Neurodegeneration: 2022 update.

Here, we review a collection of recent manuscripts and research trends on the neuropathology of neurodegeneration that are considered by the author to be among the potentially most impactful. To the greatest extent possible, we chose to focus on histopathological studies that are most relevant to experimental and diagnostic neuropathology. While there has been an abundance of important recent discoveries and developments in neurodegenerative disease research, there was a deliberate effort here to provide balance to prevent disease categories and experimental approaches from overshadowing the others. The result is a diverse series of outstanding studies, together showing the landscape of progress across neurodegenerative disorders. One is a stereological study examining dystrophic microglia in aging. We highlight the first large genetic study of primary age-related tauopathy, showing convergence and divergence from classical Alzheimer's disease. There were further advances in the neuropathological criteria and staging of chronic traumatic encephalopathy. Links suggesting a causal role for TMEM106B in TDP-43 proteinopathy emerged. Attempts to subtype Alzheimer's disease on the molecular level were made. Evidence for a role for the VEGF family in cognitive impairment was advanced. Comparison of gene expression profiles from myeloid cells in peripheral blood and brain tissues from Parkinson's disease patients revealed pathways that may lead to new mechanistic insights and biomarkers. A large autopsy series identified an increased frequency of central nervous system developmental malformations in Huntington's disease. A robust and reliable system for assessing Lewy body pathology was proposed. Finally, we continue to be plagued by the COVID-19 pandemic, with lingering concerns of a long-term link with neurodegeneration.

Neurodegeneration: 2021 update.

This article reviews a collection of manuscripts in the field of neurodegenerative disease chosen from what are considered by the author to be among the 10 most important and potentially impactful topics or research trends of 2020 relevant to the field of experimental and diagnostic neuropathology. A deliberate effort was made to provide balance among disease categories covered. The result is a varied selection that includes not just individual papers but also research topics and trends. The association of COVID-19 with longer-term neurological symptoms has launched a research trend fueled by speculation that the SARS-CoV-2 might trigger neurodegenerative changes. The onslaught of transcriptomic studies has begun to give way to proteomics, with three transformative studies published examining glial contributions to Alzheimer disease, cerebral atherosclerosis in cognitive decline, and the complex sequence of post-translational modifications of the tau protein. Plasma biomarkers for Alzheimer disease have continued to make rapid advances, especially around highly sensitive assays capable of detecting different forms of abnormal hyperphosphorylated tau in peripheral blood. Two studies using cryo-electron microscopy showed the power of the approach by continuing to elucidate the diversity of filamentous tau inclusions, and a third study gave the first glimpse of α-synuclein aggregates at near atomic resolution. Another study continued to delineate how different α-synuclein conformers ("strains") target specific brain regions and lead to neurodegeneration. In Huntington's disease, we saw compelling molecular data showing how cells adapt to endoplasmic reticulum stress through the unfolded protein response. Finally, the role of astrocytes in chronic traumatic encephalopathy has emerged as a critical area of interest.

5th Asian Oceanian Congress of Neuropathology along with the 5th Annual Conference of the Neuropathology Society of India (AOCN-NPSICON) - Meeting Abstracts.

The 5th Asian Oceanian Congress of Neuropathology along with the 5th Annual Conference of the Neuropathology Society of India (AOCN-NPSICON) was held in virtual mode on September 24-26, 2021, at National Institute of Mental Health and Neurosciences (NIMHANS), Bangalore, India, hosted by the Department of Neuropathology. It had 361 attendees from 20 countries from Asia and Oceania including India. The event brought together pathologists, clinicians and neuroscientists from all over Asia and Oceania with invited speakers from the USA, Germany and Canada. The program was very comprehensive and covered advances in the fields of neurooncology with emphasis on the upcoming WHO 2021 classification of CNS tumors, neuromuscular disorders, epilepsy and neurodegenerative disorders through key note addresses and symposia that featured 78 distinguished international and national faculty sharing their expertise. In addition, there were case-based learning modules, opportunities for paper presentations and poster sessions for young faculty and postgraduates with several awards for young investigators, best papers and posters. A highlight of the conference was a unique debate on the hot topic of the decade: Methylation-based classification of CNS tumors and a panel discussion on COVID-19. The participants were highly appreciative of the academic content.

65th Annual Meeting of the German Society of Neuropathology and Neuroanatomy (DGNN) - Meeting Abstracts.

Dear participants, dear colleagues, It is our great pleasure to welcome you to the 65th Annual Meeting of the German Society of Neuropathology and Neuroanatomy - the brain and nerve microenvironment in health and disease - which will be held as a virtual meeting from September 1-3, 2021. The meeting will bring together basic and clinical researchers, physicians as well as junior scientists and PhD students from different disciplines of basic and clinical neuroscience. We will have outstanding lectures by and with some of the most renowned international experts in the field of neuro-oncology, neuroinflammation, neurodegeneration and muscle and nerve diseases and look forward to exciting scientific discussions. There will also be a special and timely section on the effects of COVID-19 on the central and peripheral nervous system. The three days will offer exciting insights into different areas of basic and clinical neuroscience. We have also encouraged early career scientists to present their scientific findings in short talks and poster presentations. We are therefore particularly thankful that the abstracts of the meeting, which in their sum provide the best overview of the high scientific standing of the field, will be published in Free Neuropathology. Finally, we would like to thank you all for your active contribution to this conference in these difficult times. We also thank all supporters for their financial help. We wish you a stimulating and exciting conference. Yours sincerely, Prof. Dr. med. Till Acker Conference Chair (Justus Liebig University Giessen) PD. Dr. med. Anne Schänzer Dr. med. Hildegard Dohmen.

Consensus Clinical Guidance for Diagnosis and Management of Adult COVID-19 Encephalopathy Patients.

Encephalopathy, a common condition among patients hospitalized with COVID-19, can be a challenge to manage and negatively affect prognosis. While encephalopathy may present clinically as delirium, subsyndromal delirium, or coma and may be a result of systemic causes such as hypoxia, COVID-19 has also been associated with more prolonged encephalopathy due to less common but nevertheless severe complications, such as inflammation of the brain parenchyma (with or without cerebrovascular involvement), demyelination, or seizures, which may be disproportionate to COVID-19 severity and require specific management. Given the large number of patients hospitalized with severe acute respiratory syndrome coronavirus-2 infection, even these relatively unlikely complications are increasingly recognized and are particularly important because they require specific management. Therefore, the aim of this review is to provide pragmatic guidance on the management of COVID-19 encephalopathy through consensus agreement of the Global COVID-19 Neuro Research Coalition. A systematic literature search of MEDLINE, medRxiv, and bioRxiv was conducted between January 1, 2020, and June 21, 2021, with additional review of references cited within the identified bibliographies. A modified Delphi approach was then undertaken to develop recommendations, along with a parallel approach to score the strength of both the recommendations and the supporting evidence. This review presents analysis of contemporaneous evidence for the definition, epidemiology, and pathophysiology of COVID-19 encephalopathy and practical guidance for clinical assessment, investigation, and both acute and long-term management.

Inflammatory and Blood-Brain Barrier Markers after Covid-19 among People with Hiv

