Further studies of blood infectivity in an experimental model of transmissible spongiform encephalopathy, with an explanation of why blood components do not transmit Creutzfeldt-Jakob disease in humans

Creutzfeldt-Jakob disease and blood transfusion: results of the UK Transfusion Medicine Epidemiological Review study

BACKGROUND AND OBJECTIVES

This paper reports the results to 1 March 2006 of an ongoing UK study, the Transfusion Medicine Epidemiological Review (TMER), by the National CJD Surveillance Unit (NCJDSU) and the UK Blood Services (UKBS) to determine whether there is any evidence that Creutzfeldt-Jakob disease (CJD), including sporadic CJD (sCJD), familial CJD (fCJD), and variant CJD (vCJD) is transmissible via blood transfusion.

MATERIALS AND METHODS

Sporadic CJD and fCJD cases with a history of blood donation or transfusion are notified to UKBS. All vCJD cases aged > 17 years are notified to UKBS on diagnosis. A search for donation records is instigated and the fate of all donations is identified by lookback. For cases with a history of blood transfusion, hospital and UKBS records are searched to identify blood donors. Details of identified recipients and donors are checked against the NCJDSU register to establish if there are any matches.

RESULTS

CJD cases with donation history: 18/31 vCJD, 3/93 sCJD, and 3/5 fCJD cases reported as blood donors were confirmed to have donated labile components transfused to 66, 20, and 11 recipients respectively. Two vCJD recipients have appeared on the NCJDSU register as confirmed and probable vCJD cases. The latter developed symptoms of vCJD 6.5 years and 7.8 years respectively after receiving non-leucodepleted red blood cells (RBCs) from two different donors who developed clinical symptoms approximately 40 and 21 months after donating. A third recipient, given RBC donated by a further vCJD case approximately 18 months before onset of clinical symptoms, had abnormal prion protein in lymphoid tissue at post-mortem (5-years post-transfusion) but had no clinical symptoms of vCJD. CJD cases with history of transfusion: Hospital records for 7/11 vCJD and 7/52 sCJD cases included a history of transfusion of labile blood components donated by 125 and 24 donors respectively. Two recipients who developed vCJD were linked to donors who had already appeared on the NCJDSU register as vCJD cases (see above). No further links were established.

CONCLUSION

This study has identified three instances of probable transfusion transmission of vCJD infection, including two confirmed clinical cases and one pre- or sub-clinical infection. This study has not provided evidence, to date, of transmission of sCJD or fCJD by blood transfusion, but data on these forms of diseases are limited.

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.

Prion-induced amyloid heart disease with high blood infectivity in transgenic mice

We investigated extraneural manifestations in scrapie-infected transgenic mice expressing prion protein lacking the glycophosphatydylinositol membrane anchor. In the brain, blood, and heart, both abnormal protease-resistant prion protein (PrPres) and prion infectivity were readily detected by immunoblot and by inoculation into nontransgenic recipients. The titer of infectious scrapie in blood plasma exceeded 10(7) 50% infectious doses per milliliter. The hearts of these transgenic mice contained PrPres-positive amyloid deposits that led to myocardial stiffness and cardiac disease.

Human prions and plasma lipoproteins

Prions are composed solely of an alternatively folded isoform of the prion protein (PrP), designated PrP(Sc). The polyoxometalate phosphotungstic acid has been used to separate PrP(Sc) from its precursor PrP(C) by selective precipitation; notably, native PrP(Sc) has not been solubilized by using nondenaturing detergents. Because of the similarities between PrP(Sc) and lipoproteins with respect to hydrophobicity and formation of phosphotungstic acid complexes, we asked whether these molecules are bound to each other in blood. Here we report that prions from the brains of patients with sporadic Creutzfeldt-Jakob disease (CJD) bind to very low-density (VLDL) and low-density (LDL) lipoproteins but not to high-density lipoproteins (HDL) or other plasma components, as demonstrated both by affinity assay and electron microscopy. Immunoassays demonstrated that apolipoprotein B (apoB), which is the major protein component of VLDL and LDL, bound PrP(Sc) through a highly cooperative process. Approximately 50% of the PrP(Sc) bound to LDL particles was released after exposure to 4 M guanidine hydrochloride at 80 degrees C for 20 min. The apparent binding constants of native human (Hu) PrP(Sc) or denatured recombinant HuPrP(90-231) for apoB and LDL ranged from 28 to 212 pM. Whether detection of PrP(Sc) in VLDL and LDL particles can be adapted into an antemortem diagnostic test for prions in the blood of humans, livestock, and free-ranging cervids remains to be determined.

Clearance of prions during plasma protein manufacture

Protein products isolated from human plasma are an important class of therapeutics that are used to treat patients afflicted with hereditary deficiencies, trauma, and severe infections. Because of the human origin of the starting material for the production of these biological products, there is a risk of transmitting infectious agents, including viruses and the infectious agents that cause transmissible spongiform encephalopathies (TSEs). The agent that is thought to cause TSEs is a disease-associated, misfolded form of the prion protein or PrP(Sc). Unlike viruses, there are no donor screening tests for TSEs available, and PrP(Sc) is resistant to traditional viral inactivation methods. Therefore, manufacturers of plasma products are faced with special challenges to ensure product safety with respect to TSEs. Fortunately, a growing body of evidence supports the capacity of manufacturing processes to remove infectious prions from the product stream during the purification of plasma products. This can be attributed in part to the unusual physicochemical nature of PrP(Sc), which is distinct from that of soluble therapeutic proteins. Although there is no reported TSE transmission through the use of plasma products to date, many unknowns remain to be addressed through long-term epidemiologic monitoring and further experimental studies.

Preparation of soluble infectious samples from scrapie-infected brain: a new tool to study the clearance of transmissible spongiform encephalopathy agents during plasma fractionation

BACKGROUND

Concern about the safety of blood, blood components, and plasma-derived products with respect to prions has increased since the report of two blood-related infections of variant Creutzfeldt-Jakob disease in the United Kingdom. Efforts were directed toward the development of procedures able to remove or inactivate prions from blood components or plasma-derived products with brain fractions of transmissible spongiform encephalopathy (TSE)-infected rodents as spiking materials. These spiking materials, however, are loaded with pathological prion protein (PrP(TSE)) aggregates that are likely not associated to blood infectivity. The presence of these aggregates may invalidate these studies.

STUDY DESIGN AND METHODS

Brains from 263K scrapie-infected hamsters were suspended in 10 percent phosphate-buffered saline. After low-speed centrifugation, the supernatant was collected and ultracentrifuged at 220,000 x g at 25 degrees C for 30 minutes. The high-speed supernatants (S(HS)) and pellets were collected; the proteinase-resistant PrP(TSE) was measured by Western blot and infectivity by intracerebral inoculation into weanling hamsters.

RESULTS

A substantial amount of prion infectivity (more than 10(5) LD(50) per mL of a 10% suspension of brain tissues) is present in the S(HS) fraction of 263K scrapie-infected hamster brains. Concomitantly, this fraction contains none or only traces of PrP(TSE) in its aggregate form.

CONCLUSION

This study describes a simple and fast protocol to prepare infectious material from 263K scrapie-infected brains that is not contaminated with PrP(TSE) aggregates. This S(HS) fraction is likely to be the most relevant material for endogenous spiking of human blood in validation experiments aimed at demonstrating procedures to remove or inactivate TSE infectious agents.

Cellular prion protein is released on exosomes from activated platelets

Cellular prion protein (PrP(C)) is a glycophosphatidylinositol (GPI)-anchored protein, of unknown function, found in a number of tissues throughout the body, including several blood components of which platelets constitute the largest reservoir in humans. It is widely believed that a misfolded, protease-resistant form of PrP(C), PrP(Sc), is responsible for the transmissible spongiform encephalopathy (TSE) group of fatal neurodegenerative diseases. Although the pathogenesis of TSEs is poorly understood, it is known that PrP(C) must be present in order for the disease to progress; thus, it is important to determine the physiologic function of PrP(C). Resolving the location of PrP(C) in blood will provide valuable clues as to its function. PrP(C) was previously shown to be on the alpha granule membrane of resting platelets. In the current study platelet activation led to the transient expression of PrP(C) on the platelet surface and its subsequent release on both microvesicles and exosomes. The presence of PrP(C) on platelet-derived exosomes suggests a possible mechanism for PrP(C) transport in blood and for cell-to-cell transmission.

Managing the risk of transmission of variant Creutzfeldt Jakob disease by blood products

Whereas plasma-derived clotting factor concentrates now have a very good safety record for not being infectious for lipid enveloped viruses, concern has arisen about the possibility that prion diseases might be transmitted by blood products. There is epidemiological evidence that classical sporadic Creutzfeld Jakob disease (CJD) is not transmitted by blood transfusion. There is now good evidence that the abnormal prion associated with variant CJD can be transmitted by transfusion of fresh blood components and infect recipients. To reduce the risk of the pathological prion in the UK infecting recipients of clotting factor concentrates, these are now only manufactured from imported plasma collected from countries where there has not been bovine spongiform encephalopathy (BSE) in cattle and the risk of variant CJD in the population is, therefore, considered negligible. The safety of these concentrates is also enhanced because prion protein is, to an appreciable extent, excluded by the manufacturing process from the final product. To help reduce the chance of prion transmission by fresh blood products, donations are leucodepleted, there is increasing use of imported fresh frozen plasma (especially for treating children) and potential donors, who have been recipients of blood since 1980 (the beginning of the BSE epidemic in cattle) are deferred.

Cell Membrane Microparticles in Blood and Blood Products: Potentially Pathogenic Agents and Diagnostic Markers

Cell membrane microparticles (MPs) circulate in the blood of healthy donors, and their elevated counts have been documented in various pathologies. Microparticles are phospholipid microvesicles of 0.05 to 1.5 microm in size, containing certain membrane proteins of their parental cells. Thus, different phenotypes of MPs derived from platelets, blood cells, endothelial cells, and some other cell types have been identified in plasma. Microparticles are released by various stimuli including shear stress, complement attack, or proapoptotic stimulation. Microparticle release is a highly controlled process and likely independent from metabolic energy. Elevated MPs in various diseases indicate their diagnostic importance, particularly in vascular pathologies. Moreover, MPs in blood possess a broad spectrum of biologic activities. Microparticles may facilitate cell-to-cell interactions, induce cell signaling, or even transfer receptors between different cell types. The physiological roles of MPs in various tissue defense processes have been suggested and the pathophysiologic implications of MPs in thrombosis, inflammation, cancer metastasis, or response to pathogens have been proposed. This is important for transfusion medicine because MPs are present in both plasma and cellular blood products. Thus, the investigation of potentially pathogenic effects of MPs in blood products and of MP release associated with blood product processing and storage have yet to come.

Ensuring the biologic safety of plasma-derived therapeutic proteins: detection, inactivation, and removal of pathogens

Human plasma-derived proteins, such as immunoglobulins, coagulation factors, α₁-antitrypsin, fibrin sealants, and albumin, are widely used as therapeutics for many serious and life-threatening medical conditions. The human origin of these proteins ensures excellent efficacy and compatibility but may also introduce the risk of unintentional disease transmission. Historically, only viruses, particularly hepatitis and HIV, have posed serious threats to the safety of these therapeutics. Fortunately, between 1970 and 1990, the molecular biology of each of the major viruses was elucidated. These advances led to the development and implementation of effective donor screening tests, mainly based on immunoassays and nucleic acid testing, which resulted in a significant reduction of disease transmission risk. In addition, viral inactivation and removal steps were implemented and validated by manufacturers, further reducing the risk associated with known, as well as unidentified, viruses. Since the late 1990s, a different class of transmissible agent, referred to as prions, has been identified as a new risk for disease transmission. However, prion diseases are very rare, and prion transmission through plasma-derived proteins has not been reported to date. The prion-related risk is minimized by deferring donors with certain key risk factors, and by the manufacturing processes that are capable of removing prions. Advances in science and pathogen safety-related technology, compliance with good manufacturing practices by manufacturers, and increasingly stringent regulatory oversight, has meant that plasma-derived proteins have been developed into today’s highly effective therapeutics with very low risk of disease transmission.

Prions: Who Should Worry about Them?

Prion diseases, also called transmissible spongiform encephalopathies (TSEs), are a family of neurodegenerative disorders affecting both humans and animals. They are caused by the accumulation of an abnormal form of a protein known as prion that results in neuronal death and a characteristic spongiform appearance of the brain tissue. Human prion diseases can be sporadic, acquired or hereditary. Acquired prion diseases have been linked to entering contaminated food into the human food chain, failure to completely disinfect or sterilize contaminated surgical instruments, patients receiving tissues and organs from infected donors, recipients of blood and other biological contaminated products, and potentially to cross infection in dental procedures. At present, there is unfortunately no efficient therapy that can be administered to clinically infected patients with prion diseases. Moreover, there are no simple diagnostic tests that can be used to show the agent of transmissible spongiform encephalopathy during the preclinical phase of the disease. Therefore, to prevent the spread of this emerging infectious agent it is necessary to implement several health control strategies and maintain surveillance for subclinical infections.

