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Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes a highly contagious respiratory disease referred to as COVID-19. However, emerging evidence indicates that a small but growing number of COVID-19 patients also manifest neurological symptoms, suggesting that SARS-CoV-2 may infect the nervous system under some circumstances. SARS-CoV-2 primarily enters the body through the epithelial lining of the respiratory and gastrointestinal tracts, but under certain conditions this pleiotropic virus may also infect peripheral nerves and gain entry into the central nervous system (CNS). The brain is shielded by various anatomical and physiological barriers, most notably the blood-brain barrier (BBB) which functions to prevent harmful substances, including pathogens and pro-inflammatory mediators, from entering the brain. The BBB is composed of highly specialized endothelial cells, pericytes, mast cells and astrocytes that form the neurovascular unit, which regulates BBB permeability and maintains the integrity of the CNS. In this review, potential routes of viral entry and the possible mechanisms utilized by SARS-CoV-2 to penetrate the CNS, either by disrupting the BBB or infecting the peripheral nerves and using the neuronal network to initiate neuroinflammation, are briefly discussed. Furthermore, the long-term effects of SARS-CoV-2 infection on the brain and in the progression of neurodegenerative diseases known to be associated with other human coronaviruses are considered. Although the mechanisms of SARS-CoV-2 entry into the CNS and neurovirulence are currently unknown, the potential pathways described here might pave the way for future research in this area and enable the development of better therapeutic strategies.

Rubella virus (RV) is a leading cause of birth defects due to infectious agents. When contracted during pregnancy, RV infection leads to severe damage in fetuses. Despite its medical importance, compared with the related alphaviruses, very little is known about the structure of RV. The RV capsid protein is an essential structural component of virions as well as a key factor in virus-host interactions. Here we describe three crystal structures of the structural domain of the RV capsid protein. The polypeptide fold of the RV capsid protomer has not been observed previously. Combining the atomic structure of the RV capsid protein with the cryoelectron tomograms of RV particles established a low-resolution structure of the virion. Mutational studies based on this structure confirmed the role of amino acid residues in the capsid that function in the assembly of infectious virions.X-ray crystallography | cryoelectron tomography | virology R ubella virus (RV) is the only member of the Rubivirus genus which, together with alphaviruses including Chikungunya virus, Sindbis virus, and Ross River virus, make up the family Togaviridae. RV is a human pathogen that causes "German measles," a relatively mild disease characterized by rashes and low-grade fever. However, due to its teratogenic properties, RV is a major threat to the fetus when infection occurs during the first trimester of pregnancy (1). Vaccination has been very successful in controlling RV infection; however, the virus is still endemic in many areas of the world (1, 2). RV is an enveloped virus with a 9.6-kb single-stranded, positive-sense RNA genome (1, 3). The virions have particle diameters ranging from 600 to 800 Å, with most of the spherical virions having a diameter of about 700 Å (4). RV contains three structural proteins, namely, the capsid protein (∼31 kDa) and the glycoproteins E1 (58 kDa) and E2 (42-47 kDa). The capsid protein interacts with the RNA genome and forms the nucleocapsid, which is surrounded by a lipid membrane upon which E1 and E2 are arranged. Two nonstructural proteins, p90 and p150, involved with virus replication, are also encoded by the virus (1).Alphaviruses and RV share a similar gene order and expression strategy (3) but differ from each other in that alphaviruses are icosahedral, their nucleocapsids assemble in the cytoplasm, and virions bud from the plasma membrane (5). In contrast, RV virions are pleomorphic and the nucleocapsid assembles on Golgi membranes followed by budding of the virus into this organelle (6). The pleomorphic nature of RV virions has been a limiting factor in determining the structure of the virus particles.As with all Togaviruses, the structural proteins of RV are synthesized as a polyprotein precursor in association with the endoplasmic reticulum in the host cell (7) (Fig. 1A). The polyprotein is cotranslationally cleaved by the host-cell signal peptidase but, unlike alphavirus capsid proteins, the RV capsid protein remains attached to the cytoplasmic side of the membrane by virtue of the hydrophobic E2 ...

Emerging evidence suggests that host glycans influence infection by SARS-CoV-2. Here, we reveal that the receptor-binding domain (RBD) of the spike (S)-protein on SARS-CoV-2 recognizes oligosaccharides containing sialic acid (SA), with preference for the oligosaccharide of monosialylated gangliosides. Gangliosides embedded within an artificial membrane also bind the RBD. The monomeric affinities (Kd = 100-200 μM) of gangliosides for the RBD are similar to heparan sulfate, another negatively charged glycan ligand of the RBD proposed as a viral co-receptor. RBD binding and infection of SARS-CoV-2 pseudotyped lentivirus to ACE2-expressing cells is decreased upon depleting cell surface SA level using three approaches: sialyltransferase inhibition, genetic knock-out of SA biosynthesis, or neuraminidase treatment. These effects on RBD binding and pseudotyped viral entry are recapitulated with pharmacological or genetic disruption of glycolipid biosynthesis. Together, these results suggest that sialylated glycans, specifically glycolipids, facilitate viral entry of SARS-CoV-2.

