Rickettsia Deregulates Genes Coding for the Neurotoxic Cell Response Pathways in Cerebrocortical Neurons In Vitro.

Rickettsial infections of the central nervous system (CNS) are manifested by severe neurological symptoms and represent a serious life-threatening condition. Despite the considerable health danger, only a few studies have been conducted focusing on the pathogenesis induced by Rickettsia sp. in CNS. To investigate the signaling pathways associated with the neurotoxic effects of rickettsiae, we employed an experimental model of cerebrocortical neurons combined with molecular profiling and comprehensive bioinformatic analysis. The cytopathic effect induced by Rickettsia akari and Rickettsia slovaca was demonstrated by decreased neuronal viability, structural changes in cell morphology, and extensive fragmentation of neurites in vitro. Targeted profiling revealed the deregulation of genes involved in the neuroinflammatory and neurotoxic cell response pathways. Although quantitative analysis showed differences in gene expression response, functional annotation revealed that the biological processes are largely shared between both Rickettsia species. The identified enriched pathways are associated with cytokine signaling, chemotaxis of immune cells, responses to infectious agents, interactions between neurons, endothelial and glial cells, and regulation of neuronal apoptotic processes. The findings of our study provide new insight into the etiopathogenesis of CNS infection and further expand the understanding of molecular signaling associated with neuroinvasive Rickettsia species.

Association of Nonconcussive Repetitive Head Impacts and Intense Physical Activity With Levels of Phosphorylated Tau181 and Total Tau in Plasma of Young Elite Soccer Players.

Importance: Head impacts resulting in traumatic brain injury (TBI) lead to the elevation of phosphorylated tau protein (p-tau181) in plasma. To our knowledge, this study is the first to investigate dynamics of p-tau181 levels and the ratio of p-tau181 to total tau in individuals after nonconcussive head impacts. Objective: To determine the association of repetitive low-intensity head impacts on p-tau181 and total tau protein levels in the plasma of young adult elite soccer players and assess the possible association of head impacts with focused attention and cognitive flexibility. Design, Setting, and Participants: In this cohort study, young elite soccer players performed intense physical activity with and without heading the ball. The study was conducted at a university facility in Slovakia from October 1, 2021, to May 31, 2022. Eligible participants were selected based on similarities in demographic variables, excluding those with a history of TBI. Main Outcomes and Measures: The primary study outcomes were the levels of total tau protein and p-tau181 in plasma samples and the cognitive status of the study participants. Results: A total of 37 male athletes participated in the study (mean [SD] age: exercise group, 21.6 [1.6] years; heading group, 21.2 [1.5] years). We found significantly elevated levels of total tau and p-tau181 in the plasma of soccer players 1 hour after physical exercise (tau, 1.4-fold; 95% CI, 1.2-1.5; P < .001; p-tau181, 1.4-fold; 95% CI, 1.3-1.5, P < .001) and repetitive head impacts (tau, 1.3-fold; 95% CI, 1.2-1.4; P < .001; p-tau181, 1.5-fold; 95% CI, 1.4-1.7 P < .001). The ratio of p-tau181 to tau was significantly higher 1 hour after exercise and heading training, and remained elevated specifically in the heading group even after 24 hours (1.2-fold; 95% CI, 1.1-1.3; P = .002). Performance in cognitive tests revealed a significant decline in focused attention and cognitive flexibility after physical exercise and heading training; physical exercise of higher intensity without heading training was associated with a greater negative cognitive performance than heading only. Conclusions and Relevance: In this cohort study of young elite soccer players, the elevation of p-tau181 and tau was observed after acute intense physical activity and nonconcussive repetitive head impacts. The increase of p-tau181 levels relative to tau after 24 hours indicated an acute enrichment of phosphorylated tau fraction in the periphery when compared with preimpact levels; an imbalance of tau proteins may have long-lasting consequences in the brain of head-impacted individuals.

Traumatic MicroRNAs: Deconvolving the Signal After Severe Traumatic Brain Injury.

