SARS-CoV-2-mediated encephalitis: Role of AT2R receptors in the blood-brain barrier

Review of Neurological Manifestations of SARS-CoV-2

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can affect any part of the neuraxis. Many neurological conditions have been attributed to be caused by SARS-CoV-2, namely encephalopathy (acute necrotizing encephalopathy and encephalopathy with reversible splenial lesions), seizures, stroke, cranial nerve palsies, meningoencephalitis, acute disseminated encephalomyelitis (ADEM), transverse myelitis (long and short segment), Guillain-Barré syndrome (GBS) and its variants, polyneuritis cranialis, optic neuritis (ON), plexopathy, myasthenia gravis (MG), and myositis. The pathophysiology differs depending on the time frame of presentation. In patients with concomitant pulmonary disease, for instance, acute neurological illness appears to be caused by endotheliopathy and cytokine storm. Autoimmunity and molecular mimicry are causative for post-coronavirus disease 2019 (COVID-19)-sequelae. It has not yet been shown that the virus can penetrate the central nervous system (CNS) directly. This review aims to describe the disease and root pathogenic cause of the various neurological manifestations of COVID-19. We searched Pubmed/Medline and Google Scholar using the keywords "SARS-CoV-2" and "neurological illness" for articles published between January 2020 and November 2022. Then, we used the SWIFT-Review (Sciome LLC, North Carolina, United States), a text-mining workbench for systematic review, to classify the 1383 articles into MeSH hierarchical tree codes for articles on various parts of the nervous system, such as the CNS, peripheral nervous system, autonomic nervous system, neuromuscular junction, sensory system, and musculoskeletal system. Finally, we reviewed 152 articles in full text. SARS-CoV-2 RNA has been found in multiple brain areas without any histopathological changes. Despite the absence of in vivo virions or virus-infected cells, CNS inflammation has been reported, especially in the olfactory bulb and brain stem. SARS-CoV-2 genomes and proteins have been found in affected individuals' brain tissues, but corresponding neuropathologic changes are seldom found in these cases. Additionally, viral RNA can rarely be identified in neurological patients' CSF post hoc SARS-CoV-2 infection. Most patients with neurological symptoms do not have active viral replication in the nervous system and infrequently have typical clinical and laboratory characteristics of viral CNS infections. Endotheliopathy and the systemic inflammatory response to SARS-CoV-2 infection play a crucial role in developing neuro-COVID-19, with proinflammatory cytokine release mediating both pathological pathways. The systemic inflammatory mediators likely activate astrocytes and microglia across the blood-brain barrier, indirectly affecting CNS-specific immune activation and tissue injury. The management differs according to co-morbidities and the neurological disorder.

Human Brain Microvascular Endothelial Cells Exposure to SARS-CoV-2 Leads to Inflammatory Activation through NF-κB Non-Canonical Pathway and Mitochondrial Remodeling

Neurological effects of COVID-19 and long-COVID-19, as well as neuroinvasion by SARS-CoV-2, still pose several questions and are of both clinical and scientific relevance. We described the cellular and molecular effects of the human brain microvascular endothelial cells (HBMECs) in vitro exposure by SARS-CoV-2 to understand the underlying mechanisms of viral transmigration through the blood-brain barrier. Despite the low to non-productive viral replication, SARS-CoV-2-exposed cultures displayed increased immunoreactivity for cleaved caspase-3, an indicator of apoptotic cell death, tight junction protein expression, and immunolocalization. Transcriptomic profiling of SARS-CoV-2-challenged cultures revealed endothelial activation via NF-κB non-canonical pathway, including RELB overexpression and mitochondrial dysfunction. Additionally, SARS-CoV-2 led to altered secretion of key angiogenic factors and to significant changes in mitochondrial dynamics, with increased mitofusin-2 expression and increased mitochondrial networks. Endothelial activation and remodeling can further contribute to neuroinflammatory processes and lead to further BBB permeability in COVID-19.

