Alexander Peden

Preclinical vCJD after blood transfusion in a PRNP codon 129 heterozygous patient

We report a case of preclinical variant Creutzfeldt-Jakob disease (vCJD) in a patient who died from a non-neurological disorder 5 years after receiving a blood transfusion from a donor who subsequently developed vCJD. Protease-resistant prion protein (PrP(res)) was detected by western blot, paraffin-embedded tissue blot, and immunohistochemistry in the spleen, but not in the brain. Immunohistochemistry for prion protein was also positive in a cervical lymph node. The patient was a heterozygote at codon 129 of PRNP, suggesting that susceptibility to vCJD infection is not confined to the methionine homozygous PRNP genotype. These findings have major implications for future estimates and surveillance of vCJD in the UK.

Variant CJD infection in the spleen of a neurologically asymptomatic UK adult patient with haemophilia

Summary.  All UK patients with bleeding disorders treated with any UK‐sourced pooled factor concentrates between 1980 and 2001 have been informed that they may be at an increased risk of infection with variant Creutzfeldt–Jakob disease (vCJD). We describe a study to detect disease‐associated, protease‐resistant prion protein (PrPres) in 17 neurologically aysmptomatic patients with haemophilia considered to be at increased risk of vCJD. Materials from 11 autopsy and seven biopsy cases were analysed for PrPres. The tissues available from each case were variable, ranging from a single biopsy sample to a wide range of autopsy tissues. A single specimen from the spleen of one autopsy case gave a strong positive result on repeated testing for PrPres by Western blot analysis. This tissue came from a 73‐year‐old male patient with no history of neurological disease, who was heterozygous (methionine/valine) at codon 129 in the prion protein gene. He had received over 9000 units of factor VIII concentrate prepared from plasma pools known to include donations from a vCJD‐infected donor, and some 400 000 units not known to include donations from vCJD‐infected donors. He had also received 14 units of red blood cells and had undergone several surgical and invasive endoscopic procedures. Estimates of the relative risks of exposure through diet, surgery, endoscopy, blood transfusion and receipt of UK‐sourced plasma products suggest that by far the most likely route of infection in this patient was receipt of UK plasma products.

Real time quaking-induced conversion analysis of cerebrospinal fluid in sporadic Creutzfeldt-Jakob disease

Current cerebrospinal fluid (CSF) tests for sporadic Creutzfeldt–Jakob disease (sCJD) are based on the detection of surrogate markers of neuronal damage such as CSF 14‐3‐3, which are not specific for sCJD. A number of prion protein conversion assays have been developed, including real time quaking‐induced conversion (RT‐QuIC). The objective of this study is to investigate whether CSF RT‐QuIC analysis could be used as a diagnostic test in sCJD.

In vitro amplification and detection of variant Creutzfeldt–Jakob disease PrPSc

Variant Creutzfeldt–Jakob disease (vCJD) poses a serious risk of secondary transmission and the need to detect infectivity in asymptomatic individuals is therefore of major importance. Following infection, it is assumed that minute amounts of disease‐associated prion protein (PrPSc) replicate by conversion of the host cellular prion protein (PrPC). Therefore, methods of rapidly reproducing this conversion process in vitro would be valuable tools in the development of such tests. We show that one such technique, protein misfolding cyclic amplification (PMCA), can amplify vCJD PrPSc from human brain tissue, and that the degree of amplification is dependent upon the substrate PRNP codon 129 polymorphism. Both human platelets and transgenic mouse brain are shown to be suitable alternative substrate sources, and amplified PrPSc can be detected using a conformation‐dependent immunoassay (CDI), allowing the detection of putative proteinase K sensitive forms of PrPSc. Copyright

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.

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

BACKGROUND: Four recent cases of transfusion‐related transmission of variant Creutzfeldt‐Jakob disease (vCJD) highlight the need to develop a highly sensitive and specific screening test to detect infectivity in the blood of asymptomatic infected individuals. Protein misfolding cyclic amplification (PMCA), a method for the amplification of minute amounts of disease‐associated abnormal prion protein (PrPSc) to readily detectable levels, could be incorporated into such a test provided that a suitable substrate source for routine use in human PMCA reactions can be found.

Abnormal prion protein in the retina of the most commonly occurring subtype of sporadic Creutzfeldt-Jakob disease

Background: Involvement of the eye has been reported in patients with variant Creutzfeldt-Jakob disease (vCJD), but there is disagreement on whether retinal involvement occurs in sporadic Creutzfeldt-Jakob disease (sCJD). Methods: Western blotting, paraffin embedded tissue blotting, and immunohistochemistry were used to test whether the abnormal form of the prion protein (PrPSc) accumulates to detectable levels in the eye in a case of the most common subtype of sCJD (MM1). Results: Low levels of PrPSc were detectable in the retina, localised to the plexiform layers of the central retina. PrPSc was not detectable in other ocular tissues. Conclusions: The abnormal form of the prion protein is present in the retina in the most common sCJD subtype (MM1), albeit at levels lower than those found previously in vCJD and in sCJD of the VV2 subtype.

Effects of human PrPSc type and PRNP genotype in an in-vitro conversion assay.

Prion protein type and codon 129 genotype are thought to be major determinants of susceptibility and phenotype in human prion diseases. Using an in-vitro system (protein misfolding cyclic amplification) we have attempted to model human prion protein conversion using the abnormal prion protein associated with each of the major sporadic Creutzfeldt–Jakob disease subtypes, in substrates containing the normal cellular form of the prion protein of each of the three possible human PRNP codon 129 polymorphic genotypes. The prion protein type is converted with fidelity in these amplification reactions, but the efficiency of conversion depends both on the methionine/valine polymorphic status of the sporadic Creutzfeldt–Jakob disease seed and substrate homogenate, and on the abnormal prion protein type.

Distinct Stability States of Disease-Associated Human Prion Protein Identified by Conformation-Dependent Immunoassay

ABSTRACT The phenotypic and strain-related properties of human prion diseases are, according to the prion hypothesis, proposed to reside in the physicochemical properties of the conformationally altered, disease-associated isoform of the prion protein (PrPSc), which accumulates in the brains of patients suffering from Creutzfeldt-Jakob disease and related conditions, such as Gerstmann-Straussler-Scheinker disease. Molecular strain typing of human prion diseases has focused extensively on differences in the fragment size and glycosylation site occupancy of the protease-resistant prion protein (PrPres) in conjunction with the presence of mutations and polymorphisms in the prion protein gene (PRNP). Here we report the results of employing an alternative strategy that specifically addresses the conformational stability of PrPSc and that has been used previously to characterize animal prion strains transmitted to rodents. The results show that there are at least two distinct conformation stability states in human prion diseases, neither of which appears to correlate fully with the PrPres type, as judged by fragment size or glycosylation, the PRNP codon 129 status, or the presence or absence of mutations in PRNP. These results suggest that conformational stability represents a further dimension to a complete description of potentially phenotype-related properties of PrPSc in human prion diseases.

Amyloid-β accumulation in the CNS in human growth hormone recipients in the UK

Human-to-human transmission of Creutzfeldt–Jakob disease (CJD) has occurred through medical procedures resulting in iatrogenic CJD (iCJD). One of the commonest causes of iCJD was the use of human pituitary-derived growth hormone (hGH) to treat primary or secondary growth hormone deficiency. As part of a comprehensive tissue-based analysis of the largest cohort yet collected (35 cases) of UK hGH-iCJD cases, we describe the clinicopathological phenotype of hGH-iCJD in the UK. In the 33/35 hGH-iCJD cases with sufficient paraffin-embedded tissue for full pathological examination, we report the accumulation of the amyloid beta (Aβ) protein associated with Alzheimer’s disease (AD) in the brains and cerebral blood vessels in 18/33 hGH-iCJD patients and for the first time in 5/12 hGH recipients who died from causes other than CJD. Aβ accumulation was markedly less prevalent in age-matched patients who died from sporadic CJD and variant CJD. These results are consistent with the hypothesis that Aβ, which can accumulate in the pituitary gland, was present in the inoculated hGH preparations and had a seeding effect in the brains of around 50% of all hGH recipients, producing an AD-like neuropathology and cerebral amyloid angiopathy (CAA), regardless of whether CJD neuropathology had occurred. These findings indicate that Aβ seeding can occur independently and in the absence of the abnormal prion protein in the human brain. Our findings provide further evidence for the prion-like seeding properties of Aβ and give insights into the possibility of iatrogenic transmission of AD and CAA.