propagation in vitro. It exploits the adherence of infectious prion protein to beads of different materials allowing accurate and repeatable assessment of the efficacy of disinfectants of differing physicochemical natures to eliminate infectious prions. This method is technically easy, requires only a small shaker and a standard biochemical technique and could be performed in any laboratory.

Whispering gallery mode resonator sensor for in situ measurements of hydrogel gelation

Whispering gallery mode (WGM) resonators are compact and ultrasensitive devices, which enable label-free sensing at the single-molecule level. Despite their high sensitivity, WGM resonators have not been thoroughly investigated for use in dynamic biochemical processes including molecular diffusion and polymerization. In this work, the first report of using WGM sensors to continuously monitor a chemical reaction (i.e. gelation) in situ in a hydrogel is described. Specifically, we monitor and quantify the gelation dynamics of polyacrylamide hydrogels using WGM resonators and compare the results to an established measurement method based on rheology. Rheology measures changes in viscoelasticity, while WGM resonators measure changes in refractive index. Different gelation conditions were studied by varying the total monomer concentration and crosslinker concentration of the hydrogel precursor solution, and the resulting similarities and differences in the signal from the WGM resonator and rheology are elucidated. This work demonstrates that WGM alone or in combination with rheology can be used to investigate the gelation dynamics of hydrogels to provide insights into their gelation mechanisms.

Pathogen Safety of a New Intravenous Immune Globulin 10% Liquid

BACKGROUND

The manufacturing process of a new intravenous immune globulin (IVIG) 10% liquid product incorporates two dedicated pathogen safety steps: solvent/detergent (S/D) treatment and nanofiltration (20 nm). Ion-exchange chromatography (IEC) during protein purification also contributes to pathogen safety. The ability of these three process steps to inactivate/remove viruses and prions was evaluated.

OBJECTIVES

The objective of this study was to evaluate the virus and prion safety of the new IVIG 10% liquid.

METHODS

Bovine viral diarrhea virus (BVDV), human immunodeficiency virus type 1 (HIV-1), mouse encephalomyelitis virus (MEV), porcine parvovirus (PPV), and pseudorabies virus (PRV) were used as models for common human viruses. The hamster-adapted scrapie strain 263K (HAS 263K) was used for transmissible spongiform encephalopathies. Virus clearance capacity and robustness of virus reduction were determined for the three steps. Abnormal prion protein (PrP^Sc) removal and infectivity of the samples was determined.

RESULTS

S/D treatment and nanofiltration inactivated/removed enveloped viruses to below detection limits. IEC supplements viral safety and nanofiltration was highly effective in removing non-enveloped viruses and HAS 263K. Overall virus reduction factors were: ≥9.4 log₁₀ (HIV-1), ≥13.2 log₁₀ (PRV), ≥8.2 log₁₀ (BVDV), ≥11.7 log₁₀ (MEV), ≥11.6 log₁₀ (PPV), and ≥10.4 log₁₀ (HAS 263K).

CONCLUSION

Two dedicated and one supplementing steps in the manufacturing process of the new IVIG 10% liquid provide a high margin of pathogen safety.

A dual-signal strategy for the solid detection of both small molecules and proteins based on magnetic separation and highly fluorescent copper nanoclusters

Recently, a variety of analytical methods for the detection of small molecules or proteins based on small molecule-protein interaction have been developed. However, these methods often focus on either small molecules or proteins. Few efforts are made to detect both of them in the same system. In this work, a dual-signal strategy for the solid detection of both small molecules and proteins based on small molecule-protein interaction is proposed by using the streptavidin-biotin couple as a model. In our strategy, magnetic nanoparticles (MNPs) are adopted for target separation, and highly fluorescent copper nanoclusters (CuNCs) are synthesized in situ to give signals. In the absence of the targets, CuNCs are associated with the MNPs and present in the precipitate under magnetic field; whereas in the presence of either streptavidin or biotin, the CuNCs will present in the supernate. By monitoring the fluorescent intensity of each, dual-signal can be obtained for the solid detection of either the protein or the small molecule. Results show that sensitive and specific detection of both streptavidin (detection limit: 0.47nM) and biotin (detection limit: 3.1nM) can be achieved. This method can be extended for the detection of other small molecule-protein couples, and thereby has the potential for biomedical and clinical applications.

Fuzheng Huayu Recipe Ameliorates Liver Fibrosis by Restoring Balance between Epithelial-to-Mesenchymal Transition and Mesenchymal-to-Epithelial Transition in Hepatic Stellate Cells

Activation of hepatic stellate cells (HSCs) depending on epithelial-to-mesenchymal transition (EMT) reflects the key event of liver fibrosis. Contrastively, mesenchymal-to-epithelial transition (MET) of HSCs facilitates the fibrosis resolution. Here we investigated the effect of Fuzheng Huayu (FZHY) recipe, a Chinese herbal decoction made of Radix Salviae Miltiorrhizae, Semen Persicae, Cordyceps sinensis, Pollen Pini, and Gynostemma pentaphyllum, on liver fibrosis concerning the balance of EMT and MET in HSCs. In contrast to the increased TGF-β₁/BMP-7 ratio in activated HSCs, FZHY administration induced significant upregulation of BMP-7 and downregulation of TGF-β₁ at both transcription and translation levels. Restoration of TGF-β₁/BMP-7 ratio inhibited the expression of p38 MAPK and phosphorylated p38 MAPK, resulting in the reversal of epithelial-to-mesenchymal transition (EMT) to mesenchymal-to-epithelial transition (MET) as characterized by the abolishment of EMT markers (α-SMA and desmin) and reoccurrence of MET marker (E-cadherin). In vivo treatment of FZHY recipe also demonstrated the statistical reduction of activated HSCs with EMT phenotype, which attenuated the carbon tetrachloride- (CCl₄-) induced liver fibrosis in a dose-dependent manner. These findings may highlight a novel antifibrotic role of FZHY recipe on the basis of rebalancing EMT and MET in HSCs.

