The cellular and pathologic prion protein

Prion protein gene (PRNP) variation in German and Danish cervids

The structure of cellular prion proteins encoded by the prion protein gene (PRNP) impacts susceptibility to transmissible spongiform encephalopathies, including chronic wasting disease (CWD) in deer. The recent emergence of CWD in Northern European reindeer (Rangifer tarandus), moose (Alces alces alces) and red deer (Cervus elaphus), in parallel with the outbreak in North America, gives reason to investigate PRNP variation in European deer, to implement risk assessments and adjust CWD management for deer populations under threat. We here report PRNP-sequence data from 911 samples of German red, roe (Capreolus capreolus), sika (Cervus nippon) and fallow deer (Dama dama) as well as additional data from 26 Danish red deer close to the German border and four zoo species not native to Germany. No PRNP sequence variation was observed in roe and fallow deer, as previously described for populations across Europe. In contrast, a broad PRNP variation was detected in red deer, with non-synonymous polymorphisms at codons 98, 226 and 247 as well as synonymous mutations at codons 21, 78, 136 and 185. Moreover, a novel 24 bp deletion within the octapeptide repeat was detected. In summary, 14 genotypes were seen in red deer with significant differences in their geographical distribution and frequencies, including geographical clustering of certain genotypes, suggesting "PRNP-linages" in this species. Based on data from North American CWD and the genotyping results of the European CWD cases, we would predict that large proportions of wild cervids in Europe might be susceptible to CWD once introduced to naive populations.

Grp78 destabilization of infectious prions is strain-specific and modified by multiple factors including accessory chaperones and pH

Lethal neurodegenerative prion diseases result from the continuous accumulation of infectious and variably protease-resistant prion protein aggregates (PrPD) which are misfolded forms of the normally detergent soluble and protease-sensitive cellular prion protein. Molecular chaperones like Grp78 have been found to reduce the accumulation of PrPD, but how different cellular environments and other chaperones influence the ability of Grp78 to modify PrPD is poorly understood. In this work, we investigated how pH and protease-mediated structural changes in PrPD from two mouse-adapted scrapie prion strains, 22L and 87V, influenced processing by Grp78 in the presence or absence of chaperones Hsp90, DnaJC1, and Stip1. We developed a cell-free in vitro system to monitor chaperone-mediated structural changes to, and disaggregation of, PrPD. For both strains, Grp78 was most effective at structurally altering PrPD at low pH, especially when additional chaperones were present. While Grp78, DnaJC1, Stip1, and Hsp90 were unable to disaggregate the majority of PrPD from either strain, pretreatment of PrPD with proteases increased disaggregation of 22L PrPD compared to 87V, indicating strain-specific differences in aggregate structure were impacting chaperone activity. Hsp90 also induced structural changes in 87V PrPD as indicated by an increase in the susceptibility of its n-terminus to proteases. Our data suggest that, while chaperones like Grp78, DnaJC1, Stip1, and Hsp90 disaggregate only a small fraction of PrPD, they may still facilitate its clearance by altering aggregate structure and sensitizing PrPD to proteases in a strain and pH-dependent manner.

Efficient transmission of human prion diseases to a glycan-free prion protein-expressing host

It is increasingly evident that the association of glycans with the prion protein (PrP), a major post-translational modification, significantly impacts the pathogenesis of prion diseases. A recent bioassay study has provided evidence that the presence of PrP glycans decreases spongiform degeneration and disease-related PrP (PrPD) deposition in a murine model. We challenged (PRNPN181Q/197Q) transgenic (Tg) mice expressing glycan-free human PrP (TgGlyc-), with isolates from sporadic Creutzfeldt-Jakob disease subtype MM2 (sCJDMM2), sporadic fatal insomnia and familial fatal insomnia, three human prion diseases that are distinct but share histotypic and PrPD features. TgGlyc- mice accurately replicated the basic histotypic features associated with the three diseases but the transmission was characterized by high attack rates, shortened incubation periods and a greatly increased severity of the histopathology, including the presence of up to 40 times higher quantities of PrPD that formed prominent deposits. Although the engineered protease-resistant PrPD shared at least some features of the secondary structure and the presence of the anchorless PrPD variant with the wild-type PrPD, it exhibited different density gradient profiles of the PrPD aggregates and a higher stability index. The severity of the histopathological features including PrP deposition appeared to be related to the incubation period duration. These findings are clearly consistent with the protective role of the PrP glycans but also emphasize the complexity of the conformational changes that impact PrPD following glycan knockout. Future studies will determine whether these features apply broadly to other human prion diseases or are PrPD-type dependent.

