Direct Detection of Disease Associated Prions in Brain and Lymphoid Tissue Using Antibodies Recognizing the Extreme N Terminus of PrPC

A simple diagnostic test is described for the detection of TSE in bovine, ovine and human brain and lymphoid tissue that obviates the use of proteinase K as a discriminating reagent. The immunoassay utilises high affinity anti-peptide antibodies that appear blind to the normal isoform of prion protein (PrP^C). These reagents have been produced with novel N-terminal chimeric peptides and we hypothesise that the retention and stability of the extreme N-terminus of PrP in the disease-associated aggregate makes it an operationally specific marker for TSE. Accordingly, the assay involves homogenisation of the tissue directly in 8M guanidine hydrochloride, a simple one-step capture of PrP^Sc followed by detection with a europium-labelled anti-PrP^C antibody. This rapid assay clearly differentiates between levels of disease-associated PrP extracted from brain and lymphoid tissues taken from confirmed TSE positive and negative cattle and sheep. The assay can also be used to detect PrP^Sc in cases of vCJD.Key Words: BSE, scrapie and vCJD Diagnosis, DELFIA®, novel N terminal antibodies     

Direct Detection of Disease-Associated Prions in Brain and Lymphoid Tissue Using Antibodies Recognizing the Extreme N-terminus of PrPC

A simple diagnostic test is described for the detection of TSE in bovine, ovine and human brain and lymphoid tissue that obviates the use of proteinase K as a discriminating reagent. The immunoassay utilises high affinity anti-peptide antibodies that appear blind to the normal isoform of prion protein (PrP^C). These reagents have been produced with novel N-terminal chimeric peptides and we hypothesise that the retention and stability of the extreme N-terminus of PrP in the disease-associated aggregate makes it an operationally specific marker for TSE. Accordingly, the assay involves homogenisation of the tissue directly in 8M guanidine hydrochloride, a simple one-step capture of PrP^Sc followed by detection with a europium-labelled anti-PrP^C antibody. This rapid assay clearly differentiates between levels of disease-associated PrP extracted from brain and lymphoid tissues taken from confirmed TSE positive and negative cattle and sheep. The assay can also be used to detect PrP^Sc in cases of vCJD.     

Regulating Factors of PrPres Glycosylation in Creutzfeldt-Jakob Disease - Implications for the Dissemination and the Diagnosis of Human Prion Strains

Objective

The glycoprofile of pathological prion protein (PrP^res) is widely used as a diagnosis marker in Creutzfeldt-Jakob disease (CJD) and is thought to vary in a strain-specific manner. However, that the same glycoprofile of PrP^res always accumulates in the whole brain of one individual has been questioned. We aimed to determine whether and how PrP^res glycosylation is regulated in the brain of patients with sporadic and variant Creutzfeldt-Jakob disease.

Methods

PrP^res glycoprofiles in four brain regions from 134 patients with sporadic or variant CJD were analyzed as a function of the genotype at codon 129 of PRNP and the Western blot type of PrP^res.

Results

The regional distribution of PrP^res glycoforms within one individual was heterogeneous in sporadic but not in variant CJD. PrP^res glycoforms ratio significantly correlated with the genotype at codon 129 of the prion protein gene and the Western blot type of PrP^res in a region-specific manner. In some cases of sCJD, the glycoprofile of thalamic PrP^res was undistinguishable from that observed in variant CJD.

Interpretation

Regulations leading to variations of PrP^res pattern between brain regions in sCJD patients, involving host genotype and Western blot type of PrP^res may contribute to the specific brain targeting of prion strains and have direct implications for the diagnosis of the different forms of CJD.     