Application of protein misfolding cyclic amplification to detection of prions in anaerobic digestate

The exceptional physio-chemical resistance of prions to established decontamination procedures poses a challenge to assessing the suitability of applied inactivation methods. Prion detection is limited by the sensitivity level of Western blotting or by the cost and time factors of bioassays. In addition, prion detection assays can be limited by either the unique or complex nature of matrices associated with environmental samples. To investigate anaerobic digestion (AD) as a practical and economical approach for potential conversion of specified risk materials (SRM) into value added products (i.e., renewable energy), challenges associated with detection of prions in a complex matrix need to be overcome to determine potential inactivation. Protein misfolding cyclic amplification (PMCA) assay, with subsequent Western blot visualization, was used to detect prions within the AD matrix. Anaerobic digestate initially inhibited the PMCA reaction and/or Western blot detection. However, at concentrations of ≤1% of anaerobic digestate, 263K scrapie prions could be amplified and semi-quantitatively detected. Infectious 263K prions were also proven to be bioavailable in the presence of high concentrations of digestate (10-90%). Development of the PMCA application to digestate provides extremely valuable insight into the potential degradation and/or fate of prions in complex biological matrices without requiring expensive and time-consuming bioassays.

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.

Detection of exosomal prions in blood by immunochemistry techniques

In most forms of prion diseases, blood is infectious, but detection by immunochemistry techniques of the only available marker of infection (the misfolded prion protein, PrPTSE) in blood remains elusive. We developed a novel method for the detection of PrPTSE in blood of prion-infected rodents based on the finding that PrPTSE is associated with plasma exosomes. However, further purification of the exosomes on a sucrose gradient was necessary to remove plasma immunoglobulins, which interfere with PrPTSE, masking its detection by immunochemistry. Finally, we report that about 20% of plasma infectivity is associated with exosomes.

The standard scrapie cell assay: development, utility and prospects

Prion diseases are a family of fatal neurodegenerative diseases that involve the misfolding of a host protein, PrP^C. Measuring prion infectivity is necessary for determining efficacy of a treatment or infectivity of a prion purification procedure; animal bioassays are, however, very expensive and time consuming. The Standard Scrapie Cell Assay (SSCA) provides an alternative approach. The SSCA facilitates quantitative in vitro analysis of prion strains, titres and biological properties. Given its robust nature and potential for high throughput, the SSCA has substantial utility for in vitro characterization of prions and can be deployed in a number of settings. Here we provide an overview on establishing the SSCA, its use in studies of disease dissemination and pathogenesis, potential pitfalls and a number of remaining challenges.

Development of an intravenous immunoglobulin with improved safety and functional activity

The development and properties of a liquid intravenous immunoglobulin (Gammaplex(®)), of high purity, stability and functional activity, is described. Virus and TSE reduction by specific steps in the process were evaluated by spiking studies using small-scale models. The removal of procoagulant activity was determined using immunochemical and functional activity assays. Neutralisation and opsonic activity were used to demonstrate the functional activity of the IgG. The final low pH formulated product was stable at room temperature and was of high purity and functional activity. Three dedicated virus inactivation steps, i.e. solvent detergent, low pH and virus filtration, were shown to be effective. When combined with the B + I ethanol precipitation step, this gave a total reduction of >21 to >24 log for the enveloped and >10 to >13 log for the non-enveloped viruses tested. Several steps in the process were shown to contribute to TSE removal using scrapie. Potential procoagulant activity including Factor XI/XIa, was reduced to very low/undetectable levels in the final product. A new high purity liquid IVIG product has been developed, of high purity and good functional activity and stability. The process includes various steps for the removal of pathogens and procoagulant activity.

The prion protein protease sensitivity, stability and seeding activity in variably protease sensitive prionopathy brain tissue suggests molecular overlaps with sporadic Creutzfeldt-Jakob disease

INTRODUCTION

Variably protease sensitive prionopathy (VPSPr) is a recently described, sporadic human prion disease that is pathologically and biochemically distinct from the currently recognised sporadic Creutzfeldt-Jakob disease (sCJD) subtypes. The defining biochemical features of the abnormal form of the prion protein (PrPSc) in VPSPr are increased sensitivity to proteolysis and the presence of an N- and C-terminally cleaved ~8 kDa protease resistant PrPSc (PrPres) fragment. The biochemical and neuropathological profile of VPSPr has been proposed to resemble either Gerstmann-Sträussler-Scheinker syndrome (GSS) or familial CJD with the PRNP-V180I mutation. However, in some cases of VPSPr two protease resistant bands have been observed in Western blots that co-migrate with those of type 2 PrPres, suggesting that a proportion of the PrPSc present in VPSPr has properties similar to those of sCJD.