The PINK1/Parkin pathway of mitophagy exerts a protective effect during prion disease

The PINK1/Parkin pathway of mitophagy has been implicated in the pathogenesis of Parkinson's disease. In prion diseases, a transmissible neurodegenerative disease caused by the misfolded and infectious prion protein (PrPSc), expression of both PINK1 and Parkin are elevated, suggesting that PINK1/Parkin mediated mitophagy may also play a role in prion pathogenesis. Using mice in which expression of either PINK1 (PINK1KO) or Parkin (ParkinKO) has been ablated, we analyzed the potential role of PINK1 and Parkin in prion pathogenesis. Prion infected PINK1KO and ParkinKO mice succumbed to disease more rapidly (153 and 150 days, respectively) than wild-type control C57Bl/6 mice (161 days). Faster incubation times in PINK1KO and ParkinKO mice did not correlate with altered prion pathology in the brain, altered expression of proteins associated with mitochondrial dynamics, or prion-related changes in mitochondrial respiration. However, the expression level of mitochondrial respiration Complex I, a major site for the formation of reactive oxygen species (ROS), was higher in prion infected PINK1KO and ParkinKO mice when compared to prion infected control mice. Our results demonstrate a protective role for PINK1/Parkin mitophagy during prion disease, likely by helping to minimize ROS formation via Complex I, leading to slower prion disease progression.

Single-molecule immunoassay technology: Recent advances

Detecting diseases at the molecular level aids in early diagnosis and treatment. However, traditional immunological detection techniques, such as enzyme-linked immunosorbent assay (ELISA) and chemiluminescence, have detection sensitivities between 10^-16 and 10^-12 mol/L, which are inadequate for early diagnosis. Single-molecule immunoassays can reach detection sensitivities of 10^-18 mol/L and can detect biomarkers that are difficult to measure using conventional detection techniques. It can confine molecules to be detected in a small spatial area and provide absolute counting of the detected signal, offering the advantage of high efficiency and accuracy. Herein, we demonstrate the principles and equipment of two single-molecule immunoassay techniques and discuss their applications. It is shown that the detection sensitivity can be improved by 2-3 orders of magnitude compared to common chemiluminescence or ELISA assays. The microarray-based single-molecule immunoassay technique can test 66 samples in 1 h, which is more efficient than conventional immunological detection techniques. In contrast, microdroplet-based single-molecule immunoassay techniques can generate 107 droplets in 10 min, which is more than 100 times faster than a single droplet generator. By comparing the two single-molecule immunoassay techniques, we highlight our personal perspectives on the current limitations of point-of-care applications and future development trends.

What is the role of lipids in prion conversion and disease?