Strain‐specific viral properties of variant Creutzfeldt–Jakob disease (vCJD) are encoded by the agent and not by host prion protein

Human CJD, endemic sheep scrapie, epidemic bovine spongiform encephalopathy (BSE), and other transmissible spongiform encephalopathies (TSEs), are caused by a group of related but molecularly uncharacterized infectious agents. The UK‐BSE agent infected many species, including humans where it causes variant CJD (vCJD). As in most viral infections, different TSE disease phenotypes are determined by both the agent strain and the host species. TSE strains are most reliably classified by incubation time and regional neuropathology in mice expressing wild‐type (wt) prion protein (PrP). We compared vCJD to other human and animal derived TSE strains in both mice and neuronal cultures expressing wt murine PrP. Primary and serial passages of the human vCJD agent, as well as the highly selected mutant 263K sheep scrapie agent, revealed profound strain‐specific characteristics were encoded by the agent, not by host PrP. Prion theory posits that PrP converts itself into the infectious agent, and thus short incubations require identical PrP sequences in the donor and recipient host. However, wt PrP mice injected with human vCJD brain homogenates showed dramatically shorter primary incubation times than mice expressing only human PrP, a finding not in accord with a PrP species barrier. All mouse passage brains showed the vCJD agent derived from a stable BSE strain. Additionally, both vCJD brain and monotypic neuronal cultures produced a diagnostic 19 kDa PrP fragment previously observed only in BSE and vCJD primate brains. Monotypic cultures can be used to identify the intrinsic, strain‐determining molecules of TSE infectious particles. J. Cell. Biochem. 106: 220–231, 2009. © 2008 Wiley‐Liss, Inc.     

Comparative profiling of highly enriched 22L and Chandler mouse scrapie prion protein preparations

Transmissible spongiform encephalopathies (TSEs) or prion diseases are characterized by the accumulation of an aggregated isoform of the prion protein (PrP). This pathological isoform, termed PrP^Sc, appears to be the primary component of the TSE infectious agent or prion. However, it is not clear to what extent other protein cofactors may be involved in TSE pathogenesis or whether there are PrP^Sc‐associated proteins which help to determine TSE strain‐specific disease phenotypes. We enriched PrP^Sc from the brains of mice infected with either 22L or Chandler TSE strains and examined the protein content of these samples using nanospray LC‐MS/MS. These samples were compared with “mock” PrP^Sc preparations from uninfected brains. PrP was the major component of the infected samples and ferritin was the most abundant impurity. Mock enrichments contained no detectable PrP but did contain a significant amount of ferritin. Of the total proteins identified, 32% were found in both mock and infected samples. The similarities between PrP^Sc samples from 22L and Chandler TSE strains suggest that the non‐PrP^Sc protein components found in standard enrichment protocols are not strain specific.     

H-Type Bovine Spongiform Encephalopathy: Complex Molecular Features and Similarities with Human Prion Diseases

We previously reported that some cattle affected by bovine spongiform encephalopathy (BSE) showed distinct molecular features of the protease-resistant prion protein (PrP^res) in Western blot, with a 1–2 kDa higher apparent molecular mass of the unglycosylated PrP^res associated with labelling by antibodies against the 86–107 region of the bovine PrP protein (H-type BSE). By Western blot analyses of PrP^res, we now showed that the essential features initially described in cattle were observed with a panel of different antibodies and were maintained after transmission of the disease in C57Bl/6 mice. In addition, antibodies against the C-terminal region of PrP revealed a second, more C-terminally cleaved, form of PrP^res (PrP^res #2), which, in unglycosylated form, migrated as a ≈ 14 kDa fragment. Furthermore, a PrP^res fragment of ≈7 kDa, which was not labelled by C-terminus-specific antibodies and was thus presumed to be a product of cleavage at both N- and C-terminal sides of PrP protein, was also detected. Both PrP^res #2 and ≈7 kDa PrP^res were detected in cattle and in C57Bl/6 infected mice. These complex molecular features are reminiscent of findings reported in human prion diseases. This raises questions regarding the respective origins and pathogenic mechanisms in prion diseases of animals and humans.Key Words: prion, BSE, Creutzfeldt-Jakob, Gerstmann-Sträussler-Scheinker, Western blot, amyloid     

Red-Backed Vole Brain Promotes Highly Efficient In Vitro Amplification of Abnormal Prion Protein from Macaque and Human Brains Infected with Variant Creutzfeldt-Jakob Disease Agent

