Creutzfeldt-Jakob disease with Alzheimer-type A beta-reactive amyloid plaques

The Quest for Cellular Prion Protein Functions in the Aged and Neurodegenerating Brain

Cellular (also termed ‘natural’) prion protein has been extensively studied for many years for its pathogenic role in prionopathies after misfolding. However, neuroprotective properties of the protein have been demonstrated under various scenarios. In this line, the involvement of the cellular prion protein in neurodegenerative diseases other than prionopathies continues to be widely debated by the scientific community. In fact, studies on knock-out mice show a vast range of physiological functions for the protein that can be supported by its ability as a cell surface scaffold protein. In this review, we first summarize the most commonly described roles of cellular prion protein in neuroprotection, including antioxidant and antiapoptotic activities and modulation of glutamate receptors. Second, in light of recently described interaction between cellular prion protein and some amyloid misfolded proteins, we will also discuss the molecular mechanisms potentially involved in protection against neurodegeneration in pathologies such as Alzheimer’s, Parkinson’s, and Huntington’s diseases.

Production of seedable Amyloid-β peptides in model of prion diseases upon PrPSc-induced PDK1 overactivation

The presence of amyloid beta (Aβ) plaques in the brain of some individuals with Creutzfeldt-Jakob or Gertsmann-Straussler-Scheinker diseases suggests that pathogenic prions (PrP^Sc) would have stimulated the production and deposition of Aβ peptides. We here show in prion-infected neurons and mice that deregulation of the PDK1-TACE α-secretase pathway reduces the Amyloid Precursor Protein (APP) α-cleavage in favor of APP β-processing, leading to Aβ40/42 accumulation. Aβ predominates as monomers, but is also found as trimers and tetramers. Prion-induced Aβ peptides do not affect prion replication and infectivity, but display seedable properties as they can deposit in the mouse brain only when seeds of Aβ trimers are co-transmitted with PrP^Sc. Importantly, brain Aβ deposition accelerates death of prion-infected mice. Our data stress that PrP^Sc, through deregulation of the PDK1-TACE-APP pathway, provokes the accumulation of Aβ, a prerequisite for the onset of an Aβ seeds-induced Aβ pathology within a prion-infectious context.

Aβ plaques have been detected in brains of patients with prion diseases. Here, using mice, the authors show that prion infection enhances Aβ production via a PDK1-TACE mechanism and that brain deposition of Aβ induced by Aβ seeds co-transmitted with PrP^Sc contributes to mortality in prion disease.

Molecular Mechanisms for Herpes Simplex Virus Type 1 Pathogenesis in Alzheimer's Disease

This review focuses on research in the areas of epidemiology, neuropathology, molecular biology and genetics that implicates herpes simplex virus type 1 (HSV-1) as a causative agent in the pathogenesis of sporadic Alzheimer’s disease (AD). Molecular mechanisms whereby HSV-1 induces AD-related pathophysiology and pathology, including neuronal production and accumulation of amyloid beta (Aβ), hyperphosphorylation of tau proteins, dysregulation of calcium homeostasis, and impaired autophagy, are discussed. HSV-1 causes additional AD pathologies through mechanisms that promote neuroinflammation, oxidative stress, mitochondrial damage, synaptic dysfunction, and neuronal apoptosis. The AD susceptibility genes apolipoprotein E (APOE), phosphatidylinositol binding clathrin assembly protein (PICALM), complement receptor 1 (CR1) and clusterin (CLU) are involved in the HSV lifecycle. Polymorphisms in these genes may affect brain susceptibility to HSV-1 infection. APOE, for example, influences susceptibility to certain viral infections, HSV-1 viral load in the brain, and the innate immune response. The AD susceptibility gene cholesterol 25-hydroxylase (CH25H) is upregulated in the AD brain and is involved in the antiviral immune response. HSV-1 interacts with additional genes to affect cognition-related pathways and key enzymes involved in Aβ production, Aβ clearance, and hyperphosphorylation of tau proteins. Aβ itself functions as an antimicrobial peptide (AMP) against various pathogens including HSV-1. Evidence is presented supporting the hypothesis that Aβ is produced as an AMP in response to HSV-1 and other brain infections, leading to Aβ deposition and plaque formation in AD. Epidemiologic studies associating HSV-1 infection with AD and cognitive impairment are discussed. Studies are reviewed supporting subclinical chronic reactivation of latent HSV-1 in the brain as significant in the pathogenesis of AD. Finally, the rationale for and importance of clinical trials treating HSV-1-infected MCI and AD patients with antiviral medication is discussed.

