Neurotropic Mechanisms Research Articles

Legacy of neuropsychiatric symptoms associated with past COVID-19 infection: A cause of concern.

Although primarily affecting the respiratory system, growing attention is being paid to the neuropsychiatric consequences of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections. Acute and sub-acute neuropsychiatric manifestations of coronavirus disease 2019 (COVID-19) disease and their mechanisms are better studied and understood currently than they had been when the pandemic began; however, many months or years will be necessary to fully comprehend how significant the consequences of such complications will be. In this editorial, we discuss the possible long-term sequelae of the COVID-19 pandemic, deriving our considerations on experiences drawn from past coronaviruses’ outbreaks, such as the SARS and the middle east respiratory syndrome, and from the knowledge of the mechanisms of neurotropism and invasiveness of SARS-CoV-2. Acknowledging the global spread of COVID-19 and the vast number of people affected, to date amounting to many millions, the matter of this pandemic’s neuropsychiatric legacy appears concerning. Public health monitoring strategies and early interventions seem to be necessary to manage the possible emergence of a severe wave of neuropsychiatric distress among the survivors.

COVID-19 pansinusitis with abducens paralysis

Increasing numbers of the papers indicate that SARS-CoV-2 also causes neurological symptoms; the underlying mechanism has not been elucidated yet. Hypothetic mechanisms to explain the CNS involvement of SARS-CoV-2 include the neurotropic mechanisms and the cytokine storm developing during the disease process. A middle age female patient applied to the emergency department with complaints of eye pain, a double, foggy, and blurred vision and a severe throbbing headache. The outward gaze was found to be limited in her right eye. Nasopharyngeal swab for SARS-CoV-2 RNA was positive, radiological findings were supported the COVID pneumonia and diffuse sinonasal inflammation. Cranial imaging showed thickening and contrast involvement in the cavernous sinus in the postcontrast series. While shortness of breath improved, and the headache was completely resolved on the 10th day of treatment the right eye outward gaze restriction was continued. The control MRI reveals a significant reduction in cavernous thickening and contrast enhancement and complete resolution in dural thickening. In our case of COVID, cranial nerve involvement and pansinusitis developed without cytokine storm findings suggests that the virus has spread to the cavernous sinuses and dura by regional neighborhood. Neurological symptoms may appear as the first symptom of COVID.

SARS-CoV-2 may trigger inflammasome and pyroptosis in the central nervous system: a mechanistic view of neurotropism.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can enter the central nervous system and cause several neurological manifestations. Data from cerebrospinal fluid analyses and postmortem samples have been shown that SARS-CoV-2 has neuroinvasive properties. Therefore, ongoing studies have focused on mechanisms involved in neurotropism and neural injuries of SARS-CoV-2. The inflammasome is a part of the innate immune system that is responsible for the secretion and activation of several pro-inflammatory cytokines, such as interleukin-1β, interleukin-6, and interleukin-18. Since cytokine storm has been known as a major mechanism followed by SARS-CoV-2, inflammasome may trigger an inflammatory form of lytic programmed cell death (pyroptosis) following SARS-CoV-2 infection and contribute to associated neurological complications. We reviewed and discussed the possible role of inflammasome and its consequence pyroptosis following coronavirus infections as potential mechanisms of neurotropism by SARS-CoV-2. Further studies, particularly postmortem analysis of brain samples obtained from COVID-19 patients, can shed light on the possible role of the inflammasome in neurotropism of SARS-CoV-2.

Neurotropic Viruses, Astrocytes, and COVID-19.

At the end of 2019, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was discovered in China, causing a new coronavirus disease, termed COVID-19 by the WHO on February 11, 2020. At the time of this paper (January 31, 2021), more than 100 million cases have been recorded, which have claimed over 2 million lives worldwide. The most important clinical presentation of COVID-19 is severe pneumonia; however, many patients present various neurological symptoms, ranging from loss of olfaction, nausea, dizziness, and headache to encephalopathy and stroke, with a high prevalence of inflammatory central nervous system (CNS) syndromes. SARS-CoV-2 may also target the respiratory center in the brainstem and cause silent hypoxemia. However, the neurotropic mechanism(s) by which SARS-CoV-2 affects the CNS remain(s) unclear. In this paper, we first address the involvement of astrocytes in COVID-19 and then elucidate the present knowledge on SARS-CoV-2 as a neurotropic virus as well as several other neurotropic flaviviruses (with a particular emphasis on the West Nile virus, tick-borne encephalitis virus, and Zika virus) to highlight the neurotropic mechanisms that target astroglial cells in the CNS. These key homeostasis-providing cells in the CNS exhibit many functions that act as a favorable milieu for virus replication and possibly a favorable environment for SARS-CoV-2 as well. The role of astrocytes in COVID-19 pathology, related to aging and neurodegenerative disorders, and environmental factors, is discussed. Understanding these mechanisms is key to better understanding the pathophysiology of COVID-19 and for developing new strategies to mitigate the neurotropic manifestations of COVID-19.

