Transmission Of Variant Creutzfeldt-Jakob Disease Research Articles

Absence of evidence of transfusion transmission risk of Creutzfeldt-Jakob disease in the United States: Results froma 28-year lookback study.

For many years, there has been concern about the risk of transmission of classic forms of Creutzfeldt-Jakob disease (CJD) by blood transfusion, particularly after the recognition of such transmission of variant CJD (vCJD). We report on a 28-year lookback study of recipients of blood from donors who subsequently developed CJD. Patients with diagnosed CJD and a history of blood donation were identified. Blood centers were asked to provide information about the distribution of the donations and consignees were requested to provide information about the recipients of the donations. Vital status of each available recipient was determined and, if deceased, the reported cause(s) of death were obtained primarily from the National Death Index. All recipients included in the study database contributed person-time up to the last recorded review of vital status. There were 84 eligible donors who gave 3284 transfusable components, and it was possible to evaluate 1245 recipients, totaling 6495 person-years of observation. The mean observation period per recipient was 5.5 years with a maximum of 51 years. No case of CJD or prion disease was reported among the recipient population. The study suggests that CJD may not be transfusion-transmissible, a position in agreement with similar findings from two similar European reports amounting to an overall observation period of 15,500 person-years. These studies have supported the conclusion that the risk, if any, of transmission of CJD by blood products is extremely small and remains theoretical.

Development of a sensitive real-time quaking-induced conversion (RT-QuIC) assay for application in prion-infected blood.

Efforts to prevent human-to-human transmission of variant Creutzfeldt-Jakob disease (vCJD) by contaminated blood would be aided by the development of a sensitive diagnostic test that could be routinely used to screen blood donations. As blood samples from vCJD patients are extremely rare, here we describe the optimisation of real-time quaking-induced conversion (RT-QuIC) for detection of PrPSc (misfolded prion protein, a marker of prion infection) in blood samples from an established large animal model of vCJD, sheep experimentally infected with bovine spongiform encephalopathy (BSE). Comparative endpoint titration experiments with RT-QuIC, miniaturized bead protein misfolding cyclic amplification (mb-PMCA) and intracerebral inoculation of a transgenic mouse line expressing sheep PrP (tgOvARQ), demonstrated highly sensitive detection of PrPSc by RT-QuIC in a reference sheep brain homogenate. Upon addition of a capture step with iron oxide beads, the RT-QuIC assay was able to detect PrPSc in whole blood samples from BSE-infected sheep up to two years before disease onset. Both RT-QuIC and mb-PMCA also demonstrated sensitive detection of PrPSc in a reference vCJD-infected human brain homogenate, suggesting that either assay may be suitable for application to human blood samples. Our results support the further development and evaluation of RT-QuIC as a diagnostic or screening test for vCJD.

Low risk of variant Creutzfeldt-Jakob disease transmission from blood transfusions in Aotearoa New Zealand suggests donor exclusion policies can be relaxed

Low risk of variant Creutzfeldt-Jakob disease transmission from blood transfusions in Aotearoa New Zealand suggests donor exclusion policies can be relaxed

Ten-year follow-up of two cohorts with an increased risk of variant CJD: donors to individuals who later developed variant CJD and other recipients of these at-risk donors.

Transmission of variant Creutzfeldt-Jakob disease (vCJD) through blood transfusion is implicated in three deaths and one asymptomatic infection. Based on this evidence, individuals assessed to be at increased risk of vCJD through donating blood transfused to individuals who later developed vCJD, or through being other recipients of such donors, are followed up to further understand the risks of vCJD transmission through blood. To provide a ten-year follow-up of these at-risk cohorts. Blood donors to patients who later died from vCJD were identified by the Transfusion Medicine Epidemiological Review (TMER) study. A reverse risk probability assessment quantified the risk of blood transfusion or exposure through diet as the source of vCJD in the recipients. Donors to these recipients, and these donors' other recipients, with a probability risk above 1%, are classified as at increased risk of vCJD for public health purposes. These cohorts are monitored for any vCJD occurrences. A total of 112 donors and 33 other recipients of their donated blood have been classified as at increased risk. After 2397 and 492 vCJD-free years of follow-up, respectively, no deaths in either at-risk cohort were of vCJD-related causes. The at-risk cohorts have survived disease-free far longer than the estimated incubation time for dietary-acquired vCJD (donors) and transfusion-acquired disease (other recipients). However, due to our still limited understanding of, and a lack of a reliable test for, asymptomatic vCJD infection, public health follow-up is necessary for continued monitoring of at-risk cohorts.

Leukoreduction and blood-borne vCJD transmission risk.

Risk assessments for transmission of variant Creutzfeldt-Jakob disease predicted that leukocyte reduction would be inefficient at preventing transmission of the disease by blood transfusion. Nevertheless, approximately 14 years ago, a significant proportion of European countries decided to implement leukocyte reduction treatment within their human blood supplies in order to mitigate the risk of human prion disease transmission. Current epidemiological studies seem to indicate that leukocyte reduction has had a positive impact on reducing the risk. In addition, over the last 5 years, various experimental studies carried out in animal models have confirmed that leukocyte reduction provides a high, but not absolute, protection against transmission of prion disease by blood transfusion. Observations that show the efficacy of blood-borne prion transmission is more dependent on the viability of leukocytes than the level of infectivity present in the blood product make a significant contribution to understanding the risk of prion infection by blood transfusion. Considering the potential for significant numbers of subclinical variant Creutzfeldt-Jakob disease individuals in at least the United Kingdom, these findings strongly support the continuation of systematic leukoreduction for blood donations collected in individuals born before the effective prevention of human dietary exposure to bovine spongiform encephalopathy.

Investigation of variant Creutzfeldt-Jakob disease implicated organ or tissue transplantation in the United Kingdom.

Person-to-person transmission of variant Creutzfeldt-Jakob disease (vCJD) has occurred through blood transfusion and could also theoretically occur as a result of the transplantation of organs or tissues. This study aimed to investigate whether there were transplant-associated vCJD cases in the United Kingdom (UK). Medical histories were reviewed for 177 UK vCJD cases to identify situations where the transplantation of organs or tissues might have occurred. A "look-back" was then performed to trace the respective donors or recipients of the implicated organ or tissue. A single patient had undergone an organ (liver) transplant before vCJD onset, from a donor who had died of causes unrelated to vCJD. The look-back was able to trace six other organ or tissue donations made by the same donor. No other situations were identified where the receipt or donation of organs or tissues had occurred in people who went on to develop vCJD. There was considered no need, on this particular occasion, to implement public health measures associated with the organ transplantation, beyond those already in place. This study provides no evidence of transplant-associated vCJD in the UK. It is, however, important to continue to seek to identify individuals who might be at risk of vCJD by this route so that appropriate public health measures can be implemented.

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

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). 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. 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 ). 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.

Human prion diseases and the risk of their transmission during anatomical dissection.

Prion diseases (or transmissible spongiform encephalopathies) are a unique group of fatal progressive neurodegenerative diseases of the central nervous system. The infectious agent is hypothesized to consist solely of a highly protease-resistant misfolded isoform of the host prion protein. Prions display a remarkable degree of resistance to chemical and physical decontamination. Many common forms of decontamination or neutralization used in infection control are ineffective against prions, except chaotropic agents that specifically disrupt proteins. Human cadaveric prosection or dissection for the purposes of teaching and demonstration of human anatomy has a distinguished history and remains one of the fundamentals of medical education. Iatrogenic transmission of human prion diseases has been demonstrated from the inoculation or implantation of human tissues. Therefore, although the incidence of human prion diseases is rare, restrictions exist upon the use of tissues from patients reported with dementia, specifically the brain and other central nervous system material. A current concern is the potential for asymptomatic variant Creutzfeldt-Jakob disease transmission within the UK population. Therefore, despite the preventative measures, the transmission of prion disease through human tissues remains a potential risk to those working with these materials. In this review, we aim to summarize the current knowledge on human prion disease relevant to those working with human tissues in the context of anatomical dissection.

