scholarly journals Old World hantaviruses do not produce detectable amounts of dsRNA in infected cells and the 5′ termini of their genomic RNAs are monophosphorylated

2011 ◽  
Vol 92 (5) ◽  
pp. 1199-1204 ◽  
Author(s):  
Hao Wang ◽  
Antti Vaheri ◽  
Friedemann Weber ◽  
Alexander Plyusnin
Keyword(s):  
Rna Virus ◽  
Innate Immune ◽  
Hantaan Virus ◽  
Signalling Pathways ◽  
Genomic Rna ◽  
Genomic Rnas ◽  
Old World ◽  
Interferon Induction ◽  
Infected Cells ◽  
Negative Sense

dsRNA and 5′-triphosphate RNA are considered critical activators of the innate immune response because of their interaction with pattern recognition receptors. It has been reported that no dsRNA is detected in negative-sense RNA virus-infected cells and that Hantaan virus (HTNV) genomic RNA bears a 5′ monophosphate group. In this paper we examine the 5′ termini of genomic RNAs of and dsRNA production by two major groups of Old World hantaviruses. No detectable amounts of dsRNA were found in infected cells. Also, the genomic RNAs of these hantaviruses bear a 5′ monophosphate group and therefore are unable to trigger interferon induction. Taken together with the earlier data on HTNV, these results suggest that in addition to the dsRNA and genomic RNA, which may be only minimally involved in the induction of innate immunity, other cellular signalling pathways may also be involved and that these await further investigation.

scholarly journals ADAR2 Is Involved in Self and Nonself Recognition of Borna Disease Virus Genomic RNA in the Nucleus

2019 ◽  
Vol 94 (6) ◽  
Author(s):  
Mako Yanai ◽  
Shohei Kojima ◽  
Madoka Sakai ◽  
Ryo Komorizono ◽  
Keizo Tomonaga ◽  
...  
Keyword(s):  
Immune Responses ◽  
Disease Virus ◽  
Persistent Infection ◽  
Rna Virus ◽  
Innate Immune ◽  
Genomic Rna ◽  
Borna Disease Virus ◽  
Infected Cells ◽  
Nonself Recognition ◽  
Borna Disease

ABSTRACT Cells sense pathogen-derived double-stranded RNA (dsRNA) as nonself. To avoid autoimmune activation by self dsRNA, cells utilize A-to-I editing by adenosine deaminase acting on RNA 1 (ADAR1) to disrupt dsRNA structures. Considering that viruses have evolved to exploit host machinery, A-to-I editing could benefit innate immune evasion by viruses. Borna disease virus (BoDV), a nuclear-replicating RNA virus, may require escape from nonself RNA-sensing and immune responses to establish persistent infection in the nucleus; however, the strategy by which BoDV evades nonself recognition is unclear. Here, we evaluated the involvement of ADARs in BoDV infection. The infection efficiency of BoDV was markedly decreased in both ADAR1 and ADAR2 knockdown cells at the early phase of infection. Microarray analysis using ADAR2 knockdown cells revealed that ADAR2 reduces immune responses even in the absence of infection. Knockdown of ADAR2 but not ADAR1 significantly reduced the spread and titer of BoDV in infected cells. Furthermore, ADAR2 knockout decreased the infection efficiency of BoDV, and overexpression of ADAR2 rescued the reduced infectivity in ADAR2 knockdown cells. However, the growth of influenza A virus, which causes acute infection in the nucleus, was not affected by ADAR2 knockdown. Moreover, ADAR2 bound to BoDV genomic RNA and induced A-to-G mutations in the genomes of persistently infected cells. We finally demonstrated that BoDV produced in ADAR2 knockdown cells induces stronger innate immune responses than those produced in wild-type cells. Taken together, our results suggest that BoDV utilizes ADAR2 to edit its genome to appear as “self” RNA in order to maintain persistent infection in the nucleus. IMPORTANCE Cells use the editing activity of adenosine deaminase acting on RNA proteins (ADARs) to prevent autoimmune responses induced by self dsRNA, but viruses can exploit this process to their advantage. Borna disease virus (BoDV), a nuclear-replicating RNA virus, must escape nonself RNA sensing by the host to establish persistent infection in the nucleus. We evaluated whether BoDV utilizes ADARs to prevent innate immune induction. ADAR2 plays a key role throughout the BoDV life cycle. ADAR2 knockdown reduced A-to-I editing of BoDV genomic RNA, leading to the induction of a strong innate immune response. These data suggest that BoDV exploits ADAR2 to edit nonself genomic RNA to appear as self RNA for innate immune evasion and establishment of persistent infection.