Variant Creutzfeldt-Jakob disease transmission by plasma products: assessing and communicating risk in an era of scientific uncertainty

A substantial body of animal data indicates that transmissible spongiform encephalopathies (TSEs) are transmitted through blood. These data have been augmented in the past year by reports that two recipients of red cells from donors with variant Creutzfeldt-Jakob disease (vCJD) in the United Kingdom have acquired this infection. Most of the blood donations collected in countries affected by bovine spongiform encephalopathy (BSE) and vCJD also contribute plasma to fractionation pools. Thus, a number of batches of fractionated products have included plasma from donors who developed vCJD. On the basis of public health strategies influenced, in part, by risk assessments, the UK and the French authorities have instituted measures for recalling products and informing patients of the estimated risks. It is therefore relevant to review the principles used by authorities in generating risk assessments for the transmission of TSEs by blood and blood products. While the general principles are fairly straightforward, the final assessments are very dependent on the magnitude of several key parameters, which are, largely, still unknown. A critical determinant of final product risk is the extent to which the plasma fractionation process will contribute to eliminating the infectious prion agent. Therefore, regulatory and industry measures to characterize fractionation processes for their capacity to eliminate prions are to be strongly encouraged. In the interim, an understanding of the principles used to generate risk assessments should contribute to an enhanced ability to address this threat to patient safety. Authorities should recognize that adequate communication is an integral part of good risk-management practices.

In-vitro evaluation of the PALL Leukotrap Affinity Prion Reduction Filter as a secondary device following primary leucoreduction

BACKGROUND AND OBJECTIVES

A filter (PRF1) designed to remove abnormal prion proteins from red-cell units has been developed. The purpose of this study was to evaluate the quality of red cells produced using this device.

MATERIALS AND METHODS

Leucocyte-depleted red-cell units (CPD, CPD-A1 and CPD/SAGM) processed according to standard UK practices were filtered using PRF1. Filtered and control units were stored and sampled on day 1, day 7 and on the date of expiry and were tested using standard measures of red-cell quality.

RESULTS

Filtered units were found to have significantly higher percentage haemolysis levels, lower haemoglobin levels and a smaller volume compared with controls. All results, however, were well within the permitted 0.8% haemolysis level at the end of storage and all units met the UK guidelines for haemoglobin and volume. The other test parameters measured showed no significant differences between the test and control units.

CONCLUSIONS

The PRF1 filter was found to be easy to use and resulted in red-cell units that met all relevant UK and European Guidelines.

BSE safety standards: An evaluation of public health policies of Japan, Europe, and USA

Since the advent of bovine spongiform encephalopathy (BSE) in the United Kingdom in 1986, new BSE cases have recently become rare. However, in Japan and the United States, positive cases have started to be seen recently. The rise in BSE cases paved the way for the human form of this disease, the variant Creutzfeldt-Jakob disease (vCJD). The observed trends in the UK may be attributed to effective implementation of public health policies coupled with increased vigilance through advancement in science and technology, or they may well be a reflection of the natural disease progression. We aim to discuss the BSE chronology of events, and compare examination methods, costs and cost-efficiency, management, and public policies of Japan, Europe, and the USA.

Detection of ultra-low levels of pathologic prion protein in scrapie infected hamster brain homogenates using real-time immuno-PCR

Pathologic prion protein (PrP(Sc)), implicated in transmissible spongiform encephalopathies, is detected by antibody-based tests or bioassays to confirm the diagnosis of prion diseases. Presently, the Western blot or an ELISA is officially used to screen the brain stem in cattle for the presence of PrP(Sc). The immuno-polymerase chain reaction (IPCR), a technique whereby the exponential amplification ability of PCR is coupled to the detection of proteins by antibodies in an ELISA format, was applied in a modified real-time IPCR method to detect ultra-low levels of prion protein. Using IPCR, recombinant hamster PrP(C) was consistently detected at 1 fg/mL and proteinase K (PK)-digested scrapie infected hamster brain homogenates diluted to 10(-8) (approximately 10-100 infectious units) was detected with a semi-quantitative dose response. This level of detection is 1 million-fold more sensitive than the levels detected by Western blot or ELISA and poises IPCR as a method capable of detecting PrP(Sc) in the pre-clinical phase of infection. Further, the data indicate that unless complete PK digestion of PrP(C) in biological materials is verified, ultrasensitive assays such as IPCR may inaccurately classify a sample as positive.

Molecular neurology of prion disease

Prions are infectious pathogens principally composed of abnormal forms of a protein encoded in the host genome. They cause lethal neurodegenerative conditions including CJD, GSS, and kuru in humans and scrapie and bovine spongiform encephalopathy in domestic animals. Remarkably, distinct strains of prions occur despite absence of an agent-specific genome: misfolded proteins themselves may encode strain diversity--with wide implications in biology. The arrival of variant CJD, and the experimental confirmation that it is caused by infection with BSE-like prions, has focussed research on early diagnosis and treatment. Recent advances lead to considerable optimism that effective human therapies may now be developed. While several drugs have been tried in small numbers of patients, there is no clear evidence of efficacy of any agent and controlled clinical trials are urgently needed. Importantly, there is increasing recognition that fundamental processes involved in prion propagation--seeded aggregation of misfolded host proteins--are of far wider significance, not least in understanding the commoner neurodegenerative diseases that pose such a major and increasing challenge for healthcare in an ageing population.

The expression of prion protein (PrP(C)) in the megakaryocyte lineage

BACKGROUND

Cellular prion protein (PrP(C)) is a naturally occurring protein in normal individuals which adopts an abnormal conformation, termed scrapie prion protein (PrP(Sc)) that is associated with disease. There is great concern that clinically asymptomatic variant Creutzfeldt-Jacob disease (vCJD) may transmit PrP(Sc) in blood transfusion products. PrP(C) is widely expressed and has been found in human blood. The majority of cellular borne PrP(C) is associated with platelets (84%). Although PrP(C) mRNA has been demonstrated in platelets, the quantity is unknown and may not reflect the total PrP(C) present.

OBJECTIVE

To investigate the expression of PrP(C) in the megakaryocyte lineage.

METHODS

The expression of PrP(C) was studied in CD34+ cells, cultured megakaryocytes and platelets using electron microscopy, flow cytometry, semi-quantitative RT-PCR and immunofluorescence confocal microscopy.