RESULTS

Here, we have used conformation dependent immunoassay to confirm the presence of PrPSc in VPSPr that is more protease sensitive compared with sCJD. However, CDI also shows that a proportion of PrPSc in VPSPr resists PK digestion of its C-terminus, distinguishing it from GSS associated with ~8 kDa PrPres, and showing similarity to sCJD. Intensive investigation of a single VPSPr case with frozen tissue from multiple brain regions shows a broad, region-specific spectrum of protease sensitivity and differential stability of PrPSc in the absence of PK treatment. Finally, using protein misfolding cyclic amplification and real-time quaking induced conversion, we show that VPSPr PrPSc has the potential to seed conversion in vitro and that seeding activity is dispersed through a broad range of aggregate sizes. We further propose that seeding activity is associated with the ~19 and ~23 kDa PrPres rather than the ~8 kDa fragment.

CONCLUSIONS

Therefore, PrPSc in VPSPr is heterogeneous in terms of protease sensitivity and stability to denaturation with the chaotrope GdnHCl and includes a proportion with similar properties to that found in sCJD.

Mulberry water extracts inhibit atherosclerosis through suppression of the integrin-β₃/focal adhesion kinase complex and downregulation of nuclear factor κB signaling in vivo and in vitro

Previous studies have shown that mulberry water extracts (MWEs), which contain polyphenolic compounds, have an antiatherosclerotic effect in vivo and in vitro through stimulating apoptosis of vascular smooth muscle cells (VSMCs). Histological analysis was performed on atherosclerotic lesions from high-cholesterol diet (HCD)-fed rabbits after treatment with 0.5-1% MWEs for 10 weeks. Immunohistochemistry showed that the expressions of SMA, Ras, and matrix metalloproteinase-2 in the VSMCs were dose-dependently inhibited after MWE treatment. The antimigratory effects of MWEs on A7r5 VSMCs were assessed by western blot analysis of migration-related proteins, visualization of F-actin cytoskeleton, and reverse transcription polymerase chain reaction. The results showed that MWEs inhibited VSMC migration through reducing interactions of the integrin-β3/focal adhesion kinase complex, alterations of the cytoskeleton, and downregulation of glycogen synthase kinase 3β/nuclear factor κB signaling. Taken together, MWEs inhibited HCD-induced rabbit atherogenesis through blocking VSMC migration via reducing interactions of integrin-β3 and focal adhesion kinase and downregulating migration-related proteins.

Development of a bifunctional filter for prion protein and leukoreduction of red blood cell components

BACKGROUND

Leukofiltration of blood components is currently implemented worldwide as a precautionary measure against white blood cell-associated adverse effects and the potential transmission of variant Creutzfeldt-Jakob disease (vCJD). A newly developed bifunctional filter (Sepacell Prima, Asahi Kasei Medical) was assessed for prion removal, leukoreduction (LR), and whether the filter significantly affected red blood cells (RBCs).

STUDY DESIGN AND METHODS

Sepacell Prima's postfiltration effects on RBCs, including hemolysis, complement activation, and RBC chemistry, were compared with those of a conventional LR filter (Sepacell Pure RC). Prion removal was measured by Western blot after spiking RBCs with microsomal fractions derived from scrapie-infected hamster brain homogenate. Serially diluted exogenous prion solutions (0.05 mL), with or without filtration, were injected intracerebrally into Golden Syrian hamsters.

RESULTS

LR efficiency of 4.44 log with the Sepacell Prima was comparable to 4.11 log with the conventional LR filter. There were no significant differences between the two filters in hemoglobin loss, hemolysis, complement activation, and RBC biomarkers. In vitro reduction of exogenously spiked prions by the filter exceeded 3 log. The titer, 6.63 (log ID50 /mL), of prefiltration infectivity of healthy hamsters was reduced to 2.52 (log ID50 /mL) after filtration. The reduction factor was calculated as 4.20 (log ID50 ).

CONCLUSION

With confirmed removal efficacy for exogenous prion protein, this new bifunctional prion and LR filter should reduce the residual risk of vCJD transmission through blood transfusion without adding complexity to component processing.

Characterization of Thrombate III®, a pasteurized and nanofiltered therapeutic human antithrombin concentrate

Thrombate III(®) is a highly purified antithrombin concentrate that has been used by clinicians worldwide for more than two decades for the treatment of hereditary antithrombin deficiency. The manufacturing process is based on heparin-affinity chromatography and pasteurization. To modernize the process and to further enhance the pathogen safety profile of the final product, despite the absence of infectious disease transmission, a nanofiltration step was added. The biochemical characterization and pathogen safety evaluation of Thrombate III(®) manufactured using the modernized process are presented. Bioanalytical data demonstrate that the incorporation of nanofiltration has no impact on the antithrombin content, potency, and purity of the product. Scaledown models of the manufacturing process were used to assess virus and prion clearance under manufacturing setpoint conditions. Additionally, robustness of virus clearance was evaluated at or slightly outside the manufacturing operating limits. The results demonstrate that pasteurization inactivated both enveloped and non-enveloped viruses. The addition of nanofiltration substantially increased clearance capacities for both enveloped and non-enveloped viruses by approximately 4-6 log10. In addition, the process achieves 6.0 log10 ID50 prion infectivity clearance. Thus, the introduction of nanofiltration increased the pathogen safety margin of the manufacturing process without impacting the key biochemical characteristics of the product.