The molecular cause of transmissible spongiform encephalopathies (TSEs) involves the conversion of the cellular prion protein (PrP^C) into its pathogenic form, called prion scrapie (PrP^Sc), which is prone to the formation of amorphous and amyloid aggregates found in TSE patients. Although the mechanisms of conversion of PrP^C into PrP^Sc are not entirely understood, two key points are currently accepted: (i) PrP^Sc acts as a seed for the recruitment of native PrP^C, inducing the latter's conversion to PrP^Sc; and (ii) other biomolecules, such as DNA, RNA, or lipids, can act as cofactors, mediating the conversion from PrP^C to PrP^Sc. Interestingly, PrP^C is anchored by a glycosylphosphatidylinositol molecule in the outer cell membrane. Therefore, interactions with lipid membranes or alterations in the membranes themselves have been widely investigated as possible factors for conversion. Alone or in combination with RNA molecules, lipids can induce the formation of PrP in vitro-produced aggregates capable of infecting animal models. Here, we discuss the role of lipids in prion conversion and infectivity, highlighting the structural and cytotoxic aspects of lipid-prion interactions. Strikingly, disorders like Alzheimer's and Parkinson's disease also seem to be caused by changes in protein structure and share pathogenic mechanisms with TSEs. Thus, we posit that comprehending the process of PrP conversion is relevant to understanding critical events involved in a variety of neurodegenerative disorders and will contribute to developing future therapeutic strategies for these devastating conditions.

Risk of variant Creutzfeldt-Jakob disease transmission by blood transfusion in Australia

Background and Objectives

Most of the 233 worldwide cases of variant Creutzfeldt–Jakob disease (vCJD) have been reported in the United Kingdom and 3 have been associated with transfusion‐transmission. To mitigate the potential vCJD risk to blood safety, Australian Red Cross Lifeblood imposes restrictions on blood donation from people with prior residency in, or extended travel to, the United Kingdom during the risk period 1980–1996. We have modified a previously published methodology to estimate the transfusion‐transmission risk of vCJD associated with fresh component transfusion in Australia if the UK residence deferral was removed.

Materials and Methods

The prevalence of current pre‐symptomatic vCJD infection in the United Kingdom by age at infection and genotype was estimated based on risk of exposure to the bovine spongiform encephalopathy agent for the period 1980–1996. These results were used to estimate the age‐specific prevalence of undiagnosed, pre‐symptomatic vCJD in the Australian population in the current year due to prior UK residency or travel. The primary model outputs were the 2020 vCJD risks/unit of vCJD contamination, transfusion‐transmission (infections) and clinical cases.

Results

The overall (prior UK residency in and travel to United Kingdom, 1980–1996) mean risk of contamination per unit was 1 in 29,900,000. The risks of resulting vCJD transmission (infection) and clinical case were 1 in 389,000,000 and 1 in 1,450,000,000, respectively.

Conclusion

Our modelling suggests that removing the Lifeblood donation deferral for travel to, or UK residence, would result in virtually no increased risk of vCJD transfusion‐transmission and would be a safe and effective strategy for increasing the donor base.

Chronic Wasting Disease (CWD) in Cervids and the Consequences of a Mutable Protein Conformation

Chronic wasting disease (CWD) is a prion disease of cervids (deer, elk, moose, etc.). It spreads readily from CWD-contaminated environments and among wild cervids. As of 2022, North American CWD has been found in 29 states, four Canadian provinces and South Korea. The Scandinavian form of CWD originated independently. Prions propagate their pathology by inducing a natively expressed prion protein (PrPC) to adopt the prion conformation (PrPSc). PrPC and PrPSc differ solely in their conformation. Like other prion diseases, transmissible CWD prions can arise spontaneously. The CWD prions can respond to selection pressures resulting in the emergence of new strain phenotypes. Annually, 11.5 million Americans hunt and harvest nearly 6 million deer, indicating that CWD is a potential threat to an important American food source. No tested CWD strain has been shown to be zoonotic. However, this may not be true for emerging strains. Should a zoonotic CWD strain emerge, it could adversely impact the hunting economy and game meat consumers.

