Prolonged fecal shedding of replication-competent virus, lasting immune activation, and intestinal inflammation in a rhesus macaque after experimental SARS-CoV-2 infection.

Infection of an adult rhesus macaque with SARS-CoV-2 led to viral RNAemia in nose, throat, and lungs. The animal also presented extended fecal shedding of viral genomic and subgenomic messenger RNA and replication-competent virus for more than 3 weeks after infection. Positron emission tomography revealed increased intestinal glucose metabolism which was histologically related to inflammation of the ileum.

-Cyclophellitol Cyclosulfate, a Mechanism-Based Endoplasmic Reticulum α-Glucosidase II Inhibitor, Blocks Replication of SARS-CoV-2 and Other Coronaviruses.

The combined inhibition of endoplasmic reticulum (ER) α-glucosidases I and II has been shown to inhibit replication of a broad range of viruses that rely on ER protein quality control. We found, by screening a panel of deoxynojirimycin and cyclitol glycomimetics, that the mechanism-based ER α-glucosidase II inhibitor, 1,6--cyclophellitol cyclosulfate, potently blocks SARS-CoV-2 replication in lung epithelial cells, halting intracellular generation of mature spike protein, reducing production of infectious progeny, and leading to reduced syncytium formation. Through activity-based protein profiling, we confirmed ER α-glucosidase II inhibition in primary airway epithelial cells, grown at the air-liquid interface.

A Cool Look at Positive-Strand RNA Virus Replication Organelles: New Insights from Cryo-Electron Microscopy.

Positive-strand RNA viruses encompass a variety of established and emerging eukaryotic pathogens. Their genome replication is confined to specialized cytoplasmic membrane compartments known as replication organelles (ROs). These ROs derive from host membranes, transformed into distinct structures such as invaginated spherules or intricate membrane networks including single- and/or double-membrane vesicles.

Deubiquitinating activity of SARS-CoV-2 papain-like protease does not influence virus replication or innate immune responses in vivo.

The coronavirus papain-like protease (PLpro) is crucial for viral replicase polyprotein processing. Additionally, PLpro can subvert host defense mechanisms by its deubiquitinating (DUB) and deISGylating activities. To elucidate the role of these activities during SARS-CoV-2 infection, we introduced mutations that disrupt binding of PLpro to ubiquitin or ISG15.

The Main Protease of Middle East Respiratory Syndrome Coronavirus Induces Cleavage of Mitochondrial Antiviral Signaling Protein to Antagonize the Innate Immune Response.

Mitochondrial antiviral signaling protein (MAVS) is a crucial signaling adaptor in the sensing of positive-sense RNA viruses and the subsequent induction of the innate immune response. Coronaviruses have evolved multiple mechanisms to evade this response, amongst others, through their main protease (M), which is responsible for the proteolytic cleavage of the largest part of the viral replicase polyproteins pp1a and pp1ab. Additionally, it can cleave cellular substrates, such as innate immune signaling factors, to dampen the immune response.

Voclosporin and the Antiviral Effect Against SARS-CoV-2 in Immunocompromised Kidney Patients.

Introduction: Immunocompromised kidney patients are at increased risk of prolonged SARS-CoV-2 infection and related complications. Preclinical evidence demonstrates a more potent inhibitory effect of voclosporin on SARS-CoV-2 replication than tacrolimus . We investigated the potential antiviral effects of voclosporin on SARS-CoV-2 in immunocompromised patients.

Highly Potent Antisense Oligonucleotides Locked Nucleic Acid Gapmers Targeting the SARS-CoV-2 RNA Genome.

The severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has caused the current worldwide pandemic and the associated coronavirus disease 2019 with potentially lethal outcome. Although effective vaccines strongly contributed to reduce disease severity, establishing a toolbox to control current and newly emerging coronaviruses of epidemic concern requires the development of novel therapeutic compounds, to treat severely infected individuals and to prevent virus transmission. Here we present a therapeutic strategy targeting the SARS-CoV-2 RNA genome using antisense oligonucleotides (ASOs).

