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

A Practical Approach to Avoiding Iatrogenic Creutzfeldt-Jakob Disease (CJD) from Invasive Instruments

Potential Creutzfeldt-Jakob disease instrument-contamination events continue to occur, causing widespread hospital and patient concern. We propose the use of a combination of diagnostic tests (ie, spinal fluid for 14-3-3 protein or nasal brushing for misfolded prion protein) and instrument handling procedures (ie, using a regional set of dedicated instruments), which if applied to all patients admitted with symptoms of either dementia or cerebellar disease, should eliminate the risk of iatrogenic instrument infection.

Infect Control Hosp Epidemiol 2015;36(7):844–848

Variant CJD. 18 years of research and surveillance

It is now 18 years since the first identification of a case of vCJD in the UK. Since that time, there has been much speculation over how vCJD might impact human health. To date there have been 177 case reports in the UK and a further 51 cases worldwide in 11 different countries. Since establishing that BSE and vCJD are of the same strain of agent, we have also shown that there is broad similarity between UK and non-UK vCJD cases on first passage to mice. Transgenic mouse studies have indicated that all codon 129 genotypes are susceptible to vCJD and that genotype may influence whether disease appears in a clinical or asymptomatic form, supported by the appearance of the first case of potential asymptomatic vCJD infection in a PRNP 129MV patient. Following evidence of blood transfusion as a route of transmission, we have ascertained that all blood components and leucoreduced blood in a sheep model of vCJD have the ability to transmit disease. Importantly, we recently established that a PRNP 129MV patient blood recipient with an asymptomatic infection and limited PrP(Sc) deposition in the spleen could readily transmit disease into mice, demonstrating the potential for peripheral infection in the absence of clinical disease. This, along with the recent appendix survey which identified 16 positive appendices in a study of 32,441 cases, underlines the importance of continued CJD surveillance and maintaining control measures already in place to protect human health.

Ascertainment bias causes false signal of anticipation in genetic prion disease

Anticipation is the phenomenon whereby age of onset in genetic disease decreases in successive generations. Three independent reports have claimed anticipation in Creutzfeldt-Jakob disease (CJD) caused by the c.598G > A mutation in PRNP encoding a p.Glu200Lys (E200K) substitution in the prion protein. If confirmed, this finding would carry clear implications for genetic counseling. We analyzed pedigrees with this mutation from four prion centers worldwide (n = 217 individuals with the mutation) to analyze age of onset and death in affected and censored individuals. We show through simulation that selective ascertainment of individuals whose onset falls within the historical window since the mutation's 1989 discovery is sufficient to create robust false signals both of anticipation and of heritability of age of onset. In our data set, the number of years of anticipation observed depends upon how strictly the data are limited by the ascertainment window. Among individuals whose disease was directly observed at a study center, a 28-year difference between parent and child age of onset is observed (p = 0.002), but including individuals ascertained retrospectively through family history reduces this figure to 7 years (p = 0.005). Applying survival analysis to the most thoroughly ascertained subset of data eliminates the signal of anticipation. Moreover, even non-CJD deaths exhibit 16 years anticipation (p = 0.002), indicating that ascertainment bias can entirely explain observed anticipation. We suggest that reports of anticipation in genetic prion disease are driven entirely by ascertainment bias. Guidelines for future studies claiming statistical evidence for anticipation are suggested.

Managing the risk of iatrogenic transmission of Creutzfeldt-Jakob disease in the UK

BACKGROUND

With the emergence of bovine spongiform encephalopathy (BSE) and variant Creutzfeldt-Jakob disease (CJD) in the UK, there is concern about iatrogenic transmission, and the approach to managing this risk is unique.

AIM

To describe and review CJD incident management and the notification of individuals 'at increased risk' as a strategy for reducing iatrogenic transmission.

METHODS

A description of iatrogenic CJD transmission, the CJD Incidents Panel's role, the number and nature of CJD incidents reported and the individuals considered 'at increased risk' by mid-2012.

FINDINGS

Seventy-seven UK cases of CJD are likely to have resulted from iatrogenic transmission, among recipients of human-derived growth hormone (64 cases), dura mater grafts (eight cases), blood transfusions (four cases) and plasma products (one case). To limit transmission, the Panel reviewed 490 incidents and advised on look-backs, recalls of blood and plasma products, and quarantining and disposing of surgical instruments. Additionally, on Panel advice, around 6000 asymptomatic individuals have been informed they are at increased risk of CJD and have been asked to follow public health precautions.

CONCLUSION

The strategy to reduce iatrogenic transmission of CJD has been developed in a context of scientific uncertainty. The rarity of transmission events could indicate that incident-related exposures present negligible transmission risks, or--given the prolonged incubation and subclinical phenotypes of CJD--infections could be yet to occur or have been undetected. Scientific developments, including better estimates of infection prevalence, a screening test, or improvements in decontaminating surgical instruments, may change future risk management.

