Alzheimer's disease biomarker utilization at first referral enhances differential diagnostic precision with simultaneous exclusion of Creutzfeldt-Jakob disease.

Most suspected Creutzfeldt-Jakob disease (CJD) cases are eventually diagnosed with other disorders. We assessed the utility of investigating Alzheimer's disease (AD) biomarkers and neurofilament light (NfL) in patients when CJD is suspected. The study cohort consisted of cerebrospinal fluid (CSF) samples referred for CJD biomarker screening wherein amyloid beta 1-42 (Aß1-42), phosphorylated tau 181 (p-tau181), and total tau (t-tau) could be assessed via Elecsys immunoassays (n = 419) and NfL via enzyme-linked immunosorbent assay (ELISA; n = 161). In the non-CJD sub cohort (n = 371), 59% (219/371) had A+T- (abnormal Aß1-42 only) and 21% (79/371) returned A+T+ (abnormal Aß1-42 and p-tau181). In the 48 CJD subjects, a similar AD biomarker profile distribution was observed. To partially address the prevalence of likely pre-symptomatic AD, NfL was utilized to assess for neuronal damage. NfL was abnormal in 76% (25/33) of A+T- subjects 40 to 69 years of age, 80% (20/25) of whom had normal t-tau. This study reinforces AD as an important differential diagnosis of suspected CJD, highlighting that incorporating AD biomarkers and NfL at initial testing is worthwhile.

Creutzfeldt-Jakob disease surveillance in Australia: update to 31 December 2022.

Creutzfeldt-Jakob disease surveillance in Australia: update to 31 December 2022: Nationwide surveillance of Creutzfeldt-Jakob disease (CJD) and other human prion diseases is performed by the Australian National Creutzfeldt-Jakob Disease Registry (ANCJDR). National surveillance encompasses the period since 1 January 1970, with prospective surveillance occurring from 1 October 1993. Over this prospective surveillance period, considerable developments have occurred in pre-mortem diagnostics; in the delineation of new disease subtypes; and in a heightened awareness of prion diseases in healthcare settings. Surveillance practices of the ANCJDR have evolved and adapted accordingly. This report summarises the activities of the ANCJDR during 2022. Since the ANCJDR began offering diagnostic cerebrospinal fluid (CSF) 14-3-3 protein testing in Australia in September 1997, the annual number of referrals has steadily increased. In 2022, a total of 599 domestic CSF specimens were referred for diagnostic testing and 79 persons with suspected human prion disease were formally added to the national register. As of 31 December 2022, just under half of the 79 suspect case notifications (36/79) remain classified as 'incomplete'; 15 cases were classified as 'definite' and 23 as 'probable' prion disease; five cases were excluded through neuropathological examination. For 2022, fifty-five percent of all suspected human-prion-disease-related deaths in Australia underwent neuropathological examination. No cases of variant or iatrogenic CJD were identified. The SARS-CoV-2 pandemic did not affect prion disease surveillance outcomes in Australia during 2022.

Tailored behavioural tests reveal early and progressive cognitive deficits in M1000 prion disease.

Prion diseases are pathogenically linked to the normal cellular prion protein (PrPC) misfolding into abnormal conformers (PrPSc), with PrPSc accumulation underpinning both transmission and neurotoxicity. Despite achieving this canonical understanding, however fundamental questions remain incompletely resolved, including the level of pathophysiological overlap between neurotoxic and transmitting species of PrPSc and the temporal profiles of their propagation. To further investigate the likely time of occurrence of significant levels of neurotoxic species during prion disease development, the well characterised in vivo M1000 murine model was employed. Following intracerebral inoculation, detailed serial cognitive and ethological testing at specified time points suggested subtle transition to early symptomatic disease from ∼50% of the overall disease course. In addition to observing a chronological order for impaired behaviours, different behavioural tests also showed distinctive profiles of evolving cognitive impairments with the Barnes maze demonstrating a relatively simple linear worsening of spatial learning and memory over an extended period while in contrast a conditioned fear memory paradigm previously untested in murine prion disease demonstrated more complex alterations during disease progression. These observations support the likely production of neurotoxic PrPSc from at least just prior to the mid-point of murine M1000 prion disease and illustrate the likely need to tailor the types of behavioural testing across the time course of disease progression for optimal detection of cognitive deficits.

Diagnostic performance of CSF biomarkers in a well-characterized Australian cohort of sporadic Creutzfeldt-Jakob disease.