Bilateral vocal fold paralysis after COVID-19 infection. Another neuro-invasive manifestation? Case series

The agent that causes the coronavirus disease (COVID-19), associated with the severe acute respiratory syndrome (SARS-CoV-2), produces a spectrum of symptoms that mainly affect the respiratory system, the central nervous system (CNS), the regulation of hemostasis and the immune system.
 Bilateral vocal fold paralysis (BVFP) is a condition of unknown incidence among infected patients, either because it is short-lived or because of the difficulty in establishing a direct cause to the virus.
 Viral infection has been described in the literature as a cause of BVFP and there is the suspicion that a proportion of the idiopathic cases are due to undiagnosed viral infections.
 Although the neurotropic mechanisms for SARS-CoV-2 remain unclear, there is strong evidence to ensure its neuroinvasive potential.
 The most frequent etiologies of BVFP are trauma, neoplasm, and neurological, but a viral origin should not be ruled out. Causality between COVID-19 and BVFP is plausible and will require further study in the short and long term.

Neurological Consequences of SARS-CoV-2 Infection and Concurrence of Treatment-Induced Neuropsychiatric Adverse Events in COVID-19 Patients: Navigating the Uncharted.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) binds to the angiotensin-converting enzyme 2 (ACE2) receptor and invade the human cells to cause COVID-19-related pneumonia. Despite an emphasis on respiratory complications, the evidence of neurological manifestations of SARS-CoV-2 infection is rapidly growing, which is substantially contributing to morbidity and mortality. The neurological disorders associated with COVID-19 may have several pathophysiological underpinnings, which are yet to be explored. Hypothetically, SARS-CoV-2 may affect the central nervous system (CNS) either by direct mechanisms like neuronal retrograde dissemination and hematogenous dissemination, or via indirect pathways. CNS complications associated with COVID-19 include encephalitis, acute necrotizing encephalopathy, diffuse leukoencephalopathy, stroke (both ischemic and hemorrhagic), venous sinus thrombosis, meningitis, and neuroleptic malignant syndrome. These may result from different mechanisms, including direct virus infection of the CNS, virus-induced hyper-inflammatory states, and post-infection immune responses. On the other hand, the Guillain-Barre syndrome, hyposmia, hypogeusia, and myopathy are the outcomes of peripheral nervous system injury. Although the therapeutic potential of certain repurposed drugs has led to their off-label use against COVID-19, such as anti-retroviral drugs (remdesivir, favipiravir, and lopinavir-ritonavir combination), biologics (tocilizumab), antibiotics (azithromycin), antiparasitics (chloroquine and hydroxychloroquine), and corticosteroids (dexamethasone), unfortunately, the associated clinical neuropsychiatric adverse events remains a critical issue. Therefore, COVID-19 represents a major threat to the field of neuropsychiatry, as both the virus and the potential therapies may induce neurologic as well as psychiatric disorders. Notably, potential COVID-19 medications may also interact with the medications of pre-existing neuropsychiatric diseases, thereby further complicating the condition. From this perspective, this review will discuss the possible neurological manifestations and sequelae of SARS-CoV-2 infection with emphasis on the probable underlying neurotropic mechanisms. Additionally, we will highlight the concurrence of COVID-19 treatment-associated neuropsychiatric events and possible clinically relevant drug interactions, to provide a useful framework and help researchers, especially the neurologists in understanding the neurologic facets of the ongoing pandemic to control the morbidity and mortality.

Impact of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) in the Nervous System: Implications of COVID-19 in Neurodegeneration.