Rapid antemortem tests to detect individuals with transmissible spongiform encephalopathies (TSE) would contribute to public health. We investigated a technique known as protein misfolding cyclic amplification (PMCA) to amplify abnormal prion protein (PrP^TSE) from highly diluted variant Creutzfeldt-Jakob disease (vCJD)-infected human and macaque brain homogenates, seeking to improve the rapid detection of PrP^TSE in tissues and blood. Macaque vCJD PrP^TSE did not amplify using normal macaque brain homogenate as substrate (intraspecies PMCA). Next, we tested interspecies PMCA with normal brain homogenate of the southern red-backed vole (RBV), a close relative of the bank vole, seeded with macaque vCJD PrP^TSE. The RBV has a natural polymorphism at residue 170 of the PrP-encoding gene (N/N, S/S, and S/N). We investigated the effect of this polymorphism on amplification of human and macaque vCJD PrP^TSE. Meadow vole brain (170N/N PrP genotype) was also included in the panel of substrates tested. Both humans and macaques have the same 170S/S PrP genotype. Macaque PrP^TSE was best amplified with RBV 170S/S brain, although 170N/N and 170S/N were also competent substrates, while meadow vole brain was a poor substrate. In contrast, human PrP^TSE demonstrated a striking narrow selectivity for PMCA substrate and was successfully amplified only with RBV 170S/S brain. These observations suggest that macaque PrP^TSE was more permissive than human PrP^TSE in selecting the competent RBV substrate. RBV 170S/S brain was used to assess the sensitivity of PMCA with PrP^TSE from brains of humans and macaques with vCJD. PrP^TSE signals were reproducibly detected by Western blot in dilutions through 10^-12 of vCJD-infected 10% brain homogenates. This is the first report showing PrP^TSE from vCJD-infected human and macaque brains efficiently amplified with RBV brain as the substrate. Based on our estimates, PMCA showed a sensitivity that might be sufficient to detect PrP^TSE in vCJD-infected human and macaque blood.     

PrPTSE distribution in a primate model of variant, sporadic, and iatrogenic Creutzfeldt-Jakob disease

Human prion diseases, such as Creutzfeldt-Jakob disease (CJD), are neurodegenerative and fatal. Sporadic CJD (sCJD) can be transmitted between humans through medical procedures involving highly infected organs, such as the central nervous system. However, in variant CJD (vCJD), which is due to human contamination with the bovine spongiform encephalopathy (BSE) agent, lymphoreticular tissue also harbors the transmissible spongiform encephalopathy-associated prion protein (PrP(TSE)), which poses a particularly acute risk for iatrogenic transmission. Two blood transfusion-related cases are already documented. In addition, the recent observation of PrP(TSE) in spleen and muscle in sCJD raised the possibility that peripheral PrP(TSE) is not limited to vCJD cases. We aimed to clarify the peripheral pathogenesis of human TSEs by using a nonhuman primate model which mimics human diseases. A highly sensitive enzyme-linked immunosorbent assay was adapted to the detection of extraneural PrP(TSE). We show that affected organs can be divided into two groups. The first is peripheral organs accumulating large amounts of PrP(TSE), which represent a high risk of iatrogenic transmission. This category comprises only lymphoreticular organs in the vCJD/BSE model. The second is organs with small amounts of PrP(TSE) associated with nervous structures. These are the muscles, adrenal glands, and enteric nervous system in the sporadic, iatrogenic, and variant CJD models. In contrast to the first set of organs, this low level of tissue contamination is not strain restricted and seems to be linked to secondary centrifugal spread of the agent through nerves. It might represent a risk for iatrogenic transmission, formerly underestimated despite previous reports of low rates of transmission from peripheral organs of humans to nonhuman primates (5, 10). This study provides an additional experimental basis for the classification of human organs into different risk categories and a rational re-evaluation of current risk management measures.     