History of traumatic brain injury (TBI) represents a significant risk factor for development of dementia and neurodegenerative disorders in later life. While histopathological sequelae and neurological diagnostics of TBI are well defined, the molecular events linking the post-TBI signaling and neurodegenerative cascades remain unknown. It is not only due to the brain's inaccessibility to direct molecular analysis but also due to the lack of well-defined and highly informative peripheral biomarkers. MicroRNAs (miRNAs) in blood are promising candidates to address this gap. Using integrative bioinformatics pipeline including miRNA:target identification, pathway enrichment, and protein-protein interactions analysis we identified set of genes, interacting proteins, and pathways that are connected to previously reported peripheral miRNAs, deregulated following severe traumatic brain injury (sTBI) in humans. This meta-analysis revealed a spectrum of genes closely related to critical biological processes, such as neuroregeneration including axon guidance and neurite outgrowth, neurotransmission, inflammation, proliferation, apoptosis, cell adhesion, and response to DNA damage. More importantly, we have identified molecular pathways associated with neurodegenerative conditions, including Alzheimer's and Parkinson's diseases, based on purely peripheral markers. The pathway signature after acute sTBI is similar to the one observed in chronic neurodegenerative conditions, which implicates a link between the post-sTBI signaling and neurodegeneration. Identified key hub interacting proteins represent a group of novel candidates for potential therapeutic targets or biomarkers.

Changes in circulating microRNAs following head impacts in soccer.

AIM: To explore the short-term effects of accidental head impacts and repetitive headers on circulating microRNAs, accounting for the effects of high-intensity exercise alone. METHODS: Blood samples were collected from professional soccer players at rest. Repeat samples were drawn 1 h and 12 h after three conditions: (1) accidental head impacts in a match, (2) repetitive headers during training, and (3) high-intensity exercise. 89 samples were screened to detect microRNAs expressed after each exposure. Identified microRNAs were then validated in 98 samples to determine consistently deregulated microRNAs. Deregulated microRNAs were further explored using bioinformatics to identify target genes and characterize their involvement in biological pathways. RESULTS: Accidental head impacts led to deregulation of eight microRNAs that were unaffected by high-intensity exercise; target genes were linked to 12 specific signaling pathways, primarily regulating chromatin organization, Hedgehog and Wnt signaling. Repetitive headers led to deregulation of six microRNAs that were unaffected by high-intensity exercise; target genes were linked to one specific signaling pathway (TGF-ß). High-intensity exercise led to deregulation of seven microRNAs; target genes were linked to 31 specific signaling pathways. CONCLUSION: We identified microRNAs specific to accidental head impacts and repetitive headers in soccer, potentially being useful as brain injury biomarkers.

Monoclonal antibodies targeting two immunodominant epitopes on the Spike protein neutralize emerging SARS-CoV-2 variants of concern.

BACKGROUND: The emergence of new SARS-CoV-2 variants of concern B.1.1.7 (Alpha), B.1.351 (Beta), P.1 (Gamma) and B.1.617.2 (Delta) that harbor mutations in the viral S protein raised concern about activity of current vaccines and therapeutic antibodies. Independent studies have shown that mutant variants are partially or completely resistant against some of the therapeutic antibodies authorized for emergency use. METHODS: We employed hybridoma technology, ELISA-based and cell-based S-ACE2 interaction assays combined with authentic virus neutralization assays to develop second-generation antibodies, which were specifically selected for their ability to neutralize the new variants of SARS-CoV-2. FINDINGS: AX290 and AX677, two monoclonal antibodies with non-overlapping epitopes, exhibit subnanomolar or nanomolar affinities to the receptor binding domain of the viral Spike protein carrying amino acid substitutions N501Y, N439K, E484K, K417N, and a combination N501Y/E484K/K417N found in the circulating virus variants. The antibodies showed excellent neutralization of an authentic SARS-CoV-2 virus representing strains circulating in Europe in spring 2020 and also the variants of concern B.1.1.7 (Alpha), B.1.351 (Beta) and B.1.617.2 (Delta). In addition, AX677 is able to bind Omicron Spike protein just like the wild type Spike. The combination of the two antibodies prevented the appearance of escape mutations of the authentic SARS-CoV-2 virus. Prophylactic administration of AX290 and AX677, either individually or in combination, effectively reduced viral burden and inflammation in the lungs, and prevented disease in a mouse model of SARS-CoV-2 infection. INTERPRETATION: The virus-neutralizing properties were fully reproduced in chimeric mouse-human versions of the antibodies, which may represent a promising tool for COVID-19 therapy. FUNDING: The study was funded by AXON Neuroscience SE and AXON COVIDAX a.s.

Plasma Leptin Reflects Progression of Neurofibrillary Pathology in Animal Model of Tauopathy.

