BSE-associated prion-amyloid cardiomyopathy in primates

Hereditary E200K mutation within the prion protein gene alters human iPSC derived cardiomyocyte function

Cardiomyopathy is a co-morbidity of some prion diseases including genetic disease caused by mutations within the PrP gene (PRNP). Although the cellular prion protein (PrP) has been shown to protect against cardiotoxicity caused by oxidative stress, it is unclear if the cardiomyopathy is directly linked to PrP dysfunction. We differentiated cardiomyocyte cultures from donor human induced pluripotent stem cells and found a direct influence of the PRNP E200K mutation on cellular function. The PRNP E200K cardiomyocytes showed abnormal function evident in the irregularity of the rapid repolarization; a phenotype comparable with the dysfunction reported in Down Syndrome cardiomyocytes. PRNP E200K cardiomyocyte cultures also showed increased mitochondrial superoxide accompanied by increased mitochondrial membrane potential and dysfunction. To confirm that the changes were due to the E200K mutation, CRISPR-Cas9 engineering was used to correct the E200K carrier cells and insert the E200K mutation into control cells. The isotype matched cardiomyocytes showed that the lysine expressing allele does directly influence electrophysiology and mitochondrial function but some differences in severity were apparent between donor lines. Our results demonstrate that cardiomyopathy in hereditary prion disease may be directly linked to PrP dysfunction.

Analysis of non-human primate models for evaluating prion disease therapeutic efficacy

Prion disease is a fatal neurodegenerative disease caused by the conformational corruption of the prion protein (PrP), encoded by the prion protein gene (PRNP). While no disease-modifying therapy is currently available, genetic and pharmacological proofs of concept support development of therapies that lower PrP levels in the brain. In light of proposals for clinical testing of such drugs in presymptomatic individuals at risk for genetic prion disease, extensive nonclinical data are likely to be required, with extra attention paid to choice of animal models. Uniquely, the entire prion disease process can be faithfully modeled through transmission of human prions to non-human primates (NHPs), raising the question of whether NHP models should be used to assess therapeutic efficacy. Here we systematically aggregate data from N = 883 prion-inoculated animals spanning six decades of research studies. Using this dataset, we assess prion strain, route of administration, endpoint, and passage number to characterize the relationship of tested models to currently prevalent human subtypes of prion disease. We analyze the incubation times observed across diverse models and perform power calculations to assess the practicability of testing prion disease therapeutic efficacy in NHPs. We find that while some models may theoretically be able to support therapeutic efficacy studies, pilot studies would be required to confirm incubation time and attack rate before pivotal studies could be designed, cumulatively requiring several years. The models with the shortest and most tightly distributed incubation times are those with smaller brains and weaker homology to humans. Our findings indicate that it would be challenging to conduct efficacy studies in NHPs in a paradigm that honors the potential advantages of NHPs over other available models, on a timeframe that would not risk unduly delaying patient access to promising drug candidates.

Cardiomyopathy associated with Ceutzfeld-Jakob disease: a diagnosis of exclusion: a case report

Background

Creutzfeldt–Jakob disease (CJD), the most common prion disease in humans, is primarily known for its adverse neurological impact and inevitable mortality. Data regarding myocardial involvement in CJD are scarce.

Case summary

A 54-year-old female patient, presented with progressive effort dyspnoea, was diagnosed with unexplained non-ischaemic cardiomyopathy. An extensive cardiac work-up including cardiac magnetic resonance imaging (MRI) did not reveal any underlying aetiology. Simultaneously, the patient developed involuntary limb movements and progressive cognitive decline. Thalamic high-signal abnormalities on diffusion-weighted images were apparent on brain MRI. Based on these findings, she was subsequently referred to a neurology department, where she suddenly died the day after her admission. Brain autopsy demonstrated spongiform encephalopathy. A genetic analysis performed to her son revealed a mutation in the PRNP gene; all of these were consistent with CJD.

Discussion

This case describes the clinical association of CJD and cardiomyopathy and the diagnosis prion-induced cardiomyopathy by exclusion. It is not inconceivable that the coexistence of these two clinical entities may be related to genetic expression and contemporaneously deposition of infectious prions in myocardial muscle and brain tissue. Awareness of this possible association could be of important public-safety concern, and merits further collaborative cardiac-neurological work-up to elucidate this phenotype among patients with unexplained cardiomyopathy with neurological symptoms that resemble CJD.

Unexpected prion phenotypes in experimentally transfused animals: predictive models for humans?

