Involvement of the nervous system in COVID-19: The bell should toll in the brain

Viral Kinetics Model of SARS-CoV-2 Infection Informs Drug Discovery, Clinical Dose, and Regimen Selection

Quantitative systems pharmacology (QSP) has been an important tool to project safety and efficacy of novel or repurposed therapies for the SARS-CoV-2 virus. Here, we present a QSP modeling framework to predict response to antiviral therapeutics with three mechanisms of action (MoA): cell entry inhibitors, anti-replicatives, and neutralizing biologics. We parameterized three distinct model structures describing virus-host interaction by fitting to published viral kinetics data of untreated COVID-19 patients. The models were used to test theoretical behaviors and map therapeutic design criteria of the different MoAs, identifying the most rapid and robust antiviral activity from neutralizing biologic and anti-replicative MoAs. We found good agreement between model predictions and clinical viral load reduction observed with anti-replicative nirmatrelvir/ritonavir (Paxlovid®) and neutralizing biologics bamlanivimab and casirivimab/imdevimab (REGEN-COV®), building confidence in the modeling framework to inform a dose selection. Finally, the model was applied to predict antiviral response with ensovibep, a novel DARPin therapeutic designed as a neutralizing biologic. We developed a new in silico measure of antiviral activity, area under the curve (AUC) of free spike protein concentration, as a metric with larger dynamic range than viral load reduction. By benchmarking to bamlanivimab predictions, we justified dose levels of 75, 225, and 600 mg ensovibep to be administered intravenously in a Phase 2 clinical investigation. Upon trial completion, we found model predictions to be in good agreement with the observed patient data. These results demonstrate the utility of this modeling framework to guide the development of novel antiviral therapeutics.

Blood-brain barrier disruption: a culprit of cognitive decline?

Cognitive decline covers a broad spectrum of disorders, not only resulting from brain diseases but also from systemic diseases, which seriously influence the quality of life and life expectancy of patients. As a highly selective anatomical and functional interface between the brain and systemic circulation, the blood-brain barrier (BBB) plays a pivotal role in maintaining brain homeostasis and normal function. The pathogenesis underlying cognitive decline may vary, nevertheless, accumulating evidences support the role of BBB disruption as the most prevalent contributing factor. This may mainly be attributed to inflammation, metabolic dysfunction, cell senescence, oxidative/nitrosative stress and excitotoxicity. However, direct evidence showing that BBB disruption causes cognitive decline is scarce, and interestingly, manipulation of the BBB opening alone may exert beneficial or detrimental neurological effects. A broad overview of the present literature shows a close relationship between BBB disruption and cognitive decline, the risk factors of BBB disruption, as well as the cellular and molecular mechanisms underlying BBB disruption. Additionally, we discussed the possible causes leading to cognitive decline by BBB disruption and potential therapeutic strategies to prevent BBB disruption or enhance BBB repair. This review aims to foster more investigations on early diagnosis, effective therapeutics, and rapid restoration against BBB disruption, which would yield better cognitive outcomes in patients with dysregulated BBB function, although their causative relationship has not yet been completely established.

Trigeminal neuropathy presenting secondary to SARS-CoV-2 infection

Introduction

A 58-year-old woman presented to a multidisciplinary facial pain clinic in October 2021 complaining of a constant pain in the right side of her face since contracting coronavirus SARS-CoV-2 18 months earlier. The pain extending from the right temple down to her right cheek extraorally and including the maxillary teeth and right side of tongue intraorally. This was accompanied by anosmia, diplopia on lateral gaze, and dizziness.

Methods

Clinical examination was supplemented with several neurophysiological tests to confirm the diagnosis including an MRI brain scan, quantitative sensory testing, electrophysiological blink reflex testing, corneal confocal microscopy, and pain and short-form anxiety and depression questionnaires.

Results

Quantitative sensory testing showed unilateral loss of perception in thermal and mechanical sensibility and bilateral hyperalgesia indicating central sensitization. Bilateral corneal confocal microscopy showed an abnormally reduced corneal nerve fibre length on the right side. MRI, blink reflex, and masseter inhibitory testing findings were normal.

Conclusion

This case study is the first case of trigeminal neuropathy related to SARS-CoV-2 infection reported in the literature. It also discusses the successful management of the patient's trigeminal neuropathic pain.

A review of the mechanisms of blood-brain barrier disruption during COVID-19 infection

Coronaviruses are prevalent in mammals and birds, including humans and bats, and they often spread through airborne droplets. In humans, these droplets then interact with angiotensin-converting enzyme 2 (ACE2) and transmembrane serine protease 2 (TMPRSS2), which are the main receptors for the SARS-CoV-2 virus. It can infect several organs, including the brain. The blood-brain barrier (BBB) is designed to maintain the homeostatic neural microenvironment of the brain, which is necessary for healthy neuronal activity, function, and stability. It prevents viruses from entering the brain parenchyma and does not easily allow chemicals to pass into the brain while assisting numerous compounds in exiting the brain. The purpose of this review was to examine how COVID-19 influences the BBB along with the mechanisms that indicate the BBB's deterioration. In addition, the cellular mechanism through which SARS-CoV-2 causes BBB destruction by binding to ACE2 was evaluated and addressed. The mechanisms of the immunological reaction that occurs during COVID-19 infection that may contribute to the breakdown of the BBB were also reviewed. It was discovered that the integrity of the tight junction (TJs), basement membrane, and adhesion molecules was damaged during COVID-19 infection, which led to the breakdown of the BBB. Therefore, understanding how the BBB is disrupted by COVID-19 infection will provide an indication of how the SARS-CoV-2 virus is able to reach the central nervous system (CNS). The findings of this research may help in the identification of treatment options for COVID-19 that can control and manage the infection.

Astrocytes and the Psychiatric Sequelae of COVID-19: What We Learned from the Pandemic

COVID-19, initially regarded as specific lung disease, exhibits an extremely broad spectrum of symptoms. Extrapulmonary manifestations of the disease also include important neuropsychiatric symptoms with atypical characteristics. Are these disturbances linked to stress accompanying every systemic infection, or are due to specific neurobiological changes associated with COVID-19? Evidence accumulated so far indicates that the pathophysiology of COVID-19 is characterized by systemic inflammation, hypoxia resulting from respiratory failure, and neuroinflammation (either due to viral neurotropism or in response to cytokine storm), all affecting the brain. It is reasonable to hypothesize that all these events may initiate or worsen psychiatric and cognitive disorders. Damage to the brain triggers a specific type of reactive response mounted by neuroglia cells, in particular by astrocytes which are the homeostatic cell par excellence. Astrocytes undergo complex morphological, biochemical, and functional remodeling aimed at mobilizing the regenerative potential of the central nervous system. If the brain is not directly damaged, resolution of systemic pathology usually results in restoration of the physiological homeostatic status of neuroglial cells. The completeness and dynamics of this process in pathological conditions remain largely unknown. In a subset of patients, glial cells could fail to recover after infection thus promoting the onset and progression of COVID-19-related neuropsychiatric diseases. There is evidence from post-mortem examinations of the brains of COVID-19 patients of alterations in both astrocytes and microglia. In conclusion, COVID-19 activates a huge reactive response of glial cells, that physiologically act as the main controller of the inflammatory, protective and regenerative events. However, in some patients the restoration of glial physiological state does not occur, thus compromising glial function and ultimately resulting in homeostatic failure underlying a set of specific neuropsychiatric symptoms related to COVID-19.

Magnetic Resonance Imaging (MRI) Findings in COVID-19 Associated Encephalitis

We conducted this study to investigate the scope of the MRI neuroimaging manifestations in COVID-19-associated encephalitis. From January 2020 to September 2021, patients with clinical diagnosis of COVID-19-associated encephalitis, as well as concomitant abnormal imaging findings on brain MRI, were included. Two board-certified neuro-radiologists reviewed these selected brain MR images, and further discerned the abnormal imaging findings. 39 patients with the clinical diagnosis of encephalitis as well as abnormal MRI findings were included. Most (87%) of these patients were managed in ICU, and 79% had to be intubated-ventilated. 15 (38%) patients died from the disease, while the rest were discharged from the hospital. On MRI, FLAIR hyperintensities in the insular cortex were the most common finding, seen in 38% of the patients. Micro-hemorrhages on the SWI images were equally common, also seen in 38% patients. FLAIR hyperintensities in the medial temporal lobes were seen in 30%, while FLAIR hyperintensities in the posterior fossa were evident in 20%. FLAIR hyperintensities in basal ganglia and thalami were seen in 15%. Confluent FLAIR hyperintensities in deep and periventricular white matter, not explained by microvascular angiopathy, were detected in 7% of cases. Cortical-based FLAIR hyperintensities in 7%, and FLAIR hyperintensity in the splenium of the corpus callosum in 7% of patients. Finally, isolated FLAIR hyperintensity around the third ventricle was noted in 2% of patients.

Electrophysiological evidence of subclinical trigeminal dysfunction in patients with COVID-19 and smell impairment: A pilot study

Background

Smell and taste disturbances are among the most frequent neurological symptoms in patients with COVID-19. A concomitant impairment of the trigeminal nerve has been suggested in subjects with olfactory dysfunction, although it has not been confirmed with objective measurement techniques. In this study, we explored the trigeminal function and its correlations with clinical features in COVID-19 patients with impaired smell perception using electrophysiological testing.

Methods

We enrolled 16 consecutive patients with mild COVID-19 and smell impairment and 14 healthy controls (HCs). Olfactory and gustatory symptoms were assessed with self-reported questionnaires. Electrophysiological evaluation of the masseter inhibitory reflex (MIR) and blink reflex (BR) was carried out to test the trigeminal function and its connections within the brainstem.

Results

Masseter inhibitory reflex (MIR) analysis revealed higher latency of ipsilateral and contralateral early silent period in patients when compared with HCs. No significant differences between groups were detected as regards the duration of the early and late silent period. However, several patients showed a prolonged duration of the early silent period. BR evaluation disclosed only an increased amplitude of early components in patients.

Conclusions

Patients with COVID-19 and smell impairment show a subclinical trigeminal nerve impairment. Trigeminal alterations mainly involve the oligosynaptic pathway, as a result of either direct viral damage or secondary neuroinflammation of the peripheral trigeminal fibers, whereas the polysynaptic ponto-medullary circuits seem to be spared. The prolonged duration of the early silent period and the increased amplitude of early BR response might reflect a compensatory upregulation of the trigeminal function as a consequence of the olfactory dysfunction.

