Franco Cardone

Pre-symptomatic detection of prions by cyclic amplification of protein misfolding

Transmissible spongiform encephalopathies (TSEs) are neurodegenerative disorders affecting humans and animals. At present, it is not possible to recognize individuals incubating the disease before the clinical symptoms appear. We investigated the effectiveness of the “Protein Misfolding Cyclic Amplification” (PMCA) technology to detect the protease‐resistance disease‐associated prion protein (PrPres) in pre‐symptomatic stages. PMCA allowed detection of PrPres in the brain of pre‐symptomatic hamsters, enabling a clear identification of infected animals as early as two weeks after inoculation. Furthermore, PMCA was able to amplify minute quantities of PrPres from a variety of experimental and natural TSEs. Finally, PMCA allowed the demonstration of PrPres in an experimentally infected cow 32 month post‐inoculation, that did not show clinical signs and was negative by standard Western blot analysis. Our findings indicate that PMCA may be useful for the development of an ultra‐sensitive diagnostic test to minimize the risk of further propagation of TSEs.

Highly Infectious Purified Preparations of Disease-Specific Amyloid of Transmissible Spongiform Encephalopathies Are Not Devoid of Nucleic Acids of Viral Size

An efficient purification protocol for infectivity causing a transmissible spongiform encephalopathy (TSE) is described. From fractions purified by this protocol about 3 x 10(8) LD50 but only 3 ng of nucleic acids per gram of brain material can be isolated from all TSE-affected brains (hamster, human, sheep, cattle). By PAGE such fractions from brains of infected and control hamsters contained only one distinct nucleic acid band of 1.5 kg together with some broader smear of nucleic acid material. Although distilled water was used for such purifications, quite often a similar nucleic acid band was isolated from blanks containing no brain material. In all instances this material proved to be DNA. The result challenges the potentially important claim that purified infectious preparations of TSE-specific amyloid are free of nucleic acids of viral size. Nucleic acids isolated by other groups from diseased brain were not detected in preparations isolated by the new protocol. The application of this purification protocol in future studies will be helpful to decide whether TSEs are caused by agents containing nucleic acid or by protein only.

Chronic wasting disease and atypical forms of bovine spongiform encephalopathy and scrapie are not transmissible to mice expressing wild-type levels of human prion protein

The association between bovine spongiform encephalopathy (BSE) and variant Creutzfeldt-Jakob disease (vCJD) has demonstrated that cattle transmissible spongiform encephalopathies (TSEs) can pose a risk to human health and raises the possibility that other ruminant TSEs may be transmissible to humans. In recent years, several novel TSEs in sheep, cattle and deer have been described and the risk posed to humans by these agents is currently unknown. In this study, we inoculated two forms of atypical BSE (BASE and H-type BSE), a chronic wasting disease (CWD) isolate and seven isolates of atypical scrapie into gene-targeted transgenic (Tg) mice expressing the human prion protein (PrP). Upon challenge with these ruminant TSEs, gene-targeted Tg mice expressing human PrP did not show any signs of disease pathology. These data strongly suggest the presence of a substantial transmission barrier between these recently identified ruminant TSEs and humans.

Migration of dendritic cells into the brain in a mouse model of prion disease.

The immune system plays a key role in the dissemination of prion infections from the periphery to the central nervous system (CNS). While follicular dendritic cells are critical for prion replication in lymphoid tissue and subsequent neuroinvasion, myeloid dendritic cells (DCs) have been implicated in both the clearance and propagation of pathological prion protein. Since nothing is known on the ability of DCs to migrate to the CNS during prion diseases, we investigated the immunohistochemical localization of CD205(+) DCs in the brain of C57BL/6 mice intraperitoneally infected with the mouse-adapted KFu strain of Gerstmann-Sträussler-Scheinker syndrome, a human genetic prion disorder. In normal brain, CD205(+) cells were present in the meninges and choroid plexus, whereas in the majority of mice sacrificed between 120 and 300 days post infection, CD205(+) DCs were also detected in the cerebral cortex, subcortical white matter, thalamus and medulla oblongata. These findings demonstrate that DCs can enter the CNS of prion-infected mice, suggesting a possible role for these cells in the pathogenesis of prion disorders.

Molecular diagnostics of transmissible spongiform encephalopathies

Clinical criteria for the diagnosis of sporadic, iatrogenic and variant Creutzfeldt-Jakob diseases are now available and show an excellent sensitivity and specificity ( approximately 98%). Post-mortem diagnosis, based upon the identification in the brain of the pathological conformer of the prion protein (PrP(Sc)), is also very accurate, and several diagnostic kits are now available that facilitate the immunochemical measurement of PrP(Sc). Several new molecular diagnostic techniques aimed at increasing the sensitivity and specificity of PrP(Sc) detection, and at identifying markers of disease that are other than PrP(Sc), are the subject of ongoing studies. The aim of these studies is to develop preclinical screening tests for the identification of infected, but still healthy, individuals. These tests are also badly needed to check the safety of blood or blood-derived products, and to ensure meat safety in European countries.