Human tonsil-derived follicular dendritic-like cells are refractory to human prion infection in vitro and traffic disease-associated prion protein to lysosomes

The molecular mechanisms involved in human cellular susceptibility to prion infection remain poorly defined. This is due, in part, to the absence of any well characterized and relevant cultured human cells susceptible to infection with human prions, such as those involved in Creutzfeldt-Jakob disease. In variant Creutzfeldt-Jakob disease, prion replication is thought to occur first in the lymphoreticular system and then spread into the brain. We have, therefore, examined the susceptibility of a human tonsil-derived follicular dendritic cell-like cell line (HK) to prion infection. HK cells were found to display a readily detectable, time-dependent increase in cell-associated abnormal prion protein (PrP(TSE)) when exposed to medium spiked with Creutzfeldt-Jakob disease brain homogenate, resulting in a coarse granular perinuclear PrP(TSE) staining pattern. Despite their high level of cellular prion protein expression, HK cells failed to support infection, as judged by longer term maintenance of PrP(TSE) accumulation. Colocalization studies revealed that exposure of HK cells to brain homogenate resulted in increased numbers of detectable lysosomes and that these structures immunostained intensely for PrP(TSE) after exposure to Creutzfeldt-Jakob disease brain homogenate. Our data suggest that human follicular dendritic-like cells and perhaps other human cell types are able to avoid prion infection by efficient lysosomal degradation of PrP(TSE).

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.

Absolute quantification of prion protein (90-231) using stable isotope-labeled chymotryptic peptide standards in a LC-MRM AQUA workflow

Substantial evidence indicates that the disease-associated conformer of the prion protein (PrP(TSE)) constitutes the etiologic agent in prion diseases. These diseases affect multiple mammalian species. PrP(TSE) has the ability to convert the conformation of the normal prion protein (PrP(C)) into a β-sheet rich form resistant to proteinase K digestion. Common immunological techniques lack the sensitivity to detect PrP(TSE) at subfemtomole levels, whereas animal bioassays, cell culture, and in vitro conversion assays offer higher sensitivity but lack the high-throughput the immunological assays offer. Mass spectrometry is an attractive alternative to the above assays as it offers high-throughput, direct measurement of a protein's signature peptide, often with subfemtomole sensitivities. Although a liquid chromatography-multiple reaction monitoring (LC-MRM) method has been reported for PrP(TSE), the chemical composition and lack of amino acid sequence conservation of the signature peptide may compromise its accuracy and make it difficult to apply to multiple species. Here, we demonstrate that an alternative protease (chymotrypsin) can produce signature peptides suitable for a LC-MRM absolute quantification (AQUA) experiment. The new method offers several advantages, including: (1) a chymotryptic signature peptide lacking chemically active residues (Cys, Met) that can confound assay accuracy; (2) low attomole limits of detection and quantitation (LOD and LOQ); and (3) a signature peptide retaining the same amino acid sequence across most mammals naturally susceptible to prion infection as well as important laboratory models. To the authors' knowledge, this is the first report on the use of a non-tryptic peptide in a LC-MRM AQUA workflow.

Subcutaneous immunoglobulin therapy: a new option for patients with primary immunodeficiency diseases

Since the 1950s, replacement of immunoglobulin G using human immunoglobulin has been the standard treatment for primary immunodeficiency diseases with defects in antibody production. These patients suffer from recurrent and severe infections, which cause lung damage and shorten their life span. Immunoglobulins given intravenously (IVIG) every 3-4 weeks are effective in preventing serious bacterial infections and improving the quality of life for treated patients. Administration of immunoglobulin subcutaneously (SCIG) is equally effective in preventing infections and has a lower incidence of serious adverse effects compared to IVIG. The tolerability and acceptability of SCIG has been demonstrated in numerous studies showing improvements in quality of life and a preference for subcutaneous immunoglobulin therapy in patients with antibody deficiencies.

Molecular diagnosis of human prion disease

INTRODUCTION

Human prion diseases (PrDs) are transmissible fatal nervous system disorders with public health implications. They are characterized by the presence of a disease-associated form of the physiological cellular prion protein. Development of diagnostic procedures is important to avoid transmission, including through blood products. Methods used for the detection of disease-associated PrP have implications for other neurodegenerative diseases.

AREAS COVERED

In this review, the authors discuss recent progress in the understanding of the molecular background of phenotypic variability of human PrDs, and the current concepts of molecular diagnosis. Also, the authors provide a critical summary of the diagnostic methods with regard to the molecular subtypes.

EXPERT OPINION

In spite of a lack of specific tests to detect disease-associated PrP in body fluids, the constellation of clinical symptoms, detection of protein 14-3-3 in cerebrospinal fluid, electroencephalogram, cranial MRI and prion protein gene examinations, together have increased the specificity and sensitivity of in vivo diagnostics. As new forms of PrDs are reported, continuous evaluation of their incidence and the search for their etiology is crucial. Recent studies, suggesting prion-like properties of certain proteinopathies associated with Parkinson's or Alzheimer's disease, have again brought PrDs to the center of interest as a model of diseases with disordered protein processing.

Utility of mass spectrometry in the diagnosis of prion diseases

We developed a sensitive mass spectrometry-based method of quantitating the prions present in a variety of mammalian species. Calibration curves relating the area ratios of the integrated MRM signals from selected analyte peptides and their oxidized analogues to their homologous stable isotope labeled internal standards were prepared. The limit of detection (LOD) and limit of quantitation (LOQ) for the synthetic peptides from human, sheep, deer, cow, and mouse PrP were determined to be below 100 amol. Nonanalyte peptides that were characteristic of prions were included in the multiple reaction monitoring method, thereby allowing for both the quantitation and confirmation of the presence of prions in the attomole range. This method was used to quantitate the prions present in brains of hamsters or mice 5 weeks after inoculation (ic) with either four hamster-adapted prion strains (139H, drowsy, 22AH, and 22CH) or four mouse-adapted prion strains (Me7, Me7-298, RML, and 79A). The prions from different brain regions of a sheep naturally infected with scrapie were quantitated. All of the rodent-adapted prion strains were detectable in the asymptomatic animals. In sheep, prions were detectable in the obex, anterior portion of the cerebrum, and the nonobex/nonanterior portion of the cerebrum. This mass spectrometry-based approach can be used to quantitate and confirm the presence of prions before detectable pathology.

