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1.
Sci Adv ; 9(23): eadg2248, 2023 06 09.
Article in English | MEDLINE | ID: covidwho-20239375

ABSTRACT

Numerous viruses use specialized surface molecules called fusogens to enter host cells. Many of these viruses, including the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), can infect the brain and are associated with severe neurological symptoms through poorly understood mechanisms. We show that SARS-CoV-2 infection induces fusion between neurons and between neurons and glia in mouse and human brain organoids. We reveal that this is caused by the viral fusogen, as it is fully mimicked by the expression of the SARS-CoV-2 spike (S) protein or the unrelated fusogen p15 from the baboon orthoreovirus. We demonstrate that neuronal fusion is a progressive event, leads to the formation of multicellular syncytia, and causes the spread of large molecules and organelles. Last, using Ca2+ imaging, we show that fusion severely compromises neuronal activity. These results provide mechanistic insights into how SARS-CoV-2 and other viruses affect the nervous system, alter its function, and cause neuropathology.


Subject(s)
COVID-19 , Animals , Humans , Mice , SARS-CoV-2/physiology , Neurons , Brain , Neuroglia
2.
J Virol ; 97(4): e0014423, 2023 04 27.
Article in English | MEDLINE | ID: covidwho-2297692

ABSTRACT

2019 coronavirus disease (COVID-19) is a disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). In addition to respiratory illness, COVID-19 patients exhibit neurological symptoms lasting from weeks to months (long COVID). It is unclear whether these neurological manifestations are due to an infection of brain cells. We found that a small fraction of human induced pluripotent stem cell (iPSC)-derived neurons, but not astrocytes, were naturally susceptible to SARS-CoV-2. Based on the inhibitory effect of blocking antibodies, the infection seemed to depend on the receptor angiotensin-converting enzyme 2 (ACE2), despite very low levels of its expression in neurons. The presence of double-stranded RNA in the cytoplasm (the hallmark of viral replication), abundant synthesis of viral late genes localized throughout infected cells, and an increase in the level of viral RNA in the culture medium (viral release) within the first 48 h of infection suggested that the infection was productive. Productive entry of SARS-CoV-2 requires the fusion of the viral and cellular membranes, which results in the delivery of the viral genome into the cytoplasm of the target cell. The fusion is triggered by proteolytic cleavage of the viral surface spike protein, which can occur at the plasma membrane or from endosomes or lysosomes. We found that SARS-CoV-2 infection of human neurons was insensitive to nafamostat and camostat, which inhibit cellular serine proteases, including transmembrane serine protease 2 (TMPRSS2). Inhibition of cathepsin L also did not significantly block infection. In contrast, the neuronal infection was blocked by apilimod, an inhibitor of phosphatidyl-inositol 5 kinase (PIK5K), which regulates early to late endosome maturation. IMPORTANCE COVID-19 is a disease caused by the coronavirus SARS-CoV-2. Millions of patients display neurological symptoms, including headache, impairment of memory, seizures, and encephalopathy, as well as anatomical abnormalities, such as changes in brain morphology. SARS-CoV-2 infection of the human brain has been documented, but it is unclear whether the observed neurological symptoms are linked to direct brain infection. The mechanism of virus entry into neurons has also not been characterized. Here, we investigated SARS-CoV-2 infection by using a human iPSC-derived neural cell model and found that a small fraction of cortical-like neurons was naturally susceptible to infection. The productive infection was ACE2 dependent and TMPRSS2 independent. We also found that the virus used the late endosomal and lysosomal pathway for cell entry and that the infection could be blocked by apilimod, an inhibitor of cellular PIK5K.


