Table of Contents
Spotlight
Meeting Review
- Meeting ReviewThe 13th International Double-Stranded RNA Virus Symposium, Houffalize, Belgium, 24 to 28 September 2018
The triennial International Double-Stranded RNA Virus Symposium, this year organized by J. Matthijnssens, J.
Structure and Assembly
- Structure and AssemblyThe Ectodomain of the Vaccinia Virus Glycoprotein A34 Is Required for Cell Binding by Extracellular Virions and Contains a Large Region Capable of Interaction with Glycoprotein B5
Previous studies have shown that the vaccinia virus glycoproteins A34 and B5 interact, and in the absence of A34, B5 is mislocalized and not incorporated into extracellular virions. Here, using a transient-transfection assay, residues 80 to 130 of the ectodomain of A34 were determined to be sufficient for interaction with B5. Recombinant viruses expressing A34 with a full, partial, or no B5 interaction site were constructed and...
- Structure and AssemblyPackaging of the Influenza Virus Genome Is Governed by a Plastic Network of RNA- and Nucleoprotein-Mediated Interactions
The genome of influenza A virus is organized into eight viral ribonucleoproteins (vRNPs); this provides evolutionary advantages but complicates genome packaging. Although it has been shown that RNA packaging sequences and specific amino acids in the viral nucleoprotein (NP), both components of each vRNP, ensure selective packaging of one copy of each vRNP per virus particle, the required RNA-RNA and RNA-NP interactions remain largely...
- Structure and AssemblyThe Alphavirus E2 Membrane-Proximal Domain Impacts Capsid Interaction and Glycoprotein Lattice Formation
Alphaviruses include important human pathogens such as Chikungunya and the encephalitic alphaviruses. There are currently no licensed alphavirus vaccines or effective antiviral therapies, and more molecular information on virus particle structure and function is needed. Here, we highlight the important role of the E2 juxtamembrane D-loop in mediating virus budding and particle production. Our results demonstrated that this E2 region...
Genetic Diversity and Evolution
- Genetic Diversity and EvolutionExisting Host Range Mutations Constrain Further Emergence of RNA Viruses
RNA viruses mutate rapidly and frequently expand their host ranges to infect novel hosts, leading to serial host shifts. Using an RNA bacteriophage model system (Pseudomonas phage φ6), we studied the impact of preexisting host range mutations on another host range expansion. Results from both clonal Sanger and Illumina sequencing show that extant host range mutations dramatically narrow the neighborhood of potential host range...
- Genetic Diversity and EvolutionEpidemiological Evidence for Lineage-Specific Differences in the Risk of Inapparent Chikungunya Virus Infection
Chikungunya virus (CHIKV) is an understudied threat to human health. During the 2015 chikungunya epidemic in Managua, Nicaragua, we estimated the ratio of symptomatic to asymptomatic CHIKV infections, which is important for understanding transmission dynamics and the public health impact of CHIKV. This index cluster study identified and monitored persons at risk of infection, enabling capture of asymptomatic infections. We estimated...
- Genetic Diversity and EvolutionA Novel Type of Influenza A Virus-Derived Defective Interfering Particle with Nucleotide Substitutions in Its Genome
Defective interfering particles (DIPs) typically contain a highly deleted form of the viral genome, rendering them defective in virus replication. Yet upon complementation through coinfection with fully infectious standard virus (STV), interference with the viral life cycle can be observed, leading to suppressed STV replication and the release of mainly noninfectious DIPs. Interestingly, recent research indicates that DIPs may serve as...
- Genetic Diversity and EvolutionCapture of a Hyena-Specific Retroviral Envelope Gene with Placental Expression Associated in Evolution with the Unique Emergence among Carnivorans of Hemochorial Placentation in Hyaenidae
The placenta is the most diverse organ among mammals, due in part to stochastic capture of retroviral envelope genes. In carnivorans, capture of syncytin-Car1 took place 80 Mya. It is fusogenic, expressed at the syncytialized placental maternofetal interface, and conserved among all carnivorans, consistent with their shared endotheliochorial placenta. Hyenas are a remarkable exception, with a highly invasive hemochorial...