IL-6 Serum Levels in COVID-19 Patients With Vertigo

Introduction Dizziness and vertigo represent well-established symptoms of COVID-19. An overexpression of cytokines, a condition often described with the term "cytokine storm" or "hypercytokinemia", is a key characteristic of SARS-Cov-2 infection and plays a pivotal role in disease progression and prognosis. Among them, IL-6 is of major importance.  Purpose The purpose of this study is to investigate any probable IL-6 serum titer difference in COVID-19 patients with vertigo (V+) or without vertigo (V-) admitted to the COVID-19 internal medicine departments of Attikon University Hospital, Athens, Greece, within 12 months. Methods The sample consisted of 52 COVID-19 patients who were diagnosed between January 1, 2020, and December 31, 2020. Of those, 31 reported vertigos during their admission (V+), while the remaining 21 COVID-19 patients did not complain of such symptoms (V-). Results Higher IL-6 serum levels post-COVID-19 infections lead to higher incidence rates of vertigo symptoms (p<.005), regardless of gender and age (p.005).

AI-CoV Study: Autoimmune Encephalitis Associated With COVID-19 and Its Vaccines-A Systematic Review

BACKGROUND AND PURPOSE

Autoimmune encephalitis (AIE) following coronavirus disease 2019 (COVID-19) is an underexplored condition. This study aims to systematically review the clinico-investigational and pathophysiologic aspects of COVID-19 and its vaccines in association with AIE, and identify the factors predicting neurological severity and outcomes.

METHODS

Relevant data sources were searched using appropriate search terms on January 15, 2022. Studies meeting the criteria for AIE having a temporal association with COVID-19 or its vaccines were included.

RESULTS

Out of 1,894 citations, we included 61 articles comprising 88 cases: 71 of COVID-19-associated AIE, 3 of possible Bickerstaff encephalitis, and 14 of vaccine-associated AIE.There were 23 definite and 48 possible seronegative AIE cases. Anti-NMDAR (N-methyl-D-aspartate receptor; n=12, 16.9%) was the most common definite AIE. Males were more commonly affected (sex ratio=1.63) in the AIE subgroup. The neurological symptoms included alteredmental state (n=53, 74.6%), movement disorders (n=28, 39.4%), seizures (n=24, 33.8%), behavioural (n=25, 35.2%), and speech disturbances (n=17, 23.9%). The median latency to AIE diagnosis was 14 days (interquartile range=4-22 days). Female sex and ICU admission had higherrisks of sequelae, with odds ratio (OR) of 2.925 (95% confidence interval [CI]=1.005-8.516)and 3.515 (95% CI=1.160-10.650), respectively. Good immunotherapy response was seen in42/48 (87.5%) and 13/13 (100%) of COVID-19-associated and vaccine-associated AIE patients, respectively. Sequelae were reported in 22/60 (36.7%) COVID-19 associated and 10/13 (76.9%) vaccine-associated cases.

CONCLUSIONS

The study has revealed diagnostic, therapeutic, and pathophysiological aspects of AIE associated with COVID-19 and its vaccines, and its differences from postinfectious AIE.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration number CRD42021299215.

The Prevalence of Dizziness and Vertigo in COVID-19 Patients: A Systematic Review

Clinical manifestations of COVID-19 include symptoms of vertigo and dizziness, which is rather unsurprising, since SARS-CoV-2 neurotropism may inflict a broad spectrum of neuropathic effects. The widespread nature of central and peripheral audiovestibular pathways suggests that there may be several probable pathophysiological mechanisms. The cytokine storm, CNS infiltration of the virus through ACE 2 receptors, and other systemic factors can be responsible for the significant number of COVID-19 patients reported to experience symptoms of vertigo and dizziness. In this paper, we present a systematic review of clinical studies reporting the detection of dizziness and vertigo as clinical manifestations of COVID-19 and discuss their etiopathogenesis.

