Amyloid plaques in the brains of mice with Creutzfeldt-Jakob disease

Diffusion-weighted magnetic resonance imaging in dura mater graft-associated Creutzfeldt-Jakob disease

PURPOSE

To elucidate the extension patterns of the hyperintense areas on diffusion-weighted magnetic resonance imaging (DW-MRI) in patients with dura mater graft-associated Creutzfeldt-Jakob disease (dCJD).

METHODS

We collected the DW-MRI of dCJD cases identified by the CJD Surveillance Committee in Japan, between April 1999 and February 2018. The dCJD cases were classified into non-plaque and plaque-types. The relationship among the abnormal signals, the pathological classification, and the sites of grafting were analyzed.

RESULTS

We collected DW-MRI of 11 patients with dCJD, all of whom were methionine homozygous at codon 129 of the prion protein gene. The age at onset was 41 (26-76) [median (range)] years, the age at dural grafting was 19 (10-53) years, and the incubation period was 22 (16-29) years. Eight dCJD cases were classified as non-plaque-type and three cases were plaque-type. Five of the non-plaque-type cases and all the plaque-type cases were pathologically confirmed. Brain DW-MRI was performed 3 (1-22) months after the onset. Most of the non-plaque-type cases showed brighter hyperintensity in the cerebral cortex and basal ganglia on the side of dural grafting. Subsequent DW-MRI showed widespread hyperintense lesions in the brain. Regarding the plaque-type cases, initial scans showed hyperintensity in the basal ganglia and the thalamus in one patient. Another patient's lesion was confined to the basal ganglia. The third patient showed no abnormalities seven months post-onset; however, serial images showed a hyperintensity confined to the thalamus.

CONCLUSIONS

Non-plaque and plaque-types demonstrated different patterns of propagation of distinct prion strains.

Neuropathology of unconventional virus infections: molecular pathology of spongiform change and amyloid plaque deposition

To the triad of neuronal loss, gliosis and spongiform change as characteristic morphological changes associated with infection of the central nervous system, one can now add the presence of scrapie-associated filaments (SAF)/PrP rods. While the host's immune response is conspicuous by its absence, the vigorous astrocytic response is presumptive evidence of the host's ability to recognize and respond to the primary neuronal insult. We assume that the spongiform change and vacuolation of neurons are of fundamental importance in the pathogenesis of the disease, realizing that neither is specific or essential for the replication of the infectious agent. The topographical distribution of lesions is partly explained by the portal of entry and retrograde spread of the virus. The temporal progression of the lesions is more clearly determined by the host genes, best illustrated by studies of the incubation period. The molecular basis of the spongiform change is unknown but it is presumed to involve some disturbance of membrane metabolism. The recognition of PrP as a membrane glycoprotein invites proposals for its role in the development of these spongiform lesions. Extracellular amyloid occurs as plaques or congophilic angiopathy in some instances, and provides the best evidence that Alzheimer's disease (AD) is in some way related to the unconventional virus diseases. However, the protein subunit (A4) of the amyloid fibril in AD and its precursor are quite distinct from the PrP subunit which constitutes the amyloid fibril in these infectious diseases. It is still unclear whether the PrP subunit in the SAF has exactly the same composition as in the extracellular amyloid fibril. Our results suggest that only a fragment of the PrP molecule is the major constituent of the extracellular fibril. Since both PrP and A4 are derived from membrane glycoproteins, the elucidation of their normal function is likely to lead to a better understanding of the spongiform and amyloidogenic lesions in these diseases.

Creutzfeldt-Jakob disease

It is valuable to summarize the milestone study of prion diseases done in Japan for review in the journal Neuropathology in 2000. Many studies done in Japan promote world prion research activity, and also influence further research projects in other groups abroad. In this review the author focuses on the transmission experiment, the discovery of abnormal prion protein localization in the synaptic structures or follicular dendritic cells, and the genetic analysis of prion protein gene for the establishment of familial prion diseases.

