Prion strains associated with iatrogenic CJD in French and UK human growth hormone recipients

Treatment with human pituitary-derived growth hormone (hGH) was responsible for a significant proportion of iatrogenic Creutzfeldt–Jakob disease (iCJD) cases. France and the UK experienced the largest case numbers of hGH-iCJD, with 122 and 81 cases respectively. Differences in the frequency of the three PRNP codon 129 polymorphisms (MM, MV and VV) and the estimated incubation periods associated with each of these genotypes in the French and the UK hGH-iCJD cohorts led to the suggestion that the prion strains responsible for these two hGH-iCJD cohorts were different. In this study, we characterized the prion strains responsible for hGH-iCJD cases originating from UK (n = 11) and France (n = 11) using human PrP expressing mouse models. The cases included PRNP MM, MV and VV genotypes from both countries. UK and French sporadic CJD (sCJD) cases were included as controls. The prion strains identified following inoculation with hGH-iCJD homogenates corresponded to the two most frequently observed sCJD prion strains (M1CJD and V2CJD). However, in clear contradiction to the initial hypothesis, the prion strains that were identified in the UK and the French hGH-iCJD cases were not radically different. In the vast majority of the cases originating from both countries, the V2CJD strain or a mixture of M1CJD + V2CJD strains were identified. These data strongly support the contention that the differences in the epidemiological and genetic profiles observed in the UK and France hGH-iCJD cohorts cannot be attributed only to the transmission of different prion strains.

Phenotypic diversity of genetic Creutzfeldt–Jakob disease: a histo-molecular-based classification

The current classification of sporadic Creutzfeldt–Jakob disease (sCJD) includes six major clinicopathological subtypes defined by the physicochemical properties of the protease-resistant core of the pathologic prion protein (PrPSc), defining two major PrPSc types (i.e., 1 and 2), and the methionine (M)/valine (V) polymorphic codon 129 of the prion protein gene (PRNP). How these sCJD subtypes relate to the well-documented phenotypic heterogeneity of genetic CJD (gCJD) is not fully understood. We analyzed molecular and phenotypic features in 208 individuals affected by gCJD, carrying 17 different mutations, and compared them with those of a large series of sCJD cases. We identified six major groups of gCJD based on the combination PrPSc type and codon 129 genotype on PRNP mutated allele, each showing distinctive histopathological characteristics, irrespectively of the PRNP associated mutation. Five gCJD groups, named M1, M2C, M2T, V1, and V2, largely reproduced those previously described in sCJD subtypes. The sixth group shared phenotypic traits with the V2 group and was only detected in patients carrying the E200K-129M haplotype in association with a PrPSc type of intermediate size (“i”) between type 1 and type 2. Additional mutation-specific effects involved the pattern of PrP deposition (e.g., a “thickened” synaptic pattern in E200K carriers, cerebellar “stripe-like linear granular deposits” in those with insertion mutations, and intraneuronal globular dots in E200K-V2 or -M”i”). A few isolated cases linked to rare PRNP haplotypes (e.g., T183A-129M), showed atypical phenotypic features, which prevented their classification into the six major groups. The phenotypic variability of gCJD is mostly consistent with that previously found in sCJD. As in sCJD, the codon 129 genotype and physicochemical properties of PrPSc significantly correlated with the phenotypic variability of gCJD. The most common mutations linked to CJD appear to have a variable and overall less significant effect on the disease phenotype, but they significantly influence disease susceptibility often in a strain-specific manner. The criteria currently used for sCJD subtypes can be expanded and adapted to gCJD to provide an updated classification of the disease with a molecular basis.

