SARS-CoV-2 uses metabotropic glutamate receptor subtype 2 as an internalization factor to infect cells

Genome-wide association study identifies human genetic variants associated with fatal outcome from Lassa fever

Infection with Lassa virus (LASV) can cause Lassa fever, a haemorrhagic illness with an estimated fatality rate of 29.7%, but causes no or mild symptoms in many individuals. Here, to investigate whether human genetic variation underlies the heterogeneity of LASV infection, we carried out genome-wide association studies (GWAS) as well as seroprevalence surveys, human leukocyte antigen typing and high-throughput variant functional characterization assays. We analysed Lassa fever susceptibility and fatal outcomes in 533 cases of Lassa fever and 1,986 population controls recruited over a 7 year period in Nigeria and Sierra Leone. We detected genome-wide significant variant associations with Lassa fever fatal outcomes near GRM7 and LIF in the Nigerian cohort. We also show that a haplotype bearing signatures of positive selection and overlapping LARGE1, a required LASV entry factor, is associated with decreased risk of Lassa fever in the Nigerian cohort but not in the Sierra Leone cohort. Overall, we identified variants and genes that may impact the risk of severe Lassa fever, demonstrating how GWAS can provide insight into viral pathogenesis.

CD97 negatively regulates the innate immune response against RNA viruses by promoting RNF125-mediated RIG-I degradation

The G protein-coupled receptor ADGRE5 (CD97) binds to various metabolites that play crucial regulatory roles in metabolism. However, its function in the antiviral innate immune response remains to be determined. In this study, we report that CD97 inhibits virus-induced type-I interferon (IFN-I) release and enhances RNA virus replication in cells and mice. CD97 was identified as a new negative regulator of the innate immune receptor RIG-I, and RIG-1 degradation led to the suppression of the IFN-I signaling pathway. Furthermore, overexpression of CD97 promoted the ubiquitination of RIG-I, resulting in its degradation, but did not impact its mRNA expression. Mechanistically, CD97 upregulates RNF125 expression to induce RNF125-mediated RIG-I degradation via K48-linked ubiquitination at Lys181 after RNA virus infection. Most importantly, CD97-deficient mice are more resistant than wild-type mice to RNA virus infection. We also found that sanguinarine-mediated inhibition of CD97 effectively blocks VSV and SARS-CoV-2 replication. These findings elucidate a previously unknown mechanism through which CD97 negatively regulates RIG-I in the antiviral innate immune response and provide a molecular basis for the development of new therapeutic strategies and the design of targeted antiviral agents.

ACE2-independent SARS-CoV-2 virus entry through cell surface GRP78 on monocytes - evidence from a translational clinical and experimental approach

BACKGROUND

SARS-CoV-2 infects host cells via an ACE2/TMPRSS2 entry mechanism. Monocytes and macrophages, which play a key role during severe COVID-19 express only low or no ACE2, suggesting alternative entry mechanisms in these cells. In silico analyses predicted GRP78, which is constitutively expressed on monocytes and macrophages, to be a potential candidate receptor for SARS-CoV-2 virus entry.

METHODS

Hospitalized COVID-19 patients were characterized regarding their pro-inflammatory state and cell surface GRP78 (csGRP78) expression in comparison to healthy controls. RNA from CD14+ monocytes of patients and controls were subjected to transcriptome analysis that was specifically complemented by bioinformatic re-analyses of bronchoalveolar lavage fluid (BALF) datasets of COVID-19 patients with a focus on monocyte/macrophage subsets, SARS-CoV-2 infection state as well as GRP78 gene expression. Monocyte and macrophage immunohistocytochemistry on GRP78 was conducted in post-mortem lung tissues. SARS-CoV-2 spike and GRP78 protein interaction was analyzed by surface plasmon resonance, GST Pull-down and Co-Immunoprecipitation. SARS-CoV-2 pseudovirus or single spike protein uptake was quantified in csGRP78high THP-1 cells.

FINDINGS

Cytokine patterns, monocyte activation markers and transcriptomic changes indicated typical COVID-19 associated inflammation accompanied by upregulated csGRP78 expression on peripheral blood and lung monocytes/macrophages. Subsequent cell culture experiments confirmed an association between elevated pro-inflammatory cytokine levels and upregulation of csGRP78. Interaction of csGRP78 and SARS-CoV-2 spike protein with a dissociation constant of KD = 55.2 nM was validated in vitro. Infection rate analyses in ACE2low and GRP78high THP-1 cells showed increased uptake of pseudovirus expressing SARS-CoV-2 spike protein.