The most frequently utilized biomarkers to support a pre-mortem clinical diagnosis of sporadic Creutzfeldt-Jakob disease (sCJD) include concentrations of the 14-3-3 and total tau (T-tau) proteins, as well as the application of protein amplification techniques, such as the real time quaking-induced conversion (RT-QuIC) assay, in cerebrospinal fluid (CSF). Utilizing CSF from a cohort of neuropathologically confirmed (definite) sCJD (n = 50) and non-CJD controls (n = 48), we established the optimal cutpoints for the fully automated Roche Elecsys® immunoassay for T-tau and the CircuLexTM 14-3-3 Gamma ELISA and compared these to T-tau protein measured using a commercially available assay (INNOTEST hTAU Ag) and 14-3-3 protein detection by western immunoblot (WB). These CSF specimens were also assessed for presence of misfolded prion protein using the RT-QuIC assay. T-tau showed similar diagnostic performance irrespective of the assay utilized, with ~90% sensitivity and specificity. The 14-3-3 protein detection by western blot (WB) has 87.5% sensitivity and 66.7% specificity. The 14-3-3 ELISA demonstrated 81.3% sensitivity and 84.4% specificity. RT-QuIC was the single best performing assay, with a sensitivity of 92.7% and 100% specificity. Our study indicates that a combination of all three CSF biomarkers increases sensitivity and offers the best chance of case detection pre-mortem. Only a single sCJD case in our cohort was negative across the three biomarkers, emphasizing the value of autopsy brain examination on all suspected CJD cases to ensure maximal case ascertainment.

Creutzfeldt-Jakob disease surveillance in Australia: update to 31 December 2021.

Nationwide surveillance of Creutzfeldt-Jakob disease (CJD) and other human prion diseases is performed by the Australian National Creutzfeldt-Jakob Disease Registry (ANCJDR). National surveillance encompasses the period since 1 January 1970, with prospective surveillance occurring from 1 October 1993. Over this prospective surveillance period, considerable developments have occurred in pre-mortem diagnostics; in the delineation of new disease subtypes; and in a heightened awareness of prion diseases in healthcare settings. Surveillance practices of the ANCJDR have evolved and adapted accordingly. This report summarises the activities of the ANCJDR during 2021. Since the ANCJDR began offering diagnostic cerebrospinal fluid (CSF) 14-3-3 protein testing in Australia in September 1997, the annual number of referrals has steadily increased. In 2021, a total of 548 domestic CSF specimens were referred for 14-3-3 protein testing; 73 persons with suspected human prion disease were formally added to the national register. As of 31 December 2021, just over half of the 73 suspect case notifications (37/73) remain classified as 'incomplete'; 17 cases were classified as 'definite' and 13 as 'probable' prion disease; six cases were excluded through either detailed clinical follow-up (two cases) or neuropathological examination (four cases). For 2021, sixty-four percent of all suspected human-prion-disease-related deaths in Australia underwent neuropathological examination. No cases of variant or iatrogenic CJD were identified. The SARS-CoV-2 pandemic did not affect prion disease surveillance outcomes in Australia.

Cerebrospinal fluid neurofilament light chain differentiates primary psychiatric disorders from rapidly progressive, Alzheimer's disease and frontotemporal disorders in clinical settings.

INTRODUCTION: Many patients with cognitive and neuropsychiatric symptoms face diagnostic delay and misdiagnosis. We investigated whether cerebrospinal fluid (CSF) neurofilament light (NfL) and total-tau (t-tau) could assist in the clinical scenario of differentiating neurodegenerative (ND) from psychiatric disorders (PSY), and rapidly progressive disorders. METHODS: Biomarkers were examined in patients from specialist services (ND and PSY) and a national Creutzfeldt-Jakob registry (Creutzfeldt-Jakob disease [CJD] and rapidly progressive dementias/atypically rapid variants of common ND, RapidND). RESULTS: A total of 498 participants were included: 197 ND, 67 PSY, 161 CJD, 48 RapidND, and 20 controls. NfL was elevated in ND compared to PSY and controls, with highest levels in CJD and RapidND. NfL distinguished ND from PSY with 95%/78% positive/negative predictive value, 92%/87% sensitivity/specificity, 91% accuracy. NfL outperformed t-tau in most real-life clinical diagnostic dilemma scenarios, except distinguishing CJD from RapidND. DISCUSSION: We demonstrated strong generalizable evidence for the diagnostic utility of CSF NfL in differentiating ND from psychiatric disorders, with high accuracy.