Evolution of recombinant factor VIII safety: KOGENATE and Kogenate FS/Bayer

The use of factor VIII (FVIII) concentrates in the treatment of hemophilia A has raised important safety issues, historically of pathogen transmission and increasingly of inhibitor development to FVIII treatment. While manufacturing processes of current recombinant FVIII products have been shaped entirely around preventing pathogen transmission, the same modifications that afford a greater margin of safety could affect immunogenicity of the product, consequences of which could only be seen through long-term clinical experience. This review summarizes pathogen safety and inhibitor reports from clinical trials, post-marketing surveillance studies, and study reports on KOGENATE and its successor, Kogenate FS/Bayer. Although KOGENATE and Kogenate FS/Bayer are nearly identical products, subtle manufacturing improvements to address the need for greater margins of safety from a pathogen transmission perspective have also led to a potentially improved immunogenicity profile (15% in previously untreated/minimally treated patients with severe hemophilia A for Kogenate FS/Bayer). Notably, there has been no occurrence of pathogen contamination, and minimal de novo inhibitor formation in previously treated patients throughout the use of both products. Overall, KOGENATE and Kogenate FS/Bayer have a long history of safety in a variety of clinical settings, including treatment of bleeding, surgical management, and prophylaxis therapy.

Separation of native prion protein (PrP) glycoforms by copper-binding using immobilized metal affinity chromatography (IMAC)

The conformational conversion of the normal cellular prion protein (PrPC) into the pathology-associated PrPSc isoform is a key event in TSEs (transmissible spongiform encephalopathies). The host PrPC molecule contains two N-linked glycosylation sites and binds copper under physiological conditions. In contrast with PrPC, PrPSc is insoluble in non-ionic detergents and does not bind to Cu2+ ions. Hence, we utilized copper binding to separate and characterize both PrP isoforms. Infected and uninfected murine brain and bovine stem brain specimens were treated with the mild non-ionic detergent n-octyl-beta-D-glucopyranoside (octylglucoside) to maintain the native PrP conformations during isolation. The solubilized homogenates were loaded on to Cu2+-saturated IMAC (immobilized metal affinity chromatography) columns and eluted using the chelating agent EDTA. Fractions were separated by SDS/PAGE and analysed by immunoblotting using anti-PrP monoclonal antibodies for glycosylation profiling. Whereas native PrPC and denatured PrPSc were retained by a Cu2+-loaded resin, native PrPSc and PrPres [PK (proteinase K)-resistant PrP] passed through the column. We demonstrate here that the IMAC technique is appropriate to isolate and partially purify PrPC from healthy brains in its native-like and biologically relevant glycosylated copper-binding forms. The IMAC technique is also well suited for the separation of native PrPC from aggregated PrPSc in infected brains. Our results indicate that in contrast with PrPSc in uninfected as well as infected brains, PrPC is predominantly present in the glycosylated forms.

Rapid diagnosis of human prion disease using streptomycin with tonsil and brain tissues

The use of streptomycin in the pathological prion protein (PrP(sc)) detection procedures represents a new and attractive way for diagnostic purpose. With this agent, western blot readily detected PrP(sc) in 263K scrapie hamster and C57Bl/6 wild-type mice challenged with C506M3 scrapie strain. Our aim was to evaluate this new diagnosis procedure in the field of human transmissible spongiform encephalopathies (TSEs). First, we had confirmed the ability of streptomycin to precipitate PrP(res) from human brain of Creutzfeldt-Jakob disease (CJD) patient. Second, we compared the detection of PrP(res) with streptomycin against three other protocols using other precipitations. Then we assessed PrP(res) detection with streptomycin in 98 brain tissue samples from various aetiologies of human TSEs and 52 brain samples from other dementia. Finally, we applied this protocol for tonsils examination of five patients suspected of variant CJD (v-CJD). Sensitivity and specificity obtained with the streptomycin protocol were both 100% on brain tissue. For tonsil tissues, PrP(res) was clearly identified in the two post-mortem confirmed v-CJD cases, whereas no characteristic three-band pattern was seen in the three confirmed non-v-CJD samples. In this study, streptomycin demonstrated its efficiency to detect PrP(res) both in the central nervous system and in the lymphoid tissue without practical difficulty and with rapid preparation. Because of its ability to act as a good agent for PrP(sc) examination in different tissues, recovery of PrP(sc) in biological fluids using streptomycin should open further perspectives of applications in CJD diagnostics. Streptomycin effects in vivo might thus also be questioned.