Detection of prion infection in variant Creutzfeldt-Jakob disease: a blood-based assay

BACKGROUND

Variant Creutzfeldt-Jakob disease (vCJD) is a fatal neurodegenerative disorder originating from exposure to bovine-spongiform-encephalopathy-like prions. Prion infections are associated with long and clinically silent incubations. The number of asymptomatic individuals with vCJD prion infection is unknown, posing risk to others via blood transfusion, blood products, organ or tissue grafts, and contaminated medical instruments. We aimed to establish the sensitivity and specificity of a blood-based assay for detection of vCJD prion infection.

METHODS

We developed a solid-state binding matrix to capture and concentrate disease-associated prion proteins and coupled this method to direct immunodetection of surface-bound material. Quantitative assay sensitivity was assessed with a serial dilution series of 10⁻⁷ to 10⁻¹⁰ of vCJD prion-infected brain homogenate into whole human blood, with a baseline control of normal human brain homogenate in whole blood (10⁻⁶). To establish the sensitivity and specificity of the assay for detection of endogenous vCJD, we analysed a masked panel of 190 whole blood samples from 21 patients with vCJD, 27 with sporadic CJD, 42 with other neurological diseases, and 100 normal controls. Samples were masked and numbered by individuals independent of the assay and analysis. Each sample was tested twice in independent assay runs; only samples that were reactive in both runs were scored as positive overall.

FINDINGS

We were able to distinguish a 10⁻¹⁰ dilution of exogenous vCJD prion-infected brain from a 10⁻⁶ dilution of normal brain (mean chemiluminescent signal, 1·3×10⁵ [SD 1·1×10⁴] for vCJD vs 9·9×10⁴ [4·5×10³] for normal brain; p<0·0001)—an assay sensitivity that was orders of magnitude higher than any previously reported. 15 samples in the masked panel were scored as positive. All 15 samples were from patients with vCJD, showing an assay sensitivity for vCJD of 71·4% (95% CI 47·8–88·7) and a specificity of 100% (95% CIs between 97·8% and 100%).

INTERPRETATION

These initial studies provide a prototype blood test for diagnosis of vCJD in symptomatic individuals, which could allow development of large-scale screening tests for asymptomatic vCJD prion infection.

FUNDING

UK Medical Research Council.

Codistribution of amyloid beta plaques and spongiform degeneration in familial Creutzfeldt-Jakob disease with the E200K-129M haplotype

BACKGROUND

Dominantly inherited Creutzfeldt-Jakob disease (CJD) represents 5% to 15% of all CJD cases. The E200K mutation in the prion protein (PrP) gene (PRNP) is the most frequent cause of familial CJD. Coexistent amyloid beta (Abeta) plaques have been reported in some transmissible spongiform encephalopathies but to date have not been reported in familial CJD with the E200K mutation.

OBJECTIVE

To characterize a family with CJD in which Abeta plaques codistribute with spongiform degeneration.

DESIGN

Clinicopathologic and molecular study of a family with CJD with the E200K-129M haplotype.

SETTING

Alzheimer disease research center.

PARTICIPANTS

Two generations of a family.

MAIN OUTCOME MEASURES

Clinical, biochemical, and neuropathologic observations in 2 generations of a family.

RESULTS

In this kindred, 3 autopsied cases showed pathologic changes typical for the E200K-129M haplotype, including spongiform degeneration, gliosis, neuronal loss, and PrP deposition. Moreover, 2 of these cases (ages 57 and 63 years) showed numerous Abeta plaques codistributed with spongiform degeneration. APOE genotyping in 2 cases revealed that Abeta plaques were present in the APOE epsilon4 carrier but not in the APOE epsilon4 noncarrier. Two additional cases exhibited incomplete penetrance, as they had no clinical evidence of CJD at death after age 80 years but had affected siblings and children.

CONCLUSIONS

To our knowledge, this is the first description of Abeta plaques in familial CJD with the E200K mutation. The codistribution of plaques and CJD-associated changes suggests that PrP plays a central role in Abeta formation and that Abeta pathology and prion disease likely in fluence each other. The kindred described herein provides support that PrP(E200K) may result in increased Abeta deposition.