Coronavirus Disease 2019 (COVID-19), caused by the Severe Acute Respiratory Syndrome coronavirus-2 (SARS-CoV-2), began in December 2019, in Wuhan, China and was promptly declared as a pandemic by the World Health Organization (WHO). As an acute respiratory disease, COVID-19 uses the angiotensin-converting enzyme 2 (ACE2) receptor, which is the same receptor used by its predecessor, SARS-CoV, to enter and spread through the respiratory tract. Common symptoms of COVID-19 include fever, cough, fatigue and in a small population of patients, SARS-CoV-2 can cause several neurological symptoms. Neurological malaise may include severe manifestations, such as acute cerebrovascular disease and meningitis/encephalitis. Although there is evidence showing that coronaviruses can invade the central nervous system (CNS), studies are needed to address the invasion of SARS-CoV-2 in the CNS and to decipher the underlying neurotropic mechanisms used by SARS-CoV-2. This review summarizes current reports on the neurological manifestations of COVID-19 and addresses potential routes used by SARS-CoV-2 to invade the CNS.

Neurological manifestations and comorbidity associated with COVID-19: an overview.

First in 2002, severe acute respiratory syndrome coronavirus (SARS-CoV), second in 2012, Middle East respiratory syndrome coronavirus (MERS-CoV), and now the third in the December 2019, emergence of tremendously pathogenic and large-scale epidemic novel coronavirus (SARS-CoV-2) has brought the worst conditions into the human inhabitants of the twenty-first century. The SARS-CoV-2 uses the resembling receptor, angiotensin-converting enzyme 2 (ACE2) as that for SARS-CoV, and mainly feasts through the respiratory tract. The ACE2 receptor appearances have been also detected upon glial cells and neurons, which makes them a potential target of SARS-CoV-2 disease (COVID-19). Consequently, cells expressing ACE2, apart from lung and cardiovascular tissue, neurons and glial cells may act as targets and are thus vulnerable to SARS-CoV-2 systemic infection as well as its central nervous system (CNS) comorbidities. Investigation of the neurological manifestations of COVID-19 is a step towards better understanding the SARS-CoV-2 infections, inhibiting the additional spread and treating patients affected by this pandemic. In this concern, more clinical examinations for CNS involvement of SARS-CoV-2 are warranted. In this article, we have reviewed the neurological characteristic features of COVID-19 patients, latent neurotropic mechanisms of SARS-CoV-2 involvement in the comorbidity associated with CNS disorders, and neurological manifestations associated with COVID-19. Therefore, in the perspective of COVID-19 pandemic, clinicians and healthcare workers should be aware of a wide spectrum of neurological manifestations associated with COVID-19 along with their signs and symptoms for initial diagnosis and isolation of the patients.

Encefalitis aguda en pacientes COVID-19: primer reporte de casos en Perú.

En el contexto de la pandemia de COVID-19, se han descrito formas clínicas atípicas, en las que predominan síntomas extrar-respiratorios; entre ellos han sido reportados casos de manifestaciones neurológicas concurrentes. En base a la identificación de coronavirus en el sistema nervioso central en el brote SARS-CoV del 2002, se ha planteado un potencial neurotropismo del SARS-CoV-2. En la literatura mundial se han descrito escasos pacientes con encefalitis aguda asociada a SARS-CoV-2. En este reporte les presentamos dos casos de pacientes peruanos con encefalitis aguda concurrente a COVID-19, revisamos la literatura y discutimos los posibles mecanismos de neurotropismo y neuro-invasión.

Understanding the neurotropic characteristics of SARS-CoV-2: from neurological manifestations of COVID-19 to potential neurotropic mechanisms.

Coronavirus disease 2019 (COVID-19), a disease caused by the novel betacoronavirus (SARS-CoV-2), has become a global pandemic threat. The potential involvement of COVID-19 in central nervous system (CNS) has attracted considerable attention due to neurological manifestations presented throughout the disease process. In addition, SARS-CoV-2 is structurally similar to SARS-CoV, and both bind to the angiotensin-converting enzyme 2 (ACE2) receptor to enter human cells. Thus, cells expressing ACE2, such as neurons and glial cells may act as targets and are thus vulnerable to SARS-CoV-2 infection. Here, we have reviewed the neurological characteristics of COVID-19 and summarized possible mechanisms of SARS-CoV-2 invasion of the CNS. COVID-19 patients have presented with a number of different neurological symptoms such as headache, dizziness, hyposmia, and hypogeusia during the course of illness. It has also been reported recently that some cases of COVID-19 have presented with concurrent acute cerebrovascular disease (acute ischemic stroke, cerebral venous sinus thrombosis, cerebral hemorrhage, subarachnoid hemorrhage), meningitis/encephalitis, acute necrotizing hemorrhagic encephalopathy, and acute Guillain–Barré syndrome. Furthermore, SARS-CoV-2 RNA detected in a cerebrospinal fluid specimen of a patient with COVID-19 have provided direct evidence to support the theory of neurotropic involvement of SARS-CoV-2. However, the underlying neurotropic mechanisms of SARS-CoV-2 are yet to be established. SARS-CoV-2 may affect CNS through two direct mechanisms (hematogenous dissemination or neuronal retrograde dissemination) or via indirect routes. The underlying mechanisms require further elucidation in the future.

Evidence of the COVID-19 Virus Targeting the CNS: Tissue Distribution, Host-Virus Interaction, and Proposed Neurotropic Mechanisms.

The recent outbreak of coronavirus infectious disease 2019 (COVID-19) has gripped the world with apprehension and has evoked a scare of epic proportion regarding its potential to spread and infect humans worldwide. As we are in the midst of an ongoing pandemic of COVID-19, scientists are struggling to understand how it resembles and differs from the severe acute respiratory syndrome coronavirus (SARS-CoV) at the genomic and transcriptomic level. In a short time following the outbreak, it has been shown that, similar to SARS-CoV, COVID-19 virus exploits the angiotensin-converting enzyme 2 (ACE2) receptor to gain entry inside the cells. This finding raises the curiosity of investigating the expression of ACE2 in neurological tissue and determining the possible contribution of neurological tissue damage to the morbidity and mortality caused by COIVD-19. Here, we investigate the density of the expression levels of ACE2 in the CNS, the host–virus interaction and relate it to the pathogenesis and complications seen in the recent cases resulting from the COVID-19 outbreak. Also, we debate the need for a model for staging COVID-19 based on neurological tissue involvement.

MicroRNA analysis in mouse neuro-2a cells after pseudorabies virus infection.

Pseudorabies virus (PRV), an alpha herpesvirus can enter the mammalian nervous system, causing Aujezsky's disease. Previous studies have reported an alteration of microRNA (miRNA) expression levels during PRV infections. However, knowledge regarding miRNA response in nervous cells to PRV infection is still unknown. To address this issue, small RNA libraries from infected and uninfected mouse neuroblastoma cells were assessed after Illumina deep sequencing. A total of eight viral miRNA were identified, and ten host miRNAs showed significantly different expression upon PRV infection. Among these, five were analyzed by stem-loop RT-qPCR, which confirmed the above data. Interestingly, these viral miRNAs were mainly found in the large latency transcript region of PRV, and predicted to target a variety of genes, forming a complicated regulatory network. Moreover, ten cellular miRNAs were expressed differently upon PRV infection, including nine upregulated and one downregulated miRNAs. Host targets of these miRNAs obtained by bioinformatics analysis belonged to large signaling networks, mainly encompassing calcium signaling pathway, cAMP signaling pathway, MAPK signaling pathway, and other nervous-associated pathways. These findings further highlighted miRNA features in nervous cells after PRV infection and contributed to unveil the underlying mechanisms of neurotropism as well as the neuropathogenesis of PRV.

Advances in understanding the pathogenesis of CNS acute lymphoblastic leukaemia and potential for therapy.

Central nervous system acute lymphoblastic leukaemia (CNS-ALL) is a major clinical problem. CNS-directed 'prophylactic' chemo- or radio - therapy is associated with significant early and long-term toxicity. Moreover, greater than a third of the relapses occur in the CNS. To design specific, more effective and less toxic therapy and for personalized precise adjustment of prophylactic therapy there is a need for better understanding of the biology of this disease. Specifically, the precise neurotropic mechanisms of ALL are currently unclear, as is the pathogenesis of CNS relapse. Here we review and contrast the recent findings with earlier studies of pathogenesis of CNS leukaemia. We also describe the challenges in research of this devastating complication of ALL.