The close relationship between Alzheimer's disease (AD) and obesity was recognized many years ago. However, complete understanding of the pathological mechanisms underlying the interactions between degeneration of CNS and fat metabolism is still missing. The leptin a key adipokine of white adipose tissue has been suggested as one of the major mediators linking the obesity and AD. Here we investigated the association between peripheral levels of leptin, general metabolic status and stage of the pathogenesis in rat transgenic model of AD. We demonstrate significantly decreased levels of plasma leptin in animals with experimentally induced progressive neurofibrillary pathology, which represents only 62.3% (P = 0.0015) of those observed in normal wild type control animals. More detailed analysis showed a strong and statistically significant inverse correlation between the load of neurofibrillary pathology and peripheral levels of leptin (r = - 0.7248, P = 0.0177). We also observed a loss of body weight during development of neurodegeneration (about 14% less than control animals, P = 0.0004) and decrease in several metabolic parameters such as glucose, insulin, triglycerides and VLDL in plasma of the transgenic animals. Our data suggest that plasma leptin could serve as a convenient peripheral biomarker for tauopathies and Alzheimer's disease. Decrease in gene expression of leptin in fat tissue and its plasma level was found as one of the consequences of experimentally induced neurodegeneration. Our data may help to design rational diagnostic and therapeutic strategies for patients suffering from Alzheimer's disease or other forms of tauopathy.

REPIMPACT - a prospective longitudinal multisite study on the effects of repetitive head impacts in youth soccer.

Repetitive head impacts (RHI) are common in youth athletes participating in contact sports. RHI differ from concussions; they are considered hits to the head that usually do not result in acute symptoms and are therefore also referred to as "subconcussive" head impacts. RHI occur e.g., when heading the ball or during contact with another player. Evidence suggests that exposure to RHI may have cumulative effects on brain structure and function. However, little is known about brain alterations associated with RHI, or about the risk factors that may lead to clinical or behavioral sequelae. REPIMPACT is a prospective longitudinal study of competitive youth soccer players and non-contact sport controls aged 14 to 16 years. The study aims to characterize consequences of exposure to RHI with regard to behavior (i.e., cognition, and motor function), clinical sequelae (i.e., psychiatric and neurological symptoms), brain structure, function, diffusion and biochemistry, as well as blood- and saliva-derived measures of molecular processes associated with exposure to RHI (e.g., circulating microRNAs, neuroproteins and cytokines). Here we present the structure of the REPIMPACT Consortium which consists of six teams of clinicians and scientists in six countries. We further provide detailed information on the specific aims and the design of the REPIMPACT study. The manuscript also describes the progress made in the study thus far. Finally, we discuss important challenges and approaches taken to overcome these challenges.

Peripheral microRNA alteration and pathway signaling after mild traumatic brain injury.

Discovering novel diagnostic biomarkers and signatures for traumatic brain injury (TBI) represents a major challenge in the brain trauma research. Detailed analysis of post-concussive molecular pathways based on experimental data could provide a new insight into the pathophysiological sequelae and mapping of recovery mechanisms involved in TBI. MicroRNAs (miRNAs) detectable in peripheral body fluids after TBI are promising carriers of this missing knowledge. In order to define the signature of peripheral miRNAs signaling associated with mild TBI (mTBI), we performed a comprehensive meta-analysis of miRNA profiles in mTBI patients using multiple curated pathway databases. Using a bioinformatic pipeline with integrated data analysis we identified a set of genes that are connected to deregulated circulating miRNAs following the mTBI. Identified genes belong to specific pathways of MAPK, TGF-ß, WNT, TLR2/4, PI3K/AKT, insulin, and growth factor signaling. Since the enriched pathways markedly overlap among the various biological fluids, signaling associated with mTBI that is concomitantly reflected in serum, plasma and saliva is robust and unique. Furthermore, we identified a network of 33 validated interacting proteins and their regulatory miRNAs that link the post-mTBI signaling in peripheral fluids with neurodegeneration-associated interaction pathways. Presented data provide a comprehensive insight into molecular events following mTBI, and the top predicted genes represent a group of novel candidate targets to be validated in connection with mTBI.

Head impacts in youth national hockey leagues in Slovakia: a retrospective analysis of four seasons.

Traumatic brain injury in contact sports can lead to serious health consequences either immediately or later in the life of injured subjects. The objective of this study was to estimate the incidence of head impacts in the Under 18 (U18) and Under 20 (U20) junior ice-hockey leagues in Slovakia over the seasons 2013/2014-2016/2017 using data from official game statistics. Incidence risks (IR) per 1000 athlete exposures were calculated for the season and stratified by a period of the game, by month, round, and part of the season. IR of head impacts ranged from 2.09 (95%CI: 2.07-2.12) to 2.89 (95%CI: 2.87-2.92) in the U18 league and from 2.14 (95%CI: 2.12-2.17) to 4.06 (95%CI: 4.02-4.09) in the U20. Higher IR was observed in the latter periods of games. This study brings first data on the incidence of concussions in youth ice-hockey leagues in Slovakia and calls for immediate implementation of measures to prevent these injuries.

Hypertension does not alter disturbances in leptin signalling observed in experimental model of tauopathy.

Neurodegeneration is associated with hypertension and disturbance in fat metabolism. The complex interaction of neurodegenerative processes with both metabolic changes and blood pressure is still not fully elucidated. Here we demonstrate that the experimentally induced tauopathy in hypertensive transgenic animals causes significant downregulation of plasma leptin (53% of control), reduction of body weight by 11%, a 1.2-fold drop of adiposity index, and decrease in HDL cholesterol level, while the fasting glucose and insulin concentration remain unchanged. Despite of these alterations we found the leptin projection circuit including the arcuate nucleus, paraventricular nucleus in hypothalamus, and nucleus tractus solitarius in the brainstem not affected by neurofibrillary pathology. Furthermore, hypertension does not alter disturbances in leptin signalling. The presented data provide further insight into neurodegeneration-induced metabolic alterations relevant for human tauopathies.

ADAMANT: a placebo-controlled randomized phase 2 study of AADvac1, an active immunotherapy against pathological tau in Alzheimer's disease.

Alzheimer's disease (AD) pathology is partly characterized by accumulation of aberrant forms of tau protein. Here we report the results of ADAMANT, a 24-month double-blinded, parallel-arm, randomized phase 2 multicenter placebo-controlled trial of AADvac1, an active peptide vaccine designed to target pathological tau in AD (EudraCT 2015-000630-30). Eleven doses of AADvac1 were administered to patients with mild AD dementia at 40 µg per dose over the course of the trial. The primary objective was to evaluate the safety and tolerability of long-term AADvac1 treatment. The secondary objectives were to evaluate immunogenicity and efficacy of AADvac1 treatment in slowing cognitive and functional decline. A total of 196 patients were randomized 3:2 between AADvac1 and placebo. AADvac1 was safe and well tolerated (AADvac1 n = 117, placebo n = 79; serious adverse events observed in 17.1% of AADvac1-treated individuals and 24.1% of placebo-treated individuals; adverse events observed in 84.6% of AADvac1-treated individuals and 81.0% of placebo-treated individuals). The vaccine induced high levels of IgG antibodies. No significant effects were found in cognitive and functional tests on the whole study sample (Clinical Dementia Rating-Sum of the Boxes scale adjusted mean point difference -0.360 (95% CI -1.306, 0.589)), custom cognitive battery adjusted mean z-score difference of 0.0008 (95% CI -0.169, 0.172). We also present results from exploratory and post hoc analyses looking at relevant biomarkers and clinical outcomes in specific subgroups. Our results show that AADvac1 is safe and immunogenic, but larger stratified studies are needed to better evaluate its potential clinical efficacy and impact on disease biomarkers.

Humanized tau antibodies promote tau uptake by human microglia without any increase of inflammation.

Immunotherapies targeting pathological tau have recently emerged as a promising approach for treatment of neurodegenerative disorders. We have previously showed that the mouse antibody DC8E8 discriminates between healthy and pathological tau, reduces tau pathology in murine tauopathy models and inhibits neuronal internalization of AD tau species in vitro.Here we show, that DC8E8 and antibodies elicited against the first-in-man tau vaccine, AADvac1, which is based on the DC8E8 epitope peptide, both promote uptake of pathological tau by mouse primary microglia. IgG1 and IgG4 isotypes of AX004, the humanized versions of DC8E8, accelerate tau uptake by human primary microglia isolated from post-mortem aged and diseased brains. This promoting activity requires the presence of the Fc-domain of the antibodies.The IgG1 isotype of AX004 showed greater ability to promote tau uptake compared to the IgG4 isotype, while none of the antibody-tau complexes provoked increased pro-inflammatory activity of microglia. Our data suggest that IgG1 has better suitability for therapeutic development.

Neurofilament light and tau in serum after head-impact exposure in soccer.