scholarly journals Role of Sindbis Virus Capsid Protein Region II in Nucleocapsid Core Assembly and Encapsidation of Genomic RNA

2008 ◽  
Vol 82 (9) ◽  
pp. 4461-4470 ◽  
Author(s):  
Ranjit Warrier ◽  
Benjamin R. Linger ◽  
Barbara L. Golden ◽  
Richard J. Kuhn
Keyword(s):  
Amino Acids ◽  
Capsid Protein ◽  
Sindbis Virus ◽  
Rna Virus ◽  
Genomic Rna ◽  
Viral Glycoproteins ◽  
Infected Cells ◽  
Viral Genomic Rna ◽  
Region Ii

ABSTRACT Sindbis virus is an enveloped positive-sense RNA virus in the alphavirus genus. The nucleocapsid core contains the genomic RNA surrounded by 240 copies of a single capsid protein. The capsid protein is multifunctional, and its roles include acting as a protease, controlling the specificity of RNA that is encapsidated into nucleocapsid cores, and interacting with viral glycoproteins to promote the budding of mature virus and the release of the genomic RNA into the newly infected cell. The region comprising amino acids 81 to 113 was previously implicated in two processes, the encapsidation of the viral genomic RNA and the stable accumulation of nucleocapsid cores in the cytoplasm of infected cells. In the present study, specific amino acids within this region responsible for the encapsidation of the genomic RNA have been identified. The region that is responsible for nucleocapsid core accumulation has considerable overlap with the region that controls encapsidation specificity.

scholarly journals Significantly Improved Recovery of Recombinant Sonchus Yellow Net Rhabdovirus by Expressing the Negative-Strand Genomic RNA

Viruses ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 1459
Author(s):  
Xiaonan Ma ◽  
Zhenghe Li
Keyword(s):  
Matrix Protein ◽  
Plant Viruses ◽  
Biologically Active ◽  
Messenger Rnas ◽  
Genomic Rna ◽  
Genomic Rnas ◽  
Double Stranded Rna ◽  
Core Proteins ◽  
Negative Sense

Generation of recombinant negative-stranded RNA viruses (NSVs) from plasmids involves in vivo reconstitution of biologically active nucleocapsids and faces a unique antisense problem where the negative-sense viral genomic RNAs can hybridize to viral messenger RNAs. To overcome this problem, a positive-sense RNA approach has been devised through expression of viral antigenomic (ag)RNA and core proteins for assembly of antigenomic nucleocapsids. Although this detour strategy works for many NSVs, the process is still inefficient. Using Sonchus yellow net rhabdovirus (SYNV) as a model; here, we develop a negative-sense genomic RNA-based approach that increased rescue efficiency by two orders of magnitude compared to the conventional agRNA approach. The system relied on suppression of double-stranded RNA induced antiviral responses by co-expression of plant viruses-encoded RNA silencing suppressors or animal viruses-encoded double-stranded RNA antagonists. With the improved approach, we were able to recover a highly attenuated SYNV mutant with a deletion in the matrix protein gene which otherwise could not be rescued via the agRNA approach. Reverse genetics analyses of the generated mutant virus provided insights into SYNV virion assembly and morphogenesis. This approach may potentially be applicable to other NSVs of plants or animals.

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

mBio ◽  
2018 ◽  
Vol 9 (3) ◽  
Author(s):  
Jeremiah Athmer ◽  
Anthony R. Fehr ◽  
Matthew E. Grunewald ◽  
Wen Qu ◽  
D. Lori Wheeler ◽  
...  
Keyword(s):  
Innate Immune ◽  
Type I ◽  
Genomic Rna ◽  
Rna Packaging ◽  
Packaging Signal ◽  
Subgenomic Rnas ◽  
Immune Detection ◽  
Negative Sense