SARS-CoV-2 infection of human brain microvascular endothelial cells leads to inflammatory activation through NF-κB non-canonical pathway and mitochondrial remodeling

Neurological effects of COVID-19 and long-COVID-19 as well as neuroinvasion by SARS-CoV-2 still pose several questions and are of both clinical and scientific relevance. We described the cellular and molecular effects of the human brain microvascular endothelial cells (HBMECs) in vitro infection by SARS-CoV-2 to understand the underlying mechanisms of viral transmigration through the Blood-Brain Barrier. Despite the low to non-productive viral replication, SARS-CoV-2-infected cultures displayed increased apoptotic cell death and tight junction protein expression and immunolocalization. Transcriptomic profiling of infected cultures revealed endothelial activation via NF-κB non-canonical pathway, including RELB overexpression, and mitochondrial dysfunction. Additionally, SARS-CoV-2 led to altered secretion of key angiogenic factors and to significant changes in mitochondrial dynamics, with increased mitofusin-2 expression and increased mitochondrial networks. Endothelial activation and remodeling can further contribute to neuroinflammatory processes and lead to further BBB permeability in COVID-19.

SARS-CoV-2 infection of human brain microvascular endothelial cells leads to inflammatory activation through NF-κB non-canonical pathway and mitochondrial remodeling

Neurological effects of COVID-19 and long-COVID-19 as well as neuroinvasion by SARS-CoV-2 still pose several questions and are of both clinical and scientific relevance. We described the cellular and molecular effects of the human brain microvascular endothelial cells (HBMECs) in vitro infection by SARS-CoV-2 to understand the underlying mechanisms of viral transmigration through the Blood-Brain Barrier. Despite the low to non- productive viral replication, SARS-CoV-2-infected cultures displayed increased apoptotic cell death and tight junction protein expression and immunolocalization. Transcriptomic profiling of infected cultures revealed endothelial activation via NF-κB non-canonical pathway, including RELB overexpression, and mitochondrial dysfunction. Additionally, SARS-CoV-2 led to altered secretion of key angiogenic factors and to significant changes in mitochondrial dynamics, with increased mitofusin-2 expression and increased mitochondrial networks. Endothelial activation and remodeling can further contribute to neuroinflammatory processes and lead to further BBB permeability in COVID-19.

COVID-19 and neurological sequelae: Vitamin D as a possible neuroprotective and/or neuroreparative agent

SARS-CoV-2, the etiological agent of the current COVID-19 pandemic, belongs to a broad family of coronaviruses that also affect humans. SARS-CoV-2 infection usually leads to bilateral atypical pneumonia with significant impairment of respiratory function. However, the infectious capacity of SARS-CoV-2 is not limited to the respiratory system, but may also affect other vital organs such as the brain. The central nervous system is vulnerable to cell damage via direct invasion or indirect virus-related effects leading to a neuroinflammatory response, processes possibly associated with a decrease in the activity of angiotensin II converting enzyme (ACE2), the canonical cell-surface receptor for SARS-CoV-2. This enzyme regulates neuroprotective and neuroimmunomodulatory functions and can neutralize both inflammation and oxidative stress generated at the cellular level. Furthermore, there is evidence of an association between vitamin D deficiency and predisposition to the development of severe forms of COVID-19, with its possible neurological and neuropsychiatric sequelae: vitamin D has the ability to down-modulate the effects of neuroinflammatory cytokines, among other anti-inflammatory/immunomodulatory effects, thus attenuating harmful consequences of COVID-19. This review critically analyzes current evidence supporting the notion that vitamin D may act as a neuroprotective and neuroreparative agent against the neurological sequelae of COVID-19.

