scholarly journals Changes in RNA secondary structure affect NS1 protein expression during early stage influenza virus infection

2019 ◽  
Vol 16 (1) ◽  
Author(s):  
Irina Baranovskaya ◽  
Mariia Sergeeva ◽  
Artem Fadeev ◽  
Renata Kadirova ◽  
Anna Ivanova ◽  
...  
Keyword(s):  
Influenza Virus ◽  
Secondary Structure ◽  
Protein Expression ◽  
Rna Secondary Structure ◽  
Reverse Genetics ◽  
Early Stage ◽  
Influenza Virus Infection ◽  
Main Function ◽  
Ns1 Protein ◽  
Virus Strains

AbstractRNA secondary structures play a key role in splicing, gene expression, microRNA biogenesis, RNA editing, and other biological processes. The importance of RNA structures has been demonstrated in the life cycle of RNA-containing viruses, including the influenza virus. At least two regions of conserved secondary structure in NS segment (+) RNA are predicted to vary among influenza virus strains with respect to thermodynamic stability; both fall in the NS1 open reading frame. The NS1 protein is involved in multiple virus-host interaction processes, and its main function is to inhibit the cellular immune response to viral infection. Using a reverse genetics approach, four influenza virus strains were constructed featuring mutations that have different effects on RNA secondary structure. Growth curve experiments and ELISA data show that, at least in the first viral replication cycle, mutations G123A and A132G affecting RNA structure in the (82–148) NS RNA region influence NS1 protein expression.

scholarly journals Influenza virus segment 5 (+)RNA - secondary structure and new targets for antiviral strategies

2017 ◽  
Vol 7 (1) ◽  
Author(s):  
Marta Soszynska-Jozwiak ◽  
Paula Michalak ◽  
Walter N. Moss ◽  
Ryszard Kierzek ◽  
Julita Kesy ◽  
...  
Keyword(s):  
Influenza Virus ◽  
Secondary Structure ◽  
Rna Secondary Structure ◽  
New Targets

scholarly journals Interleukin-18 improves the early defence system against influenza virus infection by augmenting natural killer cell-mediated cytotoxicity

2004 ◽  
Vol 85 (2) ◽  
pp. 423-428 ◽  
Author(s):  
Beixing Liu ◽  
Isamu Mori ◽  
Md Jaber Hossain ◽  
Li Dong ◽  
Kiyoshi Takeda ◽  
...  
Keyword(s):  
Influenza Virus ◽  
Virus Infection ◽  
Natural Killer ◽  
Influenza A ◽  
Nk Cell ◽  
Early Stage ◽  
Killer Cell ◽  
Influenza Virus Infection ◽  
Virus Growth ◽  
Defence System

The role of interleukin (IL)-18 in the development of the host defence system against influenza virus infection was investigated. IL-18-deficient (IL-18−/−) C57BL/6 mice that were inoculated intranasally with the mouse-adapted strain of human influenza A/PR/8/34 (H1N1) virus showed an increased mortality with the occurrence of pathogenic changes in the lung for the first 3 days of infection, which included pronounced virus growth with massive infiltration of inflammatory cells and elevated nitric oxide production. The interferon-gamma (IFN-γ) level induced in the respiratory tract of IL-18−/− mice in the first few days after virus infection was significantly lower but, in contrast, the IL-12 level was slightly higher than the corresponding levels in wild-type C57BL/6 mice. Natural killer (NK) cell-mediated cytotoxicity in the lung of IL-18−/− mice was poorly activated. Local immune responses in the lung such as specific cytotoxic T lymphocyte and antibody production were induced upon influenza virus infection equally well in both strains of mice. These results indicate that IL-18 is involved in controlling influenza virus replication in the lung, especially at an early stage of infection, through activation of the innate immune mechanisms such as IFN and NK cells.

scholarly journals DDX3 Interacts with Influenza A Virus NS1 and NP Proteins and Exerts Antiviral Function through Regulation of Stress Granule Formation

2016 ◽  
Vol 90 (7) ◽  
pp. 3661-3675 ◽  
Author(s):  
Sathya N. Thulasi Raman ◽  
Guanqun Liu ◽  
Hyun Mi Pyo ◽  
Ya Cheng Cui ◽  
Fang Xu ◽  
...  
Keyword(s):  
Influenza Virus ◽  
Life Cycle ◽  
Virus Infection ◽  
Influenza A ◽  
Influenza Virus Infection ◽  
Ns1 Protein ◽  
Antiviral Protein ◽  
Virus Life Cycle ◽  
Interaction Partners ◽  
Infected Cells

ABSTRACTDDX3 belongs to the DEAD box RNA helicase family and is a multifunctional protein affecting the life cycle of a variety of viruses. However, its role in influenza virus infection is unknown. In this study, we explored the potential role of DDX3 in influenza virus life cycle and discovered that DDX3 is an antiviral protein. Since many host proteins affect virus life cycle by interacting with certain components of the viral machinery, we first verified whether DDX3 has any viral interaction partners. Immunoprