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The inadvertent transmission of long incubating, untreatable and fatal neurodegenerative prionopathies, notably iatrogenic Creutzfeldt–Jakob disease, following transplantation of cadaver-derived corneas, pituitary growth, hormones and dura mater, constitutes a historical precedent which has underpinned the application of precautionary principles to modern day advanced cell therapies. To date these have been reflected by geographic or medical history risk-based deferral of tissue donors. Emergent understanding of other prion-like proteinopathies, their potential independence from prions as a transmissible agent and the variable capability of scalably manufacturable stem cells and derivatives to take up and clear or to propagate prions, substantiate further commitment to qualifying neurodegenerative proteinopathy transmission risks. This is especially so for those involving direct or facilitated access to a recipient’s brain or connected visual or nervous system such as for the treatment of stroke, retinal and adult onset neurodegenerative diseases, treatments for which have already commenced. In this review, we assess the prospective global dissemination of advanced cell therapies founded on transplantation or exposure to allogeneic human cells, recap lessons learned from the historical precedents of CJD transmission and review recent advances and current limits in understanding of prion and other neurodegenerative disease prion-like susceptibility and transmission. From these we propose grounds for a reassessment of the risks of emergent advanced cell therapies to transmit neuroproteinopathies and suggestions to ACT developers and regulators for risk mitigation and extension of criteria for deferrals. Electronic supplementary material The online version of this article (10.1007/s00401-018-1941-9) contains supplementary material, which is available to authorized users.

Chronic wasting disease (CWD) is a contagious and fatal neurodegenerative disease and a serious animal health issue for deer and elk in North America. The identification of the first cases of CWD among free-ranging reindeer and moose in Europe brings back into focus the unresolved issue of whether CWD can be zoonotic like bovine spongiform encephalopathy. We used a cell-free seeded protein misfolding assay to determine whether CWD prions from elk, white-tailed deer, and reindeer in North America can convert the human prion protein to the disease-associated form. We found that prions can convert, but the efficiency of conversion is affected by polymorphic variation in the cervid and human prion protein genes. In view of the similarity of reindeer, elk, and white-tailed deer in North America to reindeer, red deer, and roe deer, respectively, in Europe, a more comprehensive and thorough assessment of the zoonotic potential of CWD might be warranted.

Human prion diseases constitute a group of infectious and invariably fatal neurodegenerative disorders associated with misfolding of the prion protein. Variant Creutzfeldt-Jakob disease (vCJD) is a zoonotic prion disease linked to oral exposure to the infectious agent that causes bovine spongiform encephalopathy (BSE) in cattle. The most recent case of definite vCJD was heterozygous (MV) at polymorphic codon 129 of the prion protein gene PRNP while all of the previous 177 definite or probable vCJD cases who underwent genetic analysis were methionine homozygous (MM). Retrospective prevalence studies conducted on lympho-reticular tissue suggest that the number of asymptomatic vCJD carriers in the United Kingdom might be around 1 in 2000 people. In addition, there have been four known cases of the transmission of vCJD infection via blood transfusion. For these reasons, a sensitive, reliable, and fast diagnostic test is currently needed. We describe a rapid and highly sensitive seeding conversion assay that detects disease-associated prion protein in the brain and cerebrospinal fluid in vCJD after 48-96 h of amplification, with 100% sensitivity and specificity. This method can amplify prions from definite, probable, and possible vCJD cases from patients who are either MM or MV at PRNP-codon 129.

The human prion diseases comprise Creutzfeldt–Jakob disease, variably protease-sensitive prionopathy, Gerstmann–Straussler–Scheinker disease, fatal familial insomnia, and kuru. Each is a uniformly fatal rare neurodegenerative disease in which conformational changes in the prion protein are thought to be the central pathophysiologic event. The majority of cases of human prion diseases occur worldwide in the form of sporadic Creutzfeldt–Jakob disease and a minority of around 10–15% are associated with mutations of the prion protein gene, termed PRNP, in the forms of genetic Creutzfeldt–Jakob disease, Gerstmann–Straussler–Scheinker disease, and fatal familial insomnia. Prion diseases are also transmissible and occur in iatrogenic and zoonotic forms (iatrogenic Creutzfeldt–Jakob disease and variant Creutzfeldt–Jakob disease respectively), adding a public health dimension to their management. Despite having a high public profile, human prion diseases are both rare and heterogeneous in their clinicopathologic phenotype, sometimes making a diagnosis challenging. A combined clinical, genetic, neuropathologic, and biochemical approach to diagnosis is therefore essential. The intensive study of these diseases continues to inform on neurodegenerative mechanisms and the role of protein misfolding in more common neurodegenerative diseases such as Parkinson disease and Alzheimer disease.

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. Electronic supplementary material The online version of this article (doi:10.1007/s00401-017-1703-0) contains supplementary material, which is available to authorized users.