Involvement of Dab1 in APP processing and beta-amyloid deposition in sporadic Creutzfeldt-Jakob patients

Alzheimer's disease and prion pathologies (e.g., Creutzfeldt-Jakob disease (CJD)) display profound neural lesions associated with aberrant protein processing and extracellular amyloid deposits. Dab1 has been implicated in the regulation of amyloid precursor protein (APP), but a direct link between human prion diseases and Dab1/APP interactions has not been published. Here we examined this putative relationship in 17 cases of sporadic CJD (sCJD) post-mortem. Biochemical analyses of brain tissue revealed two groups, which also correlated with PrP(sc) types 1 and 2. One group with PrP(sc) type 1 showed increased Dab1 phosphorylation and lower betaCTF production with an absence of Abeta deposition. The second sCJD group, which carried PrP(sc) type 2, showed lower levels of Dab1 phosphorylation and betaCTF production, and Abeta deposition. Thus, the present observations suggest a correlation between Dab1 phosphorylation, Abeta deposition and PrP(sc) type in sCJD.

Cerebral amyloid angiopathy with co-localization of prion protein and beta-amyloid in an 85-year-old patient with sporadic Creutzfeldt-Jakob disease

We report on an 85-year-old woman with hypertensive cerebral arteriolosclerosis who presented with rapidly progressive encephalopathy leading to death within 4 months. Magnetic resonance imaging showed mild cortical atrophy consistent with her age and diffuse leukoaraiosis. Her CSF 14-3-3 protein was positive. Neuropathology showed severe spongiform change and gliosis in the grey matter and immunohistochemistry revealed diffuse prion protein deposition in a predominant synaptic pattern. She had no family history of neurological disorder and genotyping did not show any prion protein gene mutation, in keeping with a diagnosis of sporadic Creutzfeldt-Jakob disease. There was also diffuse amyloid angiopathy involving the cortical and leptomeningeal arterioles of the cerebral hemispheres and cerebellum and the capillaries of the grey matter. The amyloid angiopathy expressed beta-amyloid but also prion protein and double immunostaining confirmed co-localization of both proteins in many vessel walls. Alzheimer's type pathology was restricted to a few diffuse beta-amyloid plaques in the entorhinal cortex and rare tangles in the hippocampus. Deposition of prion protein in cerebral vessels has been reported in a single case of stop codon 145 mutation of the PRNP gene. Co-localization of beta-amyloid and prion protein in the same amyloid plaque has been described in elderly patients with Creutzfeldt-Jakob or Gerstmann-Sträussler-Scheinker diseases but only exceptionally in cerebral amyloid angiopathy. In this patient, hypertensive cerebrovascular disease may have contributed to the failure to eliminate both proteins from the brain.

Alzheimer-type neuropathology in a 28 year old patient with iatrogenic Creutzfeldt-Jakob disease after dural grafting

We report the case of a 28 year old man who had received a cadaverous dura mater graft after a traumatic open skull fracture with tearing of the dura at the age of 5 years. A clinical suspicion of Creutzfeldt-Jakob disease (CJD) was confirmed by a brain biopsy 5 months prior to death and by autopsy, thus warranting the diagnosis of iatrogenic CJD (iCJD) according to WHO criteria. Immunohistochemistry showed widespread cortical depositions of disease associated prion protein (PrP(sc)) in a synaptic pattern, and western blot analysis identified PrP(sc) of type 2A according to Parchi et al. Surprisingly, we found Alzheimer-type senile plaques and cerebral amyloid angiopathy in widespread areas of the brain. Plaque-type and vascular amyloid was immunohistochemically identified as deposits of beta-A4 peptide. CERAD criteria for diagnosis of definite Alzheimer's disease (AD) were met in the absence of neurofibrillar tangles or alpha-synuclein immunoreactive inclusions. There was no family history of AD, CJD, or any other neurological disease, and genetic analysis showed no disease specific mutations of the prion protein, presenilin 1 and 2, or amyloid precursor protein genes. This case represents (a) the iCJD case with the longest incubation time after dural grafting reported so far, (b) the youngest documented patient with concomitant CJD and Alzheimer-type neuropathology to date, (c) the first description of Alzheimer-type changes in iCJD, and (d) the second case of iCJD in Austria. Despite the young patient age, the Alzheimer-type changes may be an incidental finding, possibly related to the childhood trauma.