INTERPRETATION

Our results demonstrate that csGRP78 acts as a receptor for SARS-CoV-2 spike protein to mediate ACE2-independent virus entry into monocytes.

FUNDING

Funded by the Sino-German-Center for Science Promotion (C-0040) and the Germany Ministry BMWi/K [DLR-grant 50WB1931 and RP1920 to AC, DM, TW].

Neuroimmunology of rabies: New insights into an ancient disease

Rabies is an ancient neuroinvasive viral (genus Lyssavirus, family Rhabdoviridae) disease affecting approximately 59,000 people worldwide. The central nervous system (CNS) is targeted, and rabies has a case fatality rate of almost 100% in humans and animals. Rabies is entirely preventable through proper vaccination, and thus, the highest incidence is typically observed in developing countries, mainly in Africa and Asia. However, there are still cases in European countries and the United States. Recently, demographic, increasing income levels, and the coronavirus disease 2019 (COVID-19) pandemic have caused a massive raising in the animal population, enhancing the need for preventive measures (e.g., vaccination, surveillance, and animal control programs), postexposure prophylaxis, and a better understanding of rabies pathophysiology to identify therapeutic targets, since there is no effective treatment after the onset of clinical manifestations. Here, we review the neuroimmune biology and mechanisms of rabies. Its pathogenesis involves a complex and poorly understood modulation of immune and brain functions associated with metabolic, synaptic, and neuronal impairments, resulting in fatal outcomes without significant histopathological lesions in the CNS. In this context, the neuroimmunological and neurochemical aspects of excitatory/inhibitory signaling (e.g., GABA/glutamate crosstalk) are likely related to the clinical manifestations of rabies infection. Uncovering new links between immunopathological mechanisms and neurochemical imbalance will be essential to identify novel potential therapeutic targets to reduce rabies morbidity and mortality.

Literature-Based Discovery to Elucidate the Biological Links between Resistant Hypertension and COVID-19

Multiple studies have reported new or exacerbated persistent or resistant hypertension in patients previously infected with COVID-19. We used literature-based discovery to identify and prioritize multi-scalar explanatory biology that relates resistant hypertension to COVID-19. Cross-domain text mining of 33+ million PubMed articles within a comprehensive knowledge graph was performed using SemNet 2.0. Unsupervised rank aggregation determined which concepts were most relevant utilizing the normalized HeteSim score. A series of simulations identified concepts directly related to COVID-19 and resistant hypertension or connected via one of three renin-angiotensin-aldosterone system hub nodes (mineralocorticoid receptor, epithelial sodium channel, angiotensin I receptor). The top-ranking concepts relating COVID-19 to resistant hypertension included: cGMP-dependent protein kinase II, MAP3K1, haspin, ral guanine nucleotide exchange factor, N-(3-Oxododecanoyl)-L-homoserine lactone, aspartic endopeptidases, metabotropic glutamate receptors, choline-phosphate cytidylyltransferase, protein tyrosine phosphatase, tat genes, MAP3K10, uridine kinase, dicer enzyme, CMD1B, USP17L2, FLNA, exportin 5, somatotropin releasing hormone, beta-melanocyte stimulating hormone, pegylated leptin, beta-lipoprotein, corticotropin, growth hormone-releasing peptide 2, pro-opiomelanocortin, alpha-melanocyte stimulating hormone, prolactin, thyroid hormone, poly-beta-hydroxybutyrate depolymerase, CR 1392, BCR-ABL fusion gene, high density lipoprotein sphingomyelin, pregnancy-associated murine protein 1, recQ4 helicase, immunoglobulin heavy chain variable domain, aglycotransferrin, host cell factor C1, ATP6V0D1, imipramine demethylase, TRIM40, H3C2 gene, COL1A1+COL1A2 gene, QARS gene, VPS54, TPM2, MPST, EXOSC2, ribosomal protein S10, TAP-144, gonadotropins, human gonadotropin releasing hormone 1, beta-lipotropin, octreotide, salmon calcitonin, des-n-octanoyl ghrelin, liraglutide, gastrins. Concepts were mapped to six physiological themes: altered endocrine function, 23.1%; inflammation or cytokine storm, 21.3%; lipid metabolism and atherosclerosis, 17.6%; sympathetic input to blood pressure regulation, 16.7%; altered entry of COVID-19 virus, 14.8%; and unknown, 6.5%.