Experimental Verification of a Traceback Phenomenon in Prion Infection

The clinicopathological phenotypes of sporadic Creutzfeldt-Jakob disease (sCJD) correlate with the allelotypes (M or V) of the polymorphic codon 129 of the human prion protein (PrP) gene and the electrophoretic mobility patterns of abnormal prion protein (PrP^Sc). Transmission of sCJD prions to mice expressing human PrP with a heterologous genotype (referred to as cross-sequence transmission) results in prolonged incubation periods. We previously reported that cross-sequence transmission can generate a new prion strain with unique transmissibility, designated a traceback phenomenon. To verify experimentally the traceback of sCJD-VV2 prions, we inoculated sCJD-VV2 prions into mice expressing human PrP with the 129M/M genotype. These 129M/M mice showed altered neuropathology and a novel PrP^Sc type after a long incubation period. We then passaged the brain homogenate from the 129M/M mouse inoculated with sCJD-VV2 prions into other 129M/M or 129V/V mice. Despite cross-sequence transmission, 129V/V mice were highly susceptible to these prions compared to the 129M/M mice. The neuropathology and PrP^Sc type of the 129V/V mice inoculated with the 129M/M mouse-passaged sCJD-VV2 prions were identical to those of the 129V/V mice inoculated with sCJD-VV2 prions. Moreover, we generated for the first time a type 2 PrP^Sc-specific antibody in addition to type 1 PrP^Sc-specific antibody and discovered that drastic changes in the PrP^Sc subpopulation underlie the traceback phenomenon. Here, we report the first direct evidence of the traceback in prion infection.Creutzfeldt-Jakob disease (CJD) is a lethal transmissible neurodegenerative disease caused by an abnormal isoform of prion protein (PrP^Sc), which is converted from the normal cellular isoform (PrP^C) (1, 23). The genotype (M/M, M/V, or V/V, where M and V are allelotypes) at polymorphic codon 129 of the human prion protein (PrP) gene and the type (type 1 or type 2) of PrP^Sc in the brain are major determinants of the clinicopathological phenotypes of sporadic CJD (sCJD) (15-18). Type 1 and type 2 PrP^Sc are distinguishable according to the size of the proteinase K-resistant core of PrP^Sc (PrP^res) (21 and 19 kDa, respectively), reflecting differences in the proteinase K cleavage site (at residues 82 and 97, respectively) (15, 18). According to this molecular typing system, sCJD can be classified into six subgroups (MM1, MM2, MV1, MV2, VV1, or VV2).The homology of the PrP genes between inoculated animals and the inoculum determines the susceptibility to prion infection. Transmission of sCJD prions to mice expressing human PrP with a nonhomologous genotype (referred to as cross-sequence transmission) results in a relatively long incubation period (10, 12). Meanwhile, the cross-sequence transmission can generate a new prion strain. Transmission of sCJD-VV2 prions to mice expressing human PrP with the 129M/M genotype generates unusual PrP^res intermediate in size between type 1 and type 2 (10). We have designated this unusual PrP^res with an upward size shift (Sh+) from the inoculated type 2 template MM[VV2]2^Sh+ PrP^res, where the notation is of the following form: host genotype [type of inoculated prion] type of generated PrP^res.Similar to the MM[VV2]2^Sh+ PrP^res, the intermediate-sized PrP^res has been observed in the plaque-type of dura mater graft-associated CJD (p-dCJD) (10, 13). Furthermore, a transmission study using p-dCJD prions revealed that PrP-humanized mice with the 129V/V genotype were highly susceptible to p-dCJD prions despite cross-sequence transmission (10). In addition, these 129V/V mice inoculated with p-dCJD prions produced type 2 PrP^res (10). These findings suggest that p-dCJD could be caused by cross-sequence transmission of sCJD-VV2 prions to individuals with the 129M/M genotype. We have designated this phenomenon “traceback.” The traceback phenomenon was discovered for the first time by a transmission study using variant CJD (vCJD) prions (2). Mice expressing bovine PrP were highly susceptible to vCJD prions because vCJD was caused by cross-sequence transmission of bovine spongiform encephalopathy prions to human. These findings suggest that a traceback study can be a powerful tool to identify the origin of prions (2, 10, 11). However, the traceback phenomenon has not been verified experimentally despite the abundant circumstantial evidence described above.To verify the traceback of sCJD-VV2 prions, we inoculated sCJD-VV2 prions into PrP-humanized mice with the 129M/M genotype as an experimental model of p-dCJD. Thereafter, we inoculated these MM[VV2]2^Sh+ prions into PrP-humanized mice with the 129M/M or 129V/V genotype and compared the incubation period, neuropathology, and the type of PrP^res in the brain. Here, we report the first direct evidence of the traceback in prion infection.     