Glycomic and Glycoproteomic Techniques in Neurodegenerative Disorders and Neurotrauma: Towards Personalized Markers

The proteome represents all the proteins expressed by a genome, a cell, a tissue, or an organism at any given time under defined physiological or pathological circumstances. Proteomic analysis has provided unparalleled opportunities for the discovery of expression patterns of proteins in a biological system, yielding precise and inclusive data about the system. Advances in the proteomics field opened the door to wider knowledge of the mechanisms underlying various post-translational modifications (PTMs) of proteins, including glycosylation. As of yet, the role of most of these PTMs remains unidentified. In this state-of-the-art review, we present a synopsis of glycosylation processes and the pathophysiological conditions that might ensue secondary to glycosylation shortcomings. The dynamics of protein glycosylation, a crucial mechanism that allows gene and pathway regulation, is described. We also explain how-at a biomolecular level-mutations in glycosylation-related genes may lead to neuropsychiatric manifestations and neurodegenerative disorders. We then analyze the shortcomings of glycoproteomic studies, putting into perspective their downfalls and the different advanced enrichment techniques that emanated to overcome some of these challenges. Furthermore, we summarize studies tackling the association between glycosylation and neuropsychiatric disorders and explore glycoproteomic changes in neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, Huntington disease, multiple sclerosis, and amyotrophic lateral sclerosis. We finally conclude with the role of glycomics in the area of traumatic brain injury (TBI) and provide perspectives on the clinical application of glycoproteomics as potential diagnostic tools and their application in personalized medicine.

Unzipping the Secrets of Amyloid Disassembly by the Human Disaggregase

Neurodegenerative diseases (NDs) are increasingly positioned as leading causes of global deaths. The accelerated aging of the population and its strong relationship with neurodegeneration forecast these pathologies as a huge global health problem in the upcoming years. In this scenario, there is an urgent need for understanding the basic molecular mechanisms associated with such diseases. A major molecular hallmark of most NDs is the accumulation of insoluble and toxic protein aggregates, known as amyloids, in extracellular or intracellular deposits. Here, we review the current knowledge on how molecular chaperones, and more specifically a ternary protein complex referred to as the human disaggregase, deals with amyloids. This machinery, composed of the constitutive Hsp70 (Hsc70), the class B J-protein DnaJB1 and the nucleotide exchange factor Apg2 (Hsp110), disassembles amyloids of α-synuclein implicated in Parkinson’s disease as well as of other disease-associated proteins such as tau and huntingtin. We highlight recent studies that have led to the dissection of the mechanism used by this chaperone system to perform its disaggregase activity. We also discuss whether this chaperone-mediated disassembly mechanism could be used to solubilize other amyloidogenic substrates. Finally, we evaluate the implications of the chaperone system in amyloid clearance and associated toxicity, which could be critical for the development of new therapies.

Altered cellular localisation and expression, together with unconventional protein trafficking, of prion protein, PrPC, in type 1 diabetes

AIMS/HYPOTHESIS

Normal cellular prion protein (PrP^C) is a conserved mammalian glycoprotein found on the outer plasma membrane leaflet through a glycophosphatidylinositol anchor. Although PrP^C is expressed by a wide range of tissues throughout the body, the complete repertoire of its functions has not been fully determined. The misfolded pathogenic isoform PrP^Sc (the scrapie form of PrP) is a causative agent of neurodegenerative prion diseases. The aim of this study is to evaluate PrP^C localisation, expression and trafficking in pancreases from organ donors with and without type 1 diabetes and to infer PrP^C function through studies on interacting protein partners.

METHODS

In order to evaluate localisation and trafficking of PrP^C in the human pancreas, 12 non-diabetic, 12 type 1 diabetic and 12 autoantibody-positive organ donor tissue samples were analysed using immunofluorescence analysis. Furthermore, total RNA was isolated from 29 non-diabetic, 29 type 1 diabetic and 24 autoantibody-positive donors to estimate PrP^C expression in the human pancreas. Additionally, we performed PrP^C-specific immunoblot analysis on total pancreatic protein from non-diabetic and type 1 diabetic organ donors to test whether changes in PrP^C mRNA levels leads to a concomitant increase in PrP^C protein levels in human pancreases.