Two distinct conformers of PrPD type 1 of sporadic Creutzfeldt–Jakob disease with codon 129VV genotype faithfully propagate in vivo

Current classifications of sporadic Creutzfeldt–Jakob disease (sCJD) identify five subtypes associated with different disease phenotypes. Most of these histopathological phenotypes (histotypes) co-distribute with distinct pairings of methionine (M)/valine (V) genotypes at codon 129 of the prion protein (PrP) gene and the type (1 or 2) of the disease-associated PrP (PrPD). Types 1 and 2 are defined by the molecular mass (~ 21 kDa and ~ 19 kDa, respectively) of the unglycosylated isoform of the proteinase K-resistant PrPD (resPrPD). We recently reported that the sCJDVV1 subtype (129VV homozygosity paired with PrPD type 1, T1) shows an electrophoretic profile where the resPrPD unglycosylated isoform is characterized by either one of two single bands of ~ 20 kDa (T120) and ~ 21 kDa (T121), or a doublet of ~ 21–20 kDa (T121−20). We also showed that T120 and T121 in sCJDVV have different conformational features but are associated with indistinguishable histotypes. The presence of three distinct molecular profiles of T1 is unique and raises the issue as to whether T120 and T121 represent distinct prion strains. To answer this question, brain homogenates from sCJDVV cases harboring each of the three resPrPD profiles, were inoculated to transgenic (Tg) mice expressing the human PrP-129M or PrP-129V genotypes. We found that T120 and T121 were faithfully replicated in Tg129V mice. Electrophoretic profile and incubation period of mice challenged with T121−20 resembled those of mice inoculated with T121 and T120, respectively. As in sCJDVV1, Tg129V mice challenged with T121 and T120 generated virtually undistinguishable histotypes. In Tg129M mice, T121 was not replicated while T120 and T121−20 generated a ~ 21–20 kDa doublet after lengthier incubation periods. On second passage, Tg129M mice incubation periods and regional PrP accumulation significantly differed in T120 and T121−20 challenged mice. Combined, these data indicate that T121 and T120 resPrPD represent distinct human prion strains associated with partially overlapping histotypes.

Medial Temporal Lobe Involvement in Human Prion Diseases: Implications for the Study of Focal Non Prion Neurodegenerative Pathology

Human prion and non-prion neurodegenerative diseases share pathogenic mechanisms and neuropathological features. The lesion profile of a particular entity results from specific involvement of vulnerable neuron populations and connectivity circuits by a pathogenic protein isoform with strain-like properties. The lesion profile of the medial temporal lobe (MTL) was studied in postmortem tissue of 143 patients with human prion disease (HPD) including sporadic, genetic, and acquired forms. Most cases (90%) were classified according to PrPres type and/or PRNP codon 129 status, in addition to a full neuropathological profile. Mixed histotypes represented 29.4% of total sporadic Creutzfeldt-Jakob disease (sCJD) cases. An intensity score of involvement including spongiosis and astrogliosis was determined for the amygdala, presubiculum, subiculum, entorhinal cortex, CA1 to CA4 sectors of the hippocampal cortex, and dentate gyrus. Connectivity hubs within the MTL presented the highest scores. Diverse lesion profiles were obtained for different types and subtypes of HPD. Impact of mixed PrPres types on the MTL lesion profile was higher for sCJDMV2K cases than in other histotypes. Differences between MTL profiles was globally consistent with current evidence on specific strains in HPD. These results may be relevant for the analysis of possible strain effects in focal non-prion neurodegenerative conditions limited to the MTL.

Extracellular Protein Aggregates Colocalization and Neuronal Dystrophy in Comorbid Alzheimer’s and Creutzfeldt–Jakob Disease: A Micromorphological Pilot Study on 20 Brains

Alzheimer’s disease (AD) and sporadic Creutzfeldt–Jakob disease (sCJD) are both characterized by extracellular pathologically conformed aggregates of amyloid proteins—amyloid β-protein (Aβ) and prion protein (PrPSc), respectively. To investigate the potential morphological colocalization of Aβ and PrPSc aggregates, we examined the hippocampal regions (archicortex and neocortex) of 20 subjects with confirmed comorbid AD and sCJD using neurohistopathological analyses, immunohistochemical methods, and confocal fluorescent microscopy. Our data showed that extracellular Aβ and PrPSc aggregates tended to be, in most cases, located separately, and “compound” plaques were relatively rare. We observed PrPSc plaque-like structures in the periphery of the non-compact parts of Aβ plaques, as well as in tau protein-positive dystrophic structures. The AD ABC score according to the NIA-Alzheimer’s association guidelines, and prion protein subtype with codon 129 methionine–valine (M/V) polymorphisms in sCJD, while representing key characteristics of these diseases, did not correlate with the morphology of the Aβ/PrPSc co-aggregates. However, our data showed that PrPSc aggregation could dominate during co-aggregation with non-compact Aβ in the periphery of Aβ plaques.