Accelerated, spleen-based titration of variant Creutzfeldt-Jakob disease infectivity in transgenic mice expressing human prion protein with sensitivity comparable to that of survival time bioassay

The dietary exposure of the human population to the prions responsible for the bovine spongiform encephalopathy (BSE) epizooty has led to the emergence of variant Creutzfeldt-Jakob disease (vCJD). This fatal, untreatable neurodegenerative disorder is a growing public health concern because the prevalence of the infection seems much greater than the disease incidence and because secondary transmission of vCJD by blood transfusion or use of blood products has occurred. A current limitation in variant CJD risk assessment is the lack of quantitative information on the infectivity of contaminated tissues. To address this limitation, we tested the potential of a transgenic mouse line overexpressing human prion protein (PrP), which was previously reported to propagate vCJD prions. Endpoint titration of vCJD infectivity in different tissues was evaluated by two different methods: (i) the "classical" bioassay, based on the appearance of clinical symptoms and the detection of pathological prion protein in tissues of the inoculated mouse, and (ii) a shortened bioassay based on the detection of the protein in the mouse spleen at defined time points. The two methods proved equally sensitive in quantifying infectivity, even after very-low-dose inoculation of infected material, but the time schedule was shortened from ~2.5 years to ~1 year with the spleen bioassay. Compared to the "gold-standard" RIII model routinely used for endpoint titration of vCJD/BSE prions, either method improved the sensitivity by >2 orders of magnitude and allowed reevaluating the infectious titer of spleen from a vCJD individual at disease end stage to >1,000-fold-higher values.

IMPORTANCE

Here, we provide key reevaluation of the infectious titer of variant CJD brain and spleen tissues. The highly sensitive, accelerated spleen-based assay should thus constitute a key advance for variant CJD epidemiological and risk assessment purposes and should greatly facilitate future titration studies, including, for example, those aimed at validating decontamination procedures. The overlooked notion that the lymphoid tissue exhibits a higher capacity than the brain to replicate prions even after low-dose infection raises new questions about the molecular and/or cellular determinant(s) involved, a key issue regarding potent silent carriers of variant CJD in the lymphoid tissue.

Successes and challenges in phenotype-based lead discovery for prion diseases

Creutzfeldt–Jakob disease (CJD) is a rare but invariably fatal neurodegenerative disease caused by misfolding of an endogenous protein into an alternative pathogenic conformation. The details of protein misfolding and aggregation are not well understood nor are the mechanism(s) by which the aggregated protein confers cellular toxicity. While there is as yet no clear consensus about how best to intervene therapeutically in CJD, prion infections can be propagated in cell culture and in experimental animals, affording both in vitro and in vivo models of disease. Here we review recent lead discovery efforts for CJD, with a focus on our own efforts to optimize 2-aminothiazole analogues for anti-prion potency in cells and for brain exposure in mice. The compounds that emerged from this effort were found to be efficacious in multiple animal models of prion disease even as they revealed new challenges for the field, including the emergence of resistant prion strains.

Biology and genetics of prions causing neurodegeneration

Prions are proteins that acquire alternative conformations that become self-propagating. Transformation of proteins into prions is generally accompanied by an increase in β-sheet structure and a propensity to aggregate into oligomers. Some prions are beneficial and perform cellular functions, whereas others cause neurodegeneration. In mammals, more than a dozen proteins that become prions have been identified, and a similar number has been found in fungi. In both mammals and fungi, variations in the prion conformation encipher the biological properties of distinct prion strains. Increasing evidence argues that prions cause many neurodegenerative diseases (NDs), including Alzheimer's, Parkinson's, Creutzfeldt-Jakob, and Lou Gehrig's diseases, as well as the tauopathies. The majority of NDs are sporadic, and 10% to 20% are inherited. The late onset of heritable NDs, like their sporadic counterparts, may reflect the stochastic nature of prion formation; the pathogenesis of such illnesses seems to require prion accumulation to exceed some critical threshold before neurological dysfunction manifests.

Pathogen safety of Beriate®

Plasma-derived factor VIII (FVIII) concentrates have been used successfully to treat haemophilia A since the late 1960s. To ensure the pathogen safety of the plasma-derived FVIII concentrate, Beriate(®) (formerly Beriate(®) P), donors of blood/plasma are carefully selected and all donations are screened for hepatitis B virus surface antigen (HBsAg), antibodies against HIV types 1 and 2 (HIV-1/HIV-2) and hepatitis C virus (HCV), and genomic material of hepatitis A virus (HAV), hepatitis B virus (HBV), HCV, and for high titres of parvovirus B19 (B19V). As additional quality control, plasma pools for fractionation are only released for further processing when non-reactivity has been demonstrated in serological and genome amplification assays. The manufacturing process for Beriate(®) comprises dedicated virus reduction steps such as pasteurization and the recently introduced virus filtration step, resulting in effective inactivation of various enveloped and non-enveloped viruses and effective removal of viruses and prion material larger than the mean pore size of the virus filter (19 nm). The effectiveness of these production steps has been demonstrated in virus and prion validation studies using a range of different viruses and prion preparations. The multiple precautionary measures inherent to the overall production process for Beriate(®) (and its predecessor Beriate(®) P) are reflected in an excellent safety record documented during 20 years of clinical use with no proven record of virus transmission, even before the introduction of the virus filtration step. Continued improvement of safety measures according to scientific knowledge and regulatory guidance maintains and even enhances the excellent safety profile of Beriate(®).

Population screening for variant Creutzfeldt-Jakob disease using a novel blood test: diagnostic accuracy and feasibility study

IMPORTANCE

Our study indicates a prototype blood-based variant Creutzfeldt-Jakob disease (vCJD) assay has sufficient sensitivity and specificity to justify a large study comparing vCJD prevalence in the United Kingdom with a bovine spongiform encephalopathy-unexposed population. In a clinical diagnostic capacity, the assay's likelihood ratios dramatically change an individual's pretest disease odds to posttest probabilities and can confirm vCJD infection.

OBJECTIVES

To determine the diagnostic accuracy of a prototype blood test for vCJD and hence its suitability for clinical use and for screening prion-exposed populations.

DESIGN, SETTING, AND PARTICIPANTS

Retrospective, cross-sectional diagnostic study of blood samples from national blood collection and prion disease centers in the United States and United Kingdom. Anonymized samples were representative of the US blood donor population (n = 5000), healthy UK donors (n = 200), patients with nonprion neurodegenerative diseases (n = 352), patients in whom a prion disease diagnosis was likely (n = 105), and patients with confirmed vCJD (n = 10).

MAIN OUTCOME AND MEASURE

Presence of vCJD infection determined by a prototype test (now in clinical diagnostic use) that captures, enriches, and detects disease-associated prion protein from whole blood using stainless steel powder.

RESULTS

The assay's specificity among the presumed negative American donor samples was 100% (95% CI, 99.93%-100%) and was confirmed in a healthy UK cohort (100% specificity; 95% CI, 98.2%-100%). Of potentially cross-reactive blood samples from patients with nonprion neurodegenerative diseases, no samples tested positive (100% specificity; 95% CI, 98.9%-100%). Among National Prion Clinic referrals in whom a prion disease diagnosis was likely, 2 patients with sporadic CJD tested positive (98.1% specificity; 95% CI, 93.3%-99.8%). Finally, we reconfirmed but could not refine our previous sensitivity estimate in a small blind panel of samples from unaffected individuals and patients with vCJD (70% sensitivity; 95% CI, 34.8%-93.3%).

CONCLUSIONS AND RELEVANCE

In conjunction with the assay's established high sensitivity (71.4%; 95% CI, 47.8%-88.7%), the extremely high specificity supports using the assay to screen for vCJD infection in prion-exposed populations. Additionally, the lack of cross-reactivity and false positives in a range of nonprion neurodegenerative diseases supports the use of the assay in patient diagnosis.

Blood transfusion in the perioperative period

Anemia is associated with perioperative mortality and morbidity. Since the presence of anemia and blood transfusion often go hand in hand, it can be difficult to separate the effects of anemia from the effects of perioperative transfusion. The role for blood transfusion in mitigating the mortality and morbidity associated with anemia is unclear. A restrictive transfusion strategy has been advocated for hemodynamically stable patients, as blood transfusion exposes the patient to both infectious and non-infectious complications. Further research is warranted in patients with the acute coronary syndrome, as there is insufficient evidence to make recommendations for this patient population. Additional multi-center randomized controlled trials need to be conducted in perioperative and critically ill patients with large enough sample sizes to examine differences in mortality and major complications between liberal and restrictive transfusion strategies. Further trials need to incorporate current practices in improved blood storage and leukoreduction techniques.

A case of Creutzfeldt-Jakob disease: diagnostic dilemmas of a rapidly fatal disease

Creutzfeldt-Jakob disease (CJD) is a rapidly progressive and ultimately fatal disorder of the central nervous system. It occurs worldwide with an incidence of 0.5-1 new case per million population per year. No specific treatment is available and management is limited to supportive care. Autopsy or biopsy provides a definitive diagnosis. Because of the transmissible nature of the disease and hesitancy of patients/family members to give consent for biopsy, numerous challenges in confirming the clinical diagnosis are faced by healthcare professionals. We report a case of 66-year-old male who was hospitalized due to hip fracture following a fall. Acute mental status changes followed the surgical fixation of hip fracture which triggered neurologic work up. This finally revealed suspicion and confirmation of CJD. Patient had progressive cognitive decline with akinetic mutism during further hospital stay and was later discharged home with hospice. Shorter thereafter he died at home. This case demonstrates the importance of keeping an open mind towards possibility of CJD when faced with esoteric neurologic presentations. Also this case provides insight into challenges in quarantine and sterilization of surgical instruments when these patients go through major surgeries.

UK approach to assessing assays and filters designed to reduce the risk of transfusion-transmitted vCJD

Three cases of vCJD transmission by blood transfusion have been reported in the UK, and a fourth case discovered at post-mortem. Modelling has been conducted to predict the number of cases that may occur in the future through transfusion, based on estimates of prevalence, infectivity and susceptibility, and a number of steps have been taken to reduce the risk of transmission. These include deferral of previously transfused donors, leucocyte depletion of all components, importation of plasma for certain patient groups and for fractionation, and the collection of the majority of platelets from single donors (by apheresis). However, even with these interventions, some future cases are still predicted. The UK-wide Advisory Committee on the Safety of Blood, Tissues and Organs (SaBTO) considers the evidence for clinical and cost-effectiveness of any proposed intervention, such as prion assays and filters, and makes recommendations to the governments of the UK. The development of prion assays is challenging as prions do not generate an immune response, do not have nucleic acid and are present in blood in very low concentrations against a high background of normal prion protein. It is critically important that prion assays show high levels of sensitivity and - especially -specificity for a healthy blood donor population. Assessment is impacted by the very short supply of positive human samples, necessitating the use of animal models. Filters that are capable of removing prions from blood components have been developed and CE marked, but it is again necessary to use animal models to study their efficacy. Guidelines have been produced for the assessment of the quality of red cells filtered through these devices, and a clinical safety study has recently been completed. In conclusion, the evaluation of screening assays and prion filters is challenging, time-consuming and costly, but these evaluations are critical to policy making.

Re-assessment of PrP(Sc) distribution in sporadic and variant CJD

Human prion diseases are fatal neurodegenerative disorders associated with an accumulation of PrP^Sc in the central nervous system (CNS). Of the human prion diseases, sporadic Creutzfeldt-Jakob disease (sCJD), which has no known origin, is the most common form while variant CJD (vCJD) is an acquired human prion disease reported to differ from other human prion diseases in its neurological, neuropathological, and biochemical phenotype. Peripheral tissue involvement in prion disease, as judged by PrP^Sc accumulation in the tonsil, spleen, and lymph node has been reported in vCJD as well as several animal models of prion diseases. However, this distribution of PrP^Sc has not been consistently reported for sCJD. We reexamined CNS and non-CNS tissue distribution and levels of PrP^Sc in both sCJD and vCJD. Using a sensitive immunoassay, termed SOFIA, we also assessed PrP^Sc levels in human body fluids from sCJD as well as in vCJD-infected humanized transgenic mice (Tg666). Unexpectedly, the levels of PrP^Sc in non-CNS human tissues (spleens, lymph nodes, tonsils) from both sCJD and vCJD did not differ significantly and, as expected, were several logs lower than in the brain. Using protein misfolding cyclic amplification (PMCA) followed by SOFIA, PrP^Sc was detected in cerebrospinal fluid (CSF), but not in urine or blood, in sCJD patients. In addition, using PMCA and SOFIA, we demonstrated that blood from vCJD-infected Tg666 mice showing clinical disease contained prion disease-associated seeding activity although the data was not statistically significant likely due to the limited number of samples examined. These studies provide a comparison of PrP^Sc in sCJD vs. vCJD as well as analysis of body fluids. Further, these studies also provide circumstantial evidence that in human prion diseases, as in the animal prion diseases, a direct comparison and intraspecies correlation cannot be made between the levels of PrP^Sc and infectivity.

Blood component recalls and market withdrawals: frequency, reasons, and management in the United States

In a previous article, we reviewed the management of blood component recalls and withdrawals (G. Ramsey. Transfusion Med Rev 2004;18:36-45). Since then, US rates of recall and biological product deviation for blood components have improved significantly, particularly with regard to reduced recalls for donor infectious disease risks or testing. However, analysis of the current data from the US Food and Drug Administration suggests that 1 (0.4%) in 250 blood components is involved in market withdrawals and quarantines, with 1 in 5800 components formally recalled. Most of these units, unfortunately, had already have been transfused. The U.S. Food and Drug Administration has issued several recent guidances that address transfusion service actions for dealing with specific infectious disease problems. This present article updates our 2004 recommendations as to when to notify physicians about transfused nonconforming blood components.

Unique drug screening approach for prion diseases identifies tacrolimus and astemizole as antiprion agents

Prion diseases such as Creutzfeldt-Jakob disease (CJD) are incurable and rapidly fatal neurodegenerative diseases. Because prion protein (PrP) is necessary for prion replication but dispensable for the host, we developed the PrP-FRET-enabled high throughput assay (PrP-FEHTA) to screen for compounds that decrease PrP expression. We screened a collection of drugs approved for human use and identified astemizole and tacrolimus, which reduced cell-surface PrP and inhibited prion replication in neuroblastoma cells. Tacrolimus reduced total cellular PrP levels by a nontranscriptional mechanism. Astemizole stimulated autophagy, a hitherto unreported mode of action for this pharmacophore. Astemizole, but not tacrolimus, prolonged the survival time of prion-infected mice. Astemizole is used in humans to treat seasonal allergic rhinitis in a chronic setting. Given the absence of any treatment option for CJD patients and the favorable drug characteristics of astemizole, including its ability to cross the blood-brain barrier, it may be considered as therapy for CJD patients and for prophylactic use in familial prion diseases. Importantly, our results validate PrP-FEHTA as a method to identify antiprion compounds and, more generally, FEHTA as a unique drug discovery platform.

Should We Use Preoperative Epoetin-α in the Mildly Anemic Patient Undergoing Simultaneous Total Knee Arthroplasty?

Simultaneous knee arthroplasty is associated with significant blood loss. To prevent transfusion, three preoperative doses of epoetin-α were offered to mildly anemic simultaneous knee arthroplasty patients. A retrospective review, using ICD-9 codes, identified twenty patients from 2007-2009. Epoetin-α increased hemoglobin levels preoperatively (12.6 to 13.9, p<0.01). Twenty patients who did not receive epoetin-α were matched to study patients. Study patients were transfused less (55% vs 95%, p=0.012) and had similar inpatient length of stay. The average blood loss without transfusion was 4.6g/dL. The mildly anemic patient is at high-risk for packed red cell transfusion during simultaneous knee arthroplasty. Three preoperative doses of epoetin-α in the mildly anemic patient decreased total transfusions; however, it did not affect inpatient length of stay.

The Transfusion Alternatives Preoperatively in Sickle Cell Disease (TAPS) study: a randomised, controlled, multicentre clinical trial

BACKGROUND

No consensus exists on whether preoperative blood transfusions are beneficial in patients with sickle-cell disease. We assessed whether perioperative complication rates would be altered by preoperative transfusion.

METHODS

We did a multicentre, randomised trial. Eligible patients were aged at least 1 year, had haemoglobin SS or Sβ(0)thalassaemia sickle-cell-disease subtypes, and were scheduled for low-risk or medium-risk operations. Patients were randomly assigned no transfusion or transfusion no more than 10 days before surgery. The primary outcome was the proportion of clinically important complications between randomisation and 30 days after surgery. Analysis was by intention to treat.

FINDINGS

67 (96%) of 70 enrolled patients-33 no preoperative transfusion and 34 preoperative transfusion-were assessed. 65 (97%) of 67 patients had the haemoglobin SS subtype and 54 (81%) were scheduled to undergo medium-risk surgery. 13 (39%) of 33 patients in the no-preoperative-transfusion group had clinically important complications, compared with five (15%) in the preoperative-transfusion group (p=0.023). Of these, 10 (30%) and one (3%), respectively, had serious adverse events. The unadjusted odds ratio of clinically important complications was 3.8 (95% CI 1.2-12.2, p=0.027). 10 (91%) of 11 serious adverse events were acute chest syndrome (nine in the no-preoperative-transfusion group and one in the preoperative-transfusion group). Duration of hospital stay and readmission rates did not differ between study groups.

INTERPRETATION

Preoperative transfusion was associated with decreased perioperative complications in patients with sickle-cell disease in this trial. This approach could, therefore, be beneficial for patients with the haemoglobin SS subtype who are scheduled to undergo low-risk and medium-risk surgeries.

FUNDING

NHS Blood and Transplant.

Amyotrophic lateral sclerosis and organ donation: is there risk of disease transmission?

A new protocol suggests that patients with amyotrophic lateral sclerosis (ALS) are a viable source of tissue for organ transplantation. However, multiple lines of evidence suggest that many neurodegenerative diseases, including ALS, might progress due to transcellular propagation of protein aggregation among neurons. Transmission of the disease state from donor to host thus may be possible under the permissive circumstances of graft transplantation. We argue for careful patient selection and close longitudinal follow-up of recipients when harvesting organs from individuals with neurodegenerative disease, especially dominantly inherited forms.

Snord 3A: a molecular marker and modulator of prion disease progression

Since preventive treatments for prion disease require early identification of subjects at risk, we searched for surrogate peripheral markers characterizing the asymptomatic phases of such conditions. To this effect, we subjected blood mRNA from E200K PrP CJD patients and corresponding family members to global arrays and found that the expression of Snord3A, a non-coding RNA transcript, was elevated several times in CJD patients as compared to controls, while asymptomatic carriers presented intermediate Snord3A levels. In the brains of TgMHu2ME199K mice, a mouse model mimicking for E200K CJD, Snord 3A levels were elevated in an age and disease severity dependent manner, as was the case for brains of these mice in which disease was exacerbated by copper administration. Snord3A expression was also elevated in scrapie infected mice, but not in PrP^0/0 mice, indicating that while the expression levels of this transcript may reflect diverse prion etiologies, they are not related to the loss of PrP^C’s function. Elevation of Snord3A was consistent with the activation of ATF6, representing one of the arms of the unfolded protein response system. Indeed, SnoRNAs were associated with reduced resistance to oxidative stress, and with ER stress in general, factors playing a significant role in this and other neurodegenerative conditions. We hypothesize that in addition to its function as a disease marker, Snord3A may play an important role in the mechanism of prion disease manifestation and progression.

Transfusion of prion-filtered red cells does not increase the rate of alloimmunization or transfusion reactions in patients: results of the UK trial of prion-filtered versus standard red cells in surgical patients (PRISM A)

This study, conducted for the UK Blood Transfusion Services (UKBTS), evaluated the clinical safety of red cells filtered through a CE-marked prion removal filter (P-Capt™). Patients requiring blood transfusion for elective procedures in nine UK hospitals were entered into a non-randomized open trial to assess development of red cell antibodies to standard red cell (RCC) or prion-filtered red cell concentrates (PF-RCC) at eight weeks and six months post-transfusion. Patients who received at least 1 unit of PF-RCC were compared with a control cohort given RCC only. About 917 PF-RCC and 1336 RCC units were transfused into 299 and 291 patients respectively. Twenty-six new red cell antibodies were detected post-transfusion in 10 patients in each arm, an overall alloimmunization rate of 4.4%. Neither the treatment arm [odds ratio (OR) 0.93, 95% confidence interval (CI) 0.3, 2.5] nor number of units transfused (OR 0.95, 95% CI 0.8, 1.1) had a significant effect on the proportion of patients who developed new alloantibodies. No pan-reactive antibodies or antibodies specifically against PF-RCC were detected. There was no difference in transfusion reactions between arms, and no novel transfusion-related adverse events clearly attributable to PF-RCC were seen. These data suggest that prion filtration of red cells does not reduce overall transfusion safety. This finding requires confirmation in large populations of transfused patients.

Bioassay studies support the potential for iatrogenic transmission of variant Creutzfeldt Jakob Disease through dental procedures

Background

Evidence is required to quantify the potential risks of transmission of variant Creutzfeldt Jakob (vCJD) through dental procedures. Studies, using animal models relevant to vCJD, were performed to address two questions. Firstly, whether oral tissues could become infectious following dietary exposure to BSE? Secondly, would a vCJD-contaminated dental instrument be able to transmit disease to another patient?

Methods

BSE-301V was used as a clinically relevant model for vCJD. VM-mice were challenged by injection of infected brain homogenate into the small intestine (Q1) or by five minute contact between a deliberately-contaminated dental file and the gingival margin (Q2). Ten tissues were collected from groups of challenged mice at three or four weekly intervals, respectively. Each tissue was pooled, homogenised and bioassayed in indicator mice.

