Brain biopsy in Creutzfeldt-Jakob disease: evolution of pathological changes by prion protein immunohistochemistry

Detection of Pathognomonic Biomarker PrPSc and the Contribution of Cell Free-Amplification Techniques to the Diagnosis of Prion Diseases

Transmissible spongiform encephalopathies or prion diseases are rapidly progressive neurodegenerative diseases, the clinical manifestation of which can resemble other promptly evolving neurological maladies. Therefore, the unequivocal ante-mortem diagnosis is highly challenging and was only possible by histopathological and immunohistochemical analysis of the brain at necropsy. Although surrogate biomarkers of neurological damage have become invaluable to complement clinical data and provide more accurate diagnostics at early stages, other neurodegenerative diseases show similar alterations hindering the differential diagnosis. To solve that, the detection of the pathognomonic biomarker of disease, PrP^Sc, the aberrantly folded isoform of the prion protein, could be used. However, the amounts in easily accessible tissues or body fluids at pre-clinical or early clinical stages are extremely low for the standard detection methods. The solution comes from the recent development of in vitro prion propagation techniques, such as Protein Misfolding Cyclic Amplification (PMCA) and Real Time-Quaking Induced Conversion (RT-QuIC), which have been already applied to detect minute amounts of PrP^Sc in different matrixes and make early diagnosis of prion diseases feasible in a near future. Herein, the most relevant tissues and body fluids in which PrP^Sc has been detected in animals and humans are being reviewed, especially those in which cell-free prion propagation systems have been used with diagnostic purposes.

Development of a dot blot assay with antibodies to recombinant "core" 14-3-3 protein: Evaluation of its usefulness in diagnosis of Creutzfeldt-Jakob disease

BACKGROUND AND PURPOSE

Definitive diagnosis of Creutzfeldt-Jakob disease (CJD) requires demonstration of infective prion protein (PrP(Sc)) in brain tissues by immunohistochemistry or immunoblot, making antemortem diagnosis of CJD difficult. The World Health Organization (WHO) recommends detection of 14-3-3 protein in cerebrospinal fluid (CSF) in cases of dementia, with clinical correlation, as a useful diagnostic marker for CJD, obviating the need for brain biopsy. This facility is currently available in only a few specialized centers in the West and no commercial kit is available for clinical diagnostic use in India. Hence the objective of this study was to develop an in-house sensitive assay for quantitation of 14-3-3 protein and to evaluate its diagnostic potential to detect 14-3-3 proteins in CSF as a biomarker in suspected cases of CJD.

MATERIALS AND METHODS

A minigene expressing the "core" 14-3-3 protein was synthesized by overlapping polymerase chain reaction (PCR) and the recombinant protein was produced by employing a bacterial expression system. Polyclonal antibodies raised in rabbit against the purified recombinant protein were used for developing a dot blot assay with avidin-biotin technology for signal amplification and quantitation of 14-3-3 protein in CSF.

RESULTS

The results in the present study suggest the diagnostic potential of the dot blot method with about 10-fold difference (P< 0.001) in the CSF levels of 14-3-3 protein between the CJD cases (N= 50) and disease controls (N= 70). The receiver operating characteristic (ROC) analysis of the results suggested an optimal cutoff value of 2 ng/mL.

CONCLUSIONS

We have developed an indigenous, economical, and sensitive dot blot method for the quantitation of 14-3-3 protein in CSF.

Brain biopsy in patients with suspected Creutzfeldt-Jakob disease

OBJECT

Creutzfeldt-Jakob disease (CJD) is a rare neurodegenerative disorder with diagnostic criteria defined as a combination of clinical symptoms, electroencephalography findings, cerebrospinal fluid (CSF) analysis, and MR imaging results. Special subtypes are known to present with an atypical course and test findings that can complicate the clinical diagnosis. In such patients a brain biopsy can support the clinical approach.

METHODS

The authors studied the records on 26 brain biopsies conducted in patients with suspected CJD who had been referred to the CJD Surveillance Unit in Germany between 1993 and 2005.

RESULTS

Of the 26 included patients, 11 suffered from neuropathologically confirmed CJD, which in 5 cases had been deemed clinically "probable" and in 2 had been deemed "possible." The disease in the remaining 4 patients had been categorized as "other" prior to neuropathological confirmation of CJD. The results of 15 brain biopsies showed no features of prion disease. None of these 15 patients had received a probable diagnosis of CJD, 4 had a possible diagnosis, and 11 had received a diagnosis of "other." Three of the cases classified as other and none of those with CJD presented with pleocytosis in the CSF. In 73% of the other cases, biopsy sampling did not reveal any results characteristic of CJD but did not provide specific findings on which to base a differential diagnosis. Autopsy confirmed the biopsy diagnosis of CJD in all cases, and additionally confirmed that CJD was not present in 3 patients who had nondiagnostic biopsy results.

CONCLUSIONS

Biopsy sampling may be helpful in the diagnostic approach to rare cases of dementia for which a reliable diagnosis cannot be established on the basis of clinical symptoms, CSF parameters, electroencephalography, and MR imaging results.

