The K186E amino acid substitution in the canine influenza virus H3N8 NS1 protein restores its ability to inhibit host gene expression

Canine influenza viruses (CIVs) are the causative agents of canine influenza, a contagious respiratory disease in dogs, and include the equine-origin H3N8 and the avian-origin H3N2. Influenza A virus (IAV) non-structural protein 1 (NS1) is a virulence factor essential for counteracting the innate immune response. Here, we evaluated the ability of H3N8 CIV NS1 to inhibit host innate immune responses. We found that H3N8 CIV NS1 was able to efficiently counteract interferon (IFN) responses but was unable to block general gene expression in human or canine cells. Such ability was restored by a single amino acid substitution in position 186 (K186E) that resulted in NS1 binding to the 30-kDa subunit of the cleavage and polyadenylation specificity factor (CPSF30), a cellular protein involved in pre-mRNA processing. We also examined the frequency distribution of K186 and E186 among H3N8 CIVs and equine influenza viruses (EIVs), the ancestors of H3N8 CIV, and experimentally determined the impact of amino acid 186 in the ability of different CIV and EIV NS1s to inhibit general gene expression. In all cases, the presence of E186 was responsible for the control of host gene expression. Contrastingly, the NS1 protein of H3N2 CIV harbors E186 and blocks general gene expression in canine cells. Altogether, our results confirm previous studies on the strain-dependent ability of NS1 to block general gene expression. Moreover, the observed polymorphism on amino acid 186 between H3N8 and H3N2 CIVs might be the result of adaptive changes acquired during long-term circulation of avian-origin IAVs in mammals. IMPORTANCE: Canine influenza is a respiratory disease of dogs caused by two CIV subtypes, the H3N8 and H3N2 viruses of equine and avian origin, respectively. Influenza NS1 is the main viral factor responsible for the control of host innate immune responses and changes in NS1 can play an important role in host adaptation. Here we assessed the ability of H3N8 CIV NS1 to inhibit host innate immune responses and gene expression. The H3N8 CIV NS1 did not block host gene expression but this activity was restored by a single amino acid substitution (K186E), which was responsible for NS1 binding to the host factor CPSF30. In contrast, the H3N2 CIV NS1, that contains E186, blocks general gene expression. Our results suggest that the ability to block host gene expression is not required for influenza replication in mammals but might be important in the long-term adaptation of avian-origin influenza viruses to mammals

Live attenuated influenza A virus vaccines with modified NS1 proteins for veterinary use

Influenza A viruses (IAV) spread rapidly and can infect a broad range of avian or mammalian species, having a tremendous impact in human and animal health and the global economy. IAV have evolved to develop efficient mechanisms to counteract innate immune responses, the first host mechanism that restricts IAV infection and replication. One key player in this fight against host-induced innate immune responses is the IAV non-structural 1 (NS1) protein that modulates antiviral responses and virus pathogenicity during infection. In the last decades, the implementation of reverse genetics approaches has allowed to modify the viral genome to design recombinant IAV, providing researchers a powerful platform to develop effective vaccine strategies. Among them, different levels of truncation or deletion of the NS1 protein of multiple IAV strains has resulted in attenuated viruses able to induce robust innate and adaptive immune responses, and high levels of protection against wild-type (WT) forms of IAV in multiple animal species and humans. Moreover, this strategy allows the development of novel assays to distinguish between vaccinated and/or infected animals, also known as Differentiating Infected from Vaccinated Animals (DIVA) strategy. In this review, we briefly discuss the potential of NS1 deficient or truncated IAV as safe, immunogenic and protective live-attenuated influenza vaccines (LAIV) to prevent disease caused by this important animal and human pathogen

Vaccines to prevent severe acute respiratory syndrome coronavirus-induced disease