ABSTRACTSelective 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 packagingin vitroand on viral titers. Here, we show that selective packaging is also required for viral evasion of the innate immune response and optimal pathogenicity. We engineered two distinct PS mutants in two different strains of murine hepatitis virus (MHV) that packaged increased levels of subgenomic RNAs, negative-sense genomic RNA, and even cellular RNAs. All PS mutant viruses replicated normallyin vitrobut caused dramatically reduced lethality and weight lossin vivo. PS mutant virus infection of bone marrow-derived macrophages resulted in increased interferon (IFN) production, indicating that the innate immune system limited the replication and/or pathogenesis of PS mutant virusesin vivo. PS mutant viruses remained attenuated in MAVS−/−and Toll-like receptor 7-knockout (TLR7−/−) mice, two well-known RNA sensors for CoVs, but virulence was restored in interferon alpha/beta receptor-knockout (IFNAR−/−) mice or in MAVS−/−mice treated with IFNAR-blocking antibodies. Together, these data indicate that coronaviruses promote virulence by utilizing selective packaging to avoid innate immune detection.IMPORTANCECoronaviruses (CoVs) produce many types of RNA molecules during their replication cycle, including both positive- and negative-sense genomic and subgenomic RNAs. Despite this, coronaviruses selectively package only positive-sense genomic RNA into their virions. Why CoVs selectively package their genomic RNA is not clear, as disruption of the packaging signal in MHV, which leads to loss of selective packaging, does not affect genomic RNA packaging or virus replication in cultured cells. This contrasts with other viruses, where disruption of selective packaging generally leads to altered replication. Here, we demonstrate that in the absence of selective packaging, the virulence of MHV was significantly reduced. Importantly, virulence was restored in the absence of interferon signaling, indicating that selective packaging is a mechanism used by CoVs to escape innate immune detection.

scholarly journals Noncapped Alphavirus Genomic RNAs and Their Role during Infection

2015 ◽  
Vol 89 (11) ◽  
pp. 6080-6092 ◽  
Author(s):  
K. J. Sokoloski ◽  
K. C. Haist ◽  
T. E. Morrison ◽  
S. Mukhopadhyay ◽  
R. W. Hardy
Keyword(s):  
Sindbis Virus ◽  
Rna Synthesis ◽  
Rna Virus ◽  
Genomic Rna ◽  
Concerted Effort ◽  
Genomic Rnas ◽  
Virus Particles ◽  
Molecular Determinant ◽  
Viral Particles ◽  
Positive Sense

ABSTRACTAlphaviruses are enveloped positive-sense RNA viruses that exhibit a wide host range consisting of vertebrate and invertebrate species. Previously we have reported that the infectivity of Sindbis virus (SINV), the model alphavirus, was largely a function of the cell line producing the viral particles. Mammalian-cell-derived SINV particles, on average, exhibit a higher particle-to-PFU ratio than mosquito cell-derived SINV particles. Nevertheless, the outcome of nonproductive infection, the molecular traits that determine particle infectivity and the biological importance of noninfectious particles were, prior to this study, unknown. Here, we report that the incoming genomic RNAs of noninfectious SINV particles undergo rapid degradation following infection. Moreover, these studies have led to the identification of the absence of the 5′ cap structure as a primary molecular determinant of particle infectivity. We show that the genomic RNAs of alphaviruses are not universally 5′ capped, with a significant number of noncapped genomic RNA produced early in infection. The production of noncapped viral genomic RNAs is important to the establishment and maintenance of alphaviral infection.IMPORTANCEThis report is of importance to the field of virology for three reasons. First, these studies demonstrate that noncapped Sindbis virus particles are produced as a result of viral RNA synthesis. Second, this report is, to our knowledge, the first instance of the direct measurement of the half-life of an incoming genomic RNA from a positive-sense RNA virus. Third, these studies indicate that alphaviral infection is likely a concerted effort of infectious and noninfectious viral particles.

scholarly journals Formation and Function of Liquid-Like Viral Factories in Negative-Sense Single-Stranded RNA Virus Infections

Viruses ◽  
2021 ◽  
Vol 13 (1) ◽  
pp. 126
Author(s):  
Justin M. Su ◽  
Maxwell Z. Wilson ◽  
Charles E. Samuel ◽  
Dzwokai Ma
Keyword(s):  
Rna Viruses ◽  
Rna Virus ◽  
Host Responses ◽  
Future Research ◽  
Virus Infections ◽  
Infected Cells ◽  
And Function ◽  
Negative Sense ◽  
Liquid Liquid Phase Separation