Findings

Challenge via the small intestine gave a transmission rate of 100% (mean incubation 157±17 days). Infectivity was found in both dental pulp and the gingival margin within 3 weeks of challenge and was observed in all tissues tested within the oral cavity before the appearance of clinical symptoms. Following exposure to deliberately contaminated dental files, 97% of mice developed clinical disease (mean incubation 234±33 days).

Interpretation

Infectivity was higher than expected, in a wider range of oral tissues, than was allowed for in previous risk assessments. Disease was transmitted following transient exposure of the gingiva to a contaminated dental file. These observations provide evidence that dental procedures could be a route of cross-infection for vCJD and support the enforcement of single-use for certain dental instruments.

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

BACKGROUND AND OBJECTIVES

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSION

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

Emerging pathogens and their implications for the blood supply and transfusion transmitted infections

The threat of infection by conventional transfusion-transmitted agents has been essentially eliminated from the blood supply in developed countries, thus focusing attention on the potential risk from emerging infections. Over recent years, actions have been taken to manage a number of such risks to blood safety. These illustrate the inherent variability of the agents concerned and of the measures needed to define and control the risk.

The prion protein preference of sporadic Creutzfeldt-Jakob disease subtypes

Sporadic Creutzfeldt-Jakob disease (CJD) is the most prevalent manifestation of the transmissible spongiform encephalopathies or prion diseases affecting humans. The disease encompasses a spectrum of clinical phenotypes that have been correlated with molecular subtypes that are characterized by the molecular mass of the protease-resistant fragment of the disease-related conformation of the prion protein and a polymorphism at codon 129 of the gene encoding the prion protein. A cell-free assay of prion protein misfolding was used to investigate the ability of these sporadic CJD molecular subtypes to propagate using brain-derived sources of the cellular prion protein (PrP(C)). This study confirmed the presence of three distinct sporadic CJD molecular subtypes with PrP(C) substrate requirements that reflected their codon 129 associations in vivo. However, the ability of a sporadic CJD molecular subtype to use a specific PrP(C) substrate was not determined solely by codon 129 as the efficiency of prion propagation was also influenced by the composition of the brain tissue from which the PrP(C) substrate was sourced, thus indicating that nuances in PrP(C) or additional factors may determine sporadic CJD subtype. The results of this study will aid in the design of diagnostic assays that can detect prion disease across the diversity of sporadic CJD subtypes.

Adverse effects of plasma transfusion

Plasma utilization has increased over the past two decades, and there is a growing concern that many plasma transfusions are inappropriate. Plasma transfusion is not without risk, and certain complications are more likely with plasma than other blood components. Clinical and laboratory investigations of the patients suffering reactions after infusion of fresh-frozen plasma (FFP) define the etiology and pathogenesis of the panoply of adverse effects. We review here the pathogenesis, diagnosis, and management of the risks associated with plasma transfusion. Risks commonly associated with FFP include: 1) transfusion-related acute lung injury, 2) transfusion-associated circulatory overload, and 3) allergic and/or anaphylactic reactions. Other less common risks include 1) transmission of infections, 2) febrile nonhemolytic transfusion reactions, 3) red blood cell alloimmunization, and 4) hemolytic transfusion reactions. The effects of pathogen inactivation or reduction methods on these risks are also discussed. Fortunately, a majority of the adverse effects are not lethal and are adequately treated in clinical practice.

Impact of leucocyte depletion and prion reduction filters on TSE blood borne transmission

The identification in the UK of 4 v-CJD infected patients thought to be due to the use of transfused Red Blood Cell units prepared from blood of donors incubating v-CJD raised major concerns in transfusion medicine. The demonstration of leucocyte associated infectivity using various animal models of TSE infection led to the implementation of systematic leuco-depletion (LD) of Red Blood cells concentrates (RBCs) in a number of countries. In the same models, plasma also demonstrated a significant level of infectivity which raised questions on the impact of LD on the v-CJD transmission risk. The recent development of filters combining LD and the capture of non-leucocyte associated prion infectivity meant a comparison of the benefits of LD alone versus LD/prion-reduction filters (LD/PR) on blood-borne TSE transmission could be made. Due to the similarity of blood/plasma volumes to human transfusion medicine an experimental TSE sheep model was used to characterize the abilities of whole blood, RBCs, plasma and buffy-coat to transmit the disease through the transfusion route. The impact of a standard RBCs LD filter and of two different RBCs LD/PR prototype filters on the disease transmission was then measured. Homologous recipients transfused with whole-blood, buffy-coat and RBCs developed the disease with 100% efficiency. Conversely, plasma, when intravenously administered resulted in an inconstant infection of the recipients and no disease transmission was observed in sheep that received cryo-precipitated fraction or supernatant obtained from infectious plasma. Despite their high efficacy, LD and LD/PR filtration of the Red Blood Cells concentrate did not provide absolute protection from infection. These results support the view that leuco-depletion strongly mitigates the v-CJD blood borne transmission risk and provide information about the relative benefits of prion reduction filters.

Sensitivity to biases of case-control studies on medical procedures, particularly surgery and blood transfusion, and risk of Creutzfeldt-Jakob disease

BACKGROUND

Evidence of risk of Creutzfeldt-Jakob disease (CJD) associated with medical procedures, including surgery and blood transfusion, is limited by susceptibility to bias in epidemiological studies.