RESULTS AND CONCLUSIONS

The expression of PrP(C) appeared to increase with differentiation and polyploidization in the megakaryocyte lineage. PrP(C) was located within platelet alpha-granules and its source is likely to be from megakaryocyte precursors. If PrP(Sc) has a similar distribution, these results have implications for the selection of blood donors and preparation of cell-depleted blood products.

Variation in concentration of prion protein in the peripheral blood of patients with variant and sporadic Creutzfeldt-Jakob disease detected by dissociation enhanced lanthanide fluoroimmunoassay and flow cytometry

BACKGROUND

A highly sensitive dissociation-enhanced lanthanide fluoroimmunoassay (DELFIA) and flow cytometry techniques have previously been developed and employed to characterize soluble cellular prion protein (PrP(c)) expression in whole blood and separated components from healthy adult blood donors. No previous studies with these techniques have evaluated the concentration and expression of PrP in the blood of patients with variant Creutzfeldt-Jakob disease (vCJD).

STUDY DESIGN AND METHODS

For blood from vCJD patients, sporadic CJD (sCJD) patients, non-CJD neurological controls, and healthy adults, PrP(c) was measured by DELFIA and cell-associated PrP was measured by flow cytometry.

RESULTS

DELFIA analysis identified a significant reduction in the concentration of PrP(c) in the whole blood of vCJD (p = 0.012) and non-CJD neurological patients (p = 0.0004) compared with healthy adults. A significant elevation was found in plasma PrP(c) in sCJD patients compared with healthy adult (p = 0.022) and neurological controls (p = 0.050). Flow cytometry found no significant differences between groups in expression of PrP on platelets and lymphocytes, nor in sensitivity of cellular PrP to proteinase K. Neurological controls show significantly less PrP on red cells than healthy adults.

CONCLUSION

There are differences in free and cell-associated PrP found in blood of CJD patients and control groups, some of which might be useful with other tests in disease profiling as an aid to diagnoses.

Tests de dépistage des ESST animales : présent et futur

In 1999, three rapid tests (Prionics, Bio-Rad, Enfer) have been validated by the European Commission for the post-mortem diagnosis of BSE in cattle. They are now used on a large scale over the entire Europe. In absence of antibodies specifically recognizing the native conformation PrPres, its selective determination is based on the biochemical properties of this abnormal form (PK resistance, aggregation in presence of detergents). In addition, all these tests include a denaturation step so that PrP can be detected by appropriate antibodies. When applied on "risk populations" or on "healthy animals" entering into the human food chain, these rapid tests have provided a better estimation of the epizootic and allowed an efficient removal of animals bearing a risk for human consumption. Since 2002, they have also been used for the post-mortem diagnosis of scrapie in sheep and goat. Five new tests have been recently evaluated (ID-Lelystad; Perkin-elmer, Prionics Check LIA, UCSF, Imperial college) but it is too early to know which place they will take in the field. Current tests allow a preclinical diagnosis of TSE, especially in sheep and goats for which a very early detection is possible in peripheral lymphoid tissues. However, to date, no test on living animal has been validated. Taking into account the important number of research teams now involved on this topic one may expect spectacular progress in the forthcoming years.

Expression of PrPC on cellular components of sheep blood

PrPC, a glycosylphosphatidylinositol-linked glycoprotein, plays a central role in the pathogenesis of transmissible spongiform encephalopathies (TSEs), undergoing a conformational alteration to the disease-associated isoform, commonly designated PrPSc. PrPC is expressed in many tissues other than the nervous system, although its precise function(s) remains unclear. It has previously been demonstrated that TSEs can be transmitted by blood transfusion in sheep. The aim of this work was to identify which components of blood carried the infection. As an initial step, the distribution of PrPC on cellular components of sheep blood was examined to identify potential targets for infection. Cell-surface expression of PrPC was found only on peripheral blood mononuclear cells (PBMCs); however, platelets also contained significant amounts of intracellular PrPC. The level of PrPC expressed on the cell surface of PBMCs was influenced by PrP genotype, with the highest levels found in scrapie-susceptible VRQ/VRQ sheep and the lowest levels in scrapie-resistant ARR/ARR sheep. In susceptible sheep, PrPC was expressed at varying levels on all major subsets of PBMCs, with the highest levels on the CD21+ subset of B cells, and PrP expression was upregulated dramatically on CD21+ B cells in some scrapie-infected sheep.

Protein conformation significantly influences immune responses to prion protein

In prion diseases, such as variant Creutzfeldt-Jakob disease normal cellular prion protein (PrPC), a largely alpha-helical structure is converted to an abnormal conformational isoform (PrPSc) that shows an increase in beta-sheet content. Similarly, the recombinant form of PrPC (ralpha-PrP) can be converted to a conformation dominated by beta-sheet (rbeta-PrP) by reduction and mild acidification in vitro, a process that may mimic in vivo conversion following PrPC internalization during recycling. Despite PrPSc accumulation and prion propagation in the lymphoreticular system before detectable neuroinvasion, no Ab response to PrP has been detected, probably due to immune tolerance. To investigate how the immune system may respond to alpha- and beta-PrP, we immunized Prnp(0/0) mice that are not tolerant of PrP with ralpha-PrP and rbeta-PrP. In this study, we show that although T cells stimulated by these differently folded conformers PrP recognize similar immunodominant epitopes (residues 111-130 and 191-210) the cytokine profile in response to ralpha- and rbeta-PrP was different. Challenge with ralpha-PrP elicited a strong response of IL-5 and IL-10, whereas rbeta-PrP led to an early increased production of IFN-gamma. In addition, immunization with ralpha-PrP led to production of predominantly IgG1 isotype Ab in the sera, whereas after immunization with rbeta-PrP, IgG2b was significantly produced. Thus, both humoral and cellular responses to these differently folded isoforms of the same protein are different, indicating a possible involvement of Th1 and Th2 pathway activation. These differences may be exploitable diagnostically and therapeutically for prion diseases, such as variant Creutzfeldt-Jakob disease.

