Two Commercially Available Blood-Stabilization Reagents Serve as Potent Inactivators of Coronaviruses.

The continued circulation of SARS-CoV-2 and the increasing frequency of coronavirus (CoV) outbreaks over the decades demonstrates the enduring threat that the CoV family poses. There remains a significant need to develop tools to monitor and prevent the spread of these viruses. We tested blood-stabilization reagents from two commercially available blood collection tubes (BCTs) for their ability to inactivate three different coronaviruses (MHV, OC-43, and SARS-CoV-2) and stabilize their RNA.

Nasal priming by a murine coronavirus provides protective immunity against lethal heterologous virus pneumonia.

The nasal mucosa is an important component of mucosal immunity. Immunogenic particles in inspired air are known to activate the local nasal mucosal immune system and can lead to sinonasal inflammation; however, little is known about the effect of this activation on the lung immune environment. Here, we showed that nasal inoculation of murine coronavirus (CoV) in the absence of direct lung infection primes the lung immune environment by recruiting activated monocytes (Ly6C+ inflammatory monocytes) and NK cells into the lungs.

Selective Packaging in Murine Coronavirus Promotes Virulence by Limiting Type I Interferon Responses.

Selective packaging is a mechanism used by multiple virus families to specifically incorporate genomic RNA (gRNA) into virions and exclude other types of RNA. Lineage A betacoronaviruses incorporate a 95-bp stem-loop structure, the packaging signal (PS), into the nsp15 locus of ORF1b that is both necessary and sufficient for the packaging of RNAs. However, unlike other viral PSs, where mutations generally resulted in viral replication defects, mutation of the coronavirus (CoV) PS results in large increases in subgenomic RNA packaging with minimal effects on gRNA packaging and on viral titers.

The coronavirus nucleocapsid protein is ADP-ribosylated.

ADP-ribosylation is a common post-translational modification, although how it modulates RNA virus infection is not well understood. While screening for ADP-ribosylated proteins during coronavirus (CoV) infection, we detected a ~55kDa ADP-ribosylated protein in mouse hepatitis virus (MHV)-infected cells and in virions, which we identified as the viral nucleocapsid (N) protein. The N proteins of porcine epidemic diarrhea virus (PEDV), severe acute respiratory syndrome (SARS)-CoV and Middle East respiratory syndrome (MERS)-CoV were also ADP-ribosylated.

Murine Olfactory Bulb Interneurons Survive Infection with a Neurotropic Coronavirus.

Viral infection of the central nervous system (CNS) is complicated by the mostly irreplaceable nature of neurons, as the loss of neurons has the potential to result in permanent damage to brain function. However, whether neurons or other cells in the CNS sometimes survive infection and the effects of infection on neuronal function is largely unknown. To address this question, we used the rJHM strain (rJ) of mouse hepatitis virus (MHV), a neurotropic coronavirus that causes acute encephalitis in susceptible strains of mice.

Virus-induced inflammasome activation is suppressed by prostaglandin D/DP1 signaling.

Prostaglandin D2 (PGD), an eicosanoid with both pro- and anti-inflammatory properties, is the most abundantly expressed prostaglandin in the brain. Here we show that PGD signaling through the D-prostanoid receptor 1 (DP1) receptor is necessary for optimal microglia/macrophage activation and IFN expression after infection with a neurotropic coronavirus. Genome-wide expression analyses indicated that PGD/DP1 signaling is required for up-regulation of a putative inflammasome inhibitor, PYDC3, in CD11b cells in the CNS of infected mice.

In Situ Tagged nsp15 Reveals Interactions with Coronavirus Replication/Transcription Complex-Associated Proteins.

Unlabelled: Coronavirus (CoV) replication and transcription are carried out in close proximity to restructured endoplasmic reticulum (ER) membranes in replication/transcription complexes (RTC). Many of the CoV nonstructural proteins (nsps) are required for RTC function; however, not all of their functions are known. nsp15 contains an endoribonuclease domain that is conserved in the CoV family.

The Conserved Coronavirus Macrodomain Promotes Virulence and Suppresses the Innate Immune Response during Severe Acute Respiratory Syndrome Coronavirus Infection.

Unlabelled: ADP-ribosylation is a common posttranslational modification that may have antiviral properties and impact innate immunity. To regulate this activity, macrodomain proteins enzymatically remove covalently attached ADP-ribose from protein targets. All members of the Coronavirinae, a subfamily of positive-sense RNA viruses, contain a highly conserved macrodomain within nonstructural protein 3 (nsp3).

The nsp3 macrodomain promotes virulence in mice with coronavirus-induced encephalitis.

Unlabelled: All coronaviruses encode a macrodomain containing ADP-ribose-1"-phosphatase (ADRP) activity within the N terminus of nonstructural protein 3 (nsp3). Previous work showed that mouse hepatitis virus strain A59 (MHV-A59) with a mutated catalytic site (N1348A) replicated similarly to wild-type virus but was unable to cause acute hepatitis in mice. To determine whether this attenuated phenotype is applicable to multiple disease models, we mutated the catalytic residue in the JHM strain of MHV (JHMV), which causes acute and chronic encephalomyelitis, using a newly developed bacterial artificial chromosome (BAC)-based MHV reverse genetics system.