METHODS

Sensitivity to bias was explored using a central-birth-cohort model using data from 18 case-control studies obtained after a review of 494 reports on medical procedures and risk of CJD, systematic for the period January 1, 1989 to December 31, 2011.

RESULTS

The validity of the findings in these studies may have been undermined by: recall; control selection; exposure assessment in life-time periods of different duration, out of time-at-risk of effect, or asymmetry in case/control data; and confounding by concomitant blood transfusion at the time of surgery. For sporadic CJD (sCJD), a history of surgery or blood transfusion was associated with risk in some, but not all, recent studies at a ≥10 year lag time, when controls were longitudinally sampled. Space-time aggregation of surgical events was not seen. Surgery at early clinical onset might be overrepresented among cases. Neither surgical history nor blood transfusion unlabelled for donor status, dental treatments or endoscopic examinations were linked to variant CJD (vCJD).

CONCLUSIONS

These results indicate the need for further research. Common challenges within these studies include access to and content of past medical/dental treatment records for diseases with long incubation periods.

Human prion diseases: from Kuru to variant Creutzfeldt-Jakob disease

Transmissible spongiform encephalopathies (TSEs) or prion diseases are the names given to the group of fatal neurodegenerative disorders that includes kuru, Creutzfeldt-Jakob disease (CJD), Gerstmann-Sträussler-Scheinker disease (GSS), fatal and sporadic familial insomnia and the novel prion disease variable protease-sensitive prionopathy (PSPr) in humans. Kuru was restricted to natives of the Foré linguistic group in Papua New Guinea and spread by ritualistic endocannibalism. CJD appears as sporadic, familial (genetic or hereditary) and infectious (iatrogenic) forms. Variant CJD is a zoonotic CJD type and of major public health importance, which resulted from transmission from bovine spongiform encephalopathy (BSE) through ingestion of contaminated meat products. GSS is a slowly progressive hereditary autosomal dominant disease and the first human TSE in which a mutation in a gene encoding for prion protein (PrP) was discovered. The rarest human prion disease is fatal insomnia, which may occur, in genetic and sporadic form. More recently a novel prion disease variable protease-sensitive prionopathy (PSPr) was described in humans.TSEs are caused by a still incompletely defined infectious agent known as a "prion" which is widely regarded to be an aggregate of a misfolded isoform (PrP(Sc)) of a normal cellular glycoprotein (PrP(c)). The conversion mechanism of PrP(c) into PrP(Sc) is still not certain.

Creutzfeldt-Jakob disease

Creutzfeldt-Jakob disease (CJD), a neurodegenerative disorder that is the commonest form of human prion disease or transmissible spongiform encephalopathies (TSEs). Four types of CJD are known: Sporadic (sCJD), familial or genetic (gCJD); iatrogenic (iCJD) and variant CJD (vCJD). The latter results from transmission of bovine spongiform encephalopathy (BSE) from cattle to humans. The combination of PrP(Sc) peptide (either 21 kDa or 19 kDa) and the status of the codon 129 of the gene (PRNP) encoding for PrP (either Methionine or Valine) is used to classify sCJD into 6 types: MM1 and MV1, the most common; VV2; MV2 (Brownell/Oppenheimer syndrome); MM2; VV1 and sporadic fatal insomnia, in that order of prevalence. Genetic CJD is caused by diverse mutations in the PRNP gene. The neuropathology of CJD consists of spongiform change, astro- and microgliosis and poorly defined neuronal loss. In a proportion of cases, amyloid plaques, like those of kuru, are seen. PrP immunohistochemistry reveals different types of PrP(Sc) deposits - the most common is the synaptic-type, but perivacuolar, perineuronal and plaque-like deposits may be also detected.

Candidate cell substrates, vaccine production, and transmissible spongiform encephalopathies

Transmissible spongiform encephalopathy (TSE) agents have contaminated human tissue-derived medical products, human blood components, and animal vaccines. The objective of this study was to determine the potential susceptibility to infection of 5 cell lines used or proposed for manufacture of biological products, as well as other lines. Cell lines were exposed to the infectious agents of sporadic and variant Creutzfeldt-Jakob disease and bovine spongiform encephalopathy (BSE). Exposed cultures were tested for TSE-associated prion protein (PrP(TSE)) and TSE infectivity by assay in rodents and nonhuman primates. No PrP(TSE) or infectivity has been detected in any exposed cell line under study so far. Animals inoculated with BSE brain homogenate developed typical spongiform encephalopathy. In contrast, animals inoculated with cells exposed to the BSE agent remained asymptomatic. All cell lines we studied resisted infection with 3 TSE agents, including the BSE agent.

Classical scrapie prions in ovine blood are associated with B lymphocytes and platelet-rich plasma

Background

Classical scrapie is a naturally occurring transmissible spongiform encephalopathy of sheep and goats characterized by cellular accumulation of abnormal isoforms of prion protein (PrP^Sc) in the central nervous system and the follicles of peripheral lymphoid tissues. Previous studies have shown that the whole blood and buffy coat blood fraction of scrapie infected sheep harbor prion infectivity. Although PrP^Sc has been detected in peripheral blood mononuclear cells (PBMCs), plasma, and more recently within a subpopulation of B lymphocytes, the infectivity status of these cells and plasma in sheep remains unknown. Therefore, the objective of this study was to determine whether circulating PBMCs, B lymphocytes and platelets from classical scrapie infected sheep harbor prion infectivity using a sheep bioassay.