An important effort has been performed after the emergence of severe acute respiratory syndrome (SARS) epidemic in 2003 to diagnose and prevent virus spreading. Several types of vaccines have been developed including inactivated viruses, subunit vaccines, virus-like particles (VLPs), DNA vaccines, heterologous expression systems, and vaccines derived from SARS-CoV genome by reverse genetics. This review describes several aspects essential to develop SARS-CoV vaccines, such as the correlates of protection, virus serotypes, vaccination side effects, and bio-safeguards that can be engineered into recombinant vaccine approaches based on the SARS-CoV genome. The production of effective and safe vaccines to prevent SARS has led to the development of promising vaccine candidates, in contrast to the design of vaccines for other coronaviruses, that in general has been less successful. After preclinical trials in animal models, efficacy and safety evaluation of the most promising vaccine candidates described has to be performed in humans

The K186E Amino Acid Substitution in the Canine Influenza Virus H3N8 NS1 Protein Restores Its Ability To Inhibit Host Gene Expression

Canine influenza viruses (CIVs) are the causative agents of canine influenza, a contagious respiratory disease in dogs, and include the equine-origin H3N8 and the avian-origin H3N2. Influenza A virus (IAV) non-structural protein 1 (NS1) is a virulence factor essential for counteracting the innate immune response. Here, we evaluated the ability of H3N8 CIV NS1 to inhibit host innate immune responses. We found that H3N8 CIV NS1 was able to efficiently counteract interferon (IFN) responses but was unable to block general gene expression in human or canine cells. Such ability was restored by a single amino acid substitution in position 186 (K186E) that resulted in NS1 binding to the 30-kDa subunit of the cleavage and polyadenylation specificity factor (CPSF30), a cellular protein involved in pre-mRNA processing. We also examined the frequency distribution of K186 and E186 among H3N8 CIVs and equine influenza viruses (EIVs), the ancestors of H3N8 CIV, and experimentally determined the impact of amino acid 186 in the ability of different CIV and EIV NS1s to inhibit general gene expression. In all cases, the presence of E186 was responsible for the control of host gene expression. Contrastingly, the NS1 protein of H3N2 CIV harbors E186 and blocks general gene expression in canine cells. Altogether, our results confirm previous studies on the strain-dependent ability of NS1 to block general gene expression. Moreover, the observed polymorphism on amino acid 186 between H3N8 and H3N2 CIVs might be the result of adaptive changes acquired during long-term circulation of avian-origin IAVs in mammals. IMPORTANCE: Canine influenza is a respiratory disease of dogs caused by two CIV subtypes, the H3N8 and H3N2 viruses of equine and avian origin, respectively. Influenza NS1 is the main viral factor responsible for the control of host innate immune responses and changes in NS1 can play an important role in host adaptation. Here we assessed the ability of H3N8 CIV NS1 to inhibit host innate immune responses and gene expression. The H3N8 CIV NS1 did not block host gene expression but this activity was restored by a single amino acid substitution (K186E), which was responsible for NS1 binding to the host factor CPSF30. In contrast, the H3N2 CIV NS1, that contains E186, blocks general gene expression. Our results suggest that the ability to block host gene expression is not required for influenza replication in mammals but might be important in the long-term adaptation of avian-origin influenza viruses to mammals

Effect of OAS genes on SARS-CoV-2 infection and the induction of innate immune responses

Resumen del trabajo presentado en el 8th European Congress of Virology, celebrado en Gdańsk (Polonia), del 4 al 7 de mayo de 2023Severe Acute Respiratory Syndrome 2 (SARS-CoV-2) infections cause different clinical symptoms ranging from asymptomatic patients to patients suffering severe respiratory disease leading to death in some of them. Genetic and functional studies have shown inborn-errors of interferon (IFN)-related genes in severe COVID-19 patients explaining why some young patients devoid of co-morbidities succumbed to infection. In addition, very large genomic studies identified common genetic variants affecting the expression and splicing of IFN-stimulated genes (ISGs) of the 2",5"- oligoadenylate (2-5A) synthetase (OAS) family associated with COVID-19 severity. We have sequenced the whole genome of 274 patients who required hospitalization after SARS-CoV-2 infection, finding ultrarare mutations in OAS1 and OAS3 genes. Upon double-stranded (ds)RNA binding, the OAS1, OAS2, and OAS3 proteins synthetize 2¿- 5¿olygoadenylates which activate the endonuclease RNAseL. This endonuclease degrades viral and cellular RNAs, inhibiting viral replication. We have analyzed the effect of OAS1 and OAS3 genetic variants identified in our patients, and found that some of them impair the RNAseL activation. In addition, by using OAS3 knock-out cells generated in our laboratory and performing overexpression experiments, we have shown that OAS3 negatively modulates proinflammatory responses induced by immune challenges, and that the activation of the RNAseL activity seems necessary for this function. In addition, by using OAS3 knock-out mice infected with SARS-CoV-2 or treated with the double-stranded RNA analog poly(I:C), we have shown that OAS3 deficiency leads to a higher mouse susceptibility to SARS-CoV-2 infection and that OAS3 counteracts the induction of innate immune responses in the mouse infectedlungs, leading to a higher inflammatory response in OAS3 knock-out mice, compared to the parental mice. Given the contribution of exacerbated inflammatory responses to COVID-19 disease severity, our results suggest that OAS1/OAS3 could play a role limiting the severity of the clinical symptoms after SARS-CoV-2 infection