Prion depletion and preservation of biological activity by preparative chaotrope ultracentrifugation

Prions are characterized by unusual physicochemical properties, such as insolubility and resistance to proteases, and maintain infectivity after contact with disinfectants and decontamination procedures active against conventional pathogens. To date, most methods for prion inactivation are either incomplete or unacceptably harsh for the purification of fragile biotherapeutics. Here we describe a simple prion removal procedure that takes advantage of differential sedimentation and denaturation of prions. Prion-spiked fluids were layered onto an intermediate sucrose cushion and an 8M urea solution, and subjected to single-step ultracentrifugation. Due to their insolubility, prions rapidly traveled through the sucrose cushion into the urea solution. Prion infectivity in the upper phase was reduced by at least 3.2 logs, or up to 6 logs or more. Very little soluble protein was lost from the input sample and a proof-of-principle experiment demonstrated only marginally reduced biological activity of spiked enzyme after ultracentrifugation. This procedure is likely to synergize with nanofiltration and other prion removal steps in the treatment of batches of raw and semifinal biopharmaceutical materials.

Kir2.3 knock-down decreases IK1 current in neonatal rat cardiomyocytes

Inward rectifier potassium Kir2.x channels mediate cardiac inward rectifier potassium currents (I(K1)). As a subunit of Kir2.x, the physiological role of Kir2.3 in native cardiomyocytes has not been reported. This study shows that Kir2.3 knock-down remarkably down-regulates Kir2.3 expression (Kir2.3 protein was reduced to 19.91+/-3.24% on the 2nd or 3rd day) and I(K1) current densities (at -120 mV, control vs. knock-down: -5.03+/-0.24 pA/pF, n=5 vs. -1.16+/-0.19 pA/pF, n=7, P<0.001) in neonatal rat cardiomyocytes. The data suggest that Kir2.3 plays a potentially important role in I(K1) currents in neonatal rat cardiomyocytes.

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.

Prion removal by nanofiltration under different experimental conditions

Manufacturing processes used in the production of biopharmaceutical or biological products should be evaluated for their ability to remove potential contaminants, including TSE agents. In the present study, we have evaluated scrapie prion protein (PrP Sc) removal in the presence of different starting materials, using virus removal filters of different pore sizes. Following 75 nm filtration, PrP Sc was detected in the filtrate by Western blot (WB) analysis when a "super-sonicated" microsomal fraction derived from hamster adapted scrapie strain 263K (263K MF) was used as the spike material. In contrast, no PrP Sc was detected when an untreated 263K MF was used. By using spike materials prepared in a manner designed to optimize the particle size distribution within the preparation, only 15 nm filtration was shown to remove PrP Sc to below the limits of detection of the WB assays used under all the experimental conditions. However, infectious PrP Sc was recovered following 15 nm filtration under one experimental condition. The results obtained suggest that the nature of the spike preparation is an important factor in evaluating the ability of filters to remove prions, and that procedures designed to minimize the particle size distribution of the prion spike, such as the "super-sonication" or detergent treatments described herein, should be used for the preparation of the spike materials.

Transmissible spongiform encephalopathy agent clearance by the immunoaffinity and anion-exchange chromatography steps of the ReFacto manufacturing process

ReFacto (moroctocog alfa), a recombinant factor VIII approved for the treatment of haemophilia A, is produced by a mammalian cell-culture process that includes therapeutic-grade human serum albumin (HSA) in the cell-culture medium. While to date there have been no cases of transmissible spongiform encephalopathy (TSE) resulting from the clinical use of HSA, Wyeth conducted a study to demonstrate that the ReFacto manufacturing process has significant capacity to remove a TSE agent if it were present as a contaminant in the HSA. The immunoaffinity (8A4 Sepharose) and anion-exchange (Q Sepharose) chromatography steps were evaluated for the clearance of the hamster TSE agent, strain 263K. This Good Laboratory Practice study was performed using appropriately qualified, laboratory-scale chromatography systems. Filtered brain homogenate from TSE-infected hamsters was added to loads of both chromatographic columns, and the concentration of TSE agent in the loads and product pools were determined using a validated western blot quantitation method. Replicate chromatography runs were consistent, as demonstrated by the < or =0.7 log(10) difference observed in TSE agent reduction between each pair of runs. The immunoaffinity and anion-exchanges steps demonstrated 3.8 log reduction and >5.2 log reduction respectively. These data provide a high degree of assurance that in the unlikely event of a TSE contamination of the HSA used in the ReFacto cell-culture process, the purification steps have the potential to remove the infectious agent to extremely low levels, thereby significantly reducing the risk to patients receiving ReFacto.

Multistrip Western blotting to increase quantitative data output

The qualitative and quantitative measurements of protein abundance and protein modification states are essential in understanding their role in diverse cellular processes. Traditional Western blotting technique, though sensitive, is prone to produce substantial errors and is not readily adapted to high-throughput technologies. We propose a modified immunoblotting procedure, which is based on simultaneous transfer of proteins from multiple gel-strips onto the same membrane, and is compatible with any conventional gel electrophoresis system. As a result, the data output per single blotting cycle can readily be increased up to ten-fold. In contrast to the traditional "one protein detection per electrophoresis cycle", this procedure allows simultaneous monitoring of up to nine different proteins. In addition to maintaining the ability to detect picogram quantities of protein, the modified system substantially improves data accuracy by reducing signal errors by two-fold. Multistrip Western blotting procedure allows making statistically reliable side-by-side comparisons of different or repeated sets of data. Compared to the traditional methods, this approach provides a more economical, reproducible, and effective procedure, facilitating the generation of large amounts of high-quality quantifiable data.