Background: COVID-19, the disease caused by SARS-CoV-2, has resulted in devastating morbidity and mortality worldwide. Alarming evidence indicates that long-term adverse outcomes of COVID-19 can affect all major systems of the body, including the immune, respiratory, cardiovascular, and neurological systems. While acute COVID-19 pathology does not appear to be markedly different by HIV status, long-term outcomes of COVID-19 in People with HIV (PWH) are unknown and require further investigation. This study evaluates the inflammatory profile longitudinally up to three months after COVID-19. In addition, markers of the blood-brain barrier (BBB) integrity and vascular dysfunction were also evaluated. Method(s): Plasma samples were collected from 15 males and 6 females with COVID-19 and HIV infection (COVID+/HIV+) and 9 males and 14 females with COVID-19 without HIV infection (COVID+/HIV-) between March 2020 and March 2021. Baseline samples were obtained approx. 10 days after COVID-19 diagnosis (T=0) and three months after (T=3). Mean age group for COVID+/HIV-was 45.4+/-17.8 years for males and 39.7+/-15.3 for females and for COVID+/HIV+ was 52.1+/-12.3 for males and 48.7+/-1 for females (N=15 and 6, respectively). 27 inflammatory molecules were measured by Bio-Plex Multiplex Immunoassay (Bio-Rad) and two markers of BBB and vascular dysfunction (soluble ICAM1 and S100beta) by ELISA. Result(s): Out of 27 inflammatory analytes, 20 had detectable signals. Eotaxin (CCL11) and G-CSF levels were differentially upregulated in the COVID+/HIV+ group as compared to the COVID+/HIV-group in both time point studied (Table 1). IFN-g showed sustained increased levels at T=3 in the COVID+/HIV+ group, whereas there was a significant reduction over time in the COVID+/HIV-group. At T3, inflammatory markers (IL-4, IL-8, IL-13, basic FGF, TNF-alpha, MIP-1alpha, and CCL2) either decreased or remained unchanged in both groups. In contrast, the markers of the BBB disruption and vascular dysfunction, such as S100beta and soluble ICAM-1 increased in the COVID+/HIV+ group, suggesting long-term progressive BBB and vascular alterations. Conclusion(s): HIV-1 may potentiate long COVID-19-induced neuropathology, with progressive BBB breakdown and sustained increase in eotaxin-1 and G-CSF. Plasma inflammatory markers in COVID-19 patients with or without HIV-1 co-infection.

ACE2 Receptor and TMPRSS2 Protein Expression Patterns in the Human Brainstem Reveal Anatomical Regions Potentially Vulnerable to SARS-CoV-2 Infection.

Angiotensin-converting enzyme 2 receptor (ACE2R) is a transmembrane protein expressed in various tissues throughout the body that plays a key role in the regulation of blood pressure. Recently, ACE2R has gained significant attention due to its involvement in the pathogenesis of COVID-19, the disease caused by the Severe Acute Respiratory Syndrome CoronaVirus 2 (SARS-CoV-2). While ACE2 receptors serve as entry points for the novel coronavirus, Transmembrane Serine Protease 2 (TMPRSS2), an enzyme located on the cell membrane, is required for SARS-CoV-2 S protein priming. Even though numerous studies have assessed the effects of COVID-19 on the brain, very little information is available concerning the distribution of ACE2R and TMPRSS2 in the human brain, with particular regard to their topographical expression in the brainstem. In this study, we investigated the expression of ACE2R and TMPRSS2 in the brainstem of 18 adult subjects who died due to pneumonia/respiratory insufficiency. Our findings indicate that ACE2R and TMPRSS2 are expressed in neuronal and glial cells of the brainstem, particularly at the level of the vagal nuclei of the medulla and the midbrain tegmentum, thus confirming the expression and anatomical localization of these proteins within specific human brainstem nuclei. Furthermore, our findings help to define anatomically susceptible regions to SARS-CoV-2 infection in the brainstem, advancing knowledge on the neuropathological underpinnings of neurological manifestations in COVID-19.

Multifactorial White Matter Damage in the Acute Phase and Pre-Existing Conditions May Drive Cognitive Dysfunction after SARS-CoV-2 Infection: Neuropathology-Based Evidence.

BACKGROUND: There is an urgent need to better understand the mechanisms underlying acute and long-term neurological symptoms after COVID-19. Neuropathological studies can contribute to a better understanding of some of these mechanisms. METHODS: We conducted a detailed postmortem neuropathological analysis of 32 patients who died due to COVID-19 during 2020 and 2021 in Austria. RESULTS: All cases showed diffuse white matter damage with a diffuse microglial activation of a variable severity, including one case of hemorrhagic leukoencephalopathy. Some cases revealed mild inflammatory changes, including olfactory neuritis (25%), nodular brainstem encephalitis (31%), and cranial nerve neuritis (6%), which were similar to those observed in non-COVID-19 severely ill patients. One previously immunosuppressed patient developed acute herpes simplex encephalitis. Acute vascular pathologies (acute infarcts 22%, vascular thrombosis 12%, diffuse hypoxic-ischemic brain damage 40%) and pre-existing small vessel diseases (34%) were frequent findings. Moreover, silent neurodegenerative pathologies in elderly persons were common (AD neuropathologic changes 32%, age-related neuronal and glial tau pathologies 22%, Lewy bodies 9%, argyrophilic grain disease 12.5%, TDP43 pathology 6%). CONCLUSIONS: Our results support some previous neuropathological findings of apparently multifactorial and most likely indirect brain damage in the context of SARS-CoV-2 infection rather than virus-specific damage, and they are in line with the recent experimental data on SARS-CoV-2-related diffuse white matter damage, microglial activation, and cytokine release.

Progressive multifocal leukoencephalopathy, neuroradiology-neuropathology

Introduction: Progressive multifocal leukoencepha-lopathy (PmL) is an unfavorable demyelinating disease of the CNS caused by reactivation of JC virus (JCV). JCV is a double-stranded DNA human polyomavirus predominatingly acquired in childhood. Blood samples taken from healthy persons indicate that 50-90% of adults have been exposed to this virus. JCV is an opportunistic pathogen, with PmL manifesting primarily in patients with immunodefciency or taking immunomodulatory treatments or with lymphoproliferative diseases. We report a patient who developed PmL shortly after diagnosis of follicular lymphomma. Case presentation: A 70-year-old-woman admitted to the neurological departament with hemiparesis, psy-chomotor slowing down, balance problems, dizziness and in depressed mood. the patient underwent aorto-femoral transplant 12 years ago and for 10 years was under constant observation of a hematologist due to enlarged lymph nodes. Five years ago, the patient had planoepithelial cell carcinoma removed. the patient also sufered from COViD-19 infection and sufered from depression. elevated leukocytosis and D dimers, were the only abnormal results obtained in laboratory tests. However, pulmonary embolism was excluded in Ct angio. Cytometry of blood showed follicular lymphoma. Radiological fndings: mRi and Ct scans showed multiple asymmetrical pathological areas of hyperin-tense signal in t2-dependent images, hypointense in t1-dependent ones and Ct-hypodense regions which extended continuously in control examinations. they were located in the white matter of multiple lobes of both brain hemispheres subcortically and periventric-ullary. the subcortical U-fbers were involed. they did not show contrast enhancement and mass efect. they showed peripheral ring and patchy difusion restriction particularly at their leading edge. in spite of the used steroid therapy the patient's health deteriorated rapidly. the patient died of symptoms of cardio-respiratory failure 1 month after admission to hospital. Neuropathological features: the neuropathological examination revealed numerous foci of demyelination in the white matter of the frontal lobe, the parietal lobe in the pons and in the cerebellum. myelin losses were accompanied by damage to oligodendrocytes and proliferation of macrophages. the nuclei of the damaged oligodendrocytes were enlarged and hyperchromatic, and some had a "ground-glass" appearance typical of viral infection. the astrocytes were bizarre with lobulat-ed, hiperchromatic or hypochromatic nuclei and damage of cytoplasmic procesesses (clasmatodendrosis). Conclusion(s): the triad of neuropathological injuries: destruction of oligodendrocytes with intranuclear viral inclusions ("ground-glass" appearance), multifocal demyelination and bizarre astrocytes allowed for the diagnosis of late form of classical progressive multifo-cal leukoencephalopathy (cPmL), despite the short time since diagnosis of follicular lymphoma, but with many years of enlargement of the lymph nodes.

Impact of COVID-19 pandemic on neuropathology service: Experience at one Canadian center.

The COVID-19 pandemic has had a significant impact on medical services. Many countries postponed nonemergent procedures to preserve hospital resources for the unprecedented situation. Surgical backlogs caused by the COVID-19 pandemic have been evaluated by different groups. However, the impact of this pandemic on pathology and specifically neuropathology (NP) services has received limited attention. In this study, we reviewed all NP reports of the London Health Sciences Centre from January 2018 (2 years before the pandemic declaration) until the end of the year 2021. Demographic information and pathology details were collected. For tumors, site, histopathology types, and WHO grading were analyzed. In nontumoral specimens, pathological diagnoses were compared in pre- and postpandemic time. The total number of NP samples reached its lowest in April 2020, corresponding to the first Ontario provincial lockdown, and fluctuated throughout the studied period. Among the different types of NP surgical specimens, muscle and epilepsy-related specimens showed a more significant reduction, compared to neoplastic specimens. In 2020, the proportion of tumor specimens from patients older than 40 years of age increased. Similarly, the proportion of high-grade glioma and brain metastasis diagnoses also increased. Lastly, we observed a marked increase in biopsies for temporal arteritis and other inflammatory lesions.