The recently reevaluated high prevalence of healthy carriers (1/2,000 in UK) of variant Creutzfeldt-Jakob Disease (v-CJD), whose blood might be infectious, suggests that the evolution of this prion disease might not be under full control as expected. After experimental transfusion of macaques and conventional mice with blood derived from v-CJD exposed (human and animal) individuals, we confirmed in these both models the transmissibility of v-CJD, but we also observed unexpected neurological syndromes transmissible by transfusion: despite their prion etiology confirmed through transmission experiments, these original cases would escape classical prion diagnosis, notably in the absence of detectable abnormal PrP with current techniques. It is noteworthy that macaques developed an original, yet undescribed myelopathic syndrome associating demyelination and pseudo-necrotic lesions of spinal cord, brainstem and optical tract without affecting encephalon, which is rather evocative of spinal cord disease than prion disease in human medicine. These observations strongly suggest that the spectrum of human prion diseases may extend the current field restricted to the phenotypes associated to protease-resistant PrP, and may notably include spinal cord diseases.

Ultrastructure and pathology of prion protein amyloid accumulation and cellular damage in extraneural tissues of scrapie-infected transgenic mice expressing anchorless prion protein

In most human and animal prion diseases the abnormal disease-associated prion protein (PrPSc) is deposited as non-amyloid aggregates in CNS, spleen and lymphoid organs. In contrast, in humans and transgenic mice with PrP mutations which cause expression of PrP lacking a glycosylphosphatidylinositol (GPI)-anchor, most PrPSc is in the amyloid form. In transgenic mice expressing only anchorless PrP (tg anchorless), PrPSc is deposited not only in CNS and lymphoid tissues, but also in extraneural tissues including heart, brown fat, white fat, and colon. In the present paper, we report ultrastructural studies of amyloid PrPSc deposition in extraneural tissues of scrapie-infected tg anchorless mice. Amyloid PrPSc fibrils identified by immunogold-labeling were visible at high magnification in interstitial regions and around blood vessels of heart, brown fat, white fat, colon, and lymphoid tissues. PrPSc amyloid was located on and outside the plasma membranes of adipocytes in brown fat and cardiomyocytes, and appeared to invaginate and disrupt the plasma membranes of these cell types, suggesting cellular damage. In contrast, no cellular damage was apparent near PrPSc associated with macrophages in lymphoid tissues and colon, with enteric neuronal ganglion cells in colon or with adipocytes in white fat. PrPSc localized in macrophage phagolysosomes lacked discernable fibrils and might be undergoing degradation. Furthermore, in contrast to wild-type mice expressing GPI-anchored PrP, in lymphoid tissues of tg anchorless mice, PrPSc was not associated with follicular dendritic cells (FDC), and FDC did not display typical prion-associated pathogenic changes.

Prions

Abstract. Prions gained widespread public and scientific interest in the year 2000. At that time, the human neurological Creutzfeldt–Jakob disease (CJD) was known. However, new CJD cases were diagnosed but they could not be ascribed to one of the classical CJD categories i.e. sporadic (sCJD), hereditary or acquired. Hence, they were classified as variant CJD (vCJD). Later on, experimental evidence suggested that vCJD was caused by prions postulated as unique novel infectious agents and, for example, responsible for bovine spongiform encephalopathy (BSE) also known as mad cow disease. The infection of humans by transmission of BSE prions also defined vCJD as a zoonotic disease. Prions, especially those associated with scrapie in sheep had been known for quite some time and misleadingly discussed as a slow virus. Therefore, this enigmatic pathogen and the transmission of this unusual infectious agent was a matter of a controversial scientific debate. An agent without nucleic acid did not follow the current dogma postulating DNA or RNA as inheritable information encoding molecules. Although numerous experimental results clearly demonstrated the infectious capacity of prions in several animal species, a model close to human was not readily available. Therefore, the use of rhesus monkeys (Macaca mulatta) served as a non-human primate model to elucidate prion infection under controlled experimental conditions. Not the least, transmission of BSE, human vCJD, and sCJD prions could be confirmed in our study. Any prion infection concomitant with progression of disease in humans, especially vCJD, could be analyzed only retrospectively and at late stages of disease. In contrast, the prion-infected rhesus monkeys were accessible before and after infection; the progression from early stage to late clinical stages – and eventually death of the animal – could be traced. Because of the phylogenetic proximity to humans, the rhesus monkey was superior to any rodent or other animal model. For these reasons an experimental approach had been conceived by J. Collinge in London and A. Aguzzi in Zurich and performed in a cooperative study with both research groups in the pathology unit of the German Primate Center (DPZ). The study in the DPZ lasted from 2001 until 2012. Our research in the pathology unit provided a temporal monitoring of how an initial prion infection develops eventually into disease; an approach that would have never been possible in humans since the time point of infection with prions from, for example, BSE is always unknown. Telemetry revealed a shift in sleep–wake cycles early on, long before behavioral changes or clinical symptoms appeared. Pathology confirmed non-neuronal tissue as hidden places where prions exist. The rhesus model also allowed first comparative studies of epigenetic modifications on RNA in peripheral blood and brain tissue collected from uninfected and prion-infected animals. To conclude, our studies clearly demonstrated that this model is valid since progression to disease is almost identical to human CJD.