Simian Immunodeficiency Virus Infection Mediated Changes in Jejunum and Peripheral SARS-CoV-2 Receptor ACE2 and Associated Proteins or Genes in Rhesus Macaques

Angiotensin converting enzyme-2 (ACE2) and associated proteins play a pivotal role in various physiological and pathological events, such as immune activation, inflammation, gut barrier maintenance, intestinal stem cell proliferation, and apoptosis. Although many of these clinical events are quite significant in SIV/HIV infection, expression profiling of these proteins has not been well reported. Considering the different pathological consequences in the gut after HIV infection, we hypothesized that the expression of ACE2 and associated proteins of the Renin-angiotensin system (RAS) could be compromised after SIV/HIV infection. We quantified the gene expression of ACE2 as well as AGTR1/2, ADAM17, and TMPRSS2, and compared between SIV infected and uninfected rhesus macaques (Macaca mulatta; hereafter abbreviated RMs). The gene expression analysis revealed significant downregulation of ACE2 and upregulation of AGTR2 and inflammatory cytokine IL-6 in the gut of infected RMs. Protein expression profiling also revealed significant upregulation of AGTR2 after infection. The expression of ACE2 in protein level was also decreased, but not significantly, after infection. To understand the entirety of the process in newly regenerated epithelial cells, a global transcriptomic study of enteroids raised from intestinal stem cells was performed. Interestingly, most of the genes associated with the RAS, such as DPP4, MME, ANPEP, ACE2, ENPEP, were found to be downregulated in SIV infection. HNFA1 was found to be a key regulator of ACE2 and related protein expression. Jejunum CD4+ T cell depletion and increased IL-6 mRNA, MCP-1 and AGTR2 expression may signal inflammation, monocyte/macrophage accumulation and epithelial apoptosis in accelerating SIV pathogenesis. Overall, the findings in the study suggested a possible impact of SIV/HIV infection on expression of ACE2 and RAS-associated proteins resulting in the loss of gut homeostasis. In the context of the current COVID-19 pandemic, the outcome of SARS-CoV-2 and HIV co-infection remains uncertain and needs further investigation as the significance profile of ACE2, a viral entry receptor for SARS-CoV-2, and its expression in mRNA and protein varied in the current study. There is a concern of aggravated SARS-CoV-2 outcomes due to possible serious pathological events in the gut resulting from compromised expression of RAS- associated proteins in SIV/HIV infection.

Penetration of the SARS-CoV-2 Spike Protein across the Blood–Brain Barrier, as Revealed by a Combination of a Human Cell Culture Model System and Optical Biosensing

Since the outbreak of the global pandemic caused by severe acute respiratory coronavirus 2 (SARS-CoV-2), several clinical aspects of the disease have come into attention. Besides its primary route of infection through the respiratory system, SARS-CoV-2 is known to have neuroinvasive capacity, causing multiple neurological symptoms with increased neuroinflammation and blood–brain barrier (BBB) damage. The viral spike protein disseminates via circulation during infection, and when reaching the brain could possibly cross the BBB, which was demonstrated in mice. Therefore, its medical relevance is of high importance. The aim of this study was to evaluate the barrier penetration of the S1 subunit of spike protein in model systems of human organs highly exposed to the infection. For this purpose, in vitro human BBB and intestinal barrier cell–culture systems were investigated by an optical biosensing method. We found that spike protein crossed the human brain endothelial cell barrier effectively. Additionally, spike protein passage was found in a lower amount for the intestinal barrier cell layer. These observations were corroborated with parallel specific ELISAs. The findings on the BBB model could provide a further basis for studies focusing on the mechanism and consequences of spike protein penetration across the BBB to the brain.

Update on neurological symptoms in patients infected with severe acute respiratory syndrome coronavirus-2

Novel coronavirus 19 (COVID-19) is the latest and most intense epidemic, which is caused by the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). In addition to causing respiratory symptoms, SARS-CoV-2 can have severe effects on the nervous system. Clinically, COVID-19 patients have been reported ranging from mild hypogeusia and hyposmia to severe neurological disorders, such as encephalopathy, encephalitis, strokes, and seizures syndrome. However, the pathological mechanisms of this SARS-CoV-2 neuro aggressiveness remain unclear, so it is of great significance to explore the neurological effects of SARS-CoV-2 infection. To facilitate clinicians to timely recognize the manifestations of COVID-19 patients with neurological injury and timely treatment, the author hereby reviews the latest research progress in the possible pathways, clinical manifestations, and pathogenesis of COVID-19 patients with nerve injury.