Neuropathological characterisation of French bovine spongiform encephalopathy cases

Bovine spongiform encephalopathy (BSE) in cattle is a neurodegenerative disease belonging to the transmissible spongiform encephalopathies, a group of diseases including sheep scrapie and human Creutzfeldt-Jakob disease. The pathological characteristics of BSE are vacuolation, mild gliosis, little neuronal degeneration without inflammatory process and abnormal prion protein (PrPsc) accumulation. The aim of this study was to define precisely the neuropathology of BSE in French cases by assessing the distributions of vacuolar lesions and PrPsc within cattle brains. We showed that vacuolation and PrPsc accumulation varied from one structure to the other, and most often coexisted. These distributions were in accordance with British and Portuguese data previously published. Seven types of PrPsc immunolabelling were described based on morphology and localisation. Besides mild gliosis mainly associated with vacuolation, we observed a very slight neuronal apoptosis. In addition, we saw a moderate vimentin labelling colocalised with vacuolation, a discrete ubiquitin staining and no Tau protein staining. This study provides precise histopathological data that will be completed with a quantitative study on more than 100 obex samples of French BSE cases.

Spatial pattern of prion protein deposits in patients with sporadic Creutzfeldt-Jakob disease

The spatial pattern of the prion protein (PrP) deposits was studied in the cerebral cortex and cerebellum in 10 patients with sporadic Creutzfeldt-Jakob disease (CJD). In all patients the PrP deposits were aggregated into clusters and, in 90% of cortical areas and in 50% of cerebellar sections, the clusters exhibited a regular periodicity parallel to the tissue boundary; a spatial pattern also exhibited by beta-amyloid (Abeta) deposits in Alzheimer's disease (AD). In the cerebral cortex, the incidence of regular clustering of the PrP deposits was similar in the upper and lower cortical laminae. The sizes of the PrP clusters in the upper and lower cortex were uncorrelated. No significant differences in mean cluster size of the PrP deposits were observed between brain regions. The size, location and distribution of the PrP deposit clusters suggest that PrP deposition occurs in relation to specific anatomical pathways and supports the hypothesis that prion pathology spreads through the brain via such pathways. In addition, the data suggest that there are similarities in the pathogenesis of extracellular protein deposits in prion disease and in AD.

The spatial patterns of prion protein deposits in Creutzfeldt-Jakob disease: comparison with beta-amyloid deposits in Alzheimer's disease

Similar pathological processes may be involved in the deposition of extracellular proteins in the brains of patients with Creutzfeldt-Jakob disease (CJD) and Alzheimer's disease (AD). Hence, this study compared the spatial patterns of prion protein (PrP) deposits in the cerebral cortex and hippocampus in cases of sporadic CJD with those of beta-amyloid (Abeta) deposits in sporadic AD. PrP and Abeta deposits were aggregated into clusters and, in 90% of brain areas in CJD and 57% in AD, the clusters were regularly distributed parallel to the tissue boundary. In a significant proportion of cortical analyses, the mean diameter of the clusters of PrP and Abeta deposits were similar to those of the cells of origin of the cortico-cortical pathways. Abeta deposits in AD were distributed more frequently in larger-sized clusters than PrP deposits in CJD. In addition, in the hippocampus and dentate gyrus, clustering of Abeta deposits was observed in AD but PrP deposits were rare in these regions in CJD. The size, location and distribution of the extracellular protein deposits within the cortex of both disorders was consistent with the degeneration of the cortico-cortical pathways. Furthermore, spread of the pathology along these pathways may be a pathogenic feature common to CJD and AD.

Importance of immunological and inflammatory processes in the pathogenesis and therapy of Alzheimer's disease

The contribution of autoimmune processes or inflammatory components in the etiology and pathogenesis of Alzheimer's disease (AD) has been suspected for many years. The presence of antigen-presenting, HLA-DR-positive and other immunoregulatory cells, components of complement, inflammatory cytokines and acute phase reactants have been established in tissue of AD neuropathology. Although these data do not confirm the immune response as a primary cause of AD, they indicate involvement of immune processes at least as a secondary or tertiary reaction to the preexisting pathogen and point out its driving-force role in AD pathogenesis. These processes may contribute to systemic immune response. Thus, experimental and clinical studies indicate impairments in both humoral and cellular immunity in an animal model of AD as well as in AD patients. On the other hand, anti-inflammatory drugs applied for the treatment of some chronic inflammatory diseases have been shown to reduce risk of AD in these patients. Therefore, it seems that anti-inflammatory drugs and other substances which can control the activity of immunocompetent cells and the level of endogenous immune response can be valuable in the treatment of AD patients.