A live attenuated severe acute respiratory syndrome coronavirus is immunogenic and efficacious in Golden Syrian hamsters

The immunogenicity and protective efficacy of a live attenuated vaccine consisting of a recombinant severe acute respiratory syndrome (SARS) coronavirus lacking the E gene (rSARS-CoV-ΔE) were studied using hamsters. Hamsters immunized with rSARS-CoV-ΔE developed high serum-neutralizing antibody titers and were protected from replication of homologous (SARS-CoV Urbani) and heterologous (GD03) SARS-CoV in the upper and lower respiratory tract. rSARS-CoV-ΔE-immunized hamsters remained active following wild-type virus challenge, while mock-immunized hamsters displayed decreased activity. Despite being attenuated in replication in the respiratory tract, rSARS-CoV-ΔE is an immunogenic and efficacious vaccine in hamsters.This research was supported in part by the Intramural Research Program of the NIH, NIAID; by NIH AID AI059136; and by the European Community (projects DISSECT SP22-CT-2004-511060 and Rivigene SSPE-CT-2005-022639)

Human Coronavirus Virulence Motifs and Virulence

Trabajo presentado en el XIV International Nidovirus Symposium (Nido2017), celebrado en Kansas City, Missouri (Estados Unidos), del 4 al 9 de junio de 2017We have shown that SARS-CoV E protein is a virulence factor that includes at least two virulence motifs: its ion channel (IC) activity encoded within the transmembrane domain and a PDZ binding motif (PBM) located at its carboxy-terminus. We showed that E protein pathogenicity was caused by the activation of different host signaling pathways. One of them was the activation of inflammasome, a process mediated by the conductance of Ca++ byEprotein IC activity, leading to an increased expression of IL-1beta, TNF-alpha and IL-6 levels. Another signaling pathway implied the activation of a proinflammatory response mediated by NF-kB activation. This activation was a consequence of E protein-syntenin binding mediated by PBM-PDZ interactions. This binding caused an increase of p38MAPK phosphorylation promoting the induction of acute respiratory distress syndrome (ARDS), edema and death of mice infected with a mouse adapted SARS-CoV. The relevance of p38 MAPK activation after infection with the mouse adapted SARS-CoV was confirmed by the protection of mice in the presence of an inhibitor of p38 MAPK, but not in its absence. These results illustrated the identification of an efficient coronavirus (CoV) antiviral. The presence of a virulence factor such as the PBM motif in E protein allows the virus to interact with more than 400 cell proteins containing PDZ motifs, conferring the virus the potential to control a high number of cell-signaling pathways increasing its replication and virulence. In fact, we are analyzing the proteome of the viral PBM-cellular PDZ interactions using system biology approaches. Frequently, the ARDS caused by lung infection with mild respiratory viruses is resolved before it evolves to serious edema. In contrast, after SARS-CoV infection frequently this resolution does not take place. We have shown the binding of E protein to a main mediator of edema resolution, the Na+ /K+ ATPase, and proposed that this may be one of the procedures by which edema recovery is prevented after SARS-CoV infection, either by inhibition of Na+ /K+ ATPase activity or by relocating this enzyme to another subcellular compartment. Deadly human CoVs as SARS- and MERS-CoVs have at least two viral proteins with IC activity and PBM motifs. Studies on the relevance of E and 3a SARS-CoV proteins in replication and virulence, and the interdependence among them have shown that the presence in the virus of at least E or 3a proteins was needed for virus viability. In fact, we have shown that the complementation between E and 3a proteins is mediated by the PBM motifs located at the carboxy-terminus of these proteins. Our studies on the interaction of SARS-CoV and MERS-CoV with the host, and the engineering of reverse genetics systems for each of these viruses, led us to the development of genetically stable vaccine candidates that provided full-protection against the challenge with the homologous virulent virus using mice models