The 'precautionary principle' as a guide for future drug development

During the last decade, the 'precautionary principle' health has gained importance. It is an approach to manage uncertain risks and to prevent any damage to the environment or human. A key element is to take action, even if some cause and effect relationships are not fully established scientifically. Although there are also critics of this principle, it is meanwhile, also increasingly implemented in medicine. An important subject is medicinal products of human or animal origin. Manifold official precaution-guided regulations have been stated to improve their safety, particularly to avoid any infection by viruses and pathogens causing transmissible spongiform encephalopathies. In addition to numerous regulations and decisions, it is generally recommended to substitute animal and human-derived products with adequate alternatives wherever possible. This is a great challenge for research and drug development. One option is recombinant proteins, which however, are not generally free of any risk of contamination. Therefore, the best strategy might be the development of synthetic, specifically acting drugs. The most widely used medicinal product of animal origin at present is heparin. Although there has been no indication of any viral contamination, many other reasons suggest its substitution by alternative antithrombotics. These actually promoted the research on new anticoagulants. With the approval of fondaparinux, the first synthetic, selective factor Xa, a first alternative to the porcine-derived heparin has become available. In addition, other synthetic antithrombotics are currently in clinical development. In principle, it is thus possible that the prophylaxis and therapy of thromboembolic diseases will become completely independent of animal-derived drugs, which would be in line with the precautionary principle.

Distribution of a bovine spongiform encephalopathy-derived agent over ion-exchange chromatography used in the preparation of concentrates of fibrinogen and factor VIII

BACKGROUND AND OBJECTIVES

The risk of haemophiliacs contracting variant Creutzfeldt-Jakob disease (vCJD) via treatment with factor VIII concentrates is not known. Therefore, in order to determine the extent to which the vCJD agent might be removed during the preparation of factor VIII concentrate, the partitioning of a bovine spongiform encephalopathy (BSE)-derived agent was measured over the main purification step used to prepare the Scottish National Blood Transfusion Service high-purity factor VIII concentrate (Liberate).

MATERIALS AND METHODS

Murine-passaged BSE (strain 301V), in the form of a microsomal fraction prepared from infected brain, was used to 'spike' a solution of factor VIII of intermediate purity. The 'spiked' starting material was subjected to solvent-detergent treatment and then to anion-exchange chromatography with Toyopearl DEAE-650M. All fractions were tested for 301V infectivity using a murine bioassay, including the procedures used to clean the ion-exchange media after use.

RESULTS

BSE 301V infectivity was reduced by 2.9 log(10) in the fibrinogen fraction and by 2.7 log(10) in the factor VIII fraction. Over 99% of the added 301V infectivity remained bound to the ion-exchange column after elution of factor VIII. A large quantity of infectivity was subsequently removed by washing the ion-exchange media with 2 m NaCl. No further BSE 301V infectivity was detected in column eluates after treatment with 0.1 m NaOH or a second wash with 2 m NaCl.

CONCLUSIONS

Results using a BSE-derived agent suggest that vCJD infectivity would be substantially removed by the ion-exchange process used in the preparation of fibrinogen and factor VIII concentrate. Although 301V infectivity remained bound to the ion-exchange matrix following elution of factor VIII, this appeared to be eliminated by the procedure used for cleaning the ion-exchange media after each use.

Effect of protease treatment on plasma infectivity in variant Creutzfeldt-Jakob disease mice

BACKGROUND

The emergence of variant Creutzfeldt-Jakob disease (vCJD) and of a probable transmission of the disease through blood transfusion from a presymptomatic case has underlined the need for a reliable, sensitive, and specific screening test. This study was initiated to explain why attempts to identify protease-resistant prion protein (PrPres) following treatment with proteinase K (PK) in blood or blood components have so far failed.

STUDY DESIGN AND METHODS

RIII mice were inoculated intracerebrally (i.c.) with vCJD agent. As soon as some mice became ill, blood from all mice was collected, pooled, and separated into components. Aliquots of plasma were treated with either 100 and 500 microg per mL PK or left untreated. Samples were analyzed for total protein and for PrPres by Western blot with 6H4 antibodies. Infectivity in PK-treated and untreated samples was bioassayed by i.c. inoculation into healthy mice.

RESULTS

Estimated infectivity in untreated control plasma was 20.6 IU per mL. Treatment of plasma with 100 or 500 microg per mL PK resulted in estimated infectivity levels of 8.4 and 5.2 IU per mL, respectively. Coomassie staining revealed substantial changes in the protein profile after PK treatment, with massive degradation of proteins at 500 microg per mL PK. No PrPres was detected in plasma samples by Western blotting.

CONCLUSION

Infectivity in plasma of vCJD-infected mice showed a trend toward reduction following enzymatic treatment with increasing doses of PK, possibly because of activity against proteolysis-sensitive isoforms of abnormal prion protein. It is concluded that the use of PK in protocols for the detection of PrPres may decrease the sensitivity of blood-based assays.

Proceedings of a consensus conference: the screening of blood donors for variant CJD

Since the identification, in 1996, of the first case of variant Creutzfeldt-Jakob disease (vCJD) in humans various approaches have been implemented and/or proposed to prevent this disease from being transfusion transmitted. In addition, a variety of possible laboratory-based approaches have been developed and will continue to be developed for the vCJD screening of blood donors. Various issues related to the implementation of such vCJD testing is likely to assume greater importance as diagnostic tests for vCJD becomes available for the potential screening of blood donors. The purpose of this Consensus Conference was to bring together international experts in an effort to determine which principles should guide the introduction of such testing. These experts provided the scientific and biological background of bovine spongiform encephalopathy (BSE) and vCJD, an understanding of their current epidemiology, as well as the ethical and legal issues that would impact on the implementation of a screening test for preventing the transfusion transmission of vCJD. This contentious issue is of potential considerable importance to transfusion medicine personnel worldwide, as well as to future recipients of allogeneic blood components.

Diagnosing prion diseases: needs, challenges and hopes

Prion diseases are among the most intriguing infectious diseases and are associated with unconventional proteinaceous infectious agents known as prions. Prions seem to lack nucleic acid and propagate by transmission of protein misfolding. The nature of prions and their unique mode of transmission present challenges for early diagnosis of prion diseases. In this article, state-of-the-art prion diagnostic techniques, together with the new strategies that are being used to develop sensitive, early and non-invasive diagnoses for these diseases are reviewed.