Porcine prion protein amyloid

Mammalian prions are composed of misfolded aggregated prion protein (PrP) with amyloid-like features. Prions are zoonotic disease agents that infect a wide variety of mammalian species including humans. Mammals and by-products thereof which are frequently encountered in daily life are most important for human health. It is established that bovine prions (BSE) can infect humans while there is no such evidence for any other prion susceptible species in the human food chain (sheep, goat, elk, deer) and largely prion resistant species (pig) or susceptible and resistant pets (cat and dogs, respectively). PrPs from these species have been characterized using biochemistry, biophysics and neurobiology. Recently we studied PrPs from several mammals in vitro and found evidence for generic amyloidogenicity as well as cross-seeding fibril formation activity of all PrPs on the human PrP sequence regardless if the original species was resistant or susceptible to prion disease. Porcine PrP amyloidogenicity was among the studied. Experimentally inoculated pigs as well as transgenic mouse lines overexpressing porcine PrP have, in the past, been used to investigate the possibility of prion transmission in pigs. The pig is a species with extraordinarily wide use within human daily life with over a billion pigs harvested for human consumption each year. Here we discuss the possibility that the largely prion disease resistant pig can be a clinically silent carrier of replicating prions.

Immunodeficiency viruses and prion disease

Abstract. Two threatening human diseases have emerged during the past 35 years. Human immunodeficiency virus (HIV) was transmitted from non-human primates – e.g., the chimpanzee to humans – and then spread into populations all over the world. To date, around 35 million people are infected and no vaccine is available because the virus undergoes rapid mutation, resulting in a swarm of virus strains. At best, therapeutical intervention is possible with antiviral drugs; however because of its capacity to rapidly mutate, resistant virus strains develop. Since non-human primates (NHPs) carry simian immunodeficiency virus (SIV), we could assess infection and immunity by SIV/HIV in rhesus monkeys (M. mulatta) as a model for acquired immunodeficiency syndrome (AIDS). Transmissible spongiform encephalopathy (TSE) emerged in ruminants in the 1980s and shortly thereafter appeared in humans, leading to variant Creutzfeldt–Jakob disease (vCJD). The vCJD is a terminal neurological disorder since it heavily and irreversibly damages the brain. No cure is at hand. The causative agents for TSE are prions. They are unusual pathogens and enigmatic since they lack nucleic acid as inheritable information. On the other hand, prions were suspected as infectious agents for years and suspected to be the etiological agent of scrapie in sheep. Molecular biology and medicine have clearly identified prions in recent years as the responsible agent for bovine spongiform encephalopathy in ruminants (BSE). BSE has been transmitted to humans, resulting in around 225 vCJD cases. Similar to the SIV/HIV model for Acquired Immunodeficiency Syndrome (AIDS), we could establish a prion infection model in rhesus monkeys. HIV/AIDS and vCJD are zoonoses since their original pathogens can be transmitted from animals to humans. Our experimental efforts to understand these intriguing pathogens and their corresponding diseases in rhesus monkeys as a valid model for both human diseases are summarized in this review.

Lack of prion infectivity in fixed heart tissue from patients with Creutzfeldt-Jakob disease or amyloid heart disease

In most forms of prion disease, infectivity is present primarily in the central nervous system or immune system organs such as spleen and lymph node. However, a transgenic mouse model of prion disease has demonstrated that prion infectivity can also be present as amyloid deposits in heart tissue. Deposition of infectious prions as amyloid in human heart tissue would be a significant public health concern. Although abnormal disease-associated prion protein (PrP(Sc)) has not been detected in heart tissue from several amyloid heart disease patients, it has been observed in the heart tissue of a patient with sporadic Creutzfeldt-Jakob Disease (sCJD), the most common form of human prion disease. In order to determine whether prion infectivity can be found in heart tissue, we have inoculated formaldehyde fixed brain and heart tissue from two sCJD patients, as well as prion protein positive fixed heart tissue from two amyloid heart disease patients, into transgenic mice overexpressing the human prion protein. Although the sCJD brain samples led to clinical or subclinical prion infection and deposition of PrP(Sc) in the brain, none of the inoculated heart samples resulted in disease or the accumulation of PrP(Sc). Thus, our results suggest that prion infectivity is not likely present in cardiac tissue from sCJD or amyloid heart disease patients.