Therapeutic prospects of ceRNAs in COVID-19

Since the end of 2019, COVID-19 caused by SARS-CoV-2 has spread worldwide, and the understanding of the new coronavirus is in a preliminary stage. Currently, immunotherapy, cell therapy, antiviral therapy, and Chinese herbal medicine have been applied in the clinical treatment of the new coronavirus; however, more efficient and safe drugs to control the progress of the new coronavirus are needed. Long noncoding RNAs (lncRNAs), microRNAs (miRNAs), and circular RNAs (circRNAs) may provide new therapeutic targets for novel coronavirus treatments. The first aim of this paper is to review research progress on COVID-19 in the respiratory, immune, digestive, circulatory, urinary, reproductive, and nervous systems. The second aim is to review the body systems and potential therapeutic targets of lncRNAs, miRNAs, and circRNAs in patients with COVID-19. The current research on competing endogenous RNA (ceRNA) (lncRNA-miRNA-mRNA and circRNA-miRNA-mRNA) in SARS-CoV-2 is summarized. Finally, we predict the possible therapeutic targets of four lncRNAs, MALAT1, NEAT1, TUG1, and GAS5, in COVID-19. Importantly, the role of PTEN gene in the ceRNA network predicted by lncRNA MALAT1 and lncRNA TUG1 may help in the discovery and clinical treatment of effective drugs for COVID-19.

COVID-19 neuropsychiatric repercussions: Current evidence on the subject

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection has affected the entire world, causing the coronavirus disease 2019 (COVID-19) pandemic since it was first discovered in Wuhan, China in December 2019. Among the clinical presentation of the disease, in addition to fever, fatigue, cough, dyspnea, diarrhea, nausea, vomiting, and abdominal pain, infected patients may also experience neurological and psychiatric repercussions during the course of the disease and as a post-COVID-19 sequelae. Thus, headache, dizziness, olfactory and gustatory dysfunction, cerebrovascular disorders, neuromuscular abnormalities, anxiety, depression, and post-traumatic stress disorder can occur both from the infection itself and from social distancing and quarantine. According to current evidence about this infection, the virus has the ability to infect the central nervous system (CNS) via angiotensin-converting enzyme 2 (ACE2) receptors on host cells. Several studies have shown the presence of ACE2 in nerve cells and nasal mucosa, as well as transmembrane serine protease 2, key points for interaction with the viral Spike glycoprotein and entry into the CNS, being olfactory tract and blood-brain barrier, through hematogenous dissemination, potential pathways. Thus, the presence of SARS-CoV-2 in the CNS supports the development of neuropsychiatric symptoms. The management of these manifestations seems more complex, given that the dense parenchyma and impermeability of brain tissue, despite protecting the brain from the infectious process, may hinder virus elimination. Still, some alternatives used in non-COVID-19 situations may lead to worse prognosis of acute respiratory syndrome, requiring caution. Therefore, the aim of this review is to bring more current points related to this infection in the CNS, as well as the repercussions of the isolation involved by the pandemic and to present perspectives on interventions in this scenario.

COVID-19 and cognitive impairment: neuroinvasive and blood‒brain barrier dysfunction

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has led to a global pandemic. Although COVID-19 was initially described as a respiratory disease, there is growing evidence that SARS-CoV-2 is able to invade the brains of COVID-19 patients and cause cognitive impairment. It has been reported that SARS-CoV-2 may have invasive effects on a variety of cranial nerves, including the olfactory, trigeminal, optic, and vagus nerves, and may spread to other brain regions via infected nerve endings, retrograde transport, and transsynaptic transmission. In addition, the blood-brain barrier (BBB), composed of neurovascular units (NVUs) lining the brain microvasculature, acts as a physical barrier between nerve cells and circulating cells of the immune system and is able to regulate the transfer of substances between the blood and brain parenchyma. Therefore, the BBB may be an important structure for the direct and indirect interaction of SARS-CoV-2 with the brain via the blood circulation. In this review, we assessed the potential involvement of neuroinvasion under the SARS-CoV-2 infection, and the potential impact of BBB disorder under SARS-CoV-2 infection on cognitive impairment.

An overview of the neurological aspects in COVID-19 infection

The Crown-shaped, severe acute respiratory syndrome-Coronavirus-2 (SARS-CoV-2) triggered the globally fatal illness of Coronavirus disease-2019 (COVID-19). This infection is known to be initially reported in bats and has been causing major respiratory challenges. The primary symptoms of COVID-19 include fever, fatigue and dry cough. As progressed the complications may lead to acute respiratory distress syndrome (ADRS), arrhythmia and shock. This review illustrates the neurological and neuropsychiatric impairments due to COVID-19 infection. The SARS-CoV-2 virus enters via the hematogenous or neural route, spreads to the Central Nervous System (CNS), causing a blood-brain barrier (BBB) dysfunction. Recent scientific articles have reported that SARS-CoV-2 causes several neurological issues such as encephalitis, seizures, acute stroke, delirium, meningoencephalitis and Guillain-Barré Syndrome (GBS). As a long-term effect of this disease certain neuropsychiatric conditions are witnessed such as depression and anxiety. Invasion into followed by degeneration takes place causing an uncontrolled immune response. Transcription factors like NF-κB (nuclear factor kappa light chain enhancer of activated B cells), which modulate genes responsible for inflammatory response gets over expressed. Nrf2 (nuclear factor erythroid 2- related factor 2) counterpoises the inflammation by antioxidant response towards COVID-19 infection. Like every other infection, the severity of this infection leads to deterioration of major organ systems and even leads to death. By the columns of this review, we elaborate on the neurological aspects of this life-threatening infection.