RESULTS

In non-diabetic and type 1 diabetic pancreases (the latter displaying both insulin-positive [INS(+)] and -negative [INS(-)] islets), we found PrP^C in islets co-registering with beta cells in all INS(+) islets and, strikingly, unexpected activation of PrP^C in alpha cells within diabetic INS(-) islets. We found PrP^C localised to the plasma membrane and endoplasmic reticulum (ER) but not the Golgi, defining two cellular pools and an unconventional protein trafficking mechanism bypassing the Golgi. We demonstrate PrP^C co-registration with established protein partners, neural cell adhesion molecule 1 (NCAM1) and stress-inducible phosphoprotein 1 (STI1; encoded by STIP1) on the plasma membrane and ER, respectively, linking PrP^C function with cyto-protection, signalling, differentiation and morphogenesis. We demonstrate that both PRNP (encoding PrP^C) and STIP1 gene expression are dramatically altered in type 1 diabetic and autoantibody-positive pancreases.

CONCLUSIONS/INTERPRETATION

As the first study to address PrP^C expression in non-diabetic and type 1 diabetic human pancreas, we provide new insights for PrP^C in the pathogenesis of type 1 diabetes. We evaluated the cell-type specific expression of PrP^C in the human pancreas and discovered possible connections with potential interacting proteins that we speculate might address mechanisms relevant to the role of PrP^C in the human pancreas.

Genetic Prion Disease: Insight from the Features and Experience of China National Surveillance for Creutzfeldt-Jakob Disease

Human genetic prion diseases (gPrDs) are directly associated with mutations and insertions in the PRNP (Prion Protein) gene. We collected and analyzed the data of 218 Chinese gPrD patients identified between Jan 2006 and June 2020. Nineteen different subtypes were identified and gPrDs accounted for 10.9% of all diagnosed PrDs within the same period. Some subtypes of gPrDs showed a degree of geographic association. The age at onset of Chinese gPrDs peaked in the 50-59 year group. Gerstmann-Sträussler-Scheinker syndrome (GSS) and fatal familial insomnia (FFI) cases usually displayed clinical symptoms earlier than genetic Creutzfeldt-Jakob disease (gCJD) patients with point mutations. A family history was more frequently recalled in P105L GSS and D178N FFI patients than T188K and E200K patients. None of the E196A gCJD patients reported a family history. The gCJD cases with point mutations always developed clinical manifestations typical of sporadic CJD (sCJD). EEG examination was not sensitive for gPrDs. sCJD-associated abnormalities on MRI were found in high proportions of GSS and gCJD patients. CSF 14-3-3 positivity was frequently detected in gCJD patients. Increased CSF tau was found in more than half of FFI and T188K gCJD cases, and an even higher proportion of E196A and E200K gCJD patients. 63.6% of P105L GSS cases showed a positive reaction in cerebrospinal fluid RT-QuIC. GSS and FFI cases had longer durations than most subtypes of gCJD. This is one of the largest studies of gPrDs in East Asians, and the illness profile of Chinese gPrDs is clearly distinct. Extremely high proportions of T188K and E196A occur among Chinese gPrDs; these mutations are rarely reported in Caucasians and Japanese.

Spatio-temporal analyses reveal infectious disease-driven selection in a free-ranging ungulate

Infectious diseases play an important role in wildlife population dynamics by altering individual fitness, but detecting disease-driven natural selection in free-ranging populations is difficult due to complex disease-host relationships. Chronic wasting disease (CWD) is a fatal infectious prion disease in cervids for which mutations in a single gene have been mechanistically linked to disease outcomes, providing a rare opportunity to study disease-driven selection in wildlife. In Wyoming, USA, CWD has gradually spread across mule deer (Odocoileus hemionus) populations, producing natural variation in disease history to evaluate selection pressure. We used spatial variation and a novel temporal comparison to investigate the relationship between CWD and a mutation at codon 225 of the mule deer prion protein gene that slows disease progression. We found that individuals with the 'slow' 225F allele were less likely to test positive for CWD, and the 225F allele was more common in herds exposed to CWD longer. We also found that in the past 2 decades, the 225F allele frequency increased more in herds with higher CWD prevalence. This study expanded on previous research by analysing spatio-temporal patterns of individual and herd-based disease data to present multiple lines of evidence for disease-driven selection in free-ranging wildlife.