- Genetic Diversity and EvolutionPredicting Intraserotypic Recombination in Enterovirus 71
Recombination is a mechanism that contributes to genetic diversity. We describe the first assay to study EV-A71 recombination. Results from this assay mimic what is observed in nature and can be used by others to predict future recombination events within the enterovirus species A group. In addition, our results highlight the central role played by the viral RNA-dependent RNA polymerase (RdRp) in the recombination process. Further, our...
Virus-Cell Interactions
- Virus-Cell InteractionsVectorial Release of Hepatitis E Virus in Polarized Human Hepatocytes
Hepatitis E virus (HEV) in stools is naked, while that in culture supernatants and patients’ blood is lipid associated. Its life cycle in hepatocytes, polarized cells with a basolateral side communicating with blood and an apical side connected with bile, is incompletely understood. We have developed a polarized hepatocyte model and used the cells to analyze the supernatants bathing the apical and basolateral sides and HEV subcellular...
- Virus-Cell InteractionsCellular RNA Helicase DHX9 Interacts with the Essential Epstein-Barr Virus (EBV) Protein SM and Restricts EBV Lytic Replication
This study identifies an interaction between Epstein-Barr virus (EBV) SM protein and cellular helicase DHX9, exploring the roles that this interaction plays in viral infection and host defenses. Whereas most previous studies established DHX9 as a proviral factor, we demonstrate that DHX9 may act as an inhibitor of EBV virion production. DHX9 enhanced innate antiviral pathways active against EBV and was needed for maximal expression of...
- Virus-Cell InteractionsRNA Helicase A Is an Important Host Factor Involved in Dengue Virus Replication
Dengue, caused by dengue virus, is a rapidly spreading disease, and currently there are no treatments available. Host factors involved in the viral replication of dengue virus are potential antiviral therapeutic targets. Although RHA has been shown to promote the multiplication of several viruses, such as HIV and adenovirus, its role in the flavivirus family, including dengue virus, Japanese encephalitis virus, and emerging Zika virus,...
- Virus-Cell InteractionsSpatiotemporal Differences in Presentation of CD8 T Cell Epitopes during Hepatitis B Virus Infection
The inability of patients with chronic HBV infection to clear HBV is associated with defective HBV-specific CD8+ T cells. Hence, the majority of immunotherapy developments focus on HBV-specific T cell function restoration. However, knowledge of whether distinct HBV-specific T cells can equally target all the HBV-infected hepatocytes of a chronically infected liver is lacking. In this work, analysis of CHB patient liver...
- Virus-Cell Interactions | SpotlightDefective Viral Genomes Alter How Sendai Virus Interacts with Cellular Trafficking Machinery, Leading to Heterogeneity in the Production of Viral Particles among Infected Cells
Defective viral genomes (DVGs) generated during Sendai virus infections accumulate in the cytoplasm of some infected cells and stimulate antiviral immunity and cell survival. DVGs are packaged and released as defective particles and have a significant impact on infection outcome. We show that the subpopulation of DVG-high cells poorly engages the virus packaging and budding machinery and do not effectively produce viral particles. In...
- Virus-Cell InteractionsAnalysis of a Subacute Sclerosing Panencephalitis Genotype B3 Virus from the 2009-2010 South African Measles Epidemic Shows That Hyperfusogenic F Proteins Contribute to Measles Virus Infection in the Brain
Measles virus can invade the central nervous system (CNS) and cause severe neurological complications, such as MIBE and SSPE. However, mechanisms by which MeV enters the CNS and triggers the disease remain unclear. We analyzed viruses from brain tissue of individuals with MIBE or SSPE, infected during the same epidemic, after the onset of neurological disease. Our findings indicate that the emergence of hyperfusogenic MeV F proteins is...