A Molecular Analysis Of Prion Protein Expression In Alzheimer's Disease

In Prion Diseases, misfolding of neuronal prion protein (PrPC) to a pathogenic isomer (PrPSC) is associated with neuronal death. Previous pathological studies have demonstrated increased immunoreactivity of PrPC at Aβ plaques in Alzheimer's Disease, and it has been suggested that this either reflects a role for PrPC in the neuronal response to stress or is a feature of the neuropathogenesis of atypical subtypes of Alzheimer's disease. In this paper we utilised western blotting to examine the molecular characteristics of PrP in frozen Hippocampal tissue from 7 cases of Alzheimer's Disease in which prion protein expression was demonstrated by immunohistochemistry, before using Restriction Fragment Length Polymorphism (RFLP) methodology to define the genotype of the codon 129 polymorphism of PRNP in each case. We observed PrP accumulating as globular structures at A plaques, and within ependymal cells lining the lateral ventricle. Immunohistochemistry also showed that PrPC and Superoxide dismutase-1 where deposited in a similar pattern at Aβ plaques. Western blotting revealed that PrP in Alzheimer's disease is composed of the same 208-residue peptide expressed in non-diseased brain. Quantitative western blot analysis demonstrated increased levels of PrPC in a short duration case of Alzheimer's Disease, while, in the remaining cases, levels of PrPC decreased in parallel with increasing disease duration and decreasing brain mass. RFLP genotyping revealed that all codon 129 genotypes (M/M, M/V, V/V) were represented in our study cohort. Our data suggest that increased levels of PrPC may account for PrP immunoreactivity at plaques in Alzheimer's disease, and that PrP deposition is not restricted to certain atypical subtypes of Alzheimer's disease.

Markers of A1 astrocytes stratify to molecular sub-types in sporadic Creutzfeldt–Jakob disease brain

Astrocytes are glial cells of the central nervous system that become reactive under conditions of stress. The functional properties of reactive astrocytes depend on their stimulus that induces the upregulation of specific genes. Reactive astrocytes are a neuropathological feature of prion disorders; however, their role in the disease pathogenesis is not well understood. Here, we describe our studies of one polarization state of reactive astrocytes, termed A1 astrocytes, in the frontal cortex region of 35 human sporadic Creutzfeldt–Jakob disease brains encompassing a range of molecular sub-types. Examination of two mRNA markers of A1 astrocytes, C3 and GBP2, revealed a strong linear correlation between the two following their log-normalization (P = 0.0011). Both markers were found upregulated in the sporadic Creutzfeldt–Jakob disease brain compared with age-matched control tissues (P = 0.0029 and 0.0002, for C3log and GBP2log, respectively), and stratifying samples based on codon 129 genotype revealed that C3log is highest in homozygous methionine and lowest in homozygous valine patients, which followed a linear trend (P = 0.027). Upon assessing other disease parameters, a significant positive correlation was found between GBP2log and disease duration (P = 0.031). These findings provide evidence for a divergence in the astrocytic environment amongst patients with sporadic Creutzfeldt–Jakob disease based on molecular sub-type parameters of disease. While more research will be needed to determine the global changes in the genomic profiles and resulting functional properties of reactive astrocytes in disease, considering the evidence demonstrating that A1 astrocytes harbour neurotoxic properties, the changes seen in C3log and GBP2log in the current study may reflect differences in pathogenic mechanisms amongst the sporadic Creutzfeldt–Jakob disease sub-types associated with the A1 polarization state.