A Chinese patient with the clinical features of Parkinson's disease contains a single copy of octarepeat deletion in PRNP case report

Insertion or deletion of single copy of octapeptide repeat (OR) in human PrP protein are considered as polymorphism, while of insertions of more numbers of OR and deletion of two copies of OR are associated with genetic prion diseases.Here, we reported a 58-year-old female patient who displayed clinical manifestations of Parkinson's disease (PD) but contained deletion mutation of single copy of OR in one PRNP allele. The patient complained involuntary tremor of left upper limb for 18 months and her symptoms aggravation for 6 months at the time referring to Chinese National CJD surveillance system. The tremor was pronounced at rest, exacerbated by stress and disappear during sleep. Her symptoms were partially relieved after receiving medicament for PD. Neurological examination recorded involuntary movement of left hand and gear-like muscle tension of left upper limb. Coordination movement reported positive of Romberg sign and unstable in heel-keen test. EEG recorded a mild abnormality, but without periodic sharp wave complexes (PSWC). MRI showed a mild write matter demyelination. CSF protein 14-3-3 was negative. PRNP sequencing revealed heterozygosity of single copy deletion on ORs (R1-2-3-4/R1-2-2-3-4).No family history of neurodegenerative disease was recorded. Such case with a single copy of OR deletion in PRNP displaying the feature of PD is rarely reported in Chinese mainland.

The Size and Stability of Infectious Prion Aggregates Fluctuate Dynamically during Cellular Uptake and Disaggregation

Prion diseases arise when PrP^Sc, an aggregated, infectious, and insoluble conformer of the normally soluble mammalian prion protein, PrP^C, catalyzes the conversion of PrP^C into more PrP^Sc, which then accumulates in the brain leading to disease. PrP^Sc is the primary, if not sole, component of the infectious prion. Despite the stability and protease insensitivity of PrP^Sc aggregates, they can be degraded after cellular uptake. However, how cells disassemble and degrade PrP^Sc is poorly understood. In this work, we analyzed how the protease sensitivity and size distribution of PrP^Sc aggregates from two different mouse-adapted prion strains, 22L, that can persistently infect cells and 87V, that cannot, changed during cellular uptake. We show that within the first 4 h following uptake large PrP^Sc aggregates from both prion strains become less resistant to digestion by proteinase K (PK) through a mechanism that is dependent upon the acidic environment of endocytic vesicles. We further show that during disassembly, PrP^Sc aggregates from both strains become more resistant to PK digestion through the apparent removal of protease-sensitive PrP^Sc, with PrP^Sc from the 87V strain disassembled more readily than PrP^Sc from the 22L strain. Taken together, our data demonstrate that the sizes and stabilities of PrP^Sc from different prion strains change during cellular uptake and degradation, thereby potentially impacting the ability of prions to infect cells.

Transmission characteristics of heterozygous cases of Creutzfeldt-Jakob disease with variable abnormal prion protein allotypes

In the human prion disease Creutzfeldt-Jakob disease (CJD), different CJD neuropathological subtypes are defined by the presence in normal prion protein (PrP^C) of a methionine or valine at residue 129, by the molecular mass of the infectious prion protein PrP^Sc, by the pattern of PrP^Sc deposition, and by the distribution of spongiform change in the brain. Heterozygous cases of CJD potentially add another layer of complexity to defining CJD subtypes since PrP^Sc can have either a methionine (PrP^Sc-M129) or valine (PrP^Sc-V129) at residue 129. We have recently demonstrated that the relative amount of PrP^Sc-M129 versus PrP^Sc-V129, i.e. the PrP^Sc allotype ratio, varies between heterozygous CJD cases. In order to determine if differences in PrP^Sc allotype correlated with different disease phenotypes, we have inoculated 10 cases of heterozygous CJD (7 sporadic and 3 iatrogenic) into two transgenic mouse lines overexpressing PrP^C with a methionine at codon 129. In one case, brain-region specific differences in PrP^Sc allotype appeared to correlate with differences in prion disease transmission and phenotype. In the other 9 cases inoculated, the presence of PrP^Sc-V129 was associated with plaque formation but differences in PrP^Sc allotype did not consistently correlate with disease incubation time or neuropathology. Thus, while the PrP^Sc allotype ratio may contribute to diverse prion phenotypes within a single brain, it does not appear to be a primary determinative factor of disease phenotype.