Follicular dendritic cells and dissemination of Creutzfeldt-Jakob disease

The contribution of immune system cells to the propagation of transmissible encephalopathies is not well understood. To determine how follicular dendritic cells (FDC) may act, we challenged lymphotoxin beta null and wild-type (wt) controls with a Creutzfeldt-Jakob disease (CJD) agent. There was only a small difference in incubation time to clinical disease even after peripheral challenge with low infectious doses (31 in a total of 410 days). Brain pathology with extensive microglial infiltration, identified by keratan sulfate, as well as astrocytic hypertrophy, was also equivalent in all groups despite the fact that null mice had neither FDC nor splenic metallophilic macrophages that filter particulate antigen. Because FDC accumulate pathologic prion protein (PrP) in infected but not wt mice, we studied the cellular distribution of PrP by confocal microscopy. The majority of pathologic PrP collected on the plasma membrane of FDC, as identified by the Ca(+2)-binding protein S100A. This surface distribution suggested that agent aggregated with pathologic PrP might spread by cell-to-cell contacts. While several types of leukocytes may be involved in agent dissemination, cells of myeloid lineage were found to be infectious. Moreover, perivascular tracks of microglia and abnormal PrP after intraperitoneal inoculation were consistent with hematogenous spread. In summary, FDC are not required for CJD agent spread from the periphery, although FDC may enhance spread through surface accumulation of pathologic PrP. While it is still not clear where the infectious agent replicates, macrophages can sequester appreciable levels of infectivity and hence act as reservoirs for prolonged latent infection.

Vaccination with an attenuated Creutzfeldt-Jakob disease strain prevents expression of a virulent agent

Although slow and persistent viruses often escape host defenses infection may be prevented by live vaccines. To determine whether an attenuated "slow" strain of the Creutzfeldt-Jakob disease agent (SY) could block expression of a virulent "fast" strain (FU), outbred CD-1 mice were inoculated intracerebrally with low infectious doses of SY and challenged 80 days later with higher doses of FU. For comparison, the same SY and FU samples were inoculated in two parallel control groups. All 18 superinfected mice showed incubation times identical to those inoculated with only the SY strain, yielding clinical disease >110 days later than predicted for the FU strain. Neurological signs, such as scratching and an extended clinical phase, were also characteristic for SY but not FU infection. Moreover, the widespread cortical pathology of FU was not detectable in superinfected mice. Western blot analyses further showed no strain-specific differences in prion protein (PrP) band profiles for all experimental groups, although there was approximately 10-fold more protease-resistant PrP (PrP-res) in FU brains during terminal disease. In contrast, infectivity assays revealed an approximately 10,000-fold difference between SY and FU at terminal stages, indicating that PrP-res content does not correlate with infectivity. In summary, an attenuated strain of the Creutzfeldt-Jakob disease agent evokes substantial interference against a virulent agent. Because superinfected mice had little PrP-res just before the onset of clinical disease and retained abundant cellular PrP, cellular PrP was not the factor limiting FU replication. The mechanisms underlying SY interference are not understood but could be based on host recognition of foreign molecular features shared by this class of invasive agents involving antibody production, and possibly involve defective viral particles produced by attenuated variants.

Evolution of a strain of CJD that induces BSE-like plaques

Bovine spongiform encephalopathy (BSE) has become a public health issue because a recently evolved BSE agent has infected people, yielding an unusual form of Creutzfeld-Jakob disease (CJD). A new CJD agent that provokes similar amyloid plaques and cerebellar pathology was serially propagated. First-passage rats showed obvious clinical signs and activated microglia but had negligible PrP-res (the more protease-resistant form of host PrP) or cerebellar lesions. Microglia and astrocytes may participate in strain selection because the agent evolved, stabilized, and reproducibly provoked BSE-like disease in subsequent passages. Early vacuolar change involving activated microglia and astrocytes preceded significant PrP-res accumulation by more than 50 days. These studies reveal several inflammatory host reactions to an exogenous agent.

Protected endogenous retroviral sequences copurify with infectivity in experimental Creutzfeldt-Jakob disease

Scrapie and Creutzfeldt-Jakob disease (CJD) are caused by infectious agents that are defined phenomenologically. No agent-specific molecules or particles have been identified. Biological properties, such as exponential agent replication and strain variation, as well as physical characteristics of infectivity indicate a protected viral structure. A host membrane glycoprotein of 34 kDa ("prion" protein) that aggregates at end stages of disease is clearly important in pathology and susceptibility to infection, but has no demonstrable infectivity in any purified or recombinant form. Thus a characterization of more viral-like molecules is important. In order to identify viral-like nucleic acids we previously developed methods to substantially purify the human CJD agent from experimentally infected hamster brains, and demonstrated selected retroviral-like LTR bands at pg levels that were insufficient for sequencing. To further define these and other viral-like sequences we cloned nucleic acids from highly infectious CJD fractions, and tested the efficacy of our methods using a selected retroviral probe. RNA extracted from an infectious 120 S Gaussian peak, which is reproducibly purified approximately 100,000 fold with respect to starting nucleic acids, and contains approximately 20% of the initial brain infectivity, was used to generate a cDNA library in a sequence independent amplification strategy for low levels of RNA (< 6 ng). Reconstituted strong stop experiments using several retroviral tRNA primers had indicated that Syrian hamster IAP (SHIAP) sequences should be present in both CJD and uninfected control fractions. Because SHIAP particles are extremely resistant to denaturation, their representation in a cDNA library would imply adequate extraction of other protected RNAs of viral origin. At least 900 bases of the Syrian hamster retroviral IAP genome were unambiguously identified in the cDNA library, and in independent PCR walks with selected primers, all of which were based on our cloned sequences. Sequencing confirmed the presence of protected LTR and adjacent retroviral motifs. Because these sequences were also present in control preparations they may represent normal endogenous viral contaminants that cosediment with infectivity in size and density gradients. On the other hand, LTRs can drive the expression of many diverse sequences, and it remains to be seen if CJD specific sequences are either transduced, or copackaged with, protected IAP complexes. The effective extraction and amplification of highly protected SHIAP nucleic acids of significant length sets the stage for identifying additional protected viral elements that may specify the CJD agent.

Successful transmission of Creutzfeldt-Jakob disease from human to mouse verified by prion protein accumulation in mouse brains

The accumulation of prion protein (PrP) was revealed in the brains of mice inoculated with the brain homogenate from seven patients with Creutzfeldt-Jakob disease (CJD) by immunohistochemistry using hydrolytic autoclaving. It was not found in the brains of mice inoculated with material from either two patients with Gerstmann-Sträussler syndrome or two with other dementing illnesses. PrP accumulation took the forms of diffuse neuropil accumulation in the gray matter and plaque-like accumulation in the white matter and was observed in particular areas in the supratentorial structure. Its distribution was narrower than that in the brains of mice infected with a mouse-adapted CJD strain. PrP accumulation was found not only in all histopathologically positive mice, but also in some histopathologically negative mice. In all groups of mice inoculated with the material from each CJD patient, the percentage of mice with PrP accumulation was equal to or exceeded that of mice with the histopathological findings. PrP immunohistochemistry using formic acid pretreatment stained such plaque-like accumulation less intensely than that using hydrolytic autoclaving and did not stain diffuse neuropil accumulation. Therefore, PrP accumulation which can be revealed in the brains of first-passage CJD mice by this new immunohistochemical method may be the most sensitive hallmark of successful transmission.

Creutzfeldt-Jakob disease with amyloid angiopathy: diagnosis by immunological analyses and transmission experiments

It was difficult to make a definite pathological diagnosis in a 73-year-old man with Creutzfeldt-Jakob disease (CJD) due to extensive amyloid angiopathy which lacked any severe spongiform changes. Immunostaining using anti-prion protein (PrP) antibody revealed fine granular deposits in the gray matter, after hydrolytic autoclaving pretreatment on tissue sections. Western blotting also revealed an abnormal isoform of PrP, but PrP gene analysis did not show any abnormalities. The primary transmission experiments were repeated three times and induced spongiform encephalopathy in a few mice after a long incubation period.

Early-onset dementia and extrapyramidal disease: clinicopathological variant of Gerstmann-Straussler-Scheinker or Alzheimer's disease?