Novel receptor, mutation, vaccine, and establishment of coping mode for SARS-CoV-2: current status and future

Since the outbreak of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and its resultant pneumonia in December 2019, the cumulative number of infected people worldwide has exceeded 670 million, with over 6.8 million deaths. Despite the marketing of multiple series of vaccines and the implementation of strict prevention and control measures in many countries, the spread and prevalence of SARS-CoV-2 have not been completely and effectively controlled. The latest research shows that in addition to angiotensin converting enzyme II (ACE2), dozens of protein molecules, including AXL, can act as host receptors for SARS-CoV-2 infecting human cells, and virus mutation and immune evasion never seem to stop. To sum up, this review summarizes and organizes the latest relevant literature, comprehensively reviews the genome characteristics of SARS-CoV-2 as well as receptor-based pathogenesis (including ACE2 and other new receptors), mutation and immune evasion, vaccine development and other aspects, and proposes a series of prevention and treatment opinions. It is expected to provide a theoretical basis for an in-depth understanding of the pathogenic mechanism of SARS-CoV-2 along with a research basis and new ideas for the diagnosis and classification, of COVID-19-related disease and for drug and vaccine research and development.

Alzheimer's disease risk after COVID-19: a view from the perspective of the infectious hypothesis of neurodegeneration

In light of the rising evidence of the association between viral and bacterial infections and neurodegeneration, we aimed at revisiting the infectious hypothesis of Alzheimer's disease and analyzing the possible implications of COVID-19 neurological sequelae in long-term neurodegeneration. We wondered how SARS-CoV-2 could be related to the amyloid-β cascade and how it could lead to the pathological hallmarks of the disease. We also predict a paradigm change in clinical medicine, which now has a great opportunity to conduct prospective surveillance of cognitive sequelae and progression to dementia in people who suffered severe infections together with other risk factors for Alzheimer's disease.

Tight junction protein occludin is an internalization factor for SARS-CoV-2 infection and mediates virus cell-to-cell transmission

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spreads efficiently by spike-mediated, direct cell-to-cell transmission. However, the underlying mechanism is poorly understood. Herein, we demonstrate that the tight junction protein occludin (OCLN) is critical to this process. SARS-CoV-2 infection alters OCLN distribution and expression and causes syncytium formation that leads to viral spread. OCLN knockdown fails to alter SARS-CoV-2 binding but significantly lowers internalization, syncytium formation, and transmission. OCLN overexpression also has no effect on virus binding but enhances virus internalization, cell-to-cell transmission, and replication. OCLN directly interacts with the SARS-CoV-2 spike, and the endosomal entry pathway is involved in OCLN-mediated cell-to-cell fusion rather than in the cell surface entry pathway. All SARS-CoV-2 strains tested (prototypic, alpha, beta, gamma, delta, kappa, and omicron) are dependent on OCLN for cell-to-cell transmission, although the extent of syncytium formation differs between strains. We conclude that SARS-CoV-2 utilizes OCLN as an internalization factor for cell-to-cell transmission.

Transferrin Receptor Protein 1 Cooperates with mGluR2 To Mediate the Internalization of Rabies Virus and SARS-CoV-2