Cross-Linking Cellular Prion Protein Induces Neuronal Type 2-Like Hypersensitivity.

Background: Previous reports identified proteins associated with 'apoptosis' following cross-linking PrPC with motif-specific anti-PrP antibodies in vivo and in vitro. The molecular mechanisms underlying this IgG-mediated neurotoxicity and the role of the activated proteins in the apoptotic pathways leading to neuronal death has not been properly defined. Previous reports implicated a number of proteins, including apolipoprotein E, cytoplasmic phospholipase A2, prostaglandin and calpain with anti-PrP antibody-mediated 'apoptosis', however, these proteins are also known to play an important role in allergy. In this study, we investigated whether cross-linking PrPC with anti-PrP antibodies stimulates a neuronal allergenic response. Methods: Initially, we predicted the allergenicity of the epitope sequences associated with 'neurotoxic' anti-PrP antibodies using allergenicity prediction servers. We then investigated whether anti-PrP antibody treatment of mouse primary neurons (MPN), neuroblastoma cells (N2a) and microglia (N11) cell lines lead to a neuronal allergenic response. Results: In-Silico studies showed that both tail- and globular-epitopes were allergenic. Specifically, binding regions that contain epitopes for previously reported 'neurotoxic' antibodies such as ICSM18 (146-159), ICSM35 (91-110), POM 1 (138-147) and POM 3 (95-100) lead to activation of allergenic related proteins. Following direct application of anti-PrPC antibodies on N2a cells, we identified 4 neuronal allergenic-related proteins when compared with untreated cells. Furthermore, we identified 8 neuronal allergenic-related proteins following treatment of N11 cells with anti-PrPC antibodies prior to co-culture with N2a cells when compared with untreated cells. Antibody treatment of MPN or MPN co-cultured with antibody-treated N11 led to identifying 10 and 7 allergenic-related proteins when compared with untreated cells. However, comparison with 3F4 antibody treatment revealed 5 and 4 allergenic-related proteins respectively. Of importance, we showed that the allergenic effects triggered by the anti-PrP antibodies were more potent when antibody-treated microglia were co-cultured with the neuroblastoma cell line. Finally, co-culture of N2a or MPN with N11-treated with anti-PrP antibodies resulted in significant accumulation of NO and IL6 but not TNF-α in the cell culture media supernatant. Conclusions: This study showed for the first time that anti-PrP antibody binding to PrPC triggers a neuronal hypersensitivity response and highlights the important role of microglia in triggering an IgG-mediated neuronal hypersensitivity response. Moreover, this study provides an important impetus for including allergenic assessment of therapeutic antibodies for neurodegenerative disorders to derive safe and targeted biotherapeutics.

Erratum to: Creutzfeldt-Jakob disease surveillance in Australia: update to 31 December 2020.

Erratum to Commun Dis Intell (2018) 2021;45 (https://doi.org/10.33321/cdi.2021.45.38).

Creutzfeldt-Jakob disease surveillance in Australia: update to 31 December 2020.

ABSTRACT: Nationwide surveillance of Creutzfeldt-Jakob disease and other human prion diseases is performed by the Australian National Creutzfeldt-Jakob Disease Registry (ANCJDR). National surveillance encompasses the period since 1 January 1970, with prospective surveillance occurring from 1 October 1993. Over this prospective surveillance period, considerable developments have occurred in pre-mortem diagnostics; in the delineation of new disease subtypes; and in a heightened awareness of prion diseases in healthcare settings. Surveillance practices of the ANCJDR have evolved and adapted accordingly. This report summarises the activities of the ANCJDR during 2020. Since the ANCJDR began offering diagnostic cerebrospinal fluid (CSF) 14-3-3 protein testing in Australia in September 1997, the annual number of referrals has steadily increased. In 2020, 510 domestic CSF specimens were referred for 14-3-3 protein testing and 85 persons with suspected human prion disease were formally added to the national register. As of 31 December 2020, just over half (44 cases) of the 85 suspect case notifications remain classified as 'incomplete'; 27 cases were excluded through either detailed clinical follow-up (9 cases) or neuropathological examination (18 cases); 18 cases were classified as 'definite' and eleven as 'probable' prion disease. For 2020, sixty percent of all suspected human-prion-disease-related deaths in Australia underwent neuropathological examination. No cases of variant or iatrogenic CJD were identified. The SARS-CoV-2 pandemic did not affect prion disease surveillance outcomes in Australia.