Neurofilaments in blood is a new promising preclinical biomarker for the screening of natural scrapie in sheep

Scrapie is a fatal neurodegenerative disease of sheep and goats belonging to the group of Transmissible Spongiform Encephalopathy or prion diseases. The EU has adopted mandatory measures for scrapie surveillance to safeguard public and animal health because it is highly contagious and might decimate all genetic susceptible animals in affected flocks. Definite diagnosis of scrapie relies on the detection of the pathological prion protein in brain tissues and there are still no blood biomarkers available for making diagnosis in living animals that can be used for the screening of sheep in scrapie-affected flocks. Neurofilament light (NfL) protein, a valid biomarker for neuronal and axonal damages, can now be easily measured in blood by the ultra-sensitive single molecule array (Simoa) technology. Recent work reported that serum NfL is increased in neurodegenerative diseases, including human prion diseases, but no data are available for scrapie or other animal prion diseases. Here, we found that the median serum NfL concentration in scrapie animals (56.2, IQR 42.2–84.8, n = 9) was more than 15 times higher (p = 0.00084) than that found in control samples (3.4, IQR 3.0–26.3, n = 11). Moreover, serum NfL concentration in scrapie sheep with clinical signs (n = 2; 75.3, 15.7 pg/ml) did not significantly (p = 0.541; t-test) differ from scrapie animals without clinical signs (n = 7; 61.0, 10.7 pg/ml). The receiver operating characteristic (ROC) curve analysis estimated the cut-off value of 31 pg/ml serum NfL for distinguishing scrapie-infected sheep from controls. The application of this cut-off value gives an accuracy of the test of 95% (percent error of 5.23%). These data indicate that the Simoa test for serum NfL might be a useful screening method for detecting preclinical scrapie in living sheep. Finally, the preliminary data reported here need confirmation in large and more structured studies.

Variation in the prion protein gene (PRNP) sequence of wild deer in Great Britain and mainland Europe

Susceptibility to prion diseases is largely determined by the sequence of the prion protein gene (PRNP), which encodes the prion protein (PrP). The recent emergence of chronic wasting disease (CWD) in Europe has highlighted the need to investigate PRNP gene diversity in European deer species, to better predict their susceptibility to CWD. Here we report a large genetic survey of six British deer species, including red (Cervus elaphus), sika (Cervus nippon), roe (Capreolus capreolus), fallow (Dama dama), muntjac (Muntiacus reevesii), and Chinese water deer (Hydropotes inermis), which establishes PRNP haplotype and genotype frequencies. Two smaller data sets from red deer in Norway and the Czech Republic are also included for comparison. Overall red deer show the most PRNP variation, with non-synonymous/coding polymorphisms at codons 98, 168, 226 and 247, which vary markedly in frequency between different regions. Polymorphisms P168S and I247L were only found in Scottish and Czech populations, respectively. T98A was found in all populations except Norway and the south of England. Significant regional differences in genotype frequencies were observed within both British and European red deer populations. Other deer species showed less variation, particularly roe and fallow deer, in which identical PRNP gene sequences were found in all individuals analysed. Based on comparison with PRNP sequences of North American cervids affected by CWD and limited experimental challenge data, these results suggest that a high proportion of wild deer in Great Britain may be susceptible to CWD.