Iron oxide and iron oxyhydroxide nanoparticles impair SARS-CoV-2 infection of cultured cells

Background Coronaviruses usually cause mild respiratory disease in humans but as seen recently, some human coronaviruses can cause more severe diseases, such as the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), the global spread of which has resulted in the ongoing coronavirus pandemic. Results In this study we analyzed the potential of using iron oxide nanoparticles (IONPs) coated with biocompatible molecules like dimercaptosuccinic acid (DMSA), 3-aminopropyl triethoxysilane (APS) or carboxydextran (FeraSpin™ R), as well as iron oxyhydroxide nanoparticles (IOHNPs) coated with sucrose (Venofer®), or iron salts (ferric ammonium citrate -FAC), to treat and/or prevent SARS-CoV-2 infection. At non-cytotoxic doses, IONPs and IOHNPs impaired virus replication and transcription, and the production of infectious viruses in vitro, either when the cells were treated prior to or after infection, although with different efficiencies. Moreover, our data suggest that SARS-CoV-2 infection affects the expression of genes involved in cellular iron metabolism. Furthermore, the treatment of cells with IONPs and IOHNPs affects oxidative stress and iron metabolism to different extents, likely influencing virus replication and production. Interestingly, some of the nanoparticles used in this work have already been approved for their use in humans as anti-anemic treatments, such as the IOHNP Venofer®, and as contrast agents for magnetic resonance imaging in small animals like mice, such as the FeraSpin™ R IONP. Conclusions Therefore, our results suggest that IONPs and IOHNPs may be repurposed to be used as prophylactic or therapeutic treatments in order to combat SARS-CoV-2 infection.This work was supported by the following Grants: CSIC-COV19-012/012202020E154 funded by the Spanish National Research Council Interdisciplinary Thematic Platform (PTI) Global Health (PTI Salud Global), SGL2103021 funded by the European Commission-NextGenerationEU (Regulation EU2020/2094) through CSIC’s Global Health Platform (PTI Salud Global); PDC2021-120759-100 funded by MCIN/AEI/10. 13039/50110 00110 33 and by the “European Union NextGenerationEU/PRTR”, PID2020-112685RB-100 funded by MCIN/AEI/10. 13039/50110 00110 33, and the “Atracción de Talento Investigador” programme (2017-T1/BMD-5155) funded by the “Comunidad de Madrid”. Y. Portilla was first a predoctoral FPU scholar (FPU15/06170) funded by MCIN/AEI/10. 13039/50110 00110 33 and by “ESF Investing in your future”, then a predoctoral scholar funded by CSIC-COV19-012/012202020E154 and is now a postdoctoral scholar funded by the European Commission-NextGenerationEU (Regulation EU2020/2094) through the CSIC’s Global Health Platform (PTI Salud Global, SGL2103021). D. López-García received a JAE-INTRO 2020 Fellowship from the Spanish National Research Council (CSIC, JAEINT-20-01805). V. Mulens-Arias was a postdoctoral scholar working under a Juan de La Cierva-Incorporación Contract (IJCI-2017-31447) funded by MCIN/AEI/10. 13039/50110 00110 33. N. Daviu is a predoctoral scholar (FPU18/04828) funded by MCIN/AEI/10. 13039/50110 00110 33 and by “ESF Investing in your future”. This research work was performed in the framework of the Nanomedicine CSIC HUB (ref. 202180E048).Peer reviewe