Honokiol Inhibits SARS-CoV-2 Replication in Cell Culture at a Post-Entry Step.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged in 2019, and the resulting pandemic has already caused the death of over 6 million people. There are currently few antivirals approved for treatment of the 2019 coronavirus disease (COVID-19), and more options would be beneficial, not only now but also to increase our preparedness for future coronavirus outbreaks. Honokiol is a small molecule from magnolia trees for which several biological effects have been reported, including anticancer and anti-inflammatory activities.

R-Propranolol Has Broad-Spectrum Anti-Coronavirus Activity and Suppresses Factors Involved in Pathogenic Angiogenesis.

The SARS-CoV-2 pandemic highlighted the need for broad-spectrum antivirals to increase our preparedness. Patients often require treatment by the time that blocking virus replication is less effective. Therefore, therapy should not only aim to inhibit the virus, but also to suppress pathogenic host responses, e.

Engineering potent live attenuated coronavirus vaccines by targeted inactivation of the immune evasive viral deubiquitinase.

Coronaviruses express a papain-like protease (PLpro) that is required for replicase polyprotein maturation and also serves as a deubiquitinating enzyme (DUB). In this study, using a Middle East respiratory syndrome virus (MERS-CoV) PLpro modified virus in which the DUB is selectively inactivated, we show that the PLpro DUB is an important MERS-CoV interferon antagonist and virulence factor. Although the DUB-negative rMERS-CoV replicates robustly in the lungs of human dipeptidyl peptidase 4 knock-in (hDPP4 KI) mice, it does not cause clinical symptoms.

The alphavirus nonstructural protein 2 NTPase induces a host translational shut-off through phosphorylation of eEF2 via cAMP-PKA-eEF2K signaling.

Chikungunya virus (CHIKV) is a reemerging alphavirus. Since 2005, it has infected millions of people during outbreaks in Africa, Asia, and South/Central America. CHIKV replication depends on host cell factors at many levels and is expected to have a profound effect on cellular physiology.

The Cyclophilin-Dependent Calcineurin Inhibitor Voclosporin Inhibits SARS-CoV-2 Replication in Cell Culture.

Kidney transplant recipients (KTRs) are at increased risk for a more severe course of COVID-19, due to their pre-existing comorbidity and immunosuppression. Consensus protocols recommend lowering immunosuppression in KTRs with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, but the optimal combination remains unclear. Calcineurin inhibitors (CNIs) are cornerstone immunosuppressants used in KTRs and some have been reported to possess antiviral activity against RNA viruses, including coronaviruses.

Potent Inhibition of SARS-CoV-2 nsp14 7-Methyltransferase by Sulfonamide-Based Bisubstrate Analogues.

Enzymes involved in RNA capping of SARS-CoV-2 are essential for the stability of viral RNA, translation of mRNAs, and virus evasion from innate immunity, making them attractive targets for antiviral agents. In this work, we focused on the design and synthesis of nucleoside-derived inhibitors against the SARS-CoV-2 nsp14 (7-guanine)-methyltransferase (7-MTase) that catalyzes the transfer of the methyl group from the -adenosyl-l-methionine (SAM) cofactor to the 7-guanosine cap. Seven compounds out of 39 SAM analogues showed remarkable double-digit nanomolar inhibitory activity against the 7-MTase nsp14.

Synthesis, Structure-Activity Relationships, and Antiviral Profiling of 1-Heteroaryl-2-Alkoxyphenyl Analogs as Inhibitors of SARS-CoV-2 Replication.

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of COVID-19, has led to a pandemic, that continues to be a huge public health burden. Despite the availability of vaccines, there is still a need for small-molecule antiviral drugs. In an effort to identify novel and drug-like hit matter that can be used for subsequent hit-to-lead optimization campaigns, we conducted a high-throughput screening of a 160 K compound library against SARS-CoV-2, yielding a 1-heteroaryl-2-alkoxyphenyl analog as a promising hit.

A Yellow Fever 17D Virus Replicon-Based Vaccine Platform for Emerging Coronaviruses.