Neuropathology of 30 deceased patients with COVID-19: a case series in Tehran, Iran.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can affect the nervous system and result in neurological symptoms. The most common feature of central nervous system involvement is hypoxia and congestion. This study aimed to evaluate the histopathology of cerebral tissue in deceased patients with coronavirus disease 2019 (COVID-19). Methods: In a case series study, we took cerebral samples of 30 deceased patients with COVID-19 through supraorbital bone from January to May 2021. The samples were fixed in a formalin solution, stained with haematoxylin-eosin dyes and studied by two expert pathologists. The Ethics Committee of AJA University of Medical Sciences approved this study with code IR.AJAUMS.REC.1399.030. Results: The mean age of the patients was 73.8 years, and the most common underlying disease was hypertension. Cerebral tissue samples showed hypoxic-ischaemic changes in 28 (93.3%), microhaemorrhage in six (20%), lymphocytic infiltration in five (16.7%) and thrombosis in three samples (10%). Conclusion: Hypoxic-ischaemic change was the most common neuropathology in our patient. Our study showed that many patients with severe COVID-19 may develop central nervous system involvement.

Neuropathological features of SARS-CoV-2 delta and omicron variants.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is continually evolving resulting in variants with increased transmissibility, more severe disease, reduced effectiveness of treatments or vaccines, or diagnostic detection failure. The SARS-CoV-2 Delta variant (B.1.617.2 and AY lineages) was the dominant circulating strain in the United States from July to mid-December 2021, followed by the Omicron variant (B.1.1.529 and BA lineages). Coronavirus disease 2019 (COVID-19) has been associated with neurological sequelae including loss of taste/smell, headache, encephalopathy, and stroke, yet little is known about the impact of viral strain on neuropathogenesis. Detailed postmortem brain evaluations were performed for 22 patients from Massachusetts, including 12 who died following infection with Delta variant and 5 with Omicron variant, compared to 5 patients who died earlier in the pandemic. Diffuse hypoxic injury, occasional microinfarcts and hemorrhage, perivascular fibrinogen, and rare lymphocytes were observed across the 3 groups. SARS-CoV-2 protein and RNA were not detected in any brain samples by immunohistochemistry, in situ hybridization, or real-time quantitative PCR. These results, although preliminary, demonstrate that, among a subset of severely ill patients, similar neuropathological features are present in Delta, Omicron, and non-Delta/non-Omicron variant patients, suggesting that SARS-CoV-2 variants are likely to affect the brain by common neuropathogenic mechanisms.

Cerebrospinal Fluid Protein Markers Indicate Neuro-Damage in SARS-CoV-2-Infected Nonhuman Primates.

Neurologic manifestations are among the most frequently reported complications of COVID-19. However, given the paucity of tissue samples and the highly infectious nature of the etiologic agent of COVID-19, we have limited information to understand the neuropathogenesis of COVID-19. Therefore, to better understand the impact of COVID-19 on the brain, we used mass-spectrometry-based proteomics with a data-independent acquisition mode to investigate cerebrospinal fluid (CSF) proteins collected from two different nonhuman primates, Rhesus Macaque and African Green Monkeys, for the neurologic effects of the infection. These monkeys exhibited minimal to mild pulmonary pathology but moderate to severe central nervous system (CNS) pathology. Our results indicated that CSF proteome changes after infection resolution corresponded with bronchial virus abundance during early infection and revealed substantial differences between the infected nonhuman primates and their age-matched uninfected controls, suggesting these differences could reflect altered secretion of CNS factors in response to SARS-CoV-2-induced neuropathology. We also observed the infected animals exhibited highly scattered data distributions compared to their corresponding controls indicating the heterogeneity of the CSF proteome change and the host response to the viral infection. Dysregulated CSF proteins were preferentially enriched in functional pathways associated with progressive neurodegenerative disorders, hemostasis, and innate immune responses that could influence neuroinflammatory responses following COVID-19. Mapping these dysregulated proteins to the Human Brain Protein Atlas found that they tended to be enriched in brain regions that exhibit more frequent injury following COVID-19. It, therefore, appears reasonable to speculate that such CSF protein changes could serve as signatures for neurologic injury, identify important regulatory pathways in this process, and potentially reveal therapeutic targets to prevent or attenuate the development of neurologic injuries following COVID-19.