Partitioning of TSE infectivity during ethanol fractionation of human plasma

The practice of validating processes for their capacity to inactivate a range of non-enveloped and enveloped viruses also provides confidence that plasma products will be safe from emerging viral pathogens with known aetiology. Of greater concern are diseases of unknown or poorly defined aetiology such as the group of neurological diseases collectively called the transmissible spongiform encephalopathies (TSEs), or prion diseases, for which the best known human disease is Creutzfeldt-Jakob Disease (CJD) and its variant form (vCJD). The goal of the current study was to investigate the potential for manufacturing steps used in the production of albumin and immunoglobulin products by Kistler-Nitschmann fractionation, and the utility of nanofiltration of immunoglobulin to remove TSE agents. Two different scrapie model systems were used. In the first system infectious material used for spiking was scrapie sheep brain homogenate with infectivity titres being measured in hamsters. In the second system purified scrapie agent was used (PrP fibrils) with Western blot analysis measuring reduction in the proteinase K resistant form being used as a measure of removal. The data demonstrated substantial removal of the infectious agent by the manufacturing process in both model systems although some differences were observed in partitioning of the two different infectious materials. The hamster infectivity studies were shown to be approximately 1000 fold more sensitive than the Western Blot assay. The data from both studies provide added confidence that these plasma products are safe with respect to their potential to transmit TSE.

The modern landscape of transfusion-related iatrogenic Creutzfeldt–Jakob disease and blood screening tests

The idea that blood in naturally occurring transmissible spongiform encephalopathies is not infectious has imploded in the face of recent transmissions from the blood of naturally occurring scrapie in sheep and of variant Creutzfeldt-Jakob disease in humans. Although donor exclusion criteria ensure that the number of any further iatrogenic cases will be small, the risk of future blood-borne disease transmissions could be entirely eliminated by a diagnostic preclinical screening test. A variety of methodological approaches to blood testing are under development, with different levels of success, but no method has yet achieved the critical goal of discriminating transmissible spongiform encephalopathy-infected from healthy uninfected humans.

Effectiveness of leucoreduction for removal of infectivity of transmissible spongiform encephalopathies from blood

In 1999, the UK implemented universal leucoreduction as a precaution against transmission of variant Creutzfeldt-Jakob disease by transfusion of domestic blood or red blood cells. We aimed to assess how effectively leucoreduction reduced infectivity of transmissible spongiform encephalopathies (TSEs) in blood. 450 mL of whole blood collected and pooled from scrapie-infected hamsters was leucoreduced with a commercial filter. Blood cell concentrations were quantified, and infectivity titres measured. Blood cell recovery and white blood cell removal complied with American Association of Blood Banks standards. Leucofiltration removed 42% (SD 12) of the total TSE infectivity in endogenously infected blood. Leucoreduction is necessary for the removal of white-cell-associated TSE infectivity from blood; however, it is not, by itself, sufficient to remove all blood-borne TSE infectivity.

Structural Determinants of Conformationally Selective, Prion-binding Aptamers

We have recently described the isolation of 2'-fluoropyrimidine-substituted RNA aptamers that bind selectively to disease-associated beta-sheet-rich forms of the prion protein, PrP, from a number of mammalian species. These aptamers inhibit the accumulation of protease-resistant forms of PrP in a prion-seeded, in vitro conversion assay. Here we identify the minimal portions of two of these aptamers that retain binding specificity. We determine their secondary structures by a combination of modeling and solution probing. Finally, we identify an internal site for biotinylation of a minimized, synthetic aptamer and use the resultant reagent in the detection of abnormal forms of PrP in vitro.

Possible transmission of variant Creutzfeldt-Jakob disease by blood transfusion

BACKGROUND

Variant Creutzfeldt-Jakob disease (vCJD) is a novel human prion disease caused by infection with the agent of bovine spongiform encephalopathy (BSE). Epidemiological evidence does not suggest that sporadic CJD is transmitted from person to person via blood transfusion, but this evidence may not apply to vCJD. We aimed to identify whether vCJD is transmissible through blood transfusion.

METHODS

The national CJD surveillance unit reported all cases of probable or definite vCJD to the UK blood services, which searched for donation records at blood centres and hospitals. Information on named recipients and donors was provided to the surveillance unit to establish if any matches existed between recipients or donors and the database of cases of vCJD. Recipients were also flagged at the UK Office of National Statistics to establish date and cause of death.

FINDINGS

48 individuals were identified as having received a labile blood component from a total of 15 donors who later became vCJD cases and appeared on the surveillance unit's register. One of these recipients was identified as developing symptoms of vCJD 6.5 years after receiving a transfusion of red cells donated by an individual 3.5 years before the donor developed symptoms of vCJD.

INTERPRETATION

Our findings raise the possibility that this infection was transfusion transmitted. Infection in the recipient could have been due to past dietary exposure to the BSE agent. However, the age of the patient was well beyond that of most vCJD cases, and the chance of observing a case of vCJD in a recipient in the absence of transfusion transmitted infection is about 1 in 15000 to 1 in 30000.

Emerging Infectious Threats to the Blood Supply

During the past 15 years, it has become clear that new agents and new strains of existing agents continue to emerge worldwide as protagonists of infectious disease. These emerging agents pose threats not only to the general human population but also to recipients of blood transfusions. Indeed, the modern era of blood safety perhaps began with the recognition of HIV as an emerging agent transmissible by blood transfusion. Today, emerging infectious agents that pose a threat to the blood supply are not limited to viruses, but include bacterial, protozoan, and prion agents. Preventing the transmission of these new agents by blood transfusion is often problematic, as the available tools may be inadequate. It is certain, however, that new agents will continue to emerge as threats to blood safety and these agents are likely to require novel approaches to prevent their transmission.

Similar levels of infectivity in the blood of mice infected with human-derived vCJD and GSS strains of transmissible spongiform encephalopathy

BACKGROUND

The possible transmission of variant CJD (vCJD) through blood transfusion or use of plasma-derived products prompted this study comparing infectivity in murine models of vCJD and Gerstmann-Sträussler-Scheinker (GSS) disease, a non-vCJD form of transmissible spongiform encephalopathy (TSE).

STUDY DESIGN AND METHODS

RIII/Fa/Dk (RIII) or Swiss-Webster (Swiss) mice were inoculated intracerebrally (IC) with mouse-adapted strains of vCJD or GSS (Fukuoka-1) of similar infectivity. Groups of RIII mice were euthanized 17 weeks after inoculation (during the incubation period), and another 23 weeks after inoculation (when symptomatic). Blood was collected, separated into components, and inoculated into groups of healthy mice; brains and spleens from all mice were harvested and tested for the presence of PrPres by Western blot using 6H4 MoAb.

RESULTS

Levels of 20-30 infectious doses per mL were present in buffy coat and plasma during both the incubation and symptomatic stages of disease; PLT pellet infectivity was lower (10 ID/mL) and RBCs were not infectious. The disease was transmitted more efficiently by IV than IC inoculation of plasma, but there was no difference observed with inoculation of buffy coat. The incubation period was shorter after IC inoculation of GSS- than vCJD-brain inocula. The amount of PrPres in spleens was similar for both TSE agents, but was slightly lower in brains of vCJD than GSS mice.