The tremendous global impact of the current SARS-CoV-2 pandemic, as well as other current and recent outbreaks of (re)emerging viruses, emphasize the need for fast-track development of effective vaccines. Yellow fever virus 17D (YF17D) is a live-attenuated virus vaccine with an impressive efficacy record in humans, and therefore, it is a very attractive platform for the development of novel chimeric vaccines against various pathogens. In the present study, we generated a YF17D-based replicon vaccine platform by replacing the prM and E surface proteins of YF17D with antigenic subdomains from the spike (S) proteins of three different betacoronaviruses: MERS-CoV, SARS-CoV and MHV.

Structure-function analysis of the nsp14 N7-guanine methyltransferase reveals an essential role in replication.

As coronaviruses (CoVs) replicate in the host cell cytoplasm, they rely on their own capping machinery to ensure the efficient translation of their messenger RNAs (mRNAs), protect them from degradation by cellular 5' exoribonucleases (ExoNs), and escape innate immune sensing. The CoV nonstructural protein 14 (nsp14) is a bifunctional replicase subunit harboring an N-terminal 3'-to-5' ExoN domain and a C-terminal (N7-guanine)-methyltransferase (N7-MTase) domain that is presumably involved in viral mRNA capping. Here, we aimed to integrate structural, biochemical, and virological data to assess the importance of conserved N7-MTase residues for nsp14's enzymatic activities and virus viability.

Structures and functions of coronavirus replication-transcription complexes and their relevance for SARS-CoV-2 drug design.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has killed millions of people and continues to cause massive global upheaval. Coronaviruses are positive-strand RNA viruses with an unusually large genome of ~30 kb. They express an RNA-dependent RNA polymerase and a cohort of other replication enzymes and supporting factors to transcribe and replicate their genomes.

ICTV Virus Taxonomy Profile: 2021.

The family comprises enveloped RNA viruses with a linear, positive-sense genome of approximately 12.7 to 15.7 kb.

Immunogenicity and efficacy of one and two doses of Ad26.COV2.S COVID vaccine in adult and aged NHP.

Safe and effective coronavirus disease-19 (COVID-19) vaccines are urgently needed to control the ongoing pandemic. While single-dose vaccine regimens would provide multiple advantages, two doses may improve the magnitude and durability of immunity and protective efficacy. We assessed one- and two-dose regimens of the Ad26.

Structural Insights into the Mechanisms of Action of Functionally Distinct Classes of Chikungunya Virus Nonstructural Protein 1 Inhibitors.

Chikungunya virus (CHIKV) nonstructural protein 1 (nsP1) harbors the methyltransferase (MTase) and guanylyltransferase (GTase) activities needed for viral RNA capping and represents a promising antiviral drug target. We compared the antiviral efficacies of nsP1 inhibitors belonging to the MADTP, CHVB, and FHNA series (6'-fluoro-homoneplanocin A [FHNA], its 3'-keto form, and 6'-β-fluoro-homoaristeromycin). Cell-based phenotypic cross-resistance assays revealed that the CHVB and MADTP series had similar modes of action that differed from that of the FHNA series.

Ad26.COV2.S protects Syrian hamsters against G614 spike variant SARS-CoV-2 and does not enhance respiratory disease.

Previously we have shown that a single dose of recombinant adenovirus serotype 26 (Ad26) vaccine expressing a prefusion stabilized SARS-CoV-2 spike antigen (Ad26.COV2.S) is immunogenic and provides protection in Syrian hamster and non-human primate SARS-CoV-2 infection models.

A swine arterivirus deubiquitinase stabilizes two major envelope proteins and promotes production of viral progeny.

Arteriviruses are enveloped positive-strand RNA viruses that assemble and egress using the host cell's exocytic pathway. In previous studies, we demonstrated that most arteriviruses use a unique -2 ribosomal frameshifting mechanism to produce a C-terminally modified variant of their nonstructural protein 2 (nsp2). Like full-length nsp2, the N-terminal domain of this frameshift product, nsp2TF, contains a papain-like protease (PLP2) that has deubiquitinating (DUB) activity, in addition to its role in proteolytic processing of replicase polyproteins.