Project description:A recombinant SARS-CoV lacking the envelope (E) protein is attenuated in vivo. Here we report that E protein PDZ-binding motif (PBM), a domain involved in protein-protein interactions, is a major virulence determinant in vivo. Elimination of SARS-CoV E protein PBM by using reverse genetics led to attenuated viruses (SARS-CoV-mutPBM) and to a reduction in the deleterious exacerbate immune response triggered during infection with the parental virus (SARS-CoV-wt). Cellular protein syntenin bound E protein PBM during SARS-CoV infection. Syntenin activates p38 MAPK leading to overexpression of inflammatory cytokines, and we have shown that active p38 MAPK was reduced in lungs of mice infected with SARS-CoVs lacking E protein PBM (SARS-CoV-mutPBM) as compared with the parental virus (SARS-CoV-wt), leading to a decreased expression of inflammatory cytokines and to viral attenuation. Therefore, E protein PBM is a virulence factor that activates pathogenic immune response most likely by using syntenin as a mediator of p38 MAPK induced inflammation. Three biological replicates were independently hybridized (one channel per slide) for each sample type (SARS-CoV-wt, SARS-CoV-mutPBM, Mock). Slides were Sure Print G3 Agilent 8x60K Mouse (G4852A-028005)
Project description:A recombinant SARS-CoV lacking the envelope (E) protein is attenuated in vivo. Here we report that E protein PDZ-binding motif (PBM), a domain involved in protein-protein interactions, is a major virulence determinant in vivo. Elimination of SARS-CoV E protein PBM by using reverse genetics led to attenuated viruses (SARS-CoV-mutPBM) and to a reduction in the deleterious exacerbate immune response triggered during infection with the parental virus (SARS-CoV-wt). Cellular protein syntenin bound E protein PBM during SARS-CoV infection. Syntenin activates p38 MAPK leading to overexpression of inflammatory cytokines, and we have shown that active p38 MAPK was reduced in lungs of mice infected with SARS-CoVs lacking E protein PBM (SARS-CoV-mutPBM) as compared with the parental virus (SARS-CoV-wt), leading to a decreased expression of inflammatory cytokines and to viral attenuation. Therefore, E protein PBM is a virulence factor that activates pathogenic immune response most likely by using syntenin as a mediator of p38 MAPK induced inflammation.
Project description:The three human deadly coronaviruses (CoVs) (SARS-CoV, MERS-CoV and SARS-CoV-2) have infected around eight thousand, two thousand six hundred and 262 million people so far (December 2021), causing the death of 10%, 37% and 2% of them, respectively, so their implication in health is very important. These CoVs have proteins with a PBM motif that binds to PDZ cell domains. PDZ domains are found in more than 400 cellular proteins, therefore, viruses with PBM motifs have a high potential to modify cell behavior. It was studied the implication of the E protein PBM motif of various virulent or attenuated human CoVs (hCoVs) in the pathogenesis induced by these viruses. Variants of SARS-CoV, MERS-CoV and SARS-CoV-2 that lack the E protein PBM have been generated by reverse genetics and their pathogenicity has been analyzed in mice. The PBM motifs of these three hCoVs have been shown to be virulence factors and participate in their replication. Furthermore, a collection of SARS-CoV mutants has been constructed in which the E protein PBM domain was replaced by the one derived from virulent or attenuated hCoVs, and their virulence was analyzed. A virulence gradient was observed, depending on whether the E protein PBM domain was derived from an attenuated or virulent hCoV. The gene expression patterns associated with the different PBM motifs in lungs of mice infected with SARS-CoV was analyzed by deep sequencing of the mRNAs expressed in lungs of infected mice, and it was observed that the E protein PBM motif of SARS-CoV and SARS-CoV-2 dysregulates the expression of genes related to ion transport and cell homeostasis. Specifically, a decrease of the mRNA expression of the cystic fibrosis transmembrane conductance regulator (CFTR), which is essential for edema resolution, was observed. The reduction of CFTR mRNA levels was associated with edema accumulation in lungs of mice infected with SARS-CoV and SARS-CoV-2. The effect of compounds that modulate the expression and activity of CFTR on the pathogenesis and replication of SARS-CoV-2 was studied and it was observed that these compounds drastically reduced the production of SARS-CoV-2 in cell culture and protect against SARS-CoV-2 pathogenesis. These results showed the high relevance of the PBM motif in the replication and virulence of CoVs, and have allowed the identification of cellular targets for the selection of antivirals.