Cellular prion protein electron microscopy: attempts/limits and clues to a synaptic trait. Implications in neurodegeneration process

Prion diseases are caused by an infectious agent constituted by a rogue protein called prion (PrP Sc) of neuronal origin (PrP c) and are exemplified by Creutzfeldt-Jakob disease in humans and bovine spongiform encephalopathy in cattle. Considerable efforts have been made to understand the cerebral damage caused by these diseases but a clear comprehensive view cannot be achieved without defining the neurophysiological function of PrP c. This lack of information is in part attributable to our ignorance of the precise localization of PrP c in the brain neuronal cell. One relevant option to explore this aspect is to undertake PrP immunohistochemistry at the electron-microscopy level, knowing that this challenge raises major technical constraints. In describing the attempts and restrictions of the various approaches used, we review here the efforts that have been invested in this particular field of prionology. The common result emerging from these contributions is that the synapse could be the site at which PrP c exerts its critical activity. This location suggests, in the perspective of synaptic regulation, that PrP c can be assigned multiple biological functions and supports the novel concept that prion-like changes are involved in long-term memory formation. The synaptic trait of PrP c and PrP Sc suggests that synapse loss is the key event in neuronal death. Interestingly, synaptic alterations are also considered to be predominant in the pathophysiological mechanism in Alzheimer, Parkinson and Huntington diseases. All these brain disorders, characterized by the formation of a specific amyloid protein of synaptic origin, can be classified under the heading of amyloidogenic synaptopathies.

Enhanced Aquaporin-4 immunoreactivity in sporadic Creutzfeldt-Jakob disease

Aquaporin-4 (AQP-4) is a water channel protein located on the plasma membrane of astrocytes and is regulated under various conditions. In the present study, a series of brains with sporadic Creutzfeldt-Jakob disease (sCJD) were investigated to determine the possible contribution of AQP-4 in the development of sCJD pathology. Six cases of subacute spongiform encephalopathy (SSE) and four cases of panencephalopathic (PE)-type sCJD were included. Increased AQP-4 immunoreactivity compared to that in controls was observed in all sCJD patients, particularly in the cerebral neocortex and cerebellar cortex. AQP-4 immunoreactivity was present in the cell bodies and processes of protoplasmic astrocytes in SSE and around cell bodies and processes of hypertrophic astrocytes in PE-type sCJD. Analysis of serial sections showed the development of sCJD pathology, particularly in neocortical lesions, as follows: PrP deposition; spongiform change and gliosis; enhanced staining for AQP-4; hypertrophic astrocytosis; and neuronal loss and tissue rarefaction. Strong AQP-4 immunoreactivity was present in burnt-out lesions such as those of status spongiosus. These results indicate that increased AQP-4 expression in sCJD is an early pathologic event and appears to remain until the late disease stage. We suggest that increased expression of AQP-4 is a pathologic feature of sCJD.

Oxidation reduces the fibrillation but not the neurotoxicity of the prion peptide PrP106-126

There is increasing evidence that soluble oligomers of misfolded protein may play a role in the pathogenesis of protein misfolding diseases including the transmissible spongiform encephalopathies (TSE) where the protein involved is the prion protein, PrP. The effect of oxidation on fibrillation tendency and neurotoxicity of different molecular variants of the prion peptide PrP106-126 was investigated. It was found that methionine oxidation significantly reduced amyloid fibril formation and proteinase K resistance, but it did not reduce (but rather increase slightly) the neurotoxicity of the peptides in vivo (electroretinography after intraocular injections in mice) and in vitro (in primary neuronal cultures). We furthermore found that the bovine variant of PrP106-126, containing only one methionine residue, showed both reduced fibril forming capacity and in vivo and in vitro neurotoxicity. The findings imply (I) that there is not a simple relation between the formation of amyloid fibrils and neurotoxicity of PrP106-126 derived peptides, (II) that putative, soluble, non-amyloid protofibrils, presumed to be present in increased proportions in oxidized PrP106-126, could play a role in the pathogenesis of TSE and III) that the number of methionine residues in the PrP106-126 peptide seems to have a pivotal role in determining the physical and biological properties of PrP106-126.

Autopsy case of sporadic Creutzfeldt-Jakob disease presenting with signs suggestive of brainstem and spinal cord involvement

We describe an autopsy case of MM1-type sporadic Creutzfeldt-Jakob disease (CJD), the duration of which was 93 days. The patient was a 59-year-old Japanese man with no family history of prion disease or known iatrogenic exposure to CJD. His first symptom was dysesthesia in the left arm, suggestive of cervical cord involvement, and he showed rapidly progressive neurologic signs, such as dysarthria, dysphagia, lethargy, sleep apnea and respiratory failure, suggestive of brainstem involvement. Progressive mental deterioration combined with episodes of myoclonic seizure and periodic synchronous discharges on the electroencephalogram were observed in the later disease stage. Autopsy showed typical spongiform change to be wide-spread in the cerebral and cerebellar cortices, thalamus and basal ganglia. Synaptic-type PrP deposition was marked in the cerebral cortex, thalamus and basal ganglia. In the cerebellum, although the granular, molecular and Purkinje cell layers were well preserved from neuronal loss and gliosis, PrP deposition was marked in the molecular and granular cell layers. Spongiform degeneration and neuronal loss were not seen in the brainstem and spinal cord, but relatively marked PrP deposition was observed in the quadrigeminal body, substantia nigra, pontine nucleus, inferior olivary nucleus and posterior horn. Immunohistochemical staining for HLA-DR showed proliferation of activated microglia in the cerebral and cerebellar cortices, pontine nucleus, inferior olivary nucleus and posterior horn. The mechanisms underlying the neurologic symptoms and signs were unclear, but we speculate that, in addition to widespread involvement of the cerebral cortex, PrP deposition and microglial activation in the brainstem and spinal cord were responsible.