Prion protein codon 129 polymorphism in mild cognitive impairment and dementia: the Rotterdam Study

Creutzfeldt–Jakob disease is a rare, fatal, neurodegenerative disease caused by the accumulation of abnormally folded prion proteins. The common polymorphism at codon 129 (methionine/valine) in the prion protein (PRNP) gene is the most important determinant of genetic susceptibility. Homozygotes of either allele have a higher risk of sporadic Creutzfeldt–Jakob disease. Various studies suggest that this polymorphism is also involved in other forms of dementia. We studied the association between the codon 129 polymorphism of the PRNP gene and mild cognitive impairment in 3605 participants from the Rotterdam Study using logistic regression analyses. Subsequently, we studied the association between this polymorphism and incident dementia, including Alzheimer’s disease, in 11 070 participants using Cox proportional hazard models. Analyses were adjusted for age and sex. We found the prevalence of mild cognitive impairment to be higher for carriers of the methionine/methionine genotype (odds ratio, 1.40; 95% confidence interval, 1.11–1.78; P = 0.005) as well as for carriers of the valine/valine genotype (odds ratio, 1.37; 95% confidence interval, 0.96–1.97; P = 0.08). The codon 129 polymorphism was not associated with the risk of incident dementia or Alzheimer’s disease. In conclusion, we found a statistically significant higher prevalence of mild cognitive impairment in carriers of the methionine/methionine genotype in the codon 129 polymorphism of the PRNP gene within this population-based study. No associations were found between the codon 129 polymorphism and dementia or Alzheimer’s disease in the general population.

Molecular dynamics simulation of local structural models of PrPSc reveals how codon 129 polymorphism affects propagation of PrPSc

Prions are unconventional pathogen without nucleotide genome and their pathogenic properties are defined by the primary structure and the conformation of the constituent abnormal isoform (PrPSc) of prion protein (PrP). A polymorphic codon 129 of human PrP that is valine (V129) or methionine (M129) is particularly influential on properties of PrPSc, affecting transmission efficiencies and clinicopathological features. However, how the single residue is so influential has not been elucidated because the detailed structures of PrPSc have not been determined yet due to its incompatibility with high-resolution structural analysis. Previously we created an in-register parallel β-sheet local structural model of human PrPSc encompassing residues 107 to 143 that seemed more compatible with V129 than M129, based on knowledge from α-synuclein amyloids and an NMR-based model of the amyloid of Y145Stop mutant of PrP in the literature. Here, we created an M129-compatible local structural model of PrPSc. Severe destabilization of the model by G127V mutation was consistent with the protective effects of V127 polymorphism of human PrP against prions. It was highly sensitive to the length of the hydrophobic side chain of codon 129 and replacement of M129 with leucine or valine destabilized the structures. Interestingly, the U-shaped β-arch which comprises M129 flexibly changed hydrophobic interaction networks inside the β-arch depending on the interactions with the surrounding structures, whereas the previous model with V129 maintained the similar network patterns irrespective of the surroundings. The differences between the two models may explain influences of the codon 129 polymorphism on transmissions and properties of human prions.

Molecular Characterization of the Danish Prion Diseases Cohort With Special Emphasis on Rare and Unique Cases

The purpose of this study was to perform an updated reclassification of all definite prion disease cases with available fresh-frozen samples referred to the Danish Reference Center over the past 40 years, putting a special emphasis on the molecular characterization of novel disease subtypes. Investigation of the Danish prion diseases cohort revealed rare sporadic Creutzfeldt-Jakob disease cases with mixed subtypes and subtypes with previously uncharacterized white matter plaques, a new case of sporadic fatal insomnia, and 3 novel mutations, including 2 large octapeptide repeat insertions, and a point mutation in the prion protein gene. The evaluation of methionine and valine distribution at codon 129 among the prion disease patients in the cohort revealed the increased prevalence of methionine homozygotes compared to the general population. This observation was in line with the prevalence reported in other Caucasian prion disease cohort studies. Reclassification of the old prion diseases cohort revealed unique cases, the molecular characterization of which improves prion diseases classification, diagnostic accuracy, genetic counseling of affected families, and the understanding of disease biology.