Identification of bona fide functional receptors and elucidation of the mechanism of receptor-mediated virus entry are important to reveal targets for developing therapeutics against rabies virus (RABV) and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Our previous studies suggest that metabotropic glutamate receptor subtype 2 (mGluR2) functions as an entry receptor for RABV in vitro, and is an important internalization factor for SARS-CoV-2 in vitro and in vivo. Here, we demonstrate that mGluR2 facilitates RABV internalization in vitro and infection in vivo. We found that transferrin receptor 1 (TfR1) interacts with mGluR2 and internalizes with mGluR2 and RABV in the same clathrin-coated pit. Knockdown of TfR1 blocks agonist-triggered internalization of mGluR2. Importantly, TfR1 also interacts with the SARS-CoV-2 spike protein and is important for SARS-CoV-2 internalization. Our findings identify a novel axis (mGluR2-TfR1 axis) used by RABV and SARS-CoV-2 for entry, and reveal TfR1 as a potential target for therapeutics against RABV and SARS-CoV-2. IMPORTANCE We previously found that metabotropic glutamate receptor subtype 2 (mGluR2) is an entry receptor for RABV in vitro, and an important internalization factor for SARS-CoV-2 in vitro and in vivo. However, whether mGluR2 is required for RABV infection in vivo was unknown. In addition, how mGluR2 mediates the internalization of RABV and SARS-CoV-2 needed to be resolved. Here, we found that mGluR2 gene knockout mice survived a lethal challenge with RABV. To our knowledge, mGluR2 is the first host factor to be definitively shown to play an important role in RABV street virus infection in vivo. We further found that transferrin receptor protein 1 (TfR1) directly interacts and cooperates with mGluR2 to regulate the endocytosis of RABV and SARS-CoV-2. Our study identifies a novel axis (mGluR2-TfR1 axis) used by RABV and SARS-CoV-2 for entry and opens a new door for the development of therapeutics against RABV and SARS-CoV-2.

Transferrin Receptor Protein 1 Is an Entry Factor for Rabies Virus

Rabies virus (RABV) is a prototypical neurotropic virus that causes rabies in human and animals with an almost 100% mortality rate. Once RABV enters the central nervous system, no treatment is proven to prevent death. RABV glycoprotein (G) interacts with cell surface receptors and then enters cells via clathrin-mediated endocytosis (CME); however, the key host factors involved remain largely unknown. Here, we identified transferrin receptor 1 (TfR1), a classic receptor that undergoes CME, as an entry factor for RABV. TfR1 interacts with RABV G and is involved in the endocytosis of RABV. An antibody against TfR1 or the TfR1 ectodomain soluble protein significantly blocked RABV infection in HEK293 cells, N2a cells, and mouse primary neuronal cells. We further found that the endocytosis of TfR1 is coupled with the endocytosis of RABV and that TfR1 and RABV are transported to early and late endosomes. Our results suggest that RABV hijacks the transport pathway of TfR1 for entry, thereby deepening our understanding of the entry mechanism of RABV. IMPORTANCE For most viruses, cell entry involves engagement with many distinct plasma membrane components, each of which is essential. After binding to its specific receptor(s), rabies virus (RABV) enters host cells through the process of clathrin-mediated endocytosis. However, whether the receptor-dependent clathrin-mediated endocytosis of RABV requires other plasma membrane components remain largely unknown. Here, we demonstrate that transferrin receptor 1 (TfR1) is a functional entry factor for RABV infection. The endocytosis of RABV is coupled with the endocytosis of TfR1. Our results indicate that RABV hijacks the transport pathway of TfR1 for entry, which deepens our understanding of the entry mechanism of RABV.

Cross-species transmission, evolution and zoonotic potential of coronaviruses

Coronaviruses (CoVs) continuously evolve, crossing species barriers and spreading across host ranges. Over the last two decades, several CoVs (HCoV-229E, HCoV-NL63, HCoV-HKU1, HCoV-OC43, SARS-CoV, MERS-CoV, and SARS-CoV-2) have emerged in animals and mammals, causing significant economic and human life losses. Due to CoV cross-species transmission and the evolution of novel viruses, it is critical to identify their natural reservoiurs and the circumstances under which their transmission occurs. In this review, we use genetic and ecological data to disentangle the evolution of various CoVs in wildlife, humans, and domestic mammals. We thoroughly investigate several host species and outline the epidemiology of CoVs toward specific hosts. We also discuss the cross-species transmission of CoVs at the interface of wildlife, animals, and humans. Clarifying the epidemiology and diversity of species reservoirs will significantly impact our ability to respond to the future emergence of CoVs in humans and domestic animals.

Citicoline and COVID-19: vis-à-vis conjectured

Coronavirus disease 2019 (COVID-19) is a current pandemic disease caused by a novel severe acute respiratory syndrome coronavirus virus respiratory type 2 (SARS-CoV-2). SARS-CoV-2 infection is linked with various neurological manifestations due to cytokine-induced disruption of the blood brain barrier (BBB), neuroinflammation, and peripheral neuronal injury, or due to direct SARS-CoV-2 neurotropism. Of note, many repurposed agents were included in different therapeutic protocols in the management of COVID-19. These agents did not produce an effective therapeutic eradication of SARS-CoV-2, and continuing searching for novel anti-SARS-CoV-2 agents is a type of challenge nowadays. Therefore, this study aimed to review the potential anti-inflammatory and antioxidant effects of citicoline in the management of COVID-19.