Calcitonin gene-related peptide: A biomarker for stroke in SARS-CoV-2 infection?

COVID-19 infection was mainly associated with respiratory symptoms, but lately, ischemic stroke (IS) has been reported in several cases. The incidence of IS in SARS-CoV-2 infection is increasing, and its mechanism is still not fully understood. Calcitonin gene-related peptide (CGRP) -the abundantly expressed protein in the peripheral and central nervous system- showed low expression in SARS-CoV-2 patients. This peptide is strongly implicated in regulating cerebral blood flow (CBF) and improving neurological deficits after cerebral arterial occlusion. We assume that a possible interplay between the low circulating levels of CGRP may affect CBF, thus worsening the symptoms of IS in SARS-CoV-2 patients.

Suspected Recurrence of Cranial Neuralgia Following Infection With SARS-CoV-2: A Case Report

It is understood that patients infected with the COVID-19 virus can present with headache as an initial symptom, but it is unclear if those with a history of cranial neuralgias may have a different initial COVID-19 presentation, or if infections from SARS-CoV-2 virus may cause a recurrence of previous cranial neuralgias. In this review, we report a case of cranial neuralgia recurrence that was preceded by a SARS-CoV-2 exposure. There is currently a lack of literature describing COVID-19 patients with a recurrence of a previous cranial neuralgia, and this case draws attention to potential reactivation of cranial neuralgia symptoms in COVID-19 patients, highlights key components of the pathophysiology of cranial neuralgias, and underscores the potential need to identify previous history of cranial neuralgia to more appropriately navigate management and treatment of neuralgia causing head pain as a consequence of COVID-19 infection.

Comprehensive Oncogenic Features of Coronavirus Receptors in Glioblastoma Multiforme

The COVID-19 pandemic caused by SARS-CoV-2 infection has placed health systems under excessive pressure and especially elderly people with cancer. Glioblastoma multiforme (GBM) is a malignant brain tumor with an increasing incidence in elderly individuals, and thereby GBM patients are a vulnerable population during the COVID-19 outbreak. Accumulating studies have implied that SARS-CoV-2 might invade the brain directly via coronavirus receptors. However, little is known about SARS-CoV-2 infection in the clinical development of GBM. Here, we explored the oncogenic roles of six coronavirus receptors (ACE2, DPP4, ANPEP, AXL, TMPRSS2, and ENPEP) in GBM using bioinformatics and experimental approaches. We found that ANPEP and ENPEP were significantly increased at both the mRNA and protein levels in GBM compared with normal brain tissue. Kaplan-Meier survival curves and Cox regression analysis demonstrated that high expressions of ANPEP and ENPEP are associated with poor prognosis and survival. Moreover, all receptors are positively correlated with the immune infiltration levels of monocyte. Furthermore, we identified 245 genes between COVID-19 and coronavirus receptors-correlated genes in GBM and performed a thorough analysis of their protein-protein interaction network, functional signaling pathway and molecular process. Our work explores for the first time the association of coronavirus receptors with GBM and suggests ANPEP and ENPEP as potential therapeutic targets of GBM irrespective of COVID-19.

COVID-19-Related Brain Injury: The Potential Role of Ferroptosis

The COVID-19 pandemic has caused devastating loss of life and a healthcare crisis worldwide. SARS-CoV-2 is the causative pathogen of COVID-19 and is transmitted mainly through the respiratory tract, where the virus infects host cells by binding to the ACE2 receptor. SARS-CoV-2 infection is associated with acute pneumonia, but neuropsychiatric symptoms and different brain injuries are also present. The possible routes by which SARS-CoV-2 invades the brain are unclear, as are the mechanisms underlying brain injuries with the resultant neuropsychiatric symptoms in patients with COVID-19. Ferroptosis is a unique iron-dependent form of non-apoptotic cell death, characterized by lipid peroxidation with high levels of glutathione consumption. Ferroptosis plays a primary role in various acute and chronic brain diseases, but to date, ferroptosis in COVID-19-related brain injuries has not been explored. This review discusses the mechanisms of ferroptosis and recent evidence suggesting a potential pathogenic role for ferroptosis in COVID-19-related brain injury. Furthermore, the possible routes through which SARS-CoV-2 could invade the brain are also discussed. Discoveries in these areas will open possibilities for treatment strategies to prevent or reduce brain-related complications of COVID-19.