Liquid–liquid phase separation (LLPS) represents a major physiochemical principle to organize intracellular membrane-less structures. Studies with non-segmented negative-sense (NNS) RNA viruses have uncovered a key role of LLPS in the formation of viral inclusion bodies (IBs), sites of viral protein concentration in the cytoplasm of infected cells. These studies further reveal the structural and functional complexity of viral IB factories and provide a foundation for their future research. Herein, we review the literature leading to the discovery of LLPS-driven formation of IBs in NNS RNA virus-infected cells and the identification of viral scaffold components involved, and then outline important questions and challenges for IB assembly and disassembly. We discuss the functional implications of LLPS in the life cycle of NNS RNA viruses and host responses to infection. Finally, we speculate on the potential mechanisms underlying IB maturation, a phenomenon relevant to many human diseases.

scholarly journals Low compositions of human toll-like receptor 7/8-stimulating RNA motifs in the MERS-CoV, SARS-CoV and SARS-CoV-2 genomes imply a substantial ability to evade human innate immunity

PeerJ ◽  
2021 ◽  
Vol 9 ◽  
pp. e11008
Author(s):  
Chu-Wen Yang ◽  
Mei-Fang Chen
Keyword(s):  
Large Scale ◽  
Rna Viruses ◽  
Rna Virus ◽  
Innate Immune ◽  
Computational Method ◽  
Response Analysis ◽  
Toll Like Receptor ◽  
Human Coronavirus ◽  
Genomic Rnas ◽  
Positive Strand

Background The innate immune system especially Toll-like receptor (TLR) 7/8 and the interferon pathway, constitutes an important first line of defense against single-stranded RNA viruses. However, large-scale, systematic comparisons of the TLR 7/8-stimulating potential of genomic RNAs of single-stranded RNA viruses are rare. In this study, a computational method to evaluate the human TLR 7/8-stimulating ability of single-stranded RNA virus genomes based on their human TLR 7/8-stimulating trimer compositions was used to analyze 1,002 human coronavirus genomes. Results The human TLR 7/8-stimulating potential of coronavirus genomic (positive strand) RNAs followed the order of NL63-CoV > HKU1-CoV >229E-CoV ≅ OC63-CoV > SARS-CoV-2 > MERS-CoV > SARS-CoV. These results suggest that among these coronaviruses, MERS-CoV, SARS-CoV and SARS-CoV-2 may have a higher ability to evade the human TLR 7/8-mediated innate immune response. Analysis with a logistic regression equation derived from human coronavirus data revealed that most of the 1,762 coronavirus genomic (positive strand) RNAs isolated from bats, camels, cats, civets, dogs and birds exhibited weak human TLR 7/8-stimulating potential equivalent to that of the MERS-CoV, SARS-CoV and SARS-CoV-2 genomic RNAs. Conclusions Prediction of the human TLR 7/8-stimulating potential of viral genomic RNAs may be useful for surveillance of emerging coronaviruses from nonhuman mammalian hosts.

scholarly journals Nonameric Peptide Orchestrates Signal Transduction in the Activating HLA-E/NKG2C/CD94 Immune Complex as Revealed by All-Atom Simulations

2021 ◽  
Vol 22 (13) ◽  
pp. 6670
Author(s):  
Eva Prašnikar ◽  
Andrej Perdih ◽  
Jure Borišek
Keyword(s):  
Signal Transduction ◽  
Cell Activation ◽  
Nk Cell ◽  
Innate Immune ◽  
Target Cells ◽  
Molecular Events ◽  
Activating Receptors ◽  
Molecular Machinery ◽  
Infected Cells ◽  
Bond Network

The innate immune system’s natural killer (NK) cells exert their cytolytic function against a variety of pathological challenges, including tumors and virally infected cells. Their activation depends on net signaling mediated via inhibitory and activating receptors that interact with specific ligands displayed on the surfaces of target cells. The CD94/NKG2C heterodimer is one of the NK activating receptors and performs its function by interacting with the trimeric ligand comprised of the HLA-E/β2m/nonameric peptide complex. Here, simulations of the all-atom multi-microsecond molecular dynamics in five immune complexes provide atomistic insights into the receptor–ligand molecular recognition, as well as the molecular events that facilitate the NK cell activation. We identify NKG2C, the HLA-Eα2 domain, and the nonameric peptide as the key elements involved in the molecular machinery of signal transduction via an intertwined hydrogen bond network. Overall, the study addresses the complex intricacies that are necessary to understand the mechanisms of the innate immune system.

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