Sheep prions with molecular properties intermediate between classical scrapie,BSE and CH1641–scrapie

Efforts to differentiate bovine spongiform encephalopathy (BSE) from scrapie in prion infected sheep have resulted in effective methods to decide about the absence of BSE. In rare instances uncertainties remain due to assumptions that BSE, classical scrapie and CH1641–a rare scrapie variant–could occur as mixtures. In field samples including those from fallen stock, triplex Western blotting analyses of variations in the molecular properties of the proteinase K resistant part of the disease‑associated form of prion protein (PrP^res) represents a powerful tool for quick discrimination purposes. In this study we examined 7 deviant ovine field cases of scrapie for some typical molecular aspects of PrP^res found in CH1641‑scrapie, classical scrapie and BSE. One case was most close to scrapie with respect to molecular mass of its non-glycosylated fraction and N-terminally located 12B2‑epitope content. Two cases were unlike classical scrapie but too weak to differentiate between BSE or CH1641. The other 4 cases appeared intermediate between scrapie and CH1641 with a reduced molecular mass and 12B2‑epitope content, together with the characteristic presence of a second PrP^res population. The existence of these 2 PrP^res populations was further confirmed through deglycosylation by PNGaseF. The findings indicate that discriminatory diagnosis between classical scrapie, CH1641 and BSE can remain inconclusive with current biochemical methods. Whether such intermediate cases represent mixtures of TSE strains should be further investigated e.g. in bioassays with rodent lines that are varying in their susceptibility or other techniques suitable for strain typing.     

Multiorgan Detection and Characterization of Protease-Resistant Prion Protein in a Case of Variant CJD Examined in the United States

Background

Variant Creutzfeldt–Jakob disease (vCJD) is a prion disease thought to be acquired by the consumption of prion-contaminated beef products. To date, over 200 cases have been identified around the world, but mainly in the United Kingdom. Three cases have been identified in the United States; however, these subjects were likely exposed to prion infection elsewhere. Here we report on the first of these subjects.

Methodology/Principal Findings

Neuropathological and genetic examinations were carried out using standard procedures. We assessed the presence and characteristics of protease-resistant prion protein (PrP^res) in brain and 23 other organs and tissues using immunoblots performed directly on total homogenate or following sodium phosphotungstate precipitation to increase PrP^res detectability. The brain showed a lack of typical spongiform degeneration and had large plaques, likely stemming from the extensive neuronal loss caused by the long duration (32 months) of the disease. The PrP^res found in the brain had the typical characteristics of the PrP^res present in vCJD. In addition to the brain and other organs known to be prion positive in vCJD, such as the lymphoreticular system, pituitary and adrenal glands, and gastrointestinal tract, PrP^res was also detected for the first time in the dura mater, liver, pancreas, kidney, ovary, uterus, and skin.

Conclusions/Significance

Our results indicate that the number of organs affected in vCJD is greater than previously realized and further underscore the risk of iatrogenic transmission in vCJD.     

Infrared Microspectroscopy Detects Protein Misfolding Cyclic Amplification (PMCA)-induced Conformational Alterations in Hamster Scrapie Progeny Seeds

The self-replicative conformation of misfolded prion proteins (PrP) is considered a major determinant for the seeding activity, infectiousness, and strain characteristics of prions in different host species. Prion-associated seeding activity, which converts cellular prion protein (PrP^C) into Proteinase K-resistant, infectious PrP particles (PrP^TSE), can be monitored in vitro by protein misfolding cyclic amplification (PMCA). Thus, PMCA has been established as a valuable analytical tool in prion research. Currently, however, it is under discussion whether prion strain characteristics are preserved during PMCA when parent seeds are amplified in PrP^C substrate from the identical host species. Here, we report on the comparative structural analysis of parent and progeny (PMCA-derived) PrP seeds by an improved approach of sensitive infrared microspectroscopy. Infrared microspectroscopy revealed that PMCA of native hamster 263K scrapie seeds in hamster PrP^C substrate caused conformational alterations in progeny seeds that were accompanied by an altered resistance to Proteinase K, higher sedimentation velocities in gradient ultracentrifugations, and a longer incubation time in animal bioassays. When these progeny seeds were propagated in hamsters, misfolded PrP from brain extracts of these animals showed mixed spectroscopic and biochemical properties from both parental and progeny seeds. Thus, strain modifications of 263K prions induced by PMCA seem to have been partially reversed when PMCA products were reinoculated into the original host species.     