Repeated ethanol exposure and withdrawal alters ACE2 expression in discrete brain regions: Implications for SARS-CoV-2 infection

Emerging evidence suggests that people with alcohol use disorders are at higher risk for SARS-CoV-2. SARS-CoV-2 engages angiotensin-converting enzyme 2 (ACE2) and transmembrane serine protease 2 (TMPRSS2) receptors for cellular entry. While ACE2 and TMPRSS2 genes are upregulated in the cortex of alcohol-dependent individuals, information on expression in specific brain regions and neural populations implicated in SARS-CoV-2 neuroinvasion, particularly monoaminergic neurons, is limited. We sought to clarify how chronic alcohol exposure affects ACE2 and TMPRSS2 expression in monoaminergic brainstem circuits and other putative SARS-CoV-2 entry points. C57BL/6J mice were exposed to chronic intermittent ethanol (CIE) vapor for 4 weeks and brains were examined using immunofluorescence. We observed increased ACE2 levels in the olfactory bulb and hypothalamus following CIE, which are known to mediate SARS-CoV-2 neuroinvasion. Total ACE2 immunoreactivity was also elevated in the raphe magnus (RMG), raphe obscurus (ROB), and locus coeruleus (LC), while in the dorsal raphe nucleus (DRN), ROB, and LC we observed increased colocalization of ACE2 with monoaminergic neurons. ACE2 also increased in the periaqueductal gray (PAG) and decreased in the amygdala. Whereas ACE2 was detected in most brain regions, TMPRSS2 was only detected in the olfactory bulb and DRN but was not significantly altered after CIE. Our results suggest that previous alcohol exposure may increase the risk of SARS-CoV-2 neuroinvasion and render brain circuits involved in cardiovascular and respiratory function as well as emotional processing more vulnerable to infection, making adverse outcomes more likely. Additional studies are needed to define a direct link between alcohol use and COVID-19 infection.

Ischemic stroke in 455 COVID-19 patients

There is increasing evidence that COVID-19 can be associated with ischemic stroke (COVID-stroke). The frequency and pathogenesis of COVID-stroke, however, remains largely unknown. This narrative review aimed at summarizing and discussing current knowledge about frequency and pathogenesis of COVID-stroke in 455 patients collected from the literature. COVID-stroke occurs in all age groups and predominantly in males. The anterior circulation is more frequently affected than the posterior circulation. COVID-stroke is most frequently embolic. The severity of COVID-stroke ranges from NIHSS 3 to 32. Cardiovascular risk factors are highly prevalent in patients with COVID-stroke. COVID-stroke occurs simultaneously with the onset of pulmonary manifestations or up to 40 days later. Clinical manifestations of COVID-19 are most frequently mild or even absent. The majority of patients with COVID-stroke achieve complete or partial recovery, but in one-quarter of patients, the outcome is fatal. In conclusion, the frequency of ischemic stroke has not increased since the outbreak of the SARS-CoV-2 pandemic. COVID-stroke predominantly affects males and the anterior circulation. COVID-stroke is multifactorial but predominantly embolic and more frequently attributable to cardiovascular risk factors than to coagulopathy.

Cranial neuropathy in COVID-19: a case series and review of literature

Neurological presentation of COVID-19 is increasingly being recognised. Cranial neuropathy in COVID-19 is an uncommon and under-diagnosed entity. We report a case series of 4 patients who presented with trigeminal neuropathy (two cases) and facial nerve palsy (two cases) which recovered with conservative treatment along with the review of the literature.

Role of Selenium in Viral Infections with a Major Focus on SARS-CoV-2

Viral infections have afflicted human health and despite great advancements in scientific knowledge and technologies, continue to affect our society today. The current coronavirus (COVID-19) pandemic has put a spotlight on the need to review the evidence on the impact of nutritional strategies to maintain a healthy immune system, particularly in instances where there are limited therapeutic treatments. Selenium, an essential trace element in humans, has a long history of lowering the occurrence and severity of viral infections. Much of the benefits derived from selenium are due to its incorporation into selenocysteine, an important component of proteins known as selenoproteins. Viral infections are associated with an increase in reactive oxygen species and may result in oxidative stress. Studies suggest that selenium deficiency alters immune response and viral infection by increasing oxidative stress and the rate of mutations in the viral genome, leading to an increase in pathogenicity and damage to the host. This review examines viral infections, including the novel SARS-CoV-2, in the context of selenium, in order to inform potential nutritional strategies to maintain a healthy immune system.

Neurological manifestations of coronavirus infections, before and after COVID-19: a review of animal studies

Coronavirus disease 2019 (COVID-19) is an infectious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). This virus, which was first identified in December 2019 in China, has resulted in a yet ongoing viral pandemic. Coronaviridae could potentially cause several disorders in a wide range of hosts such as birds and mammals. Although infections caused by this family of viruses are predominantly limited to the respiratory tract, Betacoronaviruses are potentially able to invade the central nervous system (CNS) as well as many other organs, thereby inducing neurological damage ranging from mild to lethal in both animals and humans. Over the past two decades, three novel CoVs, SARS-CoV-1, MERS-CoV, and SARS-CoV-2, emerging from animal reservoirs have exhibited neurotropic properties causing severe and even fatal neurological diseases. The pathobiology of these neuroinvasive viruses has yet to be fully known. Both clinical features of the previous CoV epidemics (SARS-CoV-1 and MERS-CoV) and lessons from animal models used in studying neurotropic CoVs, especially SARS and MERS, constitute beneficial tools in comprehending the exact mechanisms of virus implantation and in illustrating pathogenesis and virus dissemination pathways in the CNS. Here, we review the animal research which assessed CNS infections with previous more studied neurotropic CoVs to demonstrate how experimental studies with appliable animal models can provide scientists with a roadmap in the CNS impacts of SARS-CoV-2. Indeed, animal studies can finally help us discover the underlying mechanisms of damage to the nervous system in COVID-19 patients and find novel therapeutic agents in order to reduce mortality and morbidity associated with neurological complications of SARS-CoV-2 infection.