Treatment of microglia with Anti-PrP monoclonal antibodies induces neuronal apoptosis in vitro.

Previous reports highlighted the neurotoxic effects caused by some motif-specific anti-PrPC antibodies in vivo and in vitro. In the current study, we investigated the detailed alterations of the proteome with liquid chromatography-mass spectrometry following direct application of anti-PrPC antibodies on mouse neuroblastoma cells (N2a) and mouse primary neuronal (MPN) cells or by cross-linking microglial PrPC with anti-PrPC antibodies prior to co-culture with the N2a/MPN cells. Here, we identified 4 (3 upregulated and 1 downregulated) and 17 (11 upregulated and 6 downregulated) neuronal apoptosis-related proteins following treatment of the N2a and N11 cell lines respectively when compared with untreated cells. In contrast, we identified 1 (upregulated) and 4 (2 upregulated and 2 downregulated) neuronal apoptosis-related proteins following treatment of MPN cells and N11 when compared with untreated cells. Furthermore, we also identified 3 (2 upregulated and 1 downregulated) and 2 (1 upregulated and 1 downregulated) neuronal apoptosis-related related proteins following treatment of MPN cells and N11 when compared to treatment with an anti-PrP antibody that lacks binding specificity for mouse PrP. The apoptotic effect of the anti-PrP antibodies was confirmed with flow cytometry following labelling of Annexin V-FITC. The toxic effects of the anti-PrP antibodies was more intense when antibody-treated N11 were co-cultured with the N2a and the identified apoptosis proteome was shown to be part of the PrPC-interactome. Our observations provide a new insight into the prominent role played by microglia in causing neurotoxic effects following treatment with anti-PrPC antibodies and might be relevant to explain the antibody mediated toxicity observed in other related neurodegenerative diseases such as Alzheimer.

Intra-cerebral haemorrhage but not neurodegenerative disease appears over-represented in deaths of Australian cadaveric pituitary hormone recipients.

BACKGROUND AND PURPOSE: Recent scientific reports and epidemiological studies have engendered mounting concerns regarding the potential human-to-human transmissibility of non-prion neurodegenerative and related diseases. This study investigated whether recipients of cadaveric pituitary hormone treatments are at increased risk of death from non-prion neurodegenerative and related diseases. METHODS: A retrospective national cohort study based on death certificates of recipients of the cadaveric pituitary hormone treatments (n = 184) as part of the Australian Human Pituitary Hormone Program (AHPHP; n = 2940) 1967-1985. Standardised mortality ratios (SMR) from non-prion neurodegenerative and other diseases were estimated based on the Australian population. RESULTS: Allowing for potential diagnostic mis-attributions, there was no significant increase in the SMR from non-prion central nervous system (CNS) neurodegenerative disease, especially dementia and/or Alzheimer's disease (0.47; [95% CI: 0.19, 1.12] P = 0.081). The SMR for intra-cerebral haemorrhage, potentially related to cerebral amyloid angiopathy (CAA), was increased (2.77; [95% CI: 1.12-5.75] P = 0.009), although accommodation of possible mis-diagnosis through conflation of this category with other stroke causes of death emphasising likely intra-cranial haemorrhage showed no persisting significant increase in mortality in cadaveric pituitary hormone recipients, including all deaths recorded as due to intra-cranial haemorrhage (1.72; [95% CI: 0.80, 3.26] P = 0.123). CONCLUSION: In the setting of recent evidence strongly supporting the likelihood of brain-to-brain horizontal transmission and subsequent propagation and deposition of abnormally folded proteins associated with non-prion neurodegenerative and related disorders, this study offers further tentative support for deaths directly stemming from transmission of non-prion disease related to cadaveric pituitary hormone treatment. Acknowledging the limitations of the present study, however, ongoing detailed assessments of this potential risk are necessary.

Creutzfeldt-Jakob disease surveillance in Australia: update to 31 December 2019.