Young COVID-19 Patients Show a Higher Degree of Microglial Activation When Compared to Controls.

The severe acute respiratory syndrome-corona virus type 2 (SARS-CoV-2) is the cause of human coronavirus disease 2019 (COVID-19). Since its identification in late 2019 SARS-CoV-2 has spread rapidly around the world creating a global pandemic. Although considered mainly a respiratory disease, COVID-19 also encompasses a variety of neuropsychiatric symptoms. How infection with SARS-CoV-2 leads to brain damage has remained largely elusive so far. In particular, it has remained unclear, whether signs of immune cell and / or innate immune and reactive astrogliosis are due to direct effects of the virus or may be an expression of a non-specific reaction of the brain to a severe life-threatening disease with a considerable proportion of patients requiring intensive care and invasive ventilation activation. Therefore, we designed a case-control-study of ten patients who died of COVID-19 and ten age-matched non-COVID-19-controls to quantitatively assess microglial and astroglial response. To minimize possible effects of severe systemic inflammation and / or invasive therapeutic measures we included only patients without any clinical or pathomorphological indication of sepsis and who had not been subjected to invasive intensive care treatment. Our results show a significantly higher degree of microglia activation in younger COVID-19 patients, while the difference was less and not significant for older COVID-19 patients. The difference in the degree of reactive gliosis increased with age but was not influenced by COVID-19. These preliminary data warrants further investigation of larger patient cohorts using additional immunohistochemical markers for different microglial phenotypes.

Therapeutic Potential of Music-Based Interventions on the Stress Response and Neuroinflammatory Biomarkers in COVID-19: A Review

COVID-19 continues to strain healthcare systems around the globe. Research has shown a relationship between COVID-19 and an inflammatory response, including neuropathological outcomes. Additionally, studies have shown positive effects of engagement with music on inflammatory responses;music may have potential, as a method, to reduce inflammation triggered by COVID-19. This review compiles exhaustive research from multiple disciplines to account for this possibility. The authors utilized a meta-narrative approach to complete this review. The search was conducted using PubMed, Embase, OneSearch, Primo, Google Scholar, Clinicaltrials.gov, and the bibliographies of relevant articles. In total, 84 articles were included for full-text review, discussion, and analysis. Articles pertaining to music and acoustics encompassed a date range from 1964–2020. Articles referencing COVID-19 spanned the years 2019–2021. This work focused on associations between engagement with music, stress response, blood-brain barrier integrity, inflammation, COVID-19, and neuropathology in preclinical and clinical models. Detailed analysis revealed that engagement with music has the potential to reduce the harmful effects of COVID-19, particularly in the inflammation and blood clotting pathways associated with a range of pathophysiological and neuropathological issues. Further work is warranted to standardize and validate existing methods associating positive effects of engagement with music on the negative effects of COVID-19. © The Author(s) 2023.