CONCLUSION

Infectivity was detected in blood components of mice infected with a human-derived strain of vCJD during both the preclinical and clinical phases of disease in a similarly low range of concentrations as in mice infected with a human-derived nonvariant strain (GSS, Fukuoka-1). Other measures of virulence, including brain infectivity titers, incubation periods, and the accumulation of PrPres in spleens and brains, were also comparable in both experimental models.

Transfusion Medicine

In the vein-to-vein flow of blood from donor to patient, the role of the transfusion medicine specialist has become increasingly centered at the bedside. Three clinically centered issues in blood safety and in blood conservation are presented in this chapter.

In Section I, Dr. Patricia Hewitt presents the epidemiologic and clinical evidence regarding new variant Creutzfeldt-Jakob disease (nvCJD) in the UK and its relevance to transfusion medicine. Lessons learned from the responses by the National Blood Service to this crisis are discussed, particularly in the context of recent evidence of a case of vCJD transmission by blood transfusion and a second case of apparent transmission of abnormal prion protein without development of clinical illness.

In Section II, Dr. Christopher Silliman and his colleagues summarize recent knowledge gained regarding transfusion-related acute lung injury (TRALI), which is now the leading cause of transfusion-related mortality. Two different etiologies have been proposed: a single antibody-medicated event, involving anti-HLA Class I and Class II, or anti-granulocyte antibodies; and a two-event model, which includes the clinical condition of the patient resulting in pulmonary endothelial activation and neutrophil sequestration. The second event is the transfusion of a biologic response modifier (lipids or antibodies) in the blood component that activates primed neutrophils. Prevention, clinical treatment, and proposed definition of TRALI are discussed.

In Section III, Dr. Lawrence Goodnough and colleagues present a transfusion medicine service approach to the utilization of recombinant factor VIIa (rFVIIa) in non-approved clinical settings. rFVIIa has a potential role as a hemostatic intervention in a variety of clinical settings, yet few clinical trials have been completed to date to guide indications for its use. The policies presented here are those in place at the authors’ medical center, and will undergo periodic review and revision as relevant new information and data are generated.

Risks of blood transfusion

OBJECTIVE

To review the current status of risks of blood transfusion.

DATA SOURCES, EXTRACTIONS, AND SYNTHESIS

English-speaking literature, literature search using key works, human data, and follow-up with key bibliographic citations.

CONCLUSIONS

Substantial advances have been achieved in blood safety during the last 20 yrs, particularly for transfusion-transmitted viral infections. Currently, the most serious known risks from blood transfusion are administrative error (leading to ABO-incompatible blood transfusion), transfusion-related acute lung injury, and bacterial contamination in platelet products. Emerging pathogens, such as West Nile virus infection emphasize the need for implementation of proactive strategies, such as pathogen inactivation technologies, as well as reactive strategies, such as nucleic acid testing, to ensure continued advances in blood safety.

Residual cell content in plasma produced by three centrifugal apheresis procedures

BACKGROUND

Understanding the impact of collection procedures on the residual amount of blood cells in plasma for transfusion and for fractionation is of current interest. This prospective work evaluated plasma donations collected on an apheresis machine (PCS 2, Haemonetics) with three different automatic centrifugal apheresis procedures, currently largely used in the US (Revision G) and in Europe (Revision F), and included a new procedure that uses a high-separation core (HSC) that is designed with a second separation chamber to further separate cells from plasma.

STUDY DESIGN AND METHODS

A total of 90 collection procedures have been performed from a population of 37 donors, under comprehensively standardized conditions. There were 30 well-matched donors in each group. Plasma aliquots were taken from the plasma units within 30 minutes of the end of the collection procedures and immediately assessed for WBCs, RBCs, PLTs, and supernatant Hb.

RESULTS

In Revision F and Revision G plasma donations, the mean numbers of WBCs were 83.1 x 10(4) and 311 x 10(4) per L; PLTs, 5.01 x 10(9) and 20 x 10(9) per L; and RBCs, 58 x 10(6) and 43 x 10(6) per L, respectively [corrected]. Significantly lower values were found with the HSC procedure (mean WBC, RBC, and PLT counts, 3.01 x 10(4)/L [p < 0.05], 9 x 10(6)/L [p < 0.001], and 3.5 x 10(9)/L [p < 0.001], respectively). The amount of free Hb was similar in all three procedures.

CONCLUSION

Significant differences in numbers of cells in plasma were found depending on the centrifugal procedures used and the design of the separation bowl. The lowest level of cell contamination was found with the new HSC bowl, which without a filtration step, yielded plasma that met the standard for WBC-reduced plasma. Plasma collectors can select the most appropriate method of plasma collection based on donor criteria, use of plasma (transfusion, viral inactivation, or fractionation), and local or international regulations, when in place.

The effect of methylene blue photoinactivation and methylene blue removal on the quality of fresh-frozen plasma

BACKGROUND

T: he effects of using fresh or frozen-thawed plasma, WBC reduction of plasma before freezing, and the use of two different methylene blue (MB) removal filters on the quality of MB-treated plasma were compared.

STUDY DESIGN AND METHODS

In a paired study (n = 11/arm) plasma was frozen within 8 hours of collection, thawed, MB photoinactivated, and then filtered using one of two MB removal filters. Fresh plasma (n = 16) and plasma WBC reduced before freezing (n = 19) were MB inactivated.

RESULTS

Freeze-thawing resulted in loss of activity of FXII and VWF of 0.06 and 0.04 units per mL, respectively, but no significant loss of activity of factors II through XI or fibrinogen. Further loss of activity occurred after MB treatment: FII (0.07 IU/mL), FV (0.11 U/mL), FVII (0.08 IU/mL), FVIII (0.28 IU/mL), F IX (0.12 IU/mL), FX (0.16 IU/mL), FXI (0.28 U/mL), FXII (0.15 U/mL), VWF antigen (0.05 IU/mL), VWF activity (0.06 U/mL), and fibrinogen (0.79 g/L). Losses due to this step were significantly (5-10%) lower in fresh plasma compared to frozen-thawed plasma. Neither MB removal filter resulted in significant loss of activity of any factor studied.

CONCLUSION

MB removal, by either of the available filters, has little impact on the coagulation factor content of plasma, but freezing of plasma before MB treatment results in a small additional loss.