Nationwide surveillance of Creutzfeldt-Jakob disease and other human prion diseases is performed by the Australian National Creutzfeldt-Jakob Disease Registry (ANCJDR). National surveillance encompasses the period since 1 January 1970, with prospective surveillance occurring from 1 October 1993. Over this prospective surveillance period, considerable developments have occurred in pre-mortem diagnostics; in the delineation of new disease subtypes; and in a heightened awareness of prion diseases in healthcare settings. Surveillance practices of the ANCJDR have evolved and adapted accordingly. This report summarises the activities of the ANCJDR during 2019. Since the ANCJDR began offering diagnostic cerebrospinal fluid (CSF) 14-3-3 protein testing in Australia in September 1997, the annual number of referrals has steadily increased. In 2019, 513 domestic CSF specimens were referred for 14-3-3 protein testing and 85 persons with suspected human prion disease were formally added to the national register. As of 31 December 2019, just under half (42 cases) of the 85 suspect case notifications remain classified as 'incomplete'; 16 cases were excluded through either detailed clinical follow-up (3 cases) or neuropathological examination (13 cases); 20 cases were classified as 'definite' and seven as 'probable' prion disease. For 2019, sixty-three percent of all suspected human prion disease related deaths in Australia underwent neuropathological examination. No cases of variant or iatrogenic CJD were identified. Two possibly causal novel prion protein gene (PRNP) sequence variations were identified.

PrPSc Oligomerization Appears Dynamic, Quickly Engendering Inherent M1000 Acute Synaptotoxicity.

Prion diseases are neurodegenerative disorders pathogenically linked to cellular prion protein (PrPC) misfolding into abnormal conformers (PrPSc), with PrPSc underpinning both transmission and synaptotoxicity. Although the biophysical features of PrPSc required to induce acute synaptic dysfunction remain incompletely defined, we recently reported that acutely synaptotoxic PrPSc appeared to be oligomeric. We herein provide further insights into the kinetic and requisite biophysical characteristics of acutely synaptotoxic ex vivo PrPSc derived from the brains of mice dying from M1000 prion disease. Pooled fractions of M1000 PrPSc located within the molecular weight range approximating monomeric PrP (mM1000) generated through size exclusion chromatography were found to harbor acute synaptotoxicity equivalent to preformed oligomeric fractions (oM1000). Subsequent investigation showed mM1000 corresponded to PrPSc rapidly concatenating in physiological buffer to exist as predominantly, closely associated, small oligomers. The oligomerization of PrP in mM1000 could be substantially mitigated by treatment with the antiaggregation compound epigallocatechin gallate, thereby maintaining the PrPSc as primarily nonoligomeric with completely abrogated acute synaptotoxicity; moreover, despite epigallocatechin gallate treatment, pooled oM1000 remained oligomeric and acutely synaptotoxic. A similar tendency to rapid formation of oligomers was observed for PrPC when monomeric fractions derived from size exclusion chromatography of normal brain homogenates (mNBH) were pooled, but neither mNBH nor preformed higher-order NBH complexes (oNBH) were acutely synaptotoxic. Oligomers formed from mNBH could be reduced to mainly monomers (<100 kDa) after enzymatic digestion of nucleic acids, whereas higher-order PrP assemblies derived from pooled mM1000, oM1000, and oNBH resisted such treatment. Collectively, these findings support that oligomerization of PrPSc into small multimeric assemblies appears to be a critical biophysical feature for engendering inherent acute synaptotoxicity, with preformed oligomers found in oM1000 appearing to be stable, tightly self-associated ensembles that coexist in dynamic equilibrium with mM1000, with the latter appearing capable of rapid aggregation, albeit initially forming smaller, weakly self-associated, acutely synaptotoxic oligomers.

The cellular prion protein beyond prion diseases.

The cellular prion protein (PrPC), a cell surface glycoprotein originally identified for its central role in prion diseases (also called transmissible spongiform encephalopathies), has recently been implicated in the pathogenesis of other neurodegenerative disorders, such as Alzheimer’s and Parkinson’s diseases, by acting as a toxicity-transducing receptor for different misfolded protein isoforms, or in some case by exerting neuroprotective effects. Interestingly, PrPC has also been reported to play unexpected functions outside the nervous system, for example by contributing to myelin homeostasis, regulating specific processes of the immune system and participating in various aspects of cancer progression. Collectively, these observations point to a much broader role for PrPC in physiological and disease processes than originally assumed. In this manuscript, we provide an overview of what is known about the role of PrPC beyond prion disorders and discuss the potential implications of targeting this protein in different diseases.

Creutzfeldt-Jakob disease surveillance in Australia: update to 31 December 2018.