Subject(s)
COVID-19 , Induced Pluripotent Stem Cells , SARS-CoV-2 , Humans , Angiotensin-Converting Enzyme 2 , COVID-19/physiopathology , Endosomes/metabolism , Endosomes/virology , Induced Pluripotent Stem Cells/metabolism , Neurons/metabolism , Neurons/virology , Post-Acute COVID-19 Syndrome/physiopathology , Post-Acute COVID-19 Syndrome/virology , SARS-CoV-2/physiology , Spike Glycoprotein, Coronavirus/metabolism , Virus Internalization/drug effects , Phosphotransferases/antagonists & inhibitors , Protein Kinase Inhibitors/pharmacology , Astrocytes/virology , Cells, Cultured
4.
Proc Natl Acad Sci U S A ; 119(40): e2210990119, 2022 10 04.
Article in English | MEDLINE | ID: covidwho-2037061

ABSTRACT

Variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) challenge currently available coronavirus disease 2019 vaccines and monoclonal antibody therapies through epitope change on the receptor binding domain of the viral spike glycoprotein. Hence, there is a specific urgent need for alternative antivirals that target processes less likely to be affected by mutation, such as the membrane fusion step of viral entry into the host cell. One such antiviral class includes peptide inhibitors, which block formation of the so-called heptad repeat 1 and 2 (HR1HR2) six-helix bundle of the SARS-CoV-2 spike (S) protein and thus interfere with viral membrane fusion. We performed structural studies of the HR1HR2 bundle, revealing an extended, well-folded N-terminal region of HR2 that interacts with the HR1 triple helix. Based on this structure, we designed an extended HR2 peptide that achieves single-digit nanomolar inhibition of SARS-CoV-2 in cell-based and virus-based assays without the need for modifications such as lipidation or chemical stapling. The peptide also strongly inhibits all major SARS-CoV-2 variants to date. This extended peptide is ∼100-fold more potent than all previously published short, unmodified HR2 peptides, and it has a very long inhibition lifetime after washout in virus infection assays, suggesting that it targets a prehairpin intermediate of the SARS-CoV-2 S protein. Together, these results suggest that regions outside the HR2 helical region may offer new opportunities for potent peptide-derived therapeutics for SARS-CoV-2 and its variants, and even more distantly related viruses, and provide further support for the prehairpin intermediate of the S protein.


Subject(s)
COVID-19 Drug Treatment , Spike Glycoprotein, Coronavirus , Antiviral Agents/chemistry , Antiviral Agents/pharmacology , Humans , Peptides/chemistry , Peptides/pharmacology , SARS-CoV-2/drug effects
5.
Proc Natl Acad Sci U S A ; 119(38): e2209514119, 2022 09 20.
Article in English | MEDLINE | ID: covidwho-2017036

ABSTRACT

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) cell entry starts with membrane attachment and ends with spike (S) protein-catalyzed membrane fusion depending on two cleavage steps, namely, one usually by furin in producing cells and the second by TMPRSS2 on target cells. Endosomal cathepsins can carry out both. Using real-time three-dimensional single-virion tracking, we show that fusion and genome penetration require virion exposure to an acidic milieu of pH 6.2 to 6.8, even when furin and TMPRSS2 cleavages have occurred. We detect the sequential steps of S1-fragment dissociation, fusion, and content release from the cell surface in TMPRRS2-overexpressing cells only when exposed to acidic pH. We define a key role of an acidic environment for successful infection, found in endosomal compartments and at the surface of TMPRSS2-expressing cells in the acidic milieu of the nasal cavity.


Subject(s)
COVID-19 , Nasal Cavity , SARS-CoV-2 , Serine Endopeptidases , Virus Internalization , COVID-19/virology , Furin/genetics , Furin/metabolism , Humans , Hydrogen-Ion Concentration , Nasal Cavity/chemistry , Nasal Cavity/virology , SARS-CoV-2/physiology , Serine Endopeptidases/metabolism , Spike Glycoprotein, Coronavirus/metabolism
6.
PLoS Biol ; 20(8): e3001728, 2022 08.
Article in English | MEDLINE | ID: covidwho-1974223

ABSTRACT

Children typically experience more mild symptoms of Coronavirus Disease 2019 (COVID-19) when compared to adults. There is a strong body of evidence that children are also less susceptible to Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infection with the ancestral viral isolate. However, the emergence of SARS-CoV-2 variants of concern (VOCs) has been associated with an increased number of pediatric infections. Whether this is the result of widespread adult vaccination or fundamental changes in the biology of SARS-CoV-2 remain to be determined. Here, we use primary nasal epithelial cells (NECs) from children and adults, differentiated at an air-liquid interface to show that the ancestral SARS-CoV-2 replicates to significantly lower titers in the NECs of children compared to those of adults. This was associated with a heightened antiviral response to SARS-CoV-2 in the NECs of children. Importantly, the Delta variant also replicated to significantly lower titers in the NECs of children. This trend was markedly less pronounced in the case of Omicron. It is also striking to note that, at least in terms of viral RNA, Omicron replicated better in pediatric NECs compared to both Delta and the ancestral virus. Taken together, these data show that the nasal epithelium of children supports lower infection and replication of ancestral SARS-CoV-2, although this may be changing as the virus evolves.