BCSH guideline for the use of anti-D immunoglobulin for the prevention of haemolytic disease of the fetus and newborn.

BCSH guideline for the use of anti-D immunoglobulin for the prevention of haemolytic disease of the fetus and newborn.

Dealing with the uncertain risk of variant Creutzfeldt‐Jakob disease transmission by coagulation replacement products

The identification of variant Creutzfeldt-Jakob disease (vCJD) in the UK in 1996 led to significant concerns about the possibility of secondary transmission, however the prevalence of subclinical vCJD and risks of vCJD transmission by plasma are not known. In the UK, public health precautions have been implemented in all recipients of coagulation factor concentrates manufactured from UK plasma pools between 1980 and 2001. The recent demonstration of abnormal prion protein in a spleen sample at autopsy of a UK haemophilic patient who received coagulation factor concentrates to which a donor incubating vCJD had contributed most likely represents the first case of vCJD transmission by coagulation factor concentrates. We review the uncertainties that surround risk of vCJD transmission by coagulation factor concentrates, the challenges in dealing with undefined risks, the rationale behind current policies and the implementation of vCJD surveillance and risk management measures in bleeding disorder patients in the UK.

Comparison of nanofiltration efficacy in reducing infectivity of centrifuged versus ultracentrifuged 263K scrapie‐infected brain homogenates in “spiked” albumin solutions

The safety of plasma-derived products is of concern for possible transmission of variant Creutzfeldt-Jakob disease. The absence of validated screening tests requires the use of procedures to remove or inactivate prions during the manufacture of plasma-derived products to minimize the risk of transmission. These procedures need proper validation studies based on spiking human plasma or intermediate fractions of plasma fractionation with prions in a form as close as possible to that present in blood. Human albumin was spiked with low-speed or high-speed supernatants of 263K scrapie-infected hamster brain homogenates. Spiked albumin was then passed through a cascade of filters from 100 nm down to 20 to 15 nm. Residual infectivity was measured by bioassay. The overall removal of infectivity spiked into albumin through serial nanofiltration steps was 4 to 5 logs using low-speed supernatant and 2 to 3 logs with high-speed supernatant. These findings confirm the utility of nanofiltration in removing infectivity from plasma (or other products) spiked with scrapie brain homogenate supernatants. However, efficiency is diminished using supernatants that have been ultracentrifuged to reduce aggregated forms of the infectious agent. Thus, filtration removal data based on experiments using "standard" low-speed centrifugation supernatants might overestimate the amount of prion removal in plasma or urine-derived therapeutic products.

Risk reduction strategies for variant Creutzfeldt-Jakob disease transmission by UK plasma products

HaemophiliaVolume 17, Issue 4 p. 703-703 LETTERS TO THE EDITORS Risk reduction strategies for variant Creutzfeldt-Jakob disease transmission by UK plasma products C. PROWSE, C. PROWSE SNBTS, 21 Ellen’s Glen Road, Edinburgh EH 17 7QTSearch for more papers by this authorB. CUTHBERTSON, B. CUTHBERTSON SNBTS, 21 Ellen’s Glen Road, Edinburgh EH 17 7QTSearch for more papers by this authorM. TURNER, M. TURNER SNBTS, 21 Ellen’s Glen Road, Edinburgh EH 17 7QTSearch for more papers by this author C. PROWSE, C. PROWSE SNBTS, 21 Ellen’s Glen Road, Edinburgh EH 17 7QTSearch for more papers by this authorB. CUTHBERTSON, B. CUTHBERTSON SNBTS, 21 Ellen’s Glen Road, Edinburgh EH 17 7QTSearch for more papers by this authorM. TURNER, M. TURNER SNBTS, 21 Ellen’s Glen Road, Edinburgh EH 17 7QTSearch for more papers by this author First published: 01 March 2011 https://doi.org/10.1111/j.1365-2516.2010.02485.x Dr Christopher Verrall Prowse, SNBTS, 21 Ellen’s Glen Road, Edinburgh EH 17 7QT.Tel.: 441315366768; fax: 441315366764;e-mail: cprowse@nhs.net Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume17, Issue4July 2011Pages 703-703 RelatedInformation

Universal White Blood Cell Reduction in Europe: Has Transmission of Variant Creutzfeldt-Jakob Disease Been Prevented?

Universal white blood cell (WBC) reduction was introduced in Europe to prevent transmission of variant Creutzfeldt-Jakob disease (vCJD) by transfusion. Findings from rodent models indicate that WBC reduction should not prevent vCJD transmission because the residual plasma infectivity suffices to infect transfusion recipients even under optimistic infectivity assumptions. Although infectivity in human blood may not partition in the manner in which it is distributed in rodents, prion-reduction filters remove the residual plasma infectivity in rodent models. Precautionary introduction of prion filtration in the UK--for patients without dietary exposure to bovine spongiform encephalopathy and in the absence of a reported case of vCJD transmission attributable to infectivity residing in plasma--is consistent with the (already in place for such subjects) precautionary importation to the UK of fresh frozen plasma from low-risk countries. Thus, implementation of prion filtration in the UK does not imply that universal WBC reduction--as currently practiced in Europe--does not abrogate transmission of vCJD. Because neither a human case of vCJD transmission through transfusion of WBC-reduced red blood cells nor a case of experimental bovine spongiform encephalopathy transmission by WBC-reduced transfusion to sheep has been reported, it cannot be concluded that ordinary WBC reduction is ineffective in preventing transfusion transmission in humans. Accordingly, universal WBC reduction for the prevention of vCJD in Europe should continue.

Feasibility study of a screening assay that identifies the abnormal prion protein PrPTSE in plasma: initial results with 20,000 samples

It is likely that transmission of variant Creutzfeldt-Jakob disease (vCJD) occurs by transfusion and that the candidate infectious agent (PrP(TSE)) is present in small concentrations in the blood of infected donors in the asymptomatic phase of the disease. A new blood screening assay has been developed to detect PrP(TSE) in citrated plasma samples. Three regional Blood Transfusion Establishments (ETS) in France (ETS Alsace, ETS Bourgogne Franche-Comté, and ETS Pyrénées-Méditerranée) will screen 60,000 plasma samples (20,000 in each ETS) over a time period of approximately 9 to 12 months. Results provided in this report are those of the first testing site in Strasbourg, Alsace. The preliminary results have demonstrated an initial specificity of 97.60%. Upon repeat testing the specificity rate achieved 99.90% (20 repeat-positive samples). Based on the known epidemiology of vCJD in France, it is likely that the repeat-reactive samples are not true-positives. The screening assay was studied in terms of specificity and practicality and was found to be suitable for use in routine testing of blood donations. However, throughput must be enhanced by automation of the assay, and traceability would be improved if automated systems were used to distribute and identify samples.

Evaluation of removal of prion infectivity from red blood cells with prion reduction filters using a new rapid and highly sensitive cell culture–based infectivity assay

The clearance of infectious prions from biologic fluids is usually quantified by bioassays based on intracerebral inoculation of hamsters or mice; these tests are slow, cumbersome, imprecise, and very expensive. In the present study we describe the use of a new and highly sensitive cell culture-based infectivity assay to evaluate the performance of several prion removal prototype filters. Five units of 1- to 2-day-old ABO-compatible human red blood cells (RBCs) in saline-adenine-glucose-mannitol were obtained from an AABB-accredited blood bank. The 5 units were combined to create a homogenous pool. Scrapie-infected mouse brain homogenate of a Rocky Mountain Laboratory strain was added to the pooled RBCs. The pooled RBCs were divided into 300-mL aliquots, which were filtered with either standard leukoreduction filter or four prototypes of prion reduction filter. The levels of prion infectivity in the pre- and postfiltration samples were measured with a cell culture-based standard scrapie cell assay (SSCA). All the 22-layer prion reduction filters removed prion infectivity below the limit of detection of the SSCA (reduction in prion infectivity > or =2.0 log(10)LD(50)/mL) while the 10-layer variant showed some residual infectivity. These results demonstrate the utility of a highly sensitive cell culture-based infectivity assay for screening prion reduction filters. The use of this type of in vitro infectivity assay will substantially help expedite the screening and discovery of devices aimed at reducing the risk of variant Creutzfeldt-Jakob disease transmission through blood transfusion.

Risk reduction strategies for variant Creutzfeldt–Jakob disease transmission by UK plasma products and their impact on patients with inherited bleeding disorders

The appearance and rapid evolution of BSE in UK cattle in the mid 1980s, with compelling data supporting variant Creutzfeldt-Jakob disease (vCJD) as its human manifestation, pose a potentially severe threat to public health. Three clinical cases and one asymptomatic case of vCJD infection have been reported in UK recipients of non-leucodepleted red cell transfusions from donors subsequently diagnosed with vCJD. Plasma from both these and other donors who later developed vCJD has contributed towards plasma pools used to manufacture clotting factor concentrate. The United Kingdom Haemophilia Centre Doctors' Organisation (UKHCDO) Surveillance Study has detected asymptomatic vCJD postmortem in a haemophilic patient treated with UK plasma products including two batches of clotting factor linked to a donor who subsequently developed vCJD. Over 4000 bleeding disorder patients treated with UK plasma products are recorded on the UKHCDO National Haemophilia Database. The risk of vCJD transmission by plasma products is not known. However, public health precautions have been implemented since 2004 in all UK inherited bleeding disorder patients who received UK-sourced plasma products between 1980 and 2001 to minimize the possible risk of onward vCJD transmission. We evaluate vCJD surveillance and risk management measures taken for UK inherited bleeding disorder patients, report current data and discuss resultant challenges and future directions.

Variant Creutzfeldt‐Jakob disease and exposure to fractionated plasma products

The risk to public health of onward transmission of variant Creutzfeldt-Jakob disease (vCJD) via blood transfusion and plasma product administration is of on-going concern, particularly with the recent reported detection of abnormal prion protein in a person with haemophilia. To describe the history of fractionated plasma product exposure in clinical cases of vCJD in the UK. Through examination of records held at the National CJD Surveillance Unit (from relatives, general practices and hospitals). Nine out of 168 UK vCJD cases had a history of receipt of fractionated plasma products on 12 different occasions (1 pre-vCJD risk in 1970, the remaining between 1989-1998). According to the UK CJD Incident Panel risk assessment criteria, 11 were low-risk products and one was low or medium risk. It is unlikely that any of the UK vCJD clinical cases to date were infected through exposure to fractionated plasma products. However, the possibility that such transmission may result in vCJD cases in the future cannot be excluded.

Pathological investigation of the first blood donor and recipient pair linked by transfusion‐associated variant Creutzfeldt–Jakob disease transmission

Neuropathology and Applied NeurobiologyVolume 35, Issue 4 p. 433-436 Pathological investigation of the first blood donor and recipient pair linked by transfusion-associated variant Creutzfeldt–Jakob disease transmission M. W. Head, M. W. Head National CJD Surveillance Unit, School of Molecular & Clinical Medicine (Pathology), University of Edinburgh, Edinburgh, UKSearch for more papers by this authorH. M. Yull, H. M. Yull National CJD Surveillance Unit, School of Molecular & Clinical Medicine (Pathology), University of Edinburgh, Edinburgh, UKSearch for more papers by this authorD. L. Ritchie, D. L. Ritchie National CJD Surveillance Unit, School of Molecular & Clinical Medicine (Pathology), University of Edinburgh, Edinburgh, UKSearch for more papers by this authorM. T. Bishop, M. T. Bishop National CJD Surveillance Unit, School of Molecular & Clinical Medicine (Pathology), University of Edinburgh, Edinburgh, UKSearch for more papers by this authorJ. W. Ironside, J. W. Ironside National CJD Surveillance Unit, School of Molecular & Clinical Medicine (Pathology), University of Edinburgh, Edinburgh, UKSearch for more papers by this author M. W. Head, M. W. Head National CJD Surveillance Unit, School of Molecular & Clinical Medicine (Pathology), University of Edinburgh, Edinburgh, UKSearch for more papers by this authorH. M. Yull, H. M. Yull National CJD Surveillance Unit, School of Molecular & Clinical Medicine (Pathology), University of Edinburgh, Edinburgh, UKSearch for more papers by this authorD. L. Ritchie, D. L. Ritchie National CJD Surveillance Unit, School of Molecular & Clinical Medicine (Pathology), University of Edinburgh, Edinburgh, UKSearch for more papers by this authorM. T. Bishop, M. T. Bishop National CJD Surveillance Unit, School of Molecular & Clinical Medicine (Pathology), University of Edinburgh, Edinburgh, UKSearch for more papers by this authorJ. W. Ironside, J. W. Ironside National CJD Surveillance Unit, School of Molecular & Clinical Medicine (Pathology), University of Edinburgh, Edinburgh, UKSearch for more papers by this author First published: 30 June 2009 https://doi.org/10.1111/j.1365-2990.2009.01025.xCitations: 14Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume35, Issue4August 2009Pages 433-436 RelatedInformation