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.

Cytomegalovirus meningoencephalitis in a case of severe COVID-19 Pneumonia. A case report

The use of steroids and other immune modulatory therapies in the treatment of severe COVID-19 pneumonia predisposes patients to the reemergence of opportunistic infections. Cytomegalovirus (CMV) reactivation can be one of them. A 55-year-old gentleman with severe COVID-19 pneumonia and hypoxic respiratory failure who was ventilated and received steroids but no other immunomodulatory drugs; had altered sensorium and multiple episodes of seizures in the later course of his illness. Brain MRI showed leptomeningeal enhancement and encephalopathy changes, electroencephalography (EEG) was suggestive of diffuse encephalopathy and his cerebrospinal fluid (CSF) analysis revealed high Cytomegalovirus PCR DNA titers (103,614). The patient made a complete recovery after treatment with Ganciclovir. Altered sensorium in cases of COVID-19 can be multifactorial. High index of suspicion for reactivation of dormant infections is warranted. CMV meningoencephalitis is one of the differential diagnoses. We believe this is the first case reported of CMV meningoencephalitis in the setting of severe COVID-19 infection.

Small fiber neuropathy in the cornea of Covid-19 patients associated with the generation of ocular surface disease

Purpose

To describe the association between Sars-CoV-2 infection and small fiber neuropathy in the cornea identified by in vivo corneal confocal microscopy.

Methods

Twenty-three patients who had overcome COVID-19 were recruited to this observational retrospective study. Forty-six uninfected volunteers were also recruited and studied as a control group. All subjects were examined under in vivo confocal microscopy to obtain images of corneal subbasal nerve fibers in order to study the presence of neuroma-like structures, axonal beadings and dendritic cells. The Ocular Surface Disease Index (OSDI) questionnaire and Schirmer tear test were used as indicators of Dry Eye Disease (DED) and ocular surface pathology.

Results

Twenty-one patients (91.31%) presented alterations of the corneal subbasal plexus and corneal tissue consistent with small fiber neuropathy. Images from healthy subjects did not indicate significant nerve fiber or corneal tissue damage. Eight patients reported increased sensations of ocular dryness after COVID-19 infection and had positive DED indicators. Beaded axons were found in 82.60% of cases, mainly in patients reporting ocular irritation symptoms. Neuroma-like images were found in 65.22% patients, more frequently in those with OSDI scores >13. Dendritic cells were found in 69.56% of patients and were more frequent in younger asymptomatic patients. The presence of morphological alterations in patients up to 10 months after recovering from Sars-CoV-2 infection points to the chronic nature of the neuropathy.

Conclusions

Sars-CoV-2 infection may be inducing small fiber neuropathy in the ocular surface, sharing symptomatology and morphological landmarks with DED and diabetic neuropathy.

ACE2 expression in rat brain: Implications for COVID-19 associated neurological manifestations

We examined cell type-specific expression and distribution of rat brain angiotensin-converting enzyme 2 (ACE2), the receptor for SARS-CoV-2, in the rodent brain. ACE2 is ubiquitously present in brain vasculature, with the highest density of ACE2 expressing capillaries found in the olfactory bulb, the hypothalamic paraventricular, supraoptic, and mammillary nuclei, the midbrain substantia nigra and ventral tegmental area, and the hindbrain pontine nucleus, the pre-Bötzinger complex, and nucleus of tractus solitarius. ACE2 was expressed in astrocytes and astrocytic foot processes, pericytes and endothelial cells, key components of the blood-brain barrier. We found discrete neuronal groups immunopositive for ACE2 in brainstem respiratory rhythm generating centers, including the pontine nucleus, the parafascicular/retrotrapezoid nucleus, the parabrachial nucleus, the Bötzinger, and pre-Bötzinger complexes and the nucleus of tractus solitarius; in the arousal-related pontine reticular nucleus and gigantocellular reticular nuclei; in brainstem aminergic nuclei, including substantia nigra, ventral tegmental area, dorsal raphe, and locus coeruleus; in the epithalamic habenula, hypothalamic paraventricular and supramammillary nuclei; and in the hippocampus. Identification of ACE2-expressing neurons in rat brain within well-established functional circuits facilitates prediction of possible neurological manifestations of brain ACE2 dysregulation during and after COVID-19 infection.