- Virus-Cell InteractionsThe Host DHX9 DExH-Box Helicase Is Recruited to Chikungunya Virus Replication Complexes for Optimal Genomic RNA Translation
The reemergence of chikungunya virus (CHIKV), an alphavirus that is transmitted to humans by Aedes mosquitoes, is a serious global health threat. In the absence of effective antiviral drugs, CHIKV infection has a significant impact on human health, with chronic arthritis being one of the most serious complications. The molecular understanding of host-virus interactions is a prerequisite to the development of targeted...
- Virus-Cell InteractionsEarly Porcine Sapovirus Infection Disrupts Tight Junctions and Uses Occludin as a Coreceptor
Sapoviruses (SaVs) cause severe acute gastroenteritis in humans and animals. Although they replicate in intestinal epithelial cells, which are tightly sealed by apical-junctional complexes, such as tight junctions (TJs), the mechanisms by which SaVs hijack TJs and their proteins for successful entry and infection remain largely unknown. Here, we demonstrate that porcine SaVs (PSaVs) induce early dissociation of TJs, allowing them to...
- Virus-Cell InteractionsCell Cycle Arrest in G2/M Phase Enhances Replication of Interferon-Sensitive Cytoplasmic RNA Viruses via Inhibition of Antiviral Gene Expression
Vesicular stomatitis virus (VSV) (a rhabdovirus) and its variant VSV-ΔM51 are widely used model systems to study mechanisms of virus-host interactions. Here, we investigated how the cell cycle affects replication of VSV and VSV-ΔM51. We show that G2/M cell cycle arrest strongly enhances the replication of VSV-ΔM51 (but not of wild-type VSV) and Sendai virus (a paramyxovirus) via inhibition of antiviral gene expression, likely...
- Virus-Cell InteractionsHDAC6 Restricts Influenza A Virus by Deacetylation of the RNA Polymerase PA Subunit
Influenza A virus (IAV) continues to threaten global public health due to drug resistance and the emergence of frequently mutated strains. Thus, it is critical to find new strategies to control IAV infection. Here, we discover one host protein, HDAC6, that can inhibit viral RNA polymerase activity by deacetylating PA and thus suppresses virus RNA replication and transcription. Previously, it was reported that IAV can utilize the HDAC6-...
- Virus-Cell InteractionsMapping the pH Sensors Critical for Host Cell Entry by a Complex Nonenveloped Virus
Virus entry into a susceptible cell is the first step of infection and a significant point at which infection can be prevented. To enter effectively, viruses must sense the cellular environment and, when appropriate, initiate a series of changes that eventually jettison the protective shell and deposit virus genes into the cytoplasm. Many viruses sense pH, but how this happens and the events that follow are often poorly understood. Here...
- Virus-Cell InteractionsHepatitis C Virus Escape Studies of Human Antibody AR3A Reveal a High Barrier to Resistance and Novel Insights on Viral Antibody Evasion Mechanisms
Hepatitis C virus (HCV) is a leading cause of liver-related mortality, and limited treatment accessibility makes vaccine development a high priority. The vaccine-relevant cross-genotype-reactive antibody AR3A has shown high potency, but the ability of the virus to rapidly escape by mutating the AR3A epitope (barrier to resistance) remains unexplored. Here, we succeeded in inducing only low-level AR3A resistance, indicating a higher...
- Virus-Cell InteractionsInhibition of DNA-Sensing Pathway by Marek's Disease Virus VP23 Protein through Suppression of Interferon Regulatory Factor 7 Activation
Despite widespread vaccination, Marek’s disease (MD) continues to pose major challenges for the poultry industry worldwide. MDV causes immunosuppression and deadly lymphomas in chickens, suggesting that this virus has developed a successful immune evasion strategy. However, little is known regarding the initiation and modulation of the host innate immune response during MDV infection. This study demonstrates that the cGAS-STING DNA-...
- Virus-Cell InteractionsAutophagy Promotes Replication of Influenza A Virus In Vitro
Autophagy impacts the replication cycle of many viruses. However, the role of the autophagy machinery in IAV replication remains unclear. Therefore, we explored the detailed mechanisms utilized by IAV to promote its replication. We demonstrated that IAV NP- and M2-mediated autophagy promotes IAV replication by regulating the AKT-mTOR signaling pathway and HSP90AA1 expression. The interaction of PB2 and HSP90AA1 results in the increase...
- Virus-Cell InteractionsThe Dengue Virus Nonstructural Protein 1 (NS1) Is Secreted from Mosquito Cells in Association with the Intracellular Cholesterol Transporter Chaperone Caveolin Complex
The dengue virus protein NS1 is secreted efficiently from both infected vertebrate and mosquito cells. Previously, our group reported that NS1 secretion in mosquito cells follows an unconventional secretion pathway dependent on caveolin-1. In this work, we demonstrate that in mosquito cells, but not in vertebrate cells, NS1 secretion takes place in association with the chaperone caveolin complex, a complex formed by caveolin-1 and the...
- Virus-Cell InteractionsNovel Mutations in nsP2 Abolish Chikungunya Virus-Induced Transcriptional Shutoff and Make the Virus Less Cytopathic without Affecting Its Replication Rates
Chikungunya virus is an important human pathogen which now circulates in both the Old and New Worlds. As in the case of other Old World alphaviruses, CHIKV nsP2 not only has enzymatic functions in viral RNA replication but also is a critical inhibitor of the antiviral response and one of the determinants of CHIKV pathogenesis. In this study, we have applied a new strategy to select a variety of CHIKV nsP2 mutants that no longer...
Cellular Response to Infection
- Cellular Response to InfectionHuman Papillomavirus 16 E2 Regulates Keratinocyte Gene Expression Relevant to Cancer and the Viral Life Cycle
Human papillomavirus 16 (HPV16)-positive tumors that retain expression of E2 have a better clinical outcome than those that have lost E2 expression. It has been suggested that this is due to a loss of E2 repression of E6 and E7 expression, but this is not supported by data from tumors where there is not more E6 and E7 expression in the absence of E2. Here we report that E2 regulates host gene expression and place this regulation in the...
Transformation and Oncogenesis
- Transformation and OncogenesisOncogenic Kaposi’s Sarcoma-Associated Herpesvirus Upregulates Argininosuccinate Synthase 1, a Rate-Limiting Enzyme of the Citrulline-Nitric Oxide Cycle, To Activate the STAT3 Pathway and Promote Growth Transformation
We have previously shown that Kaposi’s sarcoma-associated herpesvirus (KSHV)-transformed cells depend on glutamine rather than glucose for energy production and amino acid and nucleotide syntheses. In this study, we have further examined how the KSHV-reprogramed metabolic pathways are regulated and discovered that KSHV hijacks the citrulline-nitric oxide (NO) cycle to promote growth proliferation and transformation. Multiple KSHV-...
Gene Delivery
- Gene DeliveryDevelopment of Stable Rotavirus Reporter Expression Systems
Development of reporter RVs has been hampered by the lack of comprehensive reverse genetics systems. Recently, we developed a plasmid-based reverse genetics system that enables generation of reporter RVs expressing NLuc luciferase. The prototype reporter RV had some disadvantages (i.e., the transgene was unstable and was expressed as a fusion protein with a partial NSP1 peptide); however, the improved reporter RV overcomes these...
Pathogenesis and Immunity
- Pathogenesis and ImmunityFunctional Analysis and Antivirulence Properties of a New Depolymerase from a Myovirus That Infects Acinetobacter baumannii Capsule K45
Currently, phage therapy has revived interest for controlling hard-to-treat bacterial infections. Acinetobacter baumannii is an emerging Gram-negative pathogen able to cause a variety of nosocomial infections. Additionally, this species is becoming more resistant to several classes of antibiotics. Here we describe the isolation of a novel lytic myophage B9 and its...
- Pathogenesis and ImmunityMechanisms of Abrupt Loss of Virus Control in a Cohort of Previous HIV Controllers
A few individuals can control HIV infection without the need for antiretroviral treatment and are referred to as HIV controllers. We have studied HIV controllers who suddenly lose this ability and present with high in vivo viral replication and decays in their CD4+ T-cell counts to identify potential immune and virological factors that were responsible for initial virus control. We identify in vitro-...