A novel mouse model of SARS-CoV-2 induced neuroinflammation

Background: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection may impact neurological function acutely or chronically, even in the absence of severe respiratory illness. Developing clinically relevant laboratory models to understand the neuropathogenesis of SARS-CoV-2 infection is an important step towards unravelling this neurologic consequence. We hypothesize that mouse adapted SARS-CoV-2 viral infection will induce neuroinflammation in immuno-competent C57BL/6J (10 weeks old male) as well as immunodeficient RAG2-/- (10 weeks old male) and BALB/c (1 year old female) mice. Method(s): All three mouse strains were inoculated intranasally with a dose of 1x103 PFU/mouse (50 microL) of either mock or the mouse-adapted (MA)10 strain of SARS-CoV-2 (BEI resource, NR-55329). Mice were euthanized on day 2, 3, 7, 15 or 30 post infection and brain samples processed for qRT-PCR, immunofluorescence, and H&E analysis. Result(s): SARS-CoV-2 MA10 resulted in a significantly higher (p < 0.05) mRNA expression for chemokine ligand 2 (CCL2) and lower (p < 0.05) mRNA expression for the blood-brain barrier component Claudin-5 in RAG2-/- and WT mice when compared to mock infection. Also, SARS-CoV-2 MA10 infection increased microglial expression in 1 year old female BALB/c mice after 2 days of infection, compared to mock infected group. At 30 days post infection, MA10 infected BALB/c mice had a higher perivascular lymphocyte cuffing in the brain. Conclusion(s): This study demonstrates that the mouse-adapted MA10 strain of SARS-CoV-2 can induce a neuroinflammatory state in the brain and more so in immunodeficient and aging mouse models. These mouse models will enable the investigation of the long-term neurological effects of SARS-CoV-2 infection. Copyright © 2022 the Alzheimer's Association.

The Adverse Outcome Pathway Framework Applied to Neurological Symptoms of COVID-19.

Several reports have shown that the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has the potential to also be neurotropic. However, the mechanisms by which SARS-CoV-2 induces neurologic injury, including neurological and/or psychological symptoms, remain unclear. In this review, the available knowledge on the neurobiological mechanisms underlying COVID-19 was organized using the AOP framework. Four AOPs leading to neurological adverse outcomes (AO), anosmia, encephalitis, stroke, and seizure, were developed. Biological key events (KEs) identified to induce these AOs included binding to ACE2, blood-brain barrier (BBB) disruption, hypoxia, neuroinflammation, and oxidative stress. The modularity of AOPs allows the construction of AOP networks to visualize core pathways and recognize neuroinflammation and BBB disruption as shared mechanisms. Furthermore, the impact on the neurological AOPs of COVID-19 by modulating and multiscale factors such as age, psychological stress, nutrition, poverty, and food insecurity was discussed. Organizing the existing knowledge along an AOP framework can represent a valuable tool to understand disease mechanisms and identify data gaps and potentially contribute to treatment, and prevention. This AOP-aligned approach also facilitates synergy between experts from different backgrounds, while the fast-evolving and disruptive nature of COVID-19 emphasizes the need for interdisciplinarity and cross-community research.

COVID-19 Pathology in the Lung, Kidney, Heart and Brain: The Different Roles of T-Cells, Macrophages, and Microthrombosis.

Here, we aim to describe COVID-19 pathology across different tissues to clarify the disease's pathophysiology. Lungs, kidneys, hearts, and brains from nine COVID-19 autopsies were compared by using antibodies against SARS-CoV-2, macrophages-microglia, T-lymphocytes, B-lymphocytes, and activated platelets. Alzheimer's Disease pathology was also assessed. PCR techniques were used to verify the presence of viral RNA. COVID-19 cases had a short clinical course (0-32 days) and their mean age was 77.4 y/o. Hypoxic changes and inflammatory infiltrates were present across all tissues. The lymphocytic component in the lungs and kidneys was predominant over that of other tissues (p < 0.001), with a significantly greater presence of T-lymphocytes in the lungs (p = 0.020), which showed the greatest presence of viral antigens. The heart showed scant SARS-CoV-2 traces in the endothelium-endocardium, foci of activated macrophages, and rare lymphocytes. The brain showed scarce SARS-CoV-2 traces, prominent microglial activation, and rare lymphocytes. The pons exhibited the highest microglial activation (p = 0.017). Microthrombosis was significantly higher in COVID-19 lungs (p = 0.023) compared with controls. The most characteristic pathological features of COVID-19 were an abundance of T-lymphocytes and microthrombosis in the lung and relevant microglial hyperactivation in the brainstem. This study suggests that the long-term sequelae of COVID-19 derive from persistent inflammation, rather than persistent viral replication.