Recovery From COVID-19-Related Olfactory Disorders and Quality of Life: Insights From an Observational Online Study

Although olfactory disorders (OD) are among the most significant symptoms of COVID-19, recovery time from COVID-19-related OD and their consequences on the quality of life remain poorly documented. We investigated the characteristics and behavioral consequences of COVID-19-related OD using a large-scale study involving 3111 French respondents (78% women) to an online questionnaire over a period of 9 months covering different epidemic waves (from 8 April 2020 to 13 January 2021). In the patients who subjectively recovered from COVID-19-related OD (N = 609), recovery occurred on average after 16 days and most of the time within 1 month ("normal" recovery range); 49 subjectively recovered in 1-2.5 months, and several cases took up to 6.5 months. Among the patients with ongoing OD (N = 2502), 974 were outside the "normal" recovery range (persistent OD) and reported OD for 1-10 months. Developing a persistent OD was more likely with increasing age and in women and was more often associated with parosmia and phantosmia. The deleterious impact of COVID-19-related OD on the quality of life was significantly aggravated by OD duration and was more pronounced in women. Because persistent OD is not infrequent after COVID-19, has deleterious consequences on the quality of life, and receives few solutions from the health practitioners, it would be beneficial to implement screening and treatment programs to minimize the long-term behavioral consequences of COVID-19-related OD.

COVID-19: a new emerging respiratory disease from the neurological perspective

Coronavirus disease 2019 (COVID-19) has become a challenging public health catastrophe worldwide. The newly emerged disease spread in almost all countries and infected 100 million persons worldwide. The infection is not limited to the respiratory system but involves various body systems and may lead to multiple organ failure. Tissue degenerative changes result from direct viral invasion, indirect consequences, or through an uncontrolled immune response. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spreads to the brain via hematogenous and neural routes accompanied with dysfunction of the blood-brain barrier. The involvement of the central nervous system is now suspected to be among the main causes of death. The present review discusses the historical background of coronaviruses, their role in previous and ongoing pandemics, the way they escape the immune system, why they are able to spread despite all undertaken measures, in addition to the neurological manifestations, long-term consequences of the disease, and various routes of viral introduction to the CNS.

In silico screening of neurokinin receptor antagonists as a therapeutic strategy for neuroinflammation in Alzheimer's disease

Neuroinflammation is one of the detrimental factors leading to neurodegeneration in Alzheimer’s disease (AD) and other neurodegenerative disorders. The activation of microglial neurokinin 1 receptor (NK1R) by substance P (SP) enhances neuroinflammation which is mediated through pro-inflammatory pathways involving NFkB, ERK1/2, and P38 and thus projects the scope and importance of NK1R inhibitors. Emphasizing the inhibitory role of N Acetyl l Tryptophan (l-NAT) on NK1R, this is the first in silico screening of l-NAT mediated NK1R antagonism. In addition, FDA- approved ligands were screened for their potential NK1R antagonism. The l-NAT was docked in XP (Extra Precision) mode while FDA-approved ligands were screened in HTVS (High Throughput Virtual Screening), SP (Standard Precision), and XP mode onto NK1R (PDB:6HLO). The l-NAT and top 3 compounds FDA-approved ligands were subjected to molecular dynamics (MD) studies of 100 ns simulation time. The XP docking of l-NAT, indacaterol, modafinil and alosetron showed good docking scores. Their 100 ns MD showed brief protein–ligand interactions with an acceptable root mean square deviation. The protein–ligand contacts depicted pi-pi stacking, pi-cation, hydrogen bonds, and water bridges with the amino acids necessary for NK1R inhibition. The variable colour band intensities on the protein–ligand contact map indicated their binding strength with amino acids. The molecular mechanics/generalized born surface area (MM-GBSA) scores suggested favourable binding free energy of the complexes. Thus, our study predicted the ability of l-NAT, indacaterol, modafinil, and alosetron as capable NK1R inhibitors that can aid to curb neuroinflammation in conditions of AD which could be further ascertained in subsequent studies.

A Review of Neurological Involvement in Patients with SARS-CoV-2 Infection

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the causative pathogen of the recent pandemic of coronavirus disease 19 (COVID-19). As the infection spreads, there is increasing evidence of neurological and psychiatric involvement in COVID-19. Headache, impaired consciousness, and olfactory and gustatory dysfunctions are common neurological manifestations described in the literature. Studies demonstrating more specific and more severe neurological involvement such as cerebrovascular insults, encephalitis and Guillain-Barre syndrome are also emerging. Respiratory failure, a significant condition that leads to mortality in COVID-19, is hypothesized to be partly due to brainstem impairment. Notably, some of these neurological complications seem to persist long after infection. This review aims to provide an update on what is currently known about neurological involvement in patients with COVID-19 due to SARS-CoV-2 infection. In this review, we demonstrate invasion routes of SARS-CoV-2, provide evidence to support the neurotropism hypothesis of the virus, and investigate the pathological mechanisms that underlie neurological complications associated with SARS-CoV-2.

JAK-STAT Pathway Inhibition and their Implications in COVID-19 Therapy

As the incidence of COVID-19 increases with time, more and more efforts are made to pave a way out for the therapeutic strategies to deal with the disease progression. Inflammation being a significant influencer in COVID-19 patients, it drives our focus onto the signaling cascades of the JAK/STAT pathway. JAK phosphorylation mediated by cytokine receptor activation leads to phosphorylation of STATs that translocate into the nucleus to translate for inflammatory mediators. The SARS-CoV-2 structural proteins like spike, nucleocapsid, membrane and envelope proteins along with the non- structural proteins 1-16 including proteases like 3CL pro and PLpro promote its entry and survival in hosts. The SARS-CoV-2 infection triggers inflammation via the JAK/STAT pathway leading to recruitment of pneumocytes, endothelial cells, macrophages, monocytes, lymphocytes, natural killer cells and dendritic cells progressing towards cytokine storm. This produces various inflammatory markers in the host that determine the disease severity. The JAK/STAT signaling also mediates immune responses via B cell and T cell differentiation.With an attempt to reduce excessive inflammation, JAK/STAT inhibitors like Ruxolitinib, Baricitinib, Tofacitinib have been employed that mediate its actions via suppressors of cytokine signaling, cytokine inducible SH2 containing protein, Protein inhibitor of activated STAT and protein tyrosine phosphatases. Even though they are implicated with multiple adverse effects, the regulatory authorities have supported its use, and numerous clinical trials are in progress to prove their safety and efficacy. On the contrary, the exact mechanism of JAK/STAT inhibition at molecular levels remains speculative for which further investigations are required.