Aggregated and protease-resistant mammalian prion protein (PrPSc) is the primary protein component of infectious prions. Enriched PrPSc preparations are often used to study the mechanisms underlying prion disease. However, most enrichment procedures are relatively nonspecific and tend to yield significant amounts of non-PrPSc components, including various proteins that could confound functional and structural studies. It is thus important to identifythese proteins and assess their potential relevance to prion pathogenesis. Following proteinase K treatment and phosphotungstic acid precipitation of brain homogenate, we have used mass spectrometry to analyze the protein content of PrPSc isolated from prion-infected mice, multiple cases of sporadic Creutzfeldt-Jakob disease (sCJD), and human growth hormone associated casesof iatrogenic CJD (iCJD). Creatine kinase was the primary protein contaminant in all PrPSc samples while many of the other proteins identified were also found in non-CJD controls, suggesting that they are not CJD specific. Interestingly, the Alzheimer’s disease associated peptide amyloid β 1-42 (Aβ1-42) was identified in the majority of the sCJD cases as well as non-CJD age-matched controls while apoliprotein E was found in greater abundance in the sCJD cases. By contrast, while some of the iCJD cases showed evidence of higher molecular weight Aβ oligomers, monomeric Aβ1-42 peptide was not detected by immunoblot and only one case had significant levels of apolipoprotein E. Our data are consistent with the age-associated deposition of Aβ1-42 in older sporadic CJD and non-CJD patients and suggest that both apolipoprotein E and Aβ1-42 abundance can differ depending upon the type of CJD.

Variably protease-sensitive prionopathy (VPSPr) is a recently described neurodegenerative disorder characterised by the presence of spongiform encephalopathy and an unusual immunostaining and immunoblotting pattern for the disease-associated prion protein (PrPSc).1 This links VPSPr to human prion diseases, which are uniformly fatal disorders. The clinical symptoms and the longer duration of illness make VPSPr distinct from sporadic or idiopathic Creutzfeldt-Jakob disease (sCJD).1 Doxycycline treatment has been evaluated in patients with prion disease, however, there is little evidence that it can reverse the clinical symptoms or reduce the underlying disease progression once established.2 We present a patient with VPSPr who received doxycycline and survived for an extended period of time in an akinetic and mute state. Neuropathological examination was performed using published methods and various anti-PrP antibodies.3 Frozen tissues from selected brain regions were available for biochemical analysis. Tissues were analysed for the presence of protease-resistant PrP (PrPres) as previously described (see online supplementary material).4 In May 2007, a registered psychiatrist suspected an organic affective disorder in a 54-year-old Austrian woman. Two months earlier, medical work-up for presumed weight loss of 16 kg within the past 18 months had been unremarkable. In June 2007, the patient was admitted to a clinic that specialised in disorders of the nervous system. Her family history was negative for neurodegenerative diseases and there was no evidence of exposure to toxins. She reported depressed mood and short-term memory problems, and difficulties with balance, walking, driving and cooking. On neuropsychological examination she was oriented to time, place, person and situation, Mini-Mental State Examination score was 22/30, clock drawing test score was 3/9. She had word-finding difficulties, ideational apraxia, acalculia and visuoconstructive deficits. She displayed affective incontinence with crying fits. She had gait ataxia, and extensor plantar responses were observed with increased tone …

Sporadic Creutzfeldt-Jakob disease (sCJD) is the most prevalent of the human prion diseases, which are fatal and transmissible neurodegenerative diseases caused by the infectious prion protein (PrPSc). The origin of sCJD is unknown, although the initiating event is thought to be the stochastic misfolding of endogenous prion protein (PrPC) into infectious PrPSc. By contrast, human growth hormone-associated cases of iatrogenic CJD (iCJD) in the United Kingdom (UK) are associated with exposure to an exogenous source of PrPSc. In both forms of CJD, heterozygosity at residue 129 for methionine (M) or valine (V) in the prion protein gene may affect disease phenotype, onset and progression. However, the relative contribution of each PrPC allotype to PrPSc in heterozygous cases of CJD is unknown. Using mass spectrometry, we determined that the relative abundance of PrPSc with M or V at residue 129 in brain specimens from MV cases of sCJD was highly variable. This result is consistent with PrPC containing an M or V at residue 129 having a similar propensity to misfold into PrPSc thus causing sCJD. By contrast, PrPSc with V at residue 129 predominated in the majority of the UK human growth hormone associated iCJD cases, consistent with exposure to infectious PrPSc containing V at residue 129. In both types of CJD, the PrPSc allotype ratio had no correlation with CJD type, age at clinical onset, or disease duration. Therefore, factors other than PrPSc allotype abundance must influence the clinical progression and phenotype of heterozygous cases of CJD., Author Summary In Creutzfeldt-Jakob disease (CJD), heterozygosity at residue 129 for methionine or valine in normal prion protein may affect disease phenotype, onset and progression. However, the relative contribution of each prion protein allotype to the infectious, disease associated form of prion protein (PrPSc) is unknown. Here we report the novel observation that in heterozygous cases of sporadic CJD the PrPSc allotype ratio is highly variable. This case-by-case variability is consistent with the origin of sporadic CJD being the spontaneous, but random, misfolding of either host prion protein allotype into infectious PrPSc. By contrast, in heterozygous cases of iatrogenic CJD in the United Kingdom resulting from exposure to contaminated human growth hormone, the PrPSc allotype ratio is much more homogeneous and consistent with exposure to infectious PrPSc containing valine at residue 129. Surprisingly, the PrPSc allotype ratio did not correlate with disease onset or duration in either disease type. Thus, factors other than PrPSc allotype ratio likely influence the clinical progression of heterozygous cases of CJD. Moreover, our results suggest that the ratio of methionine to valine in PrPSc may be a means of determining the origin of prion infection.