Glycosaminoglycan Sulphation Affects the Seeded Misfolding of a Mutant Prion Protein

Background

The accumulation of protease resistant conformers of the prion protein (PrP^res) is a key pathological feature of prion diseases. Polyanions, including RNA and glycosaminoglycans have been identified as factors that contribute to the propagation, transmission and pathogenesis of prion disease. Recent studies have suggested that the contribution of these cofactors to prion propagation may be species specific.

Methodology/Principal Finding

In this study a cell-free assay was used to investigate the molecular basis of polyanion stimulated PrP^res formation using brain tissue or cell line derived murine PrP. Enzymatic depletion of endogenous nucleic acids or heparan sulphate (HS) from the PrP^C substrate was found to specifically prevent PrP^res formation seeded by mouse derived PrP^Sc. Modification of the negative charge afforded by the sulphation of glycosaminoglycans increased the ability of a familial PrP mutant to act as a substrate for PrP^res formation, while having no effect on PrP^res formed by wildtype PrP. This difference may be due to the observed differences in the binding of wild type and mutant PrP for glycosaminoglycans.

Conclusions/Significance

Cofactor requirements for PrP^res formation are host species and prion strain specific and affected by disease associated mutations of the prion protein. This may explain both species and strain dependent propagation characteristics and provide insights into the underlying mechanisms of familial prion disease. It further highlights the challenge of designing effective therapeutics against a disease which effects a range of mammalian species, caused by range of aetiologies and prion strains.     

Host PrP glycosylation: a major factor determining the outcome of prion infection

The expression of the prion protein (PrP) is essential for transmissible spongiform encephalopathy (TSE) or prion diseases to occur, but the underlying mechanism of infection remains unresolved. To address the hypothesis that glycosylation of host PrP is a major factor influencing TSE infection, we have inoculated gene-targeted transgenic mice that have restricted N-linked glycosylation of PrP with three TSE strains. We have uniquely demonstrated that mice expressing only unglycosylated PrP can sustain a TSE infection, despite altered cellular location of the host PrP. Moreover we have shown that brain material from mice infected with TSE that have only unglycosylated PrP^Sc is capable of transmitting infection to wild-type mice, demonstrating that glycosylation of PrP is not essential for establishing infection within a host or for transmitting TSE infectivity to a new host. We have further dissected the requirement of each glycosylation site and have shown that different TSE strains have dramatically different requirements for each of the glycosylation sites of host PrP, and moreover, we have shown that the host PrP has a major role in determining the glycosylation state of de novo generated PrP^Sc.     

Assessing the presence of BSE and scrapie in slaughterhouse wastewater

Aims: This paper describes a procedure for evaluating the presence and the stability of the proteinase K-resistant form of the prion protein (PrP^res) in slaughterhouse wastewater. Methods and Results: Wastewater samples were spiked with either scrapie or bovine spongiform encephalopathy agents and PrP^res was concentrated and detected by western blotting. The detection limit was estimated to be 2–4 μg of either scrapie or BSE-infected brain tissue in 15 ml of sewage. Wastewater samples from three abattoirs were analysed, two of which had processed BSE-infected animals. No PrP^res was detected. The effect of sewage on the inoculum and the persistence of transmissible spongiform encephalopathy agents in wastewater were also considered. Conclusions: The results of the assay suggest that wastewaters from abattoirs where one positive BSE case has been identified would contain titres lower than 0·6–26 × 10⁻⁴ cattle oral ID₅₀ per litre resulting from specified risk material tissue contamination. Moreover, the effect of abattoir wastewaters is to reduce the persistence of PrP^res. Significance and Impact of the Study: The assay may be a useful tool for risk assessment studies and for reducing the potential risk of contamination with BSE via sewage sludge fertilizer procedures.     