Introduction: Blood-based biomarkers can provide valuable information on the effects of repetitive head impacts in sports. This study investigated if repetitive headers or accidental head impacts in soccer could cause structural brain injury, detected as an increase in serum neurofilament light (NfL) or tau.Methods: NfL and tau were measured in professional soccer players in pre-season. Then, the effect of three short-term exposures on biomarker levels was assessed: (1) high-intensity exercise, (2) repetitive headers, and (3) head impacts in a match.Results: We analyzed 354 samples and observed no effects on NfL from any of the three short-term exposures. Tau levels rose significantly from baseline to 1 h after (1) high-intensity exercise (Δ0.50 pg/mL, 95% CI 0.19-0.81, p < .01); the same was observed after (2) repetitive headers (Δ0.29 pg/mL, 95% CI 0.10-0.48, p < .01), but not after (3) accidental head-impact incidents (Δ0.36 pg/mL, 95% CI -0.02-0.74, p = .06). The highest absolute values were seen 1 h after high-intensity exercise (mean±SD, 1.92 ± 0.83 pg/mL).Conclusion: NfL and tau in serum were unaffected by head impacts in soccer. Importantly, tau levels seem to rise in response to exercise, emphasizing the need for control groups. Our findings highlight important characteristics and limitations when using these biomarkers in sports.

Rickettsial infections of the central nervous system.

As a result of migrations and globalization, people may face a possible increase in the incidence of central nervous system rickettsial infections (CNS R). These diseases, caused by Rickettsia species and transmitted to humans by arthropod bites, are putatively lethal. However, the diagnosis of CNS R is challenging and often delayed due to their nonspecific clinical presentation and the strict intracellular nature of rickettsiae. Furthermore, transfer of rickettsiae to the brain parenchyma is not yet understood. The aim of this review is to analyze and summarize the features and correlated findings of CNS R in order to focus attention on these intriguing but frequently neglected illnesses. We also incorporated data on CNS infections caused by Rickettsia-related microorganisms.

Therapeutic antibody targeting microtubule-binding domain prevents neuronal internalization of extracellular tau via masking neuron surface proteoglycans.

Pathologically altered tau protein is a common denominator of neurodegenerative disorders including Alzheimer's disease (AD) and other tauopathies. Therefore, promising immunotherapeutic approaches target and eliminate extracellular pathogenic tau species, which are thought to be responsible for seeding and propagation of tau pathology. Tau isoforms in misfolded states can propagate disease pathology in a template-dependent manner, proposed to be mediated by the release and internalization of extracellular tau. Monoclonal antibody DC8E8, binding four highly homologous and independent epitopes in microtubule-binding domain (MTBD) of diseased tau, inhibits tau-tau interaction, discriminates between healthy and pathologically truncated tau and reduces tau pathology in animal model in vivo. Here, we show that DC8E8 antibody acts via extracellular mechanism and does not influence viability and physiological functions of neurons. Importantly, in vitro functional assays showed that DC8E8 recognises pathogenic tau proteins of different size and origin, and potently blocks their entry into neurons. Next, we examined the mechanisms by which mouse antibody DC8E8 and its humanized version AX004 effectively block the neuronal internalization of extracellular AD tau species. We determined a novel mode of action of a therapeutic candidate antibody, which potently inhibits neuronal internalization of AD tau species by masking of epitopes present in MTBD important for interaction with neuron surface Heparan Sulfate Proteoglycans (HSPGs). We show that interference of tau-heparane sulfate interaction with DC8E8 antibody via steric hindrance represents an efficient and important therapeutic approach halting tau propagation.

miRNAs as biofluid markers for diagnostics of Alzheimer's disease: recent status and perspectives.

After many decades of research in the field of neurodegeneration, we have no effective cure for Alzheimer's disease (AD), a major form of dementia. It is mainly due to the lack of early, reliable and sensitive biomarkers and incomplete understanding of disease mechanisms at molecular level. Several recently employed biomarkers, especially their combinations, can discriminate advanced stages of AD from other forms of dementia or neuropathy. They do not provide much information on molecular mechanisms of disease rather they reflect the amount of key histopathological markers in the diseased brain. This review is focussed on novel class of potentially very promising AD biomarkers: extracellular miRNAs in body liquids, such as cerebrospinal fluid and blood. They have a great potential not only to indicate the presence of AD, but more importantly, to reflect the molecular mechanisms playing a role early at the beginning of the pathogenic pathways consequently leading to AD. We believe this comprehensive review on deregulated miRNAs in AD can be a good source of information for thorough in silico analyses aiming to identification, development and validation of miRNAs as "diseases mechanism engaged" candidate biomarkers. Having such molecules could bring us closer to the goal - successful treatment of AD.