- Pathogenesis and ImmunityEarly T Follicular Helper Cell Responses and Germinal Center Reactions Are Associated with Viremia Control in Immunized Rhesus Macaques
The modest HIV protection observed in the human RV144 vaccine trial associated antibody responses with vaccine efficacy. T follicular helper (TFH) cells are CD4+ T cells that select antibody secreting cells with high antigenic affinity in germinal centers (GCs) within secondary lymphoid organs. To evaluate the role of TFH cells in eliciting prolonged virus-specific humoral responses, we vaccinated rhesus...
- Pathogenesis and ImmunityIncreased Frequency of Virus Shedding by Herpes Simplex Virus 2-Infected Guinea Pigs in the Absence of CD4+ T Lymphocytes
Sexual transmission of HSV-2 results from viral shedding following reactivation from latency. The immune cell populations and mechanisms that control HSV-2 shedding are not well understood. This study examined the role of CD4+ T cells in control of virus shedding using a guinea pig model of genital HSV-2 infection that recapitulates the shedding of virus experienced by humans. We found that the frequency of virus-shedding...
- Pathogenesis and ImmunityHistidine-Rich Glycoprotein Inhibits HIV-1 Infection in a pH-Dependent Manner
Vaginal intercourse represents a high-risk route for HIV-1 transmission. The efficiency of male-to-female HIV-1 transmission has been estimated to be 1 in every 1,000 episodes of sexual intercourse, reflecting the high degree of protection conferred by the genital mucosa. However, the contribution of different host factors to the protection against HIV-1 at mucosal surfaces remains poorly defined. Here, we report for the first time that...
- Pathogenesis and Immunity | SpotlightA Human Gain-of-Function STING Mutation Causes Immunodeficiency and Gammaherpesvirus-Induced Pulmonary Fibrosis in Mice
A variety of human rheumatologic disease-causing mutations have recently been identified. Some of these mutations are found in viral nucleic acid-sensing proteins, but whether viruses can influence the onset or progression of these human diseases is less well understood. One such autoinflammatory disease, called STING-associated vasculopathy with onset in infancy (SAVI), affects children and leads to severe lung disease. We generated...
- Pathogenesis and ImmunityGenetic Compatibility of Reassortants between Avian H5N1 and H9N2 Influenza Viruses with Higher Pathogenicity in Mammals
Close interaction between avian influenza (AI) viruses and humans in Egypt appears to have resulted in many of the worldwide cases of human infections by both H5N1 and H9N2 AI viruses. Egypt is regarded as a hot spot of AI virus evolution. Although no natural reassortant of H5N1 and H9N2 AI viruses has been reported so far, their cocirculation in Egypt may allow emergence of reassortants that may present a significant public health risk...
- Pathogenesis and ImmunityInduction of Porcine Dermatitis and Nephropathy Syndrome in Piglets by Infection with Porcine Circovirus Type 3
Porcine circovirus type 3 (PCV3), an emerging porcine circovirus, is considered the cause of porcine dermatitis and nephropathy syndrome (PDNS)-like clinical signs and other systemic diseases in piglets and sows. To evaluate the pathogenesis of PCV3 infection in vivo, we used a PCV3 virus stock from the rescue of an infectious PCV3 DNA clone to intranasally inoculate 4- and 8-week-old specific-pathogen-free piglets and...
- Pathogenesis and ImmunityIdentification and Functional Characterization of a Novel Fc Gamma-Binding Glycoprotein in Rhesus Cytomegalovirus
Rhesus cytomegalovirus (RhCMV) offers a unique model for studying human cytomegalovirus (HCMV) pathogenesis and vaccine development. RhCMV infection of nonhuman primates greatly broadened the understanding of mechanisms by which CMVs evade or reprogram T cell and natural killer cell responses in vivo. However, the role of humoral immunity and viral modulation of anti-CMV antibodies has not been studied in this model. There is...