Enzymatic detergent treatment protocol that reduces protease-resistant prion protein load and infectivity from surgical-steel monofilaments contaminated with a human-derived prion strain

The unconventional nature of the infectious agent of prion diseases poses a challenge to conventional infection control methodologies. The extraneural tissue distribution of variant and sporadic Creutzfeldt–Jakob disease has increased concern regarding the risk of prion disease transmission via general surgical procedures and highlighted the need for decontamination procedures that can be incorporated into routine processing. In this study, the ability of preparations of enzymatic medical instrument cleaners to reduce the infectivity associated with a rodent-adapted strain of human prion disease, previously reported to be resistant to decontamination, was tested. Efficient degradation of the disease-associated prion protein by enzymatic cleaning preparations required high treatment temperatures (50–60 °C). Standard decontamination methods (1 M NaOH for 1 h or autoclaving at 134 °C for 18 min) reduced infectivity associated with the human-derived prion strain by less than 3 log10 LD50. In contrast, a 30 min treatment with the optimized enzymatic cleaning preparation protocols reduced infectivity by more than 3 log10 LD50 and when used in conjunction with autoclave cycles eliminated detectable levels of infectivity. The development of prion decontamination procedures that are compatible with routine cleaning and sterilization of medical and surgical instruments may reduce the risk of the transmission of prion disease in general surgery.

Mass spectrometric detection of attomole amounts of the prion protein by nanoLC/MS/MS

Sensitive quantitation of prions in biological samples is an extremely important and challenging analytical problem. Prions are the cause of several fatal neurodegenerative diseases known as transmissible spongiform encephalopathies (TSEs). At this time, there are no methods to diagnose TSEs in live animals or to assure a prion-free blood supply for humans. Prions have been shown to be present in blood by transfusion experiments, but based on the amount of infectivity found in these types of experiments, the amount of misfolded prion protein in blood is estimated to be only 30 to 625 amol/mL. More sensitive detection of prions in brain would allow earlier detection of disease and assure a safer food supply. We studied quantitation of the prion protein by use of nanoscale liquid chromatography coupled to a tandem mass spectrometer using the multiple reaction monitoring mode of operation. We developed a method based on the detection of VVEQMCTTQYQK obtained by reduction, alkylation, and digestion with trypsin of the prion protein. Detection of VVEQMCTTQYQK was more sensitive than for the derivative with phenylisothiocyanate (PITC) because of decreased ionization efficiency of the PITC-derivatized peptides. The VVEQMCTTQYQK method has a LOD of 20 to 30 amol for pure standards. Proof of principle is demonstrated by quantitation of the amount of PrP 27-30 in the brains of terminally ill Syrian hamsters.

Prevention and management of ovarian hyperstimulation syndrome

The Ovarian Hyperstimulation Syndrome (OHSS) represents one of the biggest nightmares of all physicians involved in Assisted Reproductive Technologies (ART). Every year, several hundreds of women are hospitalized and to date several deaths have been reported. The pivotal event in the development of OHSS is the disruption of capillary integrity that results in leakage of intravascular fluid and proteins into third space. On the molecular level, human chorionic godadotropin (HCG) either exogenous or endogenous, functions as the triggering point for the production of vascular endothelial growth factor (VEGF) that is the main mediator to increase permeability on the vascular bed. Spontaneous OHSS has also been reported, either due to inappropriate activation of a mutant FSH receptor or due to very high levels of HCG during pregnancy. The available evidence on the several preventive and therapeutic approaches with special attention to level 1 evidence when available is also presented. OHSS is a self-resolving condition and the main role of the physician is to correct and maintain the intravascular volume, to support renal function and respiration and prevent thrombotic events. An algorithm on the management of OHSS on an outpatient basis and in the hospital is based on the previous mentioned principles.

Impact of vCJD on blood supply

Variant Creutzfeldt-Jakob disease (vCJD) is an at present inevitably lethal neurodegenerative disease which can only be diagnosed definitely post mortem. The majority of the approximately 200 victims to date have resided in the UK where most contaminated beef materials entered the food chain. Three cases in the UK demonstrated that vCJD can be transmitted by blood transfusion. Since BSE and vCJD have spread to several countries outside the UK, it appears advisable that specific risk assessments be carried out in different countries and geographic areas. This review explains the approach adopted by Germany in assessing the risk and considering precautionary measures. A fundamental premise is that the feeding chain of cattle and the food chain have been successfully and permanently cleared from contaminated material. This raises the question of whether transmissions via blood transfusions could have the potential to perpetuate vCJD in mankind. A model calculation based on actual population data showed, however, that this would not be the case. Moreover, an exclusion of transfusion recipients from blood donation would add very little to the safety of blood transfusions, but would have a considerable impact on blood supply. Therefore, an exclusion of transfusion recipients was not recommended in Germany.

Current strategies to prevent transmission of prions by human plasma derivatives

Protein products prepared from pooled human plasma are an essential class of therapeutics used mostly to control bleeding and/or immunological disorders. Because of the human origin of the starting material, there is a risk that these products may possibly transmit prions causing variant Creutzfeldt-Jakob disease (vCJD). No case of transmission of prions by plasma products has been observed. Case-by-case measures implemented in various countries, and several technical factors may contribute, to various degrees, to the prevention of the risk of transmission of prions by plasma products. Those measures include (a) the epidemiological surveillance of population in countries with cases of vCJD and/or bovine spongiform encephalopathies (BSE), (b) the deferral of blood donors who traveled or resided, for specific periods of time, to countries with BSE, or who received transfusion or tissue transplant, (c) the removal of leucocytes in plasma used for fractionation, and, last but not least, (d) the removal of the prion agents during the complex industrial fractionation process used to prepare plasma products. Numerous experimental infectivity studies, involving the spiking of brain-derived infectious materials, have demonstrated that several fractionation steps, in particular ethanol fractionation, depth filtration, and chromatography, can remove several logs of prions. Removal is explained by the distinct hydrophobic and aggregative properties of the prion proteins. In addition, nanofiltration using multi-layer membranes of 75 nm or smaller, which is commonly used for removing viruses from coagulation factors and immunoglobulins products, can remove more than 3-5 logs of spiked prions, presumably by size-exclusion and trapping mechanisms. Therefore, the risk of transmission of vCJD by human plasma products appears remote, but caution should prevail since the biochemical nature of the infectious agent in human blood is still unknown.