A Novel Association of Polymorphism in the ITGA4 Gene Encoding the VLA-4 α4 Subunit with Increased Risk of Alzheimer's Disease.

Alzheimer's disease (AD) is the most prevalent cause of dementia in elderly people worldwide. Many studies support the hypothesis that the inflammation of the CNS contributes to the neurodegeneration and disease progression. The integrin molecule α4ß1, also known as very late antigen 4 (VLA-4), belongs to adhesion molecules that activate the inflammatory process through the migration of immune cells into the CNS. Therefore, the objective of our study was to analyze the association between two polymorphisms located in the ITGA4 gene encoding the α4 subunit of VLA-4 and the risk of AD. 104 late-onset AD patients and 206 control subjects from Slovakia were genotyped for ITGA4 gene SNP polymorphism rs113276800 (-269C/A) and rs1143676 (+3061A/G). The same study cohorts were also genotyped for the APOE-ε4, which is a known genetic factor associated with increased risk of AD developing. ITGA4 polymorphism analysis revealed significantly higher frequency of the +3061AG carriers in AD group compared to the controls (P ≤ 0.05). Following the APOE-ε4 stratification of study groups, the association remained significant only in APOE-ε4 noncarriers. Our study suggests a novel association of ITGA4 +3061A/G polymorphism with AD and its possible contribution to the disease pathology.

Stress-Induced Alterations of Immune Profile in Animals Suffering by Tau Protein-Driven Neurodegeneration.

Alzheimer's disease (AD) is a multifactorial disorder; neurofibrillary pathology composed of tau protein is found side by side with amyloid-ß deposits and extensive neuroinflammation. The immune system of the brain is considered as one of the factors that could influence the speed of the progression of AD neuropathology as a potential mediator of the damage induced by AD protein deposits. Alzheimer's disease pathology can be impacted by psychological stress; however, signalling pathways in background are not well known. We have explored possible avenues of how stress could influence the brain's immune system in a rat model of AD. Animals were subjected either to a single or multiple instances of immobilization stress. The analysis of a panel of immunity-related genes was used to evaluate the impact of stress on the immune response in the brain. We have identified 19 stress-responsive genes that are involved in neuroinflammation accompanying tau pathology: Nos2, Ptgs2, IL-8rb, C5, Mmp9, Cx3cr1, CD40lg, Adrb2, IL-6, IL-6r, IL-1r2, Ccl2, Ccl3, Ccl4, Ccl12, TNF-α, IL-1α, IL-1ß, IL-10. Most of them are deregulated under the stress conditions also in control animals; however, the magnitude of the response to either acute or chronic stress differs. This can lead to serious influence, most probably to acceleration of neurodegenerative phenotype in diseased animals. Several of the genes (IL-1ß, Casp1, Cx3cr1 and C5) are deregulated solely in tauopathic animals. The stress-induced changes in the inflammatory picture of the brain highlight the fact that the brain's immune response is highly responsive to environmental stimuli. The pattern of changes is indicative of an attempt to protect the brain in the short term, while being potentially detrimental to the response against a long-term pathological process such as neurofibrillary degeneration.

Neuronal Expression of Truncated Tau Efficiently Promotes Neurodegeneration in Animal Models: Pitfalls of Toxic Oligomer Analysis.

Animal models of neurodegeneration induced by neuronal expression of truncated tau protein emerge as an important tool for understanding the pathogenesis of human tauopathies and for therapy development. Here we highlight common features of truncated tau models and make a critical assessment of possible pitfalls in their analysis. Particularly, the amount of soluble tau oligomers, which are suspected to be neurotoxic agents participating on the spreading of pathology inside the brain, may be overestimated due to a post-lysis oxidative tau oligomerization. Using a mouse brain lysate spiked with recombinant truncated and full length tau forms, we show that tau oligomers might inadvertently be produced during the isolation procedure. This finding is further corroborated by the analysis of brain lysates originated from a mouse model expressing truncated tau variant. Our results underline the necessity of thiol-protecting conditions during the analysis of tau oligomers involved in the etiopathogenesis of various tauopathies including Alzheimer's disease.