Project description:PDZ (Post-synaptic density, PSD-95)/ Disc large, Dlg/ Zonula occludens, ZO-1) proteins are central in the assembly of multiprotein signalling complexes that are formed in distinctive, specialized cell regions. In these complexes different signals are orchestrated and traduced into quick and efficient responses controlling cell polarization and cell communication. Viral pathogens target host PDZ proteins by expressing viral proteins containing a PDZ binding motif (PBM). SARS-CoV-1 and -2 harbour the protein E, a viroporin with a conserved PBM in its carboxyl-terminal region. SARS-CoV-1 E protein is a pathogenicity factor that in epithelia interacts with the PDZ protein PALS1, which promote disruption of cell junctions. SARS-CoV-2 infects epithelia, but also cells from the innate immune response, including monocytes, dendritic cells, and alveolar macrophages. Identification of targets of SARS-CoV-2 E protein in immune cells might offer valuable clues to understand how SARS-CoV-2 alters immune response. Here we generated a SARS-CoV-2 E protein fused to a GFP-tag at the amino terminal. This recombinant protein was used as bait to identify associated proteins in THP-1 cells, a human monocytic cell line that can be differentiated to macrophages and dendritic cells. Analysis of the GFP-E protein interactome provided 372 proteins that fall into different functional groups. Only eight of these proteins harbor PDZ domains, including the cell polarity protein ZO-2 and the chemoattractant IL-16. Syntenin, a PDZ protein previously identified as interactor of SARS-CoV-1 E protein in epithelia, was also found in our analysis. Little is known about these PDZ proteins in immune cells, so we addressed their expression in monocytes and along the differentiation towards macrophages and dendritic cells. Our findings support the notion that viral targeting of PDZ proteins alters inflammatory response and highlight the importance of identifying the functions of PDZ proteins into maintenance of immune fitness.
Project description:The coronavirus disease 2019 (COVID-19) has caused over 6 million deaths worldwide and disrupted the global economy. The causative agent for this disease, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes mild to lethal respiratory infections. Understanding the cellular host factors that promote and inhibit for SARS-CoV-2 infection is important for identifying virial countermeasures. Moreover, new methods are needed to be to identify host genes influencing specific steps of viral infections. Here, we developed a CRISPR whole genome screen against SARS-CoV-2 spike enveloped retro-pseudoviruses with a GFP reporter to specifically identify host genes that facilitate viral entry. By including two counter screen strategies, this approach can be used to distinguish host genes affecting the pseudoviral reporter from those unique to envelope-mediated entry. First, an alternate envelope, VSV-G allowed identification of shared genes associated with retro-transcription, integration and reporter expression. Second, a recently developed Cre-Gag fusion pseudovirus bypassed retro transcription and integration by directly activating a floxed GFP reporter. Our approach correctly identified SARS-CoV-2 and VSV-G receptors ACE2 and LDLR, respectively and distinguished genes associated with retroviral reporter expression from envelope mediated entry. Overall, this work provides a new strategy for screening genes influencing envelope mediated entry without the complexity of live-viral screens which are complicated with large numbers of genes associated with all aspects of viral pathogenesis and replication. This approach should be of use for identifying genes contributing to and inhibiting SARS-CoV-2 entry and provide a platform for the analysis of newly emerging viruses.
Project description:The on-going COVID-19 pandemic requires a deeper understanding of the long-term antibody responses that persist following SARS-CoV-2 infection. To that end, we determined epitope-specific IgG antibody responses in COVID-19 convalescent sera collected at 5 months post-diagnosis and compared that to sera from naïve individuals. Each serum sample was reacted with a high-density peptide microarray representing the complete proteome of SARS-CoV-2 as 15 mer peptides with 11 amino acid overlap and homologs of spike glycoprotein, nucleoprotein, membrane protein, and envelope small membrane protein from related human coronaviruses. Binding signatures were compared between COVID-19 convalescent patients and naïve individuals using the web service tool EPIphany.