A case of progressive dementia and extrapyramidal signs beginning at age 29, with a ten year course until death, is presented. Necropsy examination showed an assortment of plaque types (including striatal plaques), neurofibrillary tangles, granulovacuolar degeneration, and depigmentation of the substantia nigra and locus ceruleus. This case had pathological features found in both Gerstmann-Straussler-Scheinker disease and in Alzheimer's disease. While somewhat similar to several other cases with features of both diseases, it differs in the presence of dystonia and striatal plaques. Although such cases may be difficult to categorize at present, they must be considered in the differential diagnosis of early onset dementia.

The mRNA encoding the scrapie agent protein is present in a variety of non-neuronal cells

PrP 27-30, a unique protease-resistant protein associated with scrapie infectivity, derives from the proteolytic cleavage of a larger precursor encoded by a host gene. To identify sites of PrP biosynthesis, in situ hybridization was done using cloned PrP cDNA as a probe. In rodent brain, PrP mRNA was expressed in neurons, ependymal cells, choroid plexus epithelium, astrocytes, pericytes, endothelial cells and meninges of both scrapie-infected and uninfected animals. PrP mRNA was also detected in vitro in isolated brain microglia cells. Pulmonary cells and heart muscle cells contained high levels of this mRNA. Hybridization was not detected in spleen, confirming earlier RNA blot experiments indicating extremely low levels of PrP mRNA in this tissue. Results indicate that PrP mRNA is a normal component in a variety of non-neuronal tissues and may explain the origin of the amyloid plaques present in the subependymal region of scrapie-infected brain.

Immunogold light and electron microscopic detection of amyloid plaques in transmissible spongiform encephalopathies

The antigenicity of the 'prion' protein amyloid fibrils was shown to be preserved after glutaraldehyde/OsO4 fixation in uranyl acetate-stained brain tissue blocks from patients with Gerstmann-Sträussler syndrome (GSS) and from mice infected with Creutzfeldt-Jakob disease (CJD). Amyloid plaques were demonstrated by light microscopy in immunogold silver-intensified semithin sections. Under the electron microscope, the amyloid fibrils were labelled in immunogold-reacted ultrathin sections using an antiserum prepared against GSS amyloid plaque cores and mouse amyloid fibrils respectively. The influence of various oxidizing agents (hydrogen peroxide, sodium metaperiodate) on the tissue preservation and the immunohistochemical detection was tested.

Gerstmann-Sträussler-Scheinker disease: immunohistological and experimental studies

The older brother of the patient from whom the Fukuoka-1 strain was isolated was found to have numerous kuru plaques, the main finding common to both siblings. Other clinicopathological features including spongiform change were absent in the older brother. Immunostaining using anti-kuru plaque core protein and anti-beta-protein peptide revealed many kuru plaques and a few senile plaques in the older brother. Experimental transmission of the disease to laboratory animals was successful, using tissues from both siblings, through inoculation of fresh brain homogenates, purified prion protein, and formalin-fixed brain homogenates. Prion protein fractions from the patient's brain shortened the incubation periods and formalin-fixed mouse brains did not lengthen the periods. The disease in the two brothers can be classified as Gerstmann-Sträussler-Scheinker disease, a familial variant of Creutzfeldt-Jakob disease. Gerstmann-Sträussler-Scheinker disease manifests a variety of clinicopathological features. Immunohistological verification of kuru plaques has major diagnostic value in assessing dementia.

Electron microscopic observations on dystrophic neurites in hamster brains infected with the 263K strain of scrapie

Increased numbers of dystrophic neurites filled with inclusions were found in the brains of Syrian hamsters inoculated with scrapie but not in control animals. These neurites were seen as single entities or as clusters of up to three. The possibility that these structures are the beginning of the formation of plaques is discussed.