Nationwide surveillance of human prion diseases (also known as transmissible spongiform encephalopathies), the most common being Creutzfeldt-Jakob disease (CJD), is performed by the Australian National Creutzfeldt-Jakob Disease Registry (ANCJDR), based at the University of Melbourne. National surveillance encompasses the period since 1 January 1970, with prospective surveillance occurring from 1 October 1993. Over this prospective surveillance period considerable developments have occurred in relation to pre-mortem diagnostics, the delineation of new disease subtypes and a heightened awareness of prion diseases in health care settings. Surveillance practices of the ANCJDR have evolved and adapted accordingly. This report summarises the activities of the ANCJDR from 1 January to 31 December 2018. Since the ANCJDR began offering diagnostic cerebrospinal fluid (CSF) 14-3-3 protein testing in Australia in September 1997, the annual number of referrals has steadily increased. In 2018, 465 domestic CSF specimens were referred for 14-3-3 protein testing and 78 persons with suspected human prion disease were formally added to the national register. The majority of the 78 suspect case notifications remain as of 31 December 2018 classified as "incomplete" (42 cases), while eleven cases were excluded by either detailed clinical follow-up (one case) or neuropathological examination (ten cases); 15 cases were classified as "definite" and ten as "probable" prion disease. Sixty-two percent of all suspected human prion disease related deaths underwent neuropathological examination. No cases of variant CJD were confirmed.

Creutzfeldt­Jakob disease surveillance in Australia: update to December 2017

Nationwide surveillance of human prion diseases (also known as transmissible spongiform encephalopathies), the most common being Creutzfeldt­Jakob disease (CJD), is performed by the Australian National Creutzfeldt­Jakob Disease Registry (ANCJDR), based at the University of Melbourne. National surveillance encompasses the period since 1970, with prospective surveillance occurring from 1993 onwards. Over this prospective surveillance period considerable developments have occurred, especially in relation to pre-mortem diagnostics, the delineation of new disease subtypes and a heightened awareness of prion diseases in the health care setting. The surveillance practices of the ANCJDR have evolved and adapted accordingly. Since the ANCJDR began offering cerebrospinal fluid (CSF) 14-3-3 protein testing in Australia in September 1997, the annual number of referrals has steadily increased to a maximum of 508 in 2017. The number of CSF test referrals in 2017 represents a 20% increase compared to that of 2016. In 2017, there was an overall stabilisation of the annual incidence rate of confirmed prion disease in Australia at expected levels; 72 persons with suspected human prion disease were added to the national register, with 72% of all suspected CJD cases undergoing neuropathological examination. The majority of the 72 suspected cases added to the register are as of 31 December 2017 still classified as "incomplete" (47 cases), while four cases were excluded by either detailed clinical follow-up (1 case) or neuropathological examination (3 cases); 19 cases were classified as definite and two as probable prion disease. No cases of variant CJD (vCJD) were confirmed.

Early existence and biochemical evolution characterise acutely synaptotoxic PrPSc.

Although considerable evidence supports that misfolded prion protein (PrPSc) is the principal component of "prions", underpinning both transmissibility and neurotoxicity, clear consensus around a number of fundamental aspects of pathogenesis has not been achieved, including the time of appearance of neurotoxic species during disease evolution. Utilizing a recently reported electrophysiology paradigm, we assessed the acute synaptotoxicity of ex vivo PrPSc prepared as crude homogenates from brains of M1000 infected wild-type mice (cM1000) harvested at time-points representing 30%, 50%, 70% and 100% of the terminal stage of disease (TSD). Acute synaptotoxicity was assessed by measuring the capacity of cM1000 to impair hippocampal CA1 region long-term potentiation (LTP) and post-tetanic potentiation (PTP) in explant slices. Of particular note, cM1000 from 30% of the TSD was able to cause significant impairment of LTP and PTP, with the induced failure of LTP increasing over subsequent time-points while the capacity of cM1000 to induce PTP failure appeared maximal even at this early stage of disease progression. Evidence that the synaptotoxicity directly related to PrP species was demonstrated by the significant rescue of LTP dysfunction at each time-point through immuno-depletion of >50% of total PrP species from cM1000 preparations. Moreover, similar to our previous observations at the terminal stage of M1000 prion disease, size fractionation chromatography revealed that capacity for acute synpatotoxicity correlated with predominance of oligomeric PrP species in infected brains across all time points, with the profile appearing maximised by 50% of the TSD. Using enhanced sensitivity western blotting, modestly proteinase K (PK)-resistant PrPSc was detectable at very low levels in cM1000 at 30% of the TSD, becoming robustly detectable by 70% of the TSD at which time substantial levels of highly PK-resistant PrPSc was also evident. Further illustrating the biochemical evolution of acutely synaptotoxic species the synaptotoxicity of cM1000 from 30%, 50% and 70% of the TSD, but not at 100% TSD, was abolished by digestion of immuno-captured PrP species with mild PK treatment (5µg/ml for an hour at 37°C), demonstrating that the predominant synaptotoxic PrPSc species up to and including 70% of the TSD were proteinase-sensitive. Overall, these findings in combination with our previous assessments of transmitting prions support that synaptotoxic and infectious M1000 PrPSc species co-exist from at least 30% of the TSD, simultaneously increasing thereafter, albeit with eventual plateauing of transmitting conformers.