Neuroinflammation and Its Impact on the Pathogenesis of COVID-19

Coronavirus disease 2019 (COVID-19) is an infectious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The clinical manifestations of COVID-19 include dry cough, difficult breathing, fever, fatigue, and may lead to pneumonia and respiratory failure. There are significant gaps in the current understanding of whether SARS-CoV-2 attacks the CNS directly or through activation of the peripheral immune system and immune cell infiltration. Although the modality of neurological impairments associated with COVID-19 has not been thoroughly investigated, the latest studies have observed that SARS-CoV-2 induces neuroinflammation and may have severe long-term consequences. Here we review the literature on possible cellular and molecular mechanisms of SARS-CoV-2 induced-neuroinflammation. Activation of the innate immune system is associated with increased cytokine levels, chemokines, and free radicals in the SARS-CoV-2-induced pathogenic response at the blood-brain barrier (BBB). BBB disruption allows immune/inflammatory cell infiltration into the CNS activating immune resident cells (such as microglia and astrocytes). This review highlights the molecular and cellular mechanisms involved in COVID-19-induced neuroinflammation, which may lead to neuronal death. A better understanding of these mechanisms will help gain substantial knowledge about the potential role of SARS-CoV-2 in neurological changes and plan possible therapeutic intervention strategies.

Central neuroinflammation in Covid-19: a systematic review of 182 cases with encephalitis, acute disseminated encephalomyelitis, and necrotizing encephalopathies

Growing evidence demonstrates the association of encephalitis, meningoencephalitis or encephalomyelitis, with SARS-CoV-2 infection. This study aims to determine the profile and possible mechanisms behind CNS inflammatory diseases in the context of Covid-19. We conducted a systematic review of case reports on Covid-19-related encephalitis, meningoencephalitis, acute necrotizing encephalitis, and acute disseminated encephalomyelitis in adults, published before January 2021. A total of 182 cases (encephalitis = 109, meningoencephalitis = 26, acute disseminated encephalomyelitis = 35, acute necrotizing (hemorrhagic) encephalitis = 12) were included. While cerebrospinal fluid (CSF) pleocytosis and increased protein level was present in less than 50%, magnetic resonance imaging (MRI) and electroencephalogram (EEG) were abnormal in 78 and 93.2% of all cases, respectively. Viral particles were detected in cerebrospinal fluid of only 13 patients and autoantibodies were present in seven patients. All patients presented with altered mental status, either in the form of impaired consciousness or psychological/cognitive decline. Seizure, cranial nerve signs, motor, and reflex abnormalities were among associated symptoms. Covid-19-associated encephalitis presents with a distinctive profile requiring thorough diagnosis and thereby a comprehensive knowledge of the disease. The clinical profile of brain inflammation in Covid-19 exhibits majority of abnormal imaging and electroencephalography findings with mild/moderate pleocytosis or proteinorrhachia as prevalent as normal cerebrospinal fluid (CSF). Oligoclonal bands and autoantibody assessments are useful in further evaluating neuro-covid patients, as supported by our pooled evidence. Despite the possibility that direct viral invasion cannot be easily estimated, it is still more likely that immune-mediated or autoimmune reactions play a more important role in SARS-CoV-2 neuroinflammation.

Expression of SARS-CoV-2-related receptors in cells of the neurovascular unit: implications for HIV-1 infection

BACKGROUND

Neurological complications are common in patients affected by COVID-19 due to the ability of SARS-CoV-2 to infect brains. While the mechanisms of this process are not fully understood, it has been proposed that SARS-CoV-2 can infect the cells of the neurovascular unit (NVU), which form the blood-brain barrier (BBB). The aim of the current study was to analyze the expression pattern of the main SARS-CoV-2 receptors in naïve and HIV-1-infected cells of the NVU in order to elucidate a possible pathway of the virus entry into the brain and a potential modulatory impact of HIV-1 in this process.