Understanding the heterogeneity of dysregulated pathways associated with the development of hepatocellular carcinoma (HCC) may provide prognostic and therapeutic avenues for disease management. As HCC involves a complex process of genetic and epigenetic modifications, we evaluated expression of both polyadenylated transcripts and microRNAs from HCC and liver samples derived from two cohorts of patients undergoing either partial hepatic resection or liver transplantation. Copy number variants were inferred from whole genome low‐pass sequencing data, and a set of 56 cancer‐related genes were screened using an oncology panel assay. HCC was associated with marked transcriptional deregulation of hundreds of protein‐coding genes. In the partially resected livers, diminished transcriptional activity was observed in genes associated with drug catabolism and increased expression in genes related to inflammatory responses and cell proliferation. Moreover, several long noncoding RNAs and microRNAs not previously linked with HCC were found to be deregulated. In liver transplant recipients, down‐regulation of genes involved in energy production and up‐regulation of genes associated with glycolysis were detected. Numerous copy number variants events were observed, with hotspots on chromosomes 1 and 17. Amplifications were more common than deletions and spanned regions containing genes potentially involved in tumorigenesis. Colony stimulating factor 1 receptor (CSF1R), fibroblast growth factor receptor 3 (FGFR3), fms‐like tyrosine kinase 3 (FLT3), nucleolar phosphoprotein B23 (NPM1), platelet‐derived growth factor receptor alpha polypeptide (PDGFRA), phosphatase and tensin homolog (PTEN), G‐protein‐coupled receptors‐like receptor Smoothened (SMO), and tumor protein P53 (TP53) were mutated in all tumors; another 26 cancer‐related genes were mutated with variable penetrance. Conclusion: Our results underscore the marked molecular heterogeneity between HCC tumors and reinforce the notion that precision medicine approaches are needed for management of individual HCC. These data will serve as a resource to generate hypotheses for further research to improve our understanding of HCC biology. (Hepatology Communications 2018; 00:000‐000)

Mast cells (MC) synthesize and store proinflammatory mediators and are centrally important in atopic diseases such as asthma and atopic dermatitis. Quercetin a and resveratrol are plant derived polyphenolic compounds with anti-inflammatory properties that inhibit MC degranulation and mediator release. However, the underlying mechanism of these inhibitory effects on MC is poorly understood and it is unclear whether this is a general effect on all MC phenotypes. We have characterized and compared the effects of quercetin with resveratrol on human (LAD2) and mouse (MC/9 and BMMC) MC mediator release, receptor expression and FcεRI signaling to better understand the mechanisms involved in quercetin and resveratrol-mediated inhibition of MC activation. Quercetin significantly decreased the expression of FcεRI by BMMC and MC/9, although the effects on MC/9 were associated with a significant reduction in cell viability. Quercetin also inhibited antigen-stimulated TNF release by BMMC. Although neither quercetin nor resveratrol significantly altered antigen-stimulated BMMC degranulation or downstream signaling events such as phosphorylation of spleen tyrosine kinase (SYK) or extracellular signal-regulated kinase 1/2 (ERK), resveratrol inhibited ERK phosphorylation and FcεRI- stimulated degranulation in LAD2. Our data suggests that quercetin and resveratrol inhibit human and mouse MC differentially and that these effects are associated with modification of FcεRI expression, signaling (phosphorylation of SYK and ERK) and mediator release.

Mast cells are long-lived, granular, myeloid-derived leukocytes that have significant protective and repair functions in tissues. Mast cells sense disruptions in the local microenvironment and are first responders to physical, chemical and biological insults. When activated, mast cells release growth factors, proteases, chemotactic proteins and cytokines thereby mobilizing and amplifying the reactions of the innate and adaptive immune system. Mast cells are therefore significant regulators of homeostatic functions and may be essential in microenvironmental changes during pathogen invasion and disease. During infection by helminths, bacteria and viruses, mast cells release antimicrobial factors to facilitate pathogen expulsion and eradication. Mast cell-derived proteases and growth factors protect tissues from insect/snake bites and exposure to ultraviolet radiation. Finally, mast cells release mediators that promote wound healing in the inflammatory, proliferative and remodelling stages. Since mast cells have such a powerful repertoire of functions, targeting mast cells may be an effective new strategy for immunotherapy of disease and design of novel vaccine adjuvants. In this review, we will examine how certain strategies that specifically target and activate mast cells can be used to treat and resolve infections, augment vaccines and heal wounds. Although these strategies may be protective in certain circumstances, mast cells activation may be deleterious if not carefully controlled and any therapeutic strategy using mast cell activators must be carefully explored.

SummaryRubella virus (RV), a member of Togaviridae, is an important human pathogen that can cause severe defects in the developing fetus. Compared to other togaviruses, RV replicates very slowly suggesting that it must employ effective mechanisms to delay the innate immune response. A recent study by our laboratory revealed that the capsid protein of RV is a potent inhibitor of apoptosis. A primary mechanism by which RV capsid interferes with programmed cell death appears to be through interaction with the pro-apoptotic Bcl-2 family member Bax. In the present study, we report that the capsid protein also blocks IRF3-dependent apoptosis induced by the double-strand RNA mimic polyinosinic-polycytidylic acid. In addition, analyses of cis-acting elements revealed that phosphorylation and membrane association are important for its anti-apoptotic function. Finally, the observation that hypo-phosphorylated capsid binds Bax just as well as wild-type capsid protein suggests that interaction with this pro-apoptotic host protein in and of itself is not sufficient to block programmed cell death. This provides additional evidence that this viral protein inhibits apoptosis through multiple mechanisms.