Subject(s)
COVID-19 , SARS-CoV-2 , Adult , Child , Epithelial Cells , Humans , SARS-CoV-2/genetics
7.
Brief Bioinform ; 23(1)2022 01 17.
Article in English | MEDLINE | ID: covidwho-1597924

ABSTRACT

The pharmacological arsenal against the COVID-19 pandemic is largely based on generic anti-inflammatory strategies or poorly scalable solutions. Moreover, as the ongoing vaccination campaign is rolling slower than wished, affordable and effective therapeutics are needed. To this end, there is increasing attention toward computational methods for drug repositioning and de novo drug design. Here, multiple data-driven computational approaches are systematically integrated to perform a virtual screening and prioritize candidate drugs for the treatment of COVID-19. From the list of prioritized drugs, a subset of representative candidates to test in human cells is selected. Two compounds, 7-hydroxystaurosporine and bafetinib, show synergistic antiviral effects in vitro and strongly inhibit viral-induced syncytia formation. Moreover, since existing drug repositioning methods provide limited usable information for de novo drug design, the relevant chemical substructures of the identified drugs are extracted to provide a chemical vocabulary that may help to design new effective drugs.


Subject(s)
Antiviral Agents/pharmacology , COVID-19 Drug Treatment , COVID-19 , Giant Cells , Pyrimidines/pharmacology , SARS-CoV-2/metabolism , Staurosporine/analogs & derivatives , A549 Cells , COVID-19/metabolism , Computational Biology , Drug Evaluation, Preclinical , Drug Repositioning , Giant Cells/metabolism , Giant Cells/virology , Humans , Staurosporine/pharmacology
8.
Proc Natl Acad Sci U S A ; 118(49)2021 11 16.
Article in English | MEDLINE | ID: covidwho-1514449

ABSTRACT

Many phylogenetically distant animal viruses, including the new coronavirus severe acute respiratory syndrome coronavirus 2, have surface proteins with polybasic sites that are cleaved by host furin and furin-like proteases. Other than priming certain viral surface proteins for fusion, cleavage generates a carboxy-terminal RXXR sequence. This C-end Rule (CendR) motif is known to bind to neuropilin (NRP) receptors on the cell surface. NRPs are ubiquitously expressed, pleiotropic cell surface receptors with important roles in growth factor signaling, vascular biology, and neurobiology, as well as immune homeostasis and activation. The CendR-NRP receptor interaction promotes endocytic internalization and tissue spreading of different cargo, including viral particles. We propose that the interaction between viral surface proteins and NRPs plays an underappreciated and prevalent role in the transmission and pathogenesis of diverse viruses and represents a promising broad-spectrum antiviral target.


Subject(s)
COVID-19/virology , Neuropilins/metabolism , Virus Internalization , COVID-19/metabolism , Humans , Neuropilins/chemistry , SARS-CoV-2/metabolism , SARS-CoV-2/pathogenicity , SARS-CoV-2/physiology , Spike Glycoprotein, Coronavirus/chemistry , Spike Glycoprotein, Coronavirus/metabolism
9.
J Virol ; 95(21): e0097521, 2021 10 13.
Article in English | MEDLINE | ID: covidwho-1361966

ABSTRACT

Repurposing FDA-approved inhibitors able to prevent infection by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) could provide a rapid path to establish new therapeutic options to mitigate the effects of coronavirus disease 2019 (COVID-19). Proteolytic cleavages of the spike (S) protein of SARS-CoV-2, mediated by the host cell proteases cathepsin and TMPRSS2, alone or in combination, are key early activation steps required for efficient infection. The PIKfyve kinase inhibitor apilimod interferes with late endosomal viral traffic and through an ill-defined mechanism prevents in vitro infection through late endosomes mediated by cathepsin. Similarly, inhibition of TMPRSS2 protease activity by camostat mesylate or nafamostat mesylate prevents infection mediated by the TMPRSS2-dependent and cathepsin-independent pathway. Here, we combined the use of apilimod with camostat mesylate or nafamostat mesylate and found an unexpected ∼5- to 10-fold increase in their effectiveness to prevent SARS-CoV-2 infection in different cell types. Comparable synergism was observed using both a chimeric vesicular stomatitis virus (VSV) containing S of SARS-CoV-2 (VSV-SARS-CoV-2) and SARS-CoV-2. The substantial ∼5-fold or higher decrease of the half-maximal effective concentrations (EC50s) suggests a plausible treatment strategy based on the combined use of these inhibitors. IMPORTANCE Infection by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is causing the coronavirus disease 2019 (COVID-2019) global pandemic. There are ongoing efforts to uncover effective antiviral agents that could mitigate the severity of the disease by controlling the ensuing viral replication. Promising candidates include small molecules that inhibit the enzymatic activities of host proteins, thus preventing SARS-CoV-2 entry and infection. They include apilimod, an inhibitor of PIKfyve kinase, and camostat mesylate and nafamostat mesylate, inhibitors of TMPRSS2 protease. Our research is significant for having uncovered an unexpected synergism in the effective inhibitory activity of apilimod used together with camostat mesylate or nafamostat mesylate.


Subject(s)
Antiviral Agents/pharmacology , Benzamidines/pharmacology , Esters/pharmacology , Guanidines/pharmacology , Hydrazones/pharmacology , Morpholines/pharmacology , Phosphatidylinositol 3-Kinases/metabolism , Pyrimidines/pharmacology , SARS-CoV-2/drug effects , Serine Endopeptidases/metabolism , Animals , Cell Line, Tumor , Chlorocebus aethiops , Drug Synergism , Humans , Phosphoinositide-3 Kinase Inhibitors/pharmacology , Protease Inhibitors/pharmacology , SARS-CoV-2/physiology , Vero Cells , Virus Internalization , COVID-19 Drug Treatment
10.
Science ; 370(6518): 856-860, 2020 11 13.
Article in English | MEDLINE | ID: covidwho-883299

ABSTRACT

The causative agent of coronavirus disease 2019 (COVID-19) is the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). For many viruses, tissue tropism is determined by the availability of virus receptors and entry cofactors on the surface of host cells. In this study, we found that neuropilin-1 (NRP1), known to bind furin-cleaved substrates, significantly potentiates SARS-CoV-2 infectivity, an effect blocked by a monoclonal blocking antibody against NRP1. A SARS-CoV-2 mutant with an altered furin cleavage site did not depend on NRP1 for infectivity. Pathological analysis of olfactory epithelium obtained from human COVID-19 autopsies revealed that SARS-CoV-2 infected NRP1-positive cells facing the nasal cavity. Our data provide insight into SARS-CoV-2 cell infectivity and define a potential target for antiviral intervention.


Subject(s)
Betacoronavirus/physiology , Coronavirus Infections/virology , Neuropilin-1/metabolism , Pneumonia, Viral/virology , Spike Glycoprotein, Coronavirus/metabolism , Virus Internalization , Angiotensin-Converting Enzyme 2 , Animals , Antibodies, Monoclonal/immunology , Betacoronavirus/genetics , COVID-19 , Caco-2 Cells , Female , HEK293 Cells , Host Microbial Interactions , Humans , Lung/metabolism , Male , Metal Nanoparticles , Mice , Mice, Inbred C57BL , Mutation , Neuropilin-1/chemistry , Neuropilin-1/genetics , Neuropilin-1/immunology , Neuropilin-2/metabolism , Olfactory Mucosa/metabolism , Olfactory Mucosa/virology , Pandemics , Peptide Fragments/metabolism , Peptidyl-Dipeptidase A/genetics , Peptidyl-Dipeptidase A/metabolism , Protein Binding , Protein Domains , Respiratory Mucosa/metabolism , SARS-CoV-2 , Serine Endopeptidases/genetics , Serine Endopeptidases/metabolism , Spike Glycoprotein, Coronavirus/chemistry
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