Highly Infectious CJD Particles Lack Prion Protein but Contain Many Viral‐Linked Peptides by LC‐MS/MS

It is widely believed that host prion protein (PrP), without nucleic acid, converts itself into an infectious form (PrP‐res) that causes transmissible encephalopathies (TSEs), such as human sporadic CJD (sCJD), endemic sheep scrapie, and epidemic BSE. There are many detailed investigations of PrP, but proteomic studies of other proteins in verified infectious TSE particles have not been pursued, even though brain homogenates without PrP retain their complete infectious titer. To define proteins that may be integral to, process, or protect an agent genome, we developed a streamlined, high‐yield purification of infectious FU‐CJD mouse brain particles with minimal PrP. Proteinase K (PK) abolished all residual particle PrP, but did not reduce infectivity, and viral‐size particles lacking PrP were ～70S (vs. 90–120S without PK). Furthermore, over 1,500 non‐PrP proteins were still present and positively identified in high titer FU‐CJD particles without detectable PrP by mass spectrometry (LC‐MS/MS); 114 of these peptides were linked to viral motifs in the environmental–viral database, and not evident in parallel uninfected controls. Host components were also identified in both PK and non‐PK treated particles from FU‐CJD mouse brain and human sCJD brain. This abundant cellular data had several surprises, including finding Huntingtin in the sCJD but not normal human brain samples. Similarly, the neural Wiskott–Aldrich sequence and multivesicular and endosome components associated with retromer APP (Alzheimer amyloid) processing were only in sCJD. These cellular findings suggest that new therapies directed at retromer–vesicular trafficking in other neurodegenerative diseases may also counteract late‐onset sCJD PrP amyloid pathology. J. Cell. Biochem. 115: 2012–2021, 2014. © 2014 Wiley Periodicals, Inc.

     

Species and Strain Glycosylation Patterns of PrPSc

Background

A key event in transmissible spongiform encephalopathies (TSEs) is the conversion of the soluble, protease-sensitive glycosylated prion protein (PrP^C) to an abnormally structured, aggregated and partially protease-resistant isoform (PrP^Sc). Both PrP isoforms bear two potential glycosylation sites and thus in a typical western blot with an anti-PrP antibody three distinct bands appear, corresponding to the di-, mono- or unglycosylated forms of the protein. The relative intensity and electrophoretic mobility of the three bands are characteristic of each TSE strain and have been used to discriminate between them.

Methodology/Principal Findings

In the present study we used lectin-based western blotting to evaluate possible variations in composition within sugar chains carried by PrP^Sc purified from subjects affected with different TSEs. Our findings indicate that in addition to the already well-documented differences in electrophoretic mobility and amounts of the glycosylated PrP^Sc forms, TSE strains also vary in the abundance of specific N-linked sugars of the PrP^Sc protein.

Conclusions/Significance

These results imply that PrP glycosylation might fine-tune the conversion of PrP^C to PrP^Sc and could play an accessory role in the appearance of some of the characteristic features of TSE strains. The differences in sugar composition could also be used as an additional tool for discrimination between the various TSEs.     

Establishment of bovine prion peptide-based monoclonal antibodies for identifying bovine prion

To obtain high titer monoclonal antibodies (McAbs) which can react with mammalian prion protein (PrP), Balb/C mice were immunized with bovine (Bo) PrP peptide (BoPrP 209—228 aa) coupled to keyhole limpet hemocyanin (KLH). The hybridoma cell lines secreting monoclonal antibodies against the pep-tide were established by cell fusion and cloning. The obtained McAbs were applied to detect recombi-nant human, bovine and hamster PrP, cellular prion protein (PrP^c) in normal bovine brain and patho-genic scrapie prion protein (PrP^Sc) accumulated in the medulla oblongata of bovine spongiform en-cephalopathy(BSE)specimen with Western blot and immunohistochemical detection, respectively. The current procedure might offer a simple, feasible method to raise high titer antibodies for studying bio-logical features of PrP in mammals, as well as detection of transmissible spongiform encephalopathy (TSE) and diagnosis of BSE, in particular.     

Transmission of human prion diseases to rodents

PrP genotypes of human prion diseases were closely related to deposition types of PrP^Sc, clinico-pathologic phenotypes and transmission rates to rodents. Wild type CJD with 129M/M, iatrogenic cases, and hereditary CJD with V1801, E200K, and M232R showed synaptic type deposition of PrP^Sc, similar phenotypes and, except for V1801, similar transmission rates. One patient with fatal familial insomnia transmitted the disease to mice. Plaque type deposition of PrP^Scinduced various phenotypes, such as GSS or Alzheimer's disease-like dementia, usually with a longer clinical course than CJD. Experimental transmission was positive from one-third of the cases with P102L but negative from other mutation cases with PrP plaques. Polymorphism at codon 129 may modify phenotypes as well as transmission rates.