Low-intensity transcranial magnetic stimulation promotes the survival and maturation of newborn oligodendrocytes in the adult mouse brain.

Neuronal activity is a potent extrinsic regulator of oligodendrocyte generation and central nervous system myelination. Clinically, repetitive transcranial magnetic stimulation (rTMS) is delivered to noninvasively modulate neuronal activity; however, the ability of rTMS to facilitate adaptive myelination has not been explored. By performing cre-lox lineage tracing, to follow the fate of oligodendrocyte progenitor cells in the adult mouse brain, we determined that low intensity rTMS (LI-rTMS), administered as an intermittent theta burst stimulation, but not as a continuous theta burst or 10 Hz stimulation, increased the number of newborn oligodendrocytes in the adult mouse cortex. LI-rTMS did not alter oligodendrogenesis per se, but instead increased cell survival and enhanced myelination. These data suggest that LI-rTMS can be used to noninvasively promote myelin addition to the brain, which has potential implications for the treatment of demyelinating diseases such as multiple sclerosis.

Prion acute synaptotoxicity is largely driven by protease-resistant PrPSc species.

Although misfolding of normal prion protein (PrPC) into abnormal conformers (PrPSc) is critical for prion disease pathogenesis our current understanding of the underlying molecular pathophysiology is rudimentary. Exploiting an electrophysiology paradigm, herein we report that at least modestly proteinase K (PK)-resistant PrPSc (PrPres) species are acutely synaptotoxic. Brief exposure to ex vivo PrPSc from two mouse-adapted prion strains (M1000 and MU02) prepared as crude brain homogenates (cM1000 and cMU02) and cell lysates from chronically M1000-infected RK13 cells (MoRK13-Inf) caused significant impairment of hippocampal CA1 region long-term potentiation (LTP), with the LTP disruption approximating that reported during the evolution of murine prion disease. Proof of PrPSc (especially PrPres) species as the synaptotoxic agent was demonstrated by: significant rescue of LTP following selective immuno-depletion of total PrP from cM1000 (dM1000); modestly PK-treated cM1000 (PK+M1000) retaining full synaptotoxicity; and restoration of the LTP impairment when employing reconstituted, PK-eluted, immuno-precipitated M1000 preparations (PK+IP-M1000). Additional detailed electrophysiological analyses exemplified by impairment of post-tetanic potentiation (PTP) suggest possible heightened pre-synaptic vulnerability to the acute synaptotoxicity. This dysfunction correlated with cumulative insufficiency of replenishment of the readily releasable pool (RRP) of vesicles during repeated high-frequency stimulation utilised for induction of LTP. Broadly comparable results with LTP and PTP impairment were obtained utilizing hippocampal slices from PrPC knockout (PrPo/o) mice, with cM1000 serial dilution assessments revealing similar sensitivity of PrPo/o and wild type (WT) slices. Size fractionation chromatography demonstrated that synaptotoxic PrP correlated with PK-resistant species >100kDa, consistent with multimeric PrPSc, with levels of these species >6 ng/ml appearing sufficient to induce synaptic dysfunction. Biochemical analyses of hippocampal slices manifesting acute synaptotoxicity demonstrated reduced levels of multiple key synaptic proteins, albeit with noteworthy differences in PrPo/o slices, while such changes were absent in hippocampi demonstrating rescued LTP through treatment with dM1000. Our findings offer important new mechanistic insights into the synaptic impairment underlying prion disease, enhancing prospects for development of targeted effective therapies.