Project description:Severe acute respiratory syndrome coronavirus (SARS-CoV) causes a respiratory disease leading to death in 10% of the infected people. A mouse adapted SARS-CoV lacking the envelope (E) protein (rSARS-CoV-MA15-?E) is attenuated in vivo. To identify E protein domains and host responses that contribute to rSARS-CoV-MA15-?E attenuation, several mutants (rSARS-CoV-MA15-E*) containing point mutations or deletions in the amino-terminal or the carboxy-terminal regions of E protein, respectively, were generated. Amino acid substitutions in the amino terminus, or deletion of domains in the internal carboxy terminal region of E protein led to viral attenuation. Attenuated viruses induced minimal lung injury and limited neutrophil influx to the lungs but, interestingly, increased CD4+ and CD8+ T cell counts in BALB/c mice. To analyze the host responses leading to rSARS-CoV-MA15-E* attenuation, the differential gene expression elicited by the native virus and the mutant ones in infected cells was analyzed. The expression levels of a large number of proinflammatory cytokines inducing lung injury was reduced in the lungs of rSARS-CoV-MA15-E* infected mice, whereas the levels of anti-inflammatory cytokines were increased, both at the mRNA and protein levels. These results suggested that the reduction in lung inflammation together with a specific antiviral T cell response, contributed to rSARS-CoV-MA15-E* attenuation. Interestingly, the attenuated viruses completely protected mice against the challenge with the lethal parental virus, being promising vaccine candidates. Three biological replicates were independently hybridized (one channel per slide) for each sample type (rSARS-CoV-MA15-wt, rSARS-CoV-MA15-?E, rSARS-CoV-MA15-?3, rSARS-CoV-MA15-?5, Mock). Slides were Sure Print G3 Agilent 8x60K Mouse (G4852A-028005)
Project description:Regulation of viral RNA biogenesis is fundamental to productive SARS-CoV-2 infection. To characterize host RNA-binding proteins involved in this process, we biochemically identified proteins bound to genomic and subgenomic SARS-CoV-2 RNAs. We find that the host protein SND1 specifically binds to the 5'-end of negative-sense viral RNA and is required for SARS-CoV-2 RNA synthesis. SND1-depleted cells form smaller replication organelles and display diminished virus growth kinetics. We discover that NSP9, a viral RNA-binding protein and direct SND1 interaction partner, is covalently linked to the 5'-ends of positive and negative-sense RNAs produced during infection. These linkages occur at replication-transcription initiation sites, consistent with NSP9 priming viral RNA synthesis. Mechanistically, SND1 remodels NSP9 occupancy and alters the covalent linkage of NSP9 to initiating nucleotides in viral RNA. Our findings implicate NSP9 in the initiation of SARS-CoV-2 RNA synthesis and unravel an unsuspected role of a cellular protein in orchestrating viral RNA production.
Project description:Severe acute respiratory syndrome coronavirus (SARS-CoV) causes lethal disease in humans, with viral E protein promoting the exacerbated inflammatory response. By deep sequencing RNAs from the lungs of infected mice, we have addressed the relevance of small, non-coding RNAs in SARS-CoV pathology. Host microRNAs (miRNAs) expressed during infection by a virulent virus encoding the E protein were significantly enriched for cytokine-mediated inflammatory pathways when compared with attenuated SARS-CoV-∆E, suggesting contribution of miRNAs to E protein-induced inflammation. The discovery of three 18-22 nt small viral RNAs (svRNAs) derived from the nsp3 and N genomic regions of SARS-CoV in mouse lung and cell cultures is also described. Depletion of these svRNAs significantly reduced viral titers and genomic RNA levels, indicating their positive contribution to virus growth. Remarkably, svRNA-N antagomirs significantly reduced in vivo lung pathology and pro-inflammatory cytokine expression, indicating that svRNAs contribute to SARS-CoV pathogenesis and highlighting the potential of these antagomirs as antivirals.
Project description:Severe acute respiratory syndrome virus (SARS-CoV) that lacks the envelope (E) gene (rSARS-CoV-ΔE) is attenuated in vivo [1,2]. To identify factors that contribute to rSARS-CoV-ΔE attenuation, gene expression in cells infected by SARS-CoV with or without E gene was compared. Twenty-five stress response genes were preferentially upregulated during infection in the absence of the E gene. In addition, genes involved in signal transduction, transcription, cell metabolism, immunoregulation, inflammation, apoptosis and cell cycle and differentiation were differentially regulated in cells infected with rSARS-CoV with or without the E gene. Administration of E protein in trans reduced the stress response in cells infected with rSARS-CoV-ΔE, with respiratory syncytial virus, or treated with drugs, such as tunicamycin and thapsigarcin that elicit cell stress by different mechanisms. In addition, SARS-CoV E protein down-regulated the signaling pathway inositol-requiring enzyme 1 (IRE-1) of the unfolded protein response, but not the PKR-like ER kinase (PERK) or activating transcription factor 6 (ATF-6) pathways, and reduced cell apoptosis. Overall, the activation of the IRE-1 pathway was not able to restore cell homeostasis, and apoptosis was induced probably as a meassure to protect the host by limiting virus production and dissemination. The expression of proinflammatory cytokines was reduced in rSARS-CoV-ΔE-infected cells compared to rSARS-CoV-infected cells, suggesting that the increase in stress responses and the reduction of inflammation in the absence of the E gene contributed to the attenuation of rSARS-CoV-ΔE. We used Affymetrix microarrays (Human Genome U133 plus 2.0) to compare global gene expression between SARS-CoV-infected, mock-infected and SARS-CoV-ΔE-infected cells. For ech type of sample three hybridizations were carried-out (independent biological replicates).