Long COVID and the Neuroendocrinology of Microbial Translocation Outside the GI Tract: Some Treatment Strategies

Similar to previous pandemics, COVID-19 has been succeeded by well-documented post-infectious sequelae, including chronic fatigue, cough, shortness of breath, myalgia, and concentration difficulties, which may last 5 to 12 weeks or longer after the acute phase of illness. Both the psychological stress of SARS-CoV-2 infection and being diagnosed with COVID-19 can upregulate cortisol, a stress hormone that disrupts the efferocytosis effectors, macrophages, and natural killer cells, leading to the excessive accumulation of senescent cells and disruption of biological barriers. This has been well-established in cancer patients who often experience unrelenting fatigue as well as gut and blood–brain barrier dysfunction upon treatment with senescence-inducing radiation or chemotherapy. In our previous research from 2020 and 2021, we linked COVID-19 to myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) via angiotensin II upregulation, premature endothelial senescence, intestinal barrier dysfunction, and microbial translocation from the gastrointestinal tract into the systemic circulation. In 2021 and 2022, these hypotheses were validated and SARS-CoV-2-induced cellular senescence as well as microbial translocation were documented in both acute SARS-CoV-2 infection, long COVID, and ME/CFS, connecting intestinal barrier dysfunction to disabling fatigue and specific infectious events. The purpose of this narrative review is to summarize what is currently known about host immune responses to translocated gut microbes and how these responses relate to fatiguing illnesses, including long COVID. To accomplish this goal, we examine the role of intestinal and blood–brain barriers in long COVID and other illnesses typified by chronic fatigue, with a special emphasis on commensal microbes functioning as viral reservoirs. Furthermore, we discuss the role of SARS-CoV-2/Mycoplasma coinfection in dysfunctional efferocytosis, emphasizing some potential novel treatment strategies, including the use of senotherapeutic drugs, HMGB1 inhibitors, Toll-like receptor 4 (TLR4) blockers, and membrane lipid replacement.

Photochemical Identification of Auxiliary Severe Acute Respiratory Syndrome Coronavirus 2 Host Entry Factors Using μMap

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the infectious agent of the COVID-19 pandemic, remains a global medical problem. Angiotensin-converting enzyme 2 (ACE2) was identified as the primary viral entry receptor, and transmembrane serine protease 2 primes the spike protein for membrane fusion. However, ACE2 expression is generally low and variable across tissues, suggesting that auxiliary receptors facilitate viral entry. Identifying these factors is critical for understanding SARS-Cov-2 pathophysiology and developing new countermeasures. However, profiling host-virus interactomes involves extensive genetic screening or complex computational predictions. Here, we leverage the photocatalytic proximity labeling platform μMap to rapidly profile the spike interactome in human cells and identify eight novel candidate receptors. We systemically validate their functionality in SARS-CoV-2 pseudoviral uptake assays with both Wuhan and Delta spike variants and show that dual expression of ACE2 with either neuropilin-2, ephrin receptor A7, solute carrier family 6 member 15, or myelin and lymphocyte protein 2 significantly enhances viral uptake. Collectively, our data show that SARS-CoV-2 synergistically engages several host factors for cell entry and establishes μMap as a powerful tool for rapidly interrogating host-virus interactomes.

Melatonin: Regulation of Viral Phase Separation and Epitranscriptomics in Post-Acute Sequelae of COVID-19

The relentless, protracted evolution of the SARS-CoV-2 virus imposes tremendous pressure on herd immunity and demands versatile adaptations by the human host genome to counter transcriptomic and epitranscriptomic alterations associated with a wide range of short- and long-term manifestations during acute infection and post-acute recovery, respectively. To promote viral replication during active infection and viral persistence, the SARS-CoV-2 envelope protein regulates host cell microenvironment including pH and ion concentrations to maintain a high oxidative environment that supports template switching, causing extensive mitochondrial damage and activation of pro-inflammatory cytokine signaling cascades. Oxidative stress and mitochondrial distress induce dynamic changes to both the host and viral RNA m6A methylome, and can trigger the derepression of long interspersed nuclear element 1 (LINE1), resulting in global hypomethylation, epigenetic changes, and genomic instability. The timely application of melatonin during early infection enhances host innate antiviral immune responses by preventing the formation of "viral factories" by nucleocapsid liquid-liquid phase separation that effectively blockades viral genome transcription and packaging, the disassembly of stress granules, and the sequestration of DEAD-box RNA helicases, including DDX3X, vital to immune signaling. Melatonin prevents membrane depolarization and protects cristae morphology to suppress glycolysis via antioxidant-dependent and -independent mechanisms. By restraining the derepression of LINE1 via multifaceted strategies, and maintaining the balance in m6A RNA modifications, melatonin could be the quintessential ancient molecule that significantly influences the outcome of the constant struggle between virus and host to gain transcriptomic and epitranscriptomic dominance over the host genome during acute infection and PASC.

Virtual Screening of Repurposed Drugs as Potential Spike Protein Inhibitors of Different SARS-CoV-2 Variants: Molecular Docking Study

Like most of the RNA viruses, SARS-CoV-2 continuously mutates. Although many mutations have an insignificant impact on the virus properties, mutations in the surface protein, especially those in the receptor-binding domain, may lead to immune or vaccine escape variants, or altered binding activities to both the cell receptor and the drugs targeting such a protein. The current study intended to assess the ability of different variants of interest (VOIs) and variants of concern (VOCs) of SARS-CoV-2 for their affinities of binding to different repurposed drugs. Seven FDA approved drugs, namely, camostat, nafamostat mesylate, fenofibrate, umifenovir, nelfinavir, cefoperazone and ceftazidime, were selected based on their reported in vitro and clinical activities against SARA-CoV-2. The S1 protein subunit from eleven different variants, including the latest highly contiguous omicron variant, were used as targets for the docking study. The docking results revealed that all tested drugs possess moderate to high binding energies to the receptor-binding domain (RBD) of the S1 protein for all different variants. Cefoperazone was found to possess the highest binding energy to the RBD of the S1 protein of all the eleven variants. Ceftazidime was the second-best drug in terms of binding affinity towards the S1 RBD of the investigated variants. On the other hand, fenofibrate showed the least binding affinity towards the RBD of the S1 protein of all eleven variants. The binding affinities of anti-spike drugs varied among different variants. Most of the interacting amino acid residues of the receptor fall within the RBD (438–506).

The AI-Assisted Identification and Clinical Efficacy of Baricitinib in the Treatment of COVID-19

During the current pandemic, the vast majority of COVID-19 patients experienced mild symptoms, but some had a potentially fatal aberrant hyperinflammatory immune reaction characterized by high levels of IL-6 and other cytokines. Modulation of this immune reaction has proven to be the only method of reducing mortality in severe and critical COVID-19. The anti-inflammatory drug baricitinib (Olumiant) has recently been strongly recommended by the WHO for use in COVID-19 patients because it reduces the risk of progressive disease and death. It is a Janus Kinase (JAK) 1/2 inhibitor approved for rheumatoid arthritis which was suggested in early 2020 as a treatment for COVID-19. In this review the AI-assisted identification of baricitinib, its antiviral and anti-inflammatory properties, and efficacy in clinical trials are discussed and compared with those of other immune modulators including glucocorticoids, IL-6 and IL-1 receptor blockers and other JAK inhibitors. Baricitinib inhibits both virus infection and cytokine signalling and is not only important for COVID-19 management but is “non-immunological”, and so should remain effective if new SARS-CoV-2 variants escape immune control. The repurposing of baricitinib is an example of how advanced artificial intelligence (AI) can quickly identify new drug candidates that have clinical benefit in previously unsuspected therapeutic areas.

Neuropathological Aspects of SARS-CoV-2 Infection: Significance for Both Alzheimer's and Parkinson's Disease

Evidence suggests that SARS-CoV-2 entry into the central nervous system can result in neurological and/or neurodegenerative diseases. In this review, routes of SARS-Cov-2 entry into the brain via neuroinvasive pathways such as transcribrial, ocular surface or hematogenous system are discussed. It is argued that SARS-Cov-2-induced cytokine storm, neuroinflammation and oxidative stress increase the risk of developing neurodegenerative diseases such as Alzheimer's disease and Parkinson's disease. Further studies on the effects of SARS-CoV-2 and its variants on protein aggregation, glia or microglia activation, and blood-brain barrier are warranted.