Creutzfeldt-Jakob disease: clinical analysis of a consecutive series of 230 neuropathologically verified cases

In this consecutive series of 230 patients with neuropathologically verified Creutzfeldt-Jakob disease (CJD), the disease was found to affect men and women with approximately equal frequency in a peak plateau between the ages of 55 and 75 years (mean, 61.5 years). Familial cases accounted for 4 to 8% of the total series. Nonspecific prodromal symptoms occurred in one third of the patients, and the neurological presentation, although usually a gradually evolving mental deterioration, was of rapid onset in 20% of patients and in 36% of patients consisted exclusively of neurological symptoms. The great majority of these symptoms were of cerebellar or visual origin. Extrapyramidal muscular rigidity, myoclonus, and characteristic periodic electroencephalographic (EEG) complexes were observed comparatively late in the illness, and some type of involuntary movement or periodic EEG activity was seen in over 95% of the patients. The median duration of illness was 4 months (mean, 7.6 months); 90% of patients died within a year of onset.

Gerstmann-Sträussler-Scheinker disease: autopsy study of a familial case

Postmortem neuropathological findings in a patient with biopsy-proved familial Gerstmann-Sträussler-Scheinker disease of eight years' duration included severe spongy change in the neocortex, extensive and often large amyloid deposits throughout the cerebral hemispheres and cerebellum, and severe astrocytic gliosis throughout all areas of gray and white matter within the brain. The degree of cortical spongy change was much greater than that in relatives who died with a similar clinical history, indicating the phenotypic heterogeneity in this familial disorder.

Amyloid plaques in Creutzfeldt-Jakob disease stain with prion protein antibodies

Amyloid plaques are found in the brains of some patients with Creutzfeldt-Jakob disease (CJD) and all patients with a related transmissible disorder, Gerstmann-Sträussler syndrome (GSS). In scrapie, a prion disease of animals, amyloid plaques have been shown to be composed of prion proteins (PrP), which form filaments of relatively uniform diameter. We report here that antisera raised against hamster scrapie PrP specifically stain amyloid plaques in the brains of both humans and rodents with CJD as well as a human subject with GSS. Earlier studies showed that these antibodies react with both rodent and human CJD PrP. The immunostained congophilic amyloid plaques in rodent brains measured 10 to 30 micron in diameter and exhibited a Maltese cross appearance. Limited proteolysis enhanced immunostaining of amyloid plaques in human brain sections from patients with CJD or GSS. Presumably proteolysis increases the exposure of those epitopes shared by human and rodent PrP. The differences in immunoreactivity between rodent and human amyloid plaques are consistent with other findings showing that cellular genes, not infectious purified prions, encode PrP.

A 54-kDa normal cellular protein may be the precursor of the scrapie agent protease-resistant protein

Scrapie is the best understood of the transmissible spongiform encephalopathies. These neurologic disorders include the human diseases kuru and Creutzfeldt-Jakob disease and are caused by pathogens with unique biological and molecular properties. One major protein, protease-resistant protein (PrP)-27-30, is present in fractions isolated from scrapie-infected hamster brain that contain highly purified scrapie agent. PrP-27-30 appears to be the major protein component of the hamster scrapie agent. An antiserum generated to electrophoretically purified hamster scrapie PrP-27-30 identified higher molecular weight proteins in immunoblots of homogenates of uninfected hamster and mouse brains. Antibodies to hamster and mouse scrapie agent proteins were obtained by immunoaffinity purification of this antiserum. These antibodies to hamster and mouse PrPs recognized a 54-kDa protein present in uninfected brain homogenates. Antibodies immunoaffinity purified from this antiserum using whole immunoblots of normal brain antigens also identified the 54-kDa protein and PrPs. Our findings demonstrate that scrapie agent proteins share epitopes with normal proteins and suggest that the 54-kDa protein is the normal protein precursor of the scrapie agent PrPs.

Unconventional pathogens causing spongiform encephalopathies absent in blood products

To determine whether unconventional pathogens causing subacute spongiform encephalopathy may be present in blood products, a newly developed hepatitis B vaccine and a widely used blood product were injected into mice and rats. As only a few aged mice in the test and the control groups showed spongiform encephalopathic change of a sparse or mild degree and which differed from that seen in rodents infected with Creutzfeldt-Jakob disease, the presence of unconventional pathogens in the tested inocula can be ruled out.

Scrapie and Creutzfeldt-Jakob disease prion proteins share physical properties and antigenic determinants

Scrapie of sheep and goats as well as Creutzfeldt-Jakob disease (CJD) of humans are neurologic disorders caused by slow infectious pathogens. The novel molecular properties of the pathogen causing scrapie have prompted introduction of the term "prion" to denote a small proteinaceous infectious particle that resists inactivation by nucleic acid-modifying procedures. Antiserum to the major hamster scrapie prion protein (PrP 27-30) was found to cross-react with murine CJD proteins. The CJD proteins had molecular weights similar to those observed for scrapie prion proteins as determined by NaDodSO4 gel electrophoresis. In addition, the CJD proteins were resistant to digestion by proteinase K and appear to polymerize into rod-shaped particles. The purification procedure developed for scrapie prions was found to be useful in purifying the CJD agent. Purification of the two infectious pathogens by virtually identical procedures provided further evidence for similarities in their molecular structures. We conclude that the molecular and biologic properties of the CJD agent are sufficiently similar to those of the scrapie prion protein that CJD should be classified as a prion disease.

Creutzfeldt-Jakob disease prion proteins in human brains

Creutzfeldt-Jakob disease is caused by a slow infectious pathogen, or prion. We found that purified fractions from the brains of two patients with Creutzfeldt-Jakob disease contained protease-resistant proteins ranging in apparent molecular weight from 10,000 to 50,000. These proteins reacted with antibodies raised against the scrapie prion protein PrP 27-30. Rod-shaped particles were found in the brain tissue of the patients that were similar to those isolated from rodents with either scrapie or experimental Creutzfeldt-Jakob disease. After being stained with Congo red dye, the protein polymers from patients with Creutzfeldt-Jakob disease exhibited green birefringence when examined under polarized light. Our findings suggest that the amyloid plaques found in the brains of patients with Creutzfeldt-Jakob disease may be composed of paracrystalline arrays of prions similar to those in prion diseases in laboratory animals.

Morphogenesis of amyloid plaques in mice with Creutzfeldt-Jakob disease

Amyloid plaques were experimentally produced in the brains of mice inoculated with human Creutzfeldt-Jakob disease (CJD) brain homogenate. Light-microscopically, these plaques were mostly round and oval and were surrounded by macrophages and astrocytes. Ultramicroscopically, amyloid plaques were present in the cytoplasm of macrophages or were surrounded by these cells. The macrophages had numerous Golgi apparatuses, endoplasmic reticula (ER), ribosomes, polysomes, and lysosomes with inoculated materials or degenerating products. The bundles of amyloid fibrils were intermingled with the cytoplasm of macrophages, and sometimes limiting membranes were absent. Some bundles of amyloid fibrils projected from the Golgi apparatuses or rough ER and were partly exposed to the extracellular spaces, but there were no amyloid fibrils in the lysosomes. These findings confirmed that amyloid fibrils in the brains of CJD-infected mice were produced by macrophages.

Antibodies to a scrapie prion protein

Scrapie is a slow infection of the nervous system which progresses in the absence of any apparent immune response. The recent development of a large-scale purification protocol for scrapie prions made it possible to obtain substantial quantities of electrophoretically purified prion protein (PrP 27-30) and we report here on the successful production of a rabbit antiserum to PrP 27-30. The antiserum reacted with PrP 27-30 and several lower molecular weight proteins as shown by Western blots; it did not react with protein preparations from uninfected brains. Discrete structures in the subependymal region of scrapie-infected hamster brains were stained immunocytochemically. These same structures also stained with Congo red dye and showed green birefringence with polarized light, a characteristic of purified prion rods. This staining pattern suggests that they are amyloid plaques.

Experimental transmission of human subacute spongiform encephalopathy to small rodents. IV. Positive transmission from a typical case of Gerstmann-Sträussler-Scheinker's disease

Spongiform encephalopathy was transmitted to mice from a patient belonging to the "Sch" family with Gerstmann-Sträussler-Scheinker's disease (GSS). Incubation periods in the first passage were much shorter than those in mice infected with Creutzfeldt-Jakob disease. Clinical and pathologic findings of mice infected with both diseases were almost identical. This is the first successful transmission from a typical GSS case without severe spongiform change which suggests the possible transmissible nature of this disorder.