Prion-removal capacity of chromatographic and ethanol precipitation steps used in the production of albumin and immunoglobulins

BACKGROUND AND OBJECTIVES

Although there is no epidemiological evidence to suggest that classical Creutzfeldt-Jakob disease (CJD) is transmitted through blood or blood products, the variant form (vCJD) has been implicated in transmission via packed red blood cells. The potential threat of the infectious agent contaminating plasma pools has led to manufacturing processes being examined for capacity to remove prions. The objective of these studies was to examine the prion-removal potential of the chromatographic purification and ethanol precipitation steps used to fractionate immunoglobulins and albumin from human plasma.

MATERIALS AND METHODS

Western blot assay was used to examine the partitioning of proteinase K-resistant scrapie prion protein (PrPsc) over DEAE Sepharose, CM Sepharose and Macro-Prep High Q chromatographic columns, utilizing microsomal scrapie 263K spiked into each scaled down feedstream and assayed after each chromatographic step. In further studies, bioassay in C57 black mice was used and spikes of 10 000 g clarified brain homogenate of scrapie ME7 were added to feedstreams before sequences of scaled down chromatographic or Cohn fractionation process steps.

RESULTS

The microsomal spiking study with Western blot detection demonstrated substantial partitioning of PrPsc away from the target proteins in all ion exchange chromatographic steps examined. The log10 reduction factors (LRF) across DEAE Sepharose and CM Sepharose columns for albumin were > or = 4.0 and > or = 3.0 respectively. The reductions across DEAE Sepharose and Macro-Prep High Q for intravenous immunoglobulin were 3.3 and > or = 4.1 respectively. Bioassay demonstrated LRFs of >or = 5.6 across the combination of DEAE Sepharose and CM Sepharose columns in the albumin process and > or = 5.4 across the combination of DEAE Sepharose and Macro-Prep High Q columns in the intravenous immunoglobulin process. Bioassay studies also demonstrated a LRF of > or = 5.6 for immunoglobulin produced by Cohn fractionation.

CONCLUSIONS

Using rodent-adapted scrapie as a model, the studies indicated that ion exchange chromatography, as well as Cohn immunoglobulin fractionation have the potential to effectively reduce the load of TSE agents should they be present in plasma pools.

Possible removal of prion agents from blood products during the manufacturing process

Blood products prepared from human blood theoretically risk contamination with infectious pathogens. Since recent reports now confirm the likely transmission of pathogenic prions through blood transfusion, effective measures to prevent transmission are required globally, although the prevalence of variant Creutzfeldt–Jakob disease outside of the UK is extremely low. Many studies evaluating the manufacturing process have been conducted for the potential removal of the prion protein from plasma derivatives. In this review, we discuss the possibility of removing prions via several processing steps, especially depth and virus-removal filtration. Through a discussion of the limitations and issues associated with such studies, we hope our review will be of help for better study design in the future.

CJD PrPsc removal by nanofiltration process: Application to a therapeutic immunoglobulin solution (Lymphoglobuline®)

The characteristic of transmissible spongiform encephalopathies (TSE) is an accumulation of partially protease resistant (PrP(res)) abnormal prion protein (PrP(sc)). This pathological prion protein is very resistant to conventional inactivation methods. The risk of transmission of TSE, such as Creutzfeldt-Jakob disease (CJD), by biopharmaceutical products prepared from human cells must be taken into account. The nanofiltration process has been proved to be effective in removing viruses and scrapie agent. The major advantages of this technique are flexibility and efficacy in removing infectious particles without altering biopharmaceutical characteristics and properties. This study focused on the removal of human PrP(sc) by means of a nanofiltration method after spiking a Lymphoglobuline solution with a CJD brain homogenate. Lymphoglobuline equine anti-human thymocyte immunoglobulin is a selective immunosuppressive agent acting mainly on human T lymphocytes. The therapeutic indications are: immunosuppression for transplantation: prevention and treatment of graft rejection; treatment of aplastic anemia. In our study, CJD homogenate was spiked at three different dilutions (low, moderate and high) in the Lymphoglobuline product. The nanofiltration process was performed on each sample. Using the western blot technique, the PrP(res) signal detected in nanofiltrates was compared to that obtained with a reference scale (dilution series of CJD brain homogenate in Lymphoglobuline detected by western blot and elaborated on 3.3 log). After nanofiltration, the PrP(res) western blot signal was detected with a significant reduction in the less dilute sample, whereas the signal was undetectable in the two other samples. These are the first data in CJD demonstrating a clearance between 1.6 and 3.3 log with a Lymphoglobuline recovery of over 93%. The nanofiltration process confirms its relative efficacy in removing human CJD PrP(sc).