METHODS

The gene and protein expression profile of ACE2, TMPRSS2, ADAM17, BSG, DPP4, AGTR2, ANPEP, cathepsin B, and cathepsin L was assessed by qPCR, immunoblotting, and immunostaining, respectively. In addition, we investigated if brain endothelial cells can be affected by the exposure to the S1 subunit of the S protein, the domain responsible for the direct binding of SARS-CoV-2 to the ACE2 receptors.

RESULTS

The receptors involved in SARS-CoV-2 infection are co-expressed in the cells of the NVU, especially in astrocytes and microglial cells. These receptors are functionally active as exposure of endothelial cells to the SARS CoV-2 S1 protein subunit altered the expression pattern of tight junction proteins, such as claudin-5 and ZO-1. Additionally, HIV-1 infection upregulated ACE2 and TMPRSS2 expression in brain astrocytes and microglia cells.

CONCLUSIONS

These findings provide key insight into SARS-CoV-2 recognition by cells of the NVU and may help to develop possible treatment of CNS complications of COVID-19.

Expression of SARS-CoV-2-related Receptors in Cells of the Neurovascular Unit: Implications for HIV-1 Infection

Background. Neurological complications are common in patients affected by COVID-19 due to the ability of SARS-CoV-2 to infect brains. While the mechanisms of this process are not fully understood, it has been proposed that SARS-CoV-2 can infect the cells of the neurovascular units (NVU), which form the blood-brain barrier (BBB). The aim of the current study was to analyze the expression pattern of the main SARS-CoV-2 receptors in naïve and HIV-1-infected cells of the NVU in order to elucidate a possible pathway of the virus entry into the brain and a potential modulatory impact of HIV-1 in this process. Methods. The gene and protein expression profile of ACE2, TMPRSS2, ADAM17, BSG, DPP4, AGTR2, ANPEP, cathepsin B and cathepsin L was assessed by qPCR and immunoblotting, respectively. In addition, we investigated if brain endothelial cells can be affected by the exposure to the S1 subunit of the S protein, the domain responsible for the direct binding of SARS-CoV-2 to the ACE2 receptors. Results. The receptors involved in SARS-CoV-2 infection are coexpressed in the cells of the NVU, especially in astrocytes and microglial cells. These receptors are functionally active as exposure of endothelial cells to the SARS CoV-2 S1 protein subunit altered the expression pattern of tight junction proteins, such as claudin-5 and ZO-1. Additionally, HIV-1 infection upregulated ACE2 and TMPRSS2 expression in brain astrocytes and microglia cells. Conclusions. These findings provide key insight into SARS-CoV-2 recognition by cells of the NVU and may help to develop possible treatment of CNS complications of COVID-19.

A rapid review of the pathoetiology, presentation, and management of delirium in adults with COVID-19

Background COVID-19 causes significant morbidity and mortality. Despite the high prevalence of delirium and delirium-related symptoms in COVID-19 patients, data and evidence-based recommendations on the pathophysiology and management of delirium are limited. Objective We conducted a rapid review of COVID-19-related delirium literature to provide a synthesis of literature on the prevalence, pathoetiology, and management of delirium in these patients. Methods Systematic searches of Medline, Embase, PsycInfo, LitCovid, WHO-COVID-19, and Web of Science electronic databases were conducted. Grey literature was also reviewed, including preprint servers, archives, and websites of relevant organizations. Search results were limited to the English language. We included literature focused on adults with COVID-19 and delirium. Papers were excluded if they did not mention signs or symptoms of delirium. Results 229 studies described prevalence, pathoetiology, and/or management of delirium in adults with COVID-19. Delirium was rarely assessed with validated tools. Delirium affected >50% of all patients with COVID-19 admitted to the ICU. The etiology of COVID-19 delirium is likely multifactorial, with some evidence of direct brain effect. Prevention remains the cornerstone of management in these patients. To date, there is no evidence to suggest specific pharmacological strategies. Discussion Delirium is common in COVID-19 and may manifest from both indirect and direct effects on the central nervous system. Further research is required to investigate contributing mechanisms. As there is limited empirical literature on delirium management in COVID-19, management with non-pharmacological measures and judicious use of pharmacotherapy is suggested.