The spectrum of safety: Variant Creutzfeldt-Jakob disease in the United Kingdom

Beginning in the mid 1980s, an epidemic of bovine spongiform encephalopathy (BSE) was seen among cattle in the United Kingdom. The cause was recognized as a prion agent transmitted in the meat and bone meal products used as animal feed, a practice that was banned in 1988. Unfortunately, by that time, infected cattle had already entered the human food supply, and by 1996, several individuals were identified with a variant form of Creutzfeldt-Jakob disease (CJD), caused by the same infectious agent that had caused the disease in cattle. In the United Kingdom, 137 cases of variant CJD have been reported to date. The culprit prion protein causes no immune response and contains no nucleic acid, making preclinical detection impossible. It is also very resistant to conventional forms of inactivation and decontamination. Although no cases of variant CJD have been linked to transfusion of infected blood, there is concern that the prion agent may be transmissible in blood, and evidence from sheep models suggests that it can be. Because it is impossible to detect presymptomatic individuals who carry the etiologic prion agent, the United Kingdom has adopted measures to secure the safety of its blood supply and to minimize potential routes of infection.

Variant Creutzfeldt-Jakob disease and its transmission by blood

Variant Creutzfeldt-Jakob disease (vCJD) is a novel acquired human prion disease resulting from human exposure to the agent causing bovine spongiform encephalopathy (BSE). vCJD differs from all other human prion diseases in that the disease-associated form of the prion protein and infectivity are present in lymphoid tissues throughout the body. Lymphoid tissues and lymphocytes are implicated in the peripheral pathogenesis of prion diseases (where infectivity may be detected during the preclinical phase of the illness), giving rise to concerns that blood and blood products may also contain infectivity, thus representing a possible source of iatrogenic spread of vCJD. These concerns have been reinforced by the recent transmission of BSE in an experimental sheep model by blood transfusion from an infected animal in the preclinical phase of the illness. Studies in other animal models suggest that most infectivity in blood may be cell-associated, with lower levels in the plasma, and there is evidence to indicate that any infectivity present may be reduced during the process of plasma fractionation. At present, the attempts to detect disease-associated prion protein and infectivity in buffy coat from vCJD patients have been negative, but these studies have been limited in size and in the sensitivity of the detection systems employed. Further studies are required to develop more sensitive means of detection of disease-associated prion protein in blood; such techniques could also be employed for screening purposes, both individually and to help ascertain more precisely the likely numbers of future cases of vCJD.

Organ distribution of prion proteins in variant Creutzfeldt-Jakob disease

In this article we give an overview of the transmissible spongiform encephalopathies, with emphasis on the evidence for the distribution of abnormal prions in tissues. The normal prion protein is distributed ubiquitously throughout human body tissues. Endogenous expression of the normal prion protein, as well as auxiliary proteins, plays a part in accumulation of the abnormal prion protein. As exemplified by variant Creutzfeldt-Jakob disease (vCJD) the abnormal prion protein can accumulate in the host lymphoid system, in particular the follicular dendritic cells. The route for the disease-related prion neuroinvasion is likely to involve the peripheral nervous system. An alternative route may involve blood constituents. Both animal studies and studies on vCJD patients suggest a potential for abnormal prion distribution in several peripheral tissues other than the lymphoreticular system. In human beings the abnormal prion has been reported in the brain, tonsils, spleen, lymph node, retina, and proximal optic nerve. Infectivity, although present in peripheral tissues, is at lower levels than in the central nervous system (CNS). Animal models suggest that the growth of infectivity in the CNS is likely to be gradual with maximum values during the clinical phase of disease. That tissues may harbour the abnormal prion, at different levels of infectivity, during the incubation period of the disease raises concerns of iatrogenic transmission of the disease either after surgery, blood transfusion, or accidental organ transplantation from donors in the preclinical phase of the disease.

Evaluation of virus and prion reduction in a new intravenous immunoglobulin manufacturing process

BACKGROUND AND OBJECTIVES

Minimizing the transmission risk of infectious diseases is of primary importance in the manufacture of products derived from human plasma. A novel chromatography-based intravenous immunoglobulin (IGIV) manufacturing process was developed and the reduction of virus and transmissible spongiform encephalopathies (TSE) during the manufacturing process was assessed. Mechanistically distinct steps that could affect virus reduction were identified, and the robustness of virus reduction over the range of process conditions was determined.

MATERIALS AND METHODS

Virus and TSE reduction by processing steps were assessed using a scaled-down version of the IGIV manufacturing process.

RESULTS

Virus and TSE reduction at manufacturing process set points were well within safety standards. Robustness studies verified that the reproducibility of virus reduction was maintained at or beyond operating parameter extremes. Virus reduction across two combined manufacturing steps was lower than the sum of virus-reduction values across the individual steps, indicating mechanistic similarity of the two steps with respect to virus reduction. Only reduction from mechanistically distinct steps was claimed.

CONCLUSIONS

This comprehensive approach to pathogen safety provides the new immunoglobulin manufacturing process with a detailed, yet realistic, assessment of the risk of transmission of infectious pathogens.

Botulinum toxin A: a review of 1,085 oral and maxillofacial patient treatments

PURPOSE

Botulinum toxin A (Botox; Allergan, Inc, Irvine, CA) has been used safely and effectively for the management of rhytids and dynamic lines of the face. Much of the initial anecdotal experience with Botox has changed with experience and is reported by the author.

PATIENTS AND METHODS

In a 56-month period, 439 vials of Botox were used for primarily cosmetic improvement of facial lines and rhytids. Four hundred seventeen patients underwent 1,085 treatment episodes with an estimated 17,000 injections that were tracked on a database and reviewed.

RESULTS

Botox is a safe and effective treatment for the temporary improvement of facial lines and dynamic rhytids in selected anatomic regions. The techniques of reconstitution, storage, use, dose, and technique may not be as sensitive as originally described.

CONCLUSION

When following minimal guidelines, the use of Botox for cosmetic facial applications is safe, predictable, and without serious complications and provides generalized patient satisfaction.

Transmissible spongiform encephalopathy update and implications for blood safety

At this time, the accumulated evidence does not support the implementation of measures targeted against the risk of transfusion transmission of sporadic, familial, or iatrogenic CJD. Evolving information about vCJD, however, suggests that policy makers need to consider implementing measures to protect against exposure to vCJD, if such measures themselves do not lead to decreased blood safety. Surveillance of human TSEs and investigation of the risk of transfusion transmission must continue in order to provide further refinements in blood safety policy.