Results

Serial rectal mucosal biopsy and immunohistochemistry were used to detect preclinical infection in lambs transfused with whole blood or blood cell fractions from preclinical or clinical scrapie infected sheep. PrP^Sc immunolabeling was detected in antemortem rectal and postmortem lymphoid tissues from recipient lambs receiving PBMCs (15/15), CD72⁺ B lymphocytes (3/3), CD21⁺ B lymphocytes (3/3) or platelet-rich plasma (2/3) fractions. As expected, whole blood (11/13) and buffy coat (5/5) recipients showed positive PrP^Sc labeling in lymphoid follicles. However, at 549 days post-transfusion, PrP^Sc was not detected in rectal or other lymphoid tissues in three sheep receiving platelet-poor plasma fraction.

Conclusions

Prion infectivity was detected in circulating PBMCs, CD72⁺ pan B lymphocytes, the CD21⁺ subpopulation of B lymphocytes and platelet-rich plasma of classical scrapie infected sheep using a sheep bioassay. Combining platelets with B lymphocytes might enhance PrP^Sc detection levels in blood samples.

Limited efficacy of steam sterilization to inactivate vCJD infectivity

BACKGROUND

The transmission of bovine spongiform encephalopathy (BSE) to humans as variant Creutzfeldt-Jakob Disease (vCJD) raised concerns about potential secondary transmissions due to the resistance of the agents causing transmissible spongiform encephalopathies (TSEs), sometimes known as prions, to commonly used methods of sterilization, notably steam sterilization (or autoclaving). It has been suggested that surgical instruments and other medical devices might retain sufficient infected tissue debris after cleaning and steam sterilization to infect patients on whom they are subsequently used.

AIM

To determine whether concerns about the lack of efficacy of steam sterilization of vCJD were justified.

METHODS

The reduction in infectivity of brain macerates of vCJD brain after steam sterilization using the standard temperatures and time recommended for autoclaving in UK hospitals (134-137°C for 3 min) was measured.

FINDINGS

Reductions in titre of 10(2.3) to >10(3.6) ID(50) were found. In three of four samples, infectivity was recovered after steam sterilization.

CONCLUSION

As noted previously, TSE strains derived from BSE sources appear to be more resistant to steam sterilization and other forms of heat inactivation than other TSE sources.

Sensitive and specific detection of sporadic Creutzfeldt-Jakob disease brain prion protein using real-time quaking-induced conversion

Real-time quaking-induced conversion (RT-QuIC) is an assay in which disease-associated prion protein (PrP) initiates a rapid conformational transition in recombinant PrP (recPrP), resulting in the formation of amyloid that can be monitored in real time using the dye thioflavin T. It therefore has potential advantages over analogous cell-free PrP conversion assays such as protein misfolding cyclic amplification (PMCA). The QuIC assay and the related amyloid seeding assay have been developed largely using rodent-passaged sheep scrapie strains. Given the potential RT-QuIC has for Creutzfeldt-Jakob disease (CJD) research and human prion test development, this study characterized the behaviour of a range of CJD brain specimens with hamster and human recPrP in the RT-QuIC assay. The results showed that RT-QuIC is a rapid, sensitive and specific test for the form of abnormal PrP found in the most commonly occurring forms of sporadic CJD. The assay appeared to be largely independent of species-related sequence differences between human and hamster recPrP and of the methionine/valine polymorphism at codon 129 of the human PrP gene. However, with the same conditions and substrate, the assay was less efficient in detecting the abnormal PrP that characterizes variant CJD brain. Comparison of these QuIC results with those previously obtained using PMCA suggested that these two seemingly similar assays differ in important respects.

Surveillance of transfusion-transmissible infections comparison of systems in five developed countries

Most industrialized countries maintain surveillance programs for monitoring transmissible infection in blood donations, revising approaches to methodology and risk assessment as new threats emerge. A comparison of programs in the United States, Canada, France, the UK, and Australia indicates that they have similar function, although the structure of blood programs vary as does the extent and nature of formal ties with public health. The emergence of HIV in the late 1970s and early 1980s was key in recognizing that surveillance systems specific to blood transfusion were essential. Hence, most industrialized countries monitor transfusion-transmissible infections in donors and evaluate the impact of new testing and of predonation screening strategies. Emerging infections since HIV have had different transmission pathways and challenged blood programs to draw upon resources for a rapid and effective response, with recognition that the original focus on sexual/drug-related risk of HIV and hepatitis was inadequate. The focus of surveillance programs on new and emerging pathogens fulfills a key role in risk assessment and policy formulation. The precise nature of such activities varies by country because of the structure of the blood programs and surveillance systems, the strategic focus of the blood programs, and the epidemiology of disease in each country.

Prion diseases: risks, characteristics, and infection control considerations in dentistry

Prion diseases are a group of fatal neurodegenerative diseases that are rapidly progressive and fatal, with no definite cure. There are no reported cases of prion disease transmission arising from dental procedures. Nevertheless, there is a theoretical but real risk of transmission of prion disease from dental instruments. A review was made of studies up to 2008 to provide an update of the characteristics, risk of transmission, and the infection-control implications of prions in the field of dentistry. As the prions are resistant to conventional sterilization methods, highly-specific, cross-infection control measures are required when managing patients infected with these.