Antibody-based immunotherapeutic attempts in experimental animal models of prion diseases

Background: There has been a dramatic decrease in the risk of transmission of bovine spongiform encephalopathy to humans. In contrast, the risk of human-to-human transmission of variant Creutzfeldt-Jakob disease (vCJD) via medical treatments became potentially high since 4 vCJD cases were reported to be possibly transmitted through blood transfusion in the UK. However, no treatments are yet available for curing prion diseases. Objective: Conversion of the normal prion protein, PrPC, to the amyloidogenic PrP, PrPSc, plays a pivotal role in the pathogenesis. Recently, certain anti-PrP or anti-37/67-kDa laminin receptor (LRP/LR) antibodies were shown to have the potential to cure chronically infected cells, clearing PrPSc from the cells. This has raised the possibility of antibody based-immunotherapy for prion diseases. This article aims to introduce and discuss the recently published attempts of immunotherapy in prion diseases. Methods: Bibliographic research was carried out using the PubMed database. Patent literature was searched using the UK Intellectual Property Office website. Results/conclusion: No satisfying consequences in animals could be detected with anti-PrP antibodies directly infused into the brains of animals by the intraventricular route or by anti-PrP or anti-LRP/LR single chain fragment antibodies directly delivered into the brain by virus vector-mediated gene transfer. This is probably because such delivery systems failed to deliver the antibodies to the neurons relevant for the treatments.

Human platelets as a substrate source for the in vitro amplification of the abnormal prion protein (PrPSc) associated with variant Creutzfeldt‐Jakob disease

Four recent cases of transfusion-related transmission of variant Creutzfeldt-Jakob disease (vCJD) highlight the need to develop a highly sensitive and specific screening test to detect infectivity in the blood of asymptomatic infected individuals. Protein misfolding cyclic amplification (PMCA), a method for the amplification of minute amounts of disease-associated abnormal prion protein (PrP(Sc)) to readily detectable levels, could be incorporated into such a test provided that a suitable substrate source for routine use in human PMCA reactions can be found. With the use of seed sources from individuals with variant and sporadic CJD, the use of human platelets (PLTs) as a PMCA substrate source was evaluated. The effects of seed/substrate prion protein gene (PRNP) codon 129 genotype compatibility on amplification efficiency and freeze-thaw on a substrate's ability to support amplification and the degree of amplification achieved by serial PMCA (sPMCA) were investigated. Seed/substrate PRNP codon 129 compatibility was found to have a major influence on PrP(Sc) amplification efficiency. Individual substrates, of the same PRNP codon 129 genotype, could be pooled and stored frozen for use in subsequent PMCA reactions. A consistent 10-fold increase in PrP(Sc) detection sensitivity was achieved after each round of sPMCA, resulting in a 10,000-fold increase in detection sensitivity after four rounds, with no evidence of de novo PrP(Sc) production detected in the unseeded PLT substrate. Providing issues of seed/substrate PRNP codon 129 compatibility are taken into consideration human PLTs are a suitable, readily available, renewable substrate source for use in human PMCA applications.