Role of Cellular Lipids in Positive-Sense RNA Virus Replication Complex Assembly and Function

Positive-sense RNA viruses are responsible for frequent and often devastating diseases in humans, animals, and plants. However, the development of effective vaccines and anti-viral therapies targeted towards these pathogens has been hindered by an incomplete understanding of the molecular mechanisms involved in viral replication. One common feature of all positive-sense RNA viruses is the manipulation of host intracellular membranes for the assembly of functional viral RNA replication complexes. This review will discuss the interplay between cellular membranes and positive-sense RNA virus replication, and will focus specifically on the potential structural and functional roles for cellular lipids in this process

An ACE2 Microbody Containing a Single Immunoglobulin Fc Domain Is a Potent Inhibitor of SARS-CoV-2

Soluble forms of angiotensin-converting enzyme 2 (ACE2) have recently been shown to inhibit severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. We report on an improved soluble ACE2, termed a “microbody,” in which the ACE2 ectodomain is fused to Fc domain 3 of the immunoglobulin (Ig) heavy chain. The protein is smaller than previously described ACE2-Ig Fc fusion proteins and contains an H345A mutation in the ACE2 catalytic active site that inactivates the enzyme without reducing its affinity for the SARS-CoV-2 spike. The disulfide-bonded ACE2 microbody protein inhibits entry of SARS-CoV-2 spike protein pseudotyped virus and replication of live SARS-CoV-2 in vitro and in a mouse model. Its potency is 10-fold higher than soluble ACE2, and it can act after virus bound to the cell. The microbody inhibits the entry of β coronaviruses and virus with the variant D614G spike. The ACE2 microbody may be a valuable therapeutic for coronavirus disease 2019 (COVID-19) that is active against viral variants and future coronaviruses

Gut Microbiome Dysbiosis in Antibiotic-Treated COVID-19 Patients is Associated with Microbial Translocation and Bacteremia

Although microbial populations in the gut microbiome are associated with COVID-19 severity, a causal impact on patient health has not been established. Here we provide evidence that gut microbiome dysbiosis is associated with translocation of bacteria into the blood during COVID-19, causing life-threatening secondary infections. We first demonstrate SARS-CoV-2 infection induces gut microbiome dysbiosis in mice, which correlated with alterations to Paneth cells and goblet cells, and markers of barrier permeability. Samples collected from 96 COVID-19 patients at two different clinical sites also revealed substantial gut microbiome dysbiosis, including blooms of opportunistic pathogenic bacterial genera known to include antimicrobial-resistant species. Analysis of blood culture results testing for secondary microbial bloodstream infections with paired microbiome data indicates that bacteria may translocate from the gut into the systemic circulation of COVID-19 patients. These results are consistent with a direct role for gut microbiome dysbiosis in enabling dangerous secondary infections during COVID-19

Special Issue “Transmission Dynamics of Insect Viruses”

At the close of this Special Issue of Viruses on the Transmission Dynamics of Insect Viruses, we would like to thank all of the authors for their submissions and the great work expanding our knowledge of insect virus biology and transmission [...

Complementary transcriptomic, lipidomic, and targeted functional genetic analyses in cultured Drosophila cells highlight the role of glycerophospholipid metabolism in Flock House virus RNA replication

Abstract Background Cellular membranes are crucial host components utilized by positive-strand RNA viruses for replication of their genomes. Published studies have suggested that the synthesis and distribution of membrane lipids are particularly important for the assembly and function of positive-strand RNA virus replication complexes. However, the impact of specific lipid metabolism pathways in this process have not been well defined, nor have potential changes in lipid expression associated with positive-strand RNA virus replication been examined in detail. Results In this study we used parallel and complementary global and targeted approaches to examine the impact of lipid metabolism on the replication of the well-studied model alphanodavirus Flock House virus (FHV). We found that FHV RNA replication in cultured Drosophila S2 cells stimulated the transcriptional upregulation of several lipid metabolism genes, and was also associated with increased phosphatidylcholine accumulation with preferential increases in lipid molecules with longer and unsaturated acyl chains. Furthermore, targeted RNA interference-mediated downregulation of candidate glycerophospholipid metabolism genes revealed a functional role of several genes in virus replication. In particular, we found that downregulation of Cct1 or Cct2, which encode essential enzymes for phosphatidylcholine biosynthesis, suppressed FHV RNA replication. Conclusion These results indicate that glycerophospholipid metabolism, and in particular phosphatidylcholine biosynthesis, plays an important role in FHV RNA replication. Furthermore, they provide a framework in which to further explore the impact of specific steps in lipid metabolism on FHV replication, and potentially identify novel cellular targets for the development of drugs to inhibit positive-strand RNA viruses.http://deepblue.lib.umich.edu/bitstream/2027.42/112821/1/12864_2009_Article_2777.pd

Alphavirus Virulence Determinants

Alphaviruses are important pathogens that continue to cause outbreaks of disease in humans and animals worldwide. Diseases caused by alphavirus infections include acute symptoms of fever, rash, and nausea as well as chronic arthritis and severe-to-fatal conditions including myocarditis and encephalitis. Despite their prevalence and the significant public health threat they pose, there are currently no effective antiviral treatments or vaccines against alphaviruses. Various genetic determinants of alphavirus virulence, including genomic RNA elements and specific protein residues and domains, have been described by researchers to play key roles in the development of disease, the immune response to infection, and virus transmissibility. Here, we focus on the determinants that are currently described in the literature. Understanding how these molecular determinants shape viral infections can lead to new strategies for the development of therapies and vaccines to combat these viruses

Hepatitis C Virus NS2 Coordinates Virus Particle Assembly through Physical Interactions with the E1-E2 Glycoprotein and NS3-NS4A Enzyme Complexes ▿

The hepatitis C virus (HCV) NS2 protein is essential for particle assembly, but its function in this process is unknown. We previously identified critical genetic interactions between NS2 and the viral E1-E2 glycoprotein and NS3-NS4A enzyme complexes. Based on these data, we hypothesized that interactions between these viral proteins are essential for HCV particle assembly. To identify interaction partners of NS2, we developed methods to site-specifically biotinylate NS2 in vivo and affinity capture NS2-containing protein complexes from virus-producing cells with streptavidin magnetic beads. By using these methods, we confirmed that NS2 physically interacts with E1, E2, and NS3 but did not stably interact with viral core or NS5A proteins. We further characterized these protein complexes by blue native polyacrylamide gel electrophoresis and identified ≈520-kDa and ≈680-kDa complexes containing E2, NS2, and NS3. The formation of NS2 protein complexes was dependent on coexpression of the viral p7 protein and enhanced by cotranslation of viral proteins as a polyprotein. Further characterization indicated that the glycoprotein complex interacts with NS2 via E2, and the pattern of N-linked glycosylation on E1 and E2 suggested that these interactions occur in the early secretory pathway. Importantly, several mutations that inhibited virus assembly were shown to inhibit NS2 protein complex formation, and NS2 was essential for mediating the interaction between E2 and NS3. These studies demonstrate that NS2 plays a central organizing role in HCV particle assembly by bringing together viral structural and nonstructural proteins