Two‐dimensional mapping of three phenotype‐associated isoforms of the prion protein in sporadic Creutzfeldt‐Jakob disease

Transmissible spongiform encephalopathies (TSE), or prion diseases, are mammalian neurodegenerative disorders characterized by a conformational modification of the host‐encoded prion protein (PrPC) into an isoform which is detergent‐insoluble and partially resistant to protease treatment (PrPSc). Distinct types of PrPSc, differing in conformation and variation in the relative amount of their glycoforms, have been associated with different phenotypes of TSE. In sporadic Creutzfeldt‐Jakob disease (sCJD), two major types of PrPSc, with proteinase K (PK)‐resistant fragments of 21 and 19 kDa, have been described. No consensus exists, however, on the molecular classification of PrPSc in sCJD, since further heterogeneity within PrPSc conformers has been reported. We studied 19 subjects with dementia or dementia/ataxia at onset and 12 subjects with ataxia at onset. Following two‐dimensional gel electrophoresis, we characterized PrPC and PrPSc species in normal and sCJD brains by immunoblotting with antibodies recognizing N‐terminal and C‐terminal PrP regions. Three types of PrPSc were detected in detergent‐insoluble fractions from sCJD brains, mainly consisting of full‐length PrPSc in subjects with rapidly progressive dementia, and two different sets of amino‐truncated PrPSc glycoforms in subjects with dementia/ataxia and ataxia at onset. Examination of the PrPSc core fragment, following PK treatment and deglycosylation, confirmed the existence of three distinctive patterns. These findings have immediate implications for the molecular classification of sCJD.

Prion protein glycotype analysis in familial and sporadic Creutzfeldt-Jakob disease patients

Creutzfeldt-Jakob disease (CJD) and other transmissible spongiform encephalopathies (TSEs) are characterised by the accumulation of a pathological conformer of PrP, named PrPsc. Molecular weight and glycosylation of the protease-resistant core of PrPsc (PrP27-30) are heterogeneous in different forms of TSEs. We analysed PrP27-30 glycotypes in a large number of TSE-affected patients: 50 sporadic CJD (sCJD), 1 iatrogenic CJD, 1 Gerstmann-Sträussler-Scheinker syndrome (GSS) with the Pro102Leu mutation of PrP, 3 familial CJD (fCJD) with the Glu200Lys mutation and, for the first time, 7 fCJD with the Val210ll3e mutation. All patients were screened for the polymorphic codon 129 of the PrP gene. PrP27-30 deglycosylation and PrPsc immunohistochemistry were performed in selected cases. We found that two PrP27-30 glycotypes (type 1A and type 2A) are produced in sCJD. Type 1A is more frequently associated with methionine than valine in position 129. Type 1A is also formed in Val210lle fCJD. In Glu200Lys fCJD and GSS patients, we found that PrP27-30 has the same mobility of type 1 but different glycosylation ratios (type 1B). Our findings indicate that the polymorphic residue 129 of PrP has a leading role in determining the proteinase degradation site of PrPsc while mutant residues 102 or 200 influence only the glycosylation pattern.

Increased CSF levels of prostaglandin E2 in variant Creutzfeldt–Jakob disease

The concentration of the cyclooxygenase product prostaglandin E2 was sixfold higher in CSF samples from 18 cases of variant Creutzfeldt–Jakob disease (CJD) than in a group of eight subjects with other noninflammatory neurologic diseases, and comparable to those found in a group of six patients affected by diseases with a known inflammatory component. This finding suggests that cyclooxygenase activity may have a role in variant CJD pathogenesis, as previously reported in sporadic CJD.

Creutzfeldt-Jakob disease associated with the R208H mutation in the prion protein gene

The authors investigated a patient who died of apparent sporadic Creutzfeldt-Jakob disease (CJD) but carried a R208H substitution in the prion protein (PrP). The patient phenotype was indistinguishable from typical sporadic CJD (i.e., MM1 subtype). In addition, pathologic PrP, PrPSc, originated from both the normal and the mutated PRNP allele and had the same characteristics as PrPSc type 1. The authors propose that the R208H mutation influences disease susceptibility without significantly affecting PrPSc properties or disease phenotype.

Preparation of soluble infectious samples from scrapie-infected brain: a new tool to study the clearance of transmissible spongiform encephalopathy agents during plasma fractionation

BACKGROUND:  Concern about the safety of blood, blood components, and plasma‐derived products with respect to prions has increased since the report of two blood‐related infections of variant Creutzfeldt‐Jakob disease in the United Kingdom. Efforts were directed toward the development of procedures able to remove or inactivate prions from blood components or plasma‐derived products with brain fractions of transmissible spongiform encephalopathy (TSE)‐infected rodents as spiking materials. These spiking materials, however, are loaded with pathological prion protein (PrPTSE) aggregates that are likely not associated to blood infectivity. The presence of these aggregates may invalidate these studies.