Neuropathologic characteristics of spinal cord lesions in sporadic Creutzfeldt-Jakob disease

We investigated the neuropathologic features of spinal cord lesions in 23 patients with sporadic Creutzfeldt-Jakob disease (sCJD), paying particular attention to neuronal loss and gliosis, pyramidal tract degeneration and prion protein (PrP) deposition. The study included 9 cases of subacute spongiform encephalopathy, 13 cases of panencephalopathic-type sCJD and 1 case of sporadic fatal insomnia (sFI). In the spinal gray matter, although gliosis was present in some patients with disease of relatively long duration, the number of neurons, including large motor neurons, was well preserved regardless of disease duration. Pyramidal tract degeneration was observed in some patients with disease lasting more than 14 months but not in the patient with sFI. PrP deposition was present in the spinal cord of all sCJD patients, and was identified predominantly in the posterior horn, particularly in the substantia gelatinosa, regardless of disease duration or disease classification based on cerebral pathology. Relatively prominent PrP deposition was also observed in Clarke's column. The density of PrP deposition in the sCJD spinal cord was not associated with disease duration or neuronal degeneration. Our results indicate that PrP deposition in the spinal cord is an early pathologic event in sCJD and may remain to the end stage. Although no VV1, VV2 or MV2 cases were included in our study, we suggest that stereotypic accumulation of PrP is a consistent pathologic feature of sCJD and that the spinal cord remains relatively resistant to the pathologic process of sCJD, at least in patients with MM1 sCJD.

Immunoquantitative PCR for prion protein detection in sporadic Creutzfeldt-Jakob disease

BACKGROUND

The most common human prion disorder is Creutzfeldt-Jakob disease (CJD); it includes sporadic, familial, iatrogenic, and variant subtypes. Diagnostic tests aim at detection with the highest specificity of very small deposits of abnormal prion protein (PrP).

METHODS

We used immunoquantitative PCR (iqPCR) to detect proteinase K-resistant PrP (PrPRes) in tissue from the middle frontal gyrus of 7 patients with sporadic CJD and 7 non-CJD cases. We compared iqPCR with routine optimized ELISA, Western blotting, and immunohistochemical analyses.

RESULTS

The 4 methods showed similar 100% sensitivity and specificity for the diagnosis of CJD. Along with high specificity, however, iqPCR had a threshold for PrP(Res) detection at least 10-fold lower than that of the classic ELISA.

CONCLUSIONS

iqPCR is a new method for PrPRes detection that combines 100% specificity with a detection threshold at least 10-fold lower than classic techniques. This method may improve the detection of minute PrPRes deposits in tissues and body fluids and thus be useful for diagnostic and sterilization applications.

Neuropathologic characteristics of brainstem lesions in sporadic Creutzfeldt-Jakob disease

We investigated whether the brainstem is affected by the pathologic process of sporadic Creutzfeldt-Jakob disease (sCJD), with particular attention to brainstem atrophy, neuronal loss, pyramidal tract degeneration, and prion protein (PrP) deposition, in 33 patients with sCJD. Brainstem atrophy, particularly in the pontine base, was relatively prominent in patients with disease of unusually prolonged duration. Neuronal loss and pyramidal tract degeneration were also identified in some but not all patients with prolonged disease. Neuronal loss was relatively prominent in the pontine nucleus and less so in the substantia nigra and inferior olivary nucleus; motor nuclei of the brainstem tegmentum were well preserved. PrP deposition was present in the brainstem in all patients, and was identified predominantly in the substantia nigra, quadrigeminal body, pontine nucleus, and inferior olivary nucleus. PrP deposition was less prominent in the red nucleus and tegmentum of the pons and medulla oblongata. PrP deposition occurred least or not at all in the pyramidal tract. The density of PrP deposition in the sCJD brainstem was not associated with disease duration or neuronal degeneration until the late stage. Our results show that atrophy, neuronal loss, and pyramidal tract degeneration occur in the sCJD brainstem, particularly in patients with an unusually prolonged disease course. These findings are not associated directly with PrP deposition and may reflect end-stage sCJD. No VV1, VV2, or MV2 cases were included in our study; however, we suggest that widespread and relatively stereotypic PrP deposition is a consistent pathologic feature of sCJD, at least in MM1 sCJD patients. Although accumulation of PrP in the brainstem appears to be an early pathologic event in sCJD, and may remain into the late disease stage, the brainstem remains relatively resistant to the pathologic process of sCJD.