ABO phenotype and SARS-CoV-2 infection: Is there any correlation?

COVID-19 is the currently evolving viral disease worldwide. It mainly targets the respiratory organs, tissues and causes illness. A plethora of studies has been performing to bring proper treatment and prevent people from the infection. Likewise, susceptibility to some infectious diseases has been associated with blood group phenotypes. The co-relationship of blood group with the occurrence of SARS-CoV-2 infection and death has been examined in numerous studies. This review explained the described studies regarding the correlation of blood group and the other essential factors with COVID-19.

The Other Side of SARS-CoV-2 Infection: Neurological Sequelae in Patients

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has spread around the globe causing coronavirus disease 2019 (COVID-19). Because it affects the respiratory system, common symptoms are cough and breathing difficulties with fever and fatigue. Also, some cases progress to acute respiratory distress syndrome (ARDS). The acute phase of COVID-19 has been also related to nervous system symptoms, including loss of taste and smell as well as encephalitis and cerebrovascular disorders. However, it remains unclear if neurological complications are due to the direct viral infection of the nervous system, or they appear as a consequence of the immune reaction against the virus in patients who presented pre-existing deficits or had a certain detrimental immune response. Importantly, the medium and long-term consequences of the infection by SARS-CoV-2 in the nervous system remain at present unknown. This review article aims to give an overview of the current neurological symptoms associated with COVID-19, as well as attempting to provide an insight beyond the acute affectation.

Prevalence and characteristics of new-onset pain in COVID-19 survivours, a controlled study

BACKGROUND

We assessed whether COVID-19 is associated with de novo pain and de novo chronic pain (CP).

METHODS

This controlled cross-sectional study was based on phone interviews of patients discharged from hospital after COVID-19 compared to the control group composed of individuals hospitalized during the same period due to non-COVID-19 causes. Patients were classified as having previous CP based on the ICD-11/IASP criteria, de novo pain (i.e. any new type of pain, irrespective of the pain status before hospital stay), and de novo CP (i.e. persistent or recurring de novo pain, lasting more than 3 months) after COVID-19. We assessed pain prevalence and its characteristics, including headache profile, pain location, intensity, interference, and its relationship with fatigue, and persistent anosmia. Forty-six COVID-19 and 73 control patients were included. Both groups had similar sociodemographic characteristics and past medical history.

RESULTS

Length of in-hospital-stay and ICU admission rates were significantly higher amongst COVID-19 survivours, while mechanical ventilation requirement was similar between groups. Pre-hospitalisation pain was lower in COVID-19 compared to control group (10.9% vs. 42.5%; p = 0.001). However, the COVID-19 group had a significantly higher prevalence of de novo pain (65.2% vs. 11.0%, p = 0.001), as well as more de novo headache (39.1%) compared to controls (2.7%, p = 0.001). New-onset CP was 19.6% in COVID-19 patients and 1.4% (p = 0.002) in controls. These differences remained significant (p = 0.001) even after analysing exclusively (COVID: n = 40; controls: n = 34) patients who did not report previous pain before the hospital stay. No statistically significant differences were found for mean new-onset pain intensity and interference with daily activities between both groups. COVID-19 pain was more frequently located in the head/neck and lower limbs (p < 0.05). New-onset fatigue was more common in COVID-19 survivours necessitating inpatient hospital care (66.8%) compared to controls (2.5%, p = 0.001). COVID-19 patients who reported anosmia had more new-onset pain (83.3%) compared to those who did not (48.0%, p = 0.024).

CONCLUSION

COVID-19 was associated with a significantly higher prevalence of de novo CP, chronic daily headache, and new-onset pain in general, which was associated with persistent anosmia.

SIGNIFICANCE

There exists de novo pain in a substantial number of COVID-19 survivours, and some develop chronic pain. New-onset pain after the infection was more common in patients who reported anosmia after hospital discharge.

A case of COVID-19 with multiple cranial neuropathies

Various neurological manifestations involving the central and peripheral nervous system have been reported in association with COVID-19. Most common associations reported are encephalopathy, headache, ischemic, hemorrhagic stroke and transient ischemic attack, Miller Fisher syndrome, cranial neuropathies and Guillain-Barre syndrome. Of the cranial neuropathies, anosmia, and dysgeusia are the most common reported symptoms. This is a case of COVID-19 with ipsilateral fifth and seventh cranial nerve involvement with complete resolution of symptoms over a period of 3 weeks. The neurological symptoms started within 5 days of respiratory symptoms. We conclude that isolated cranial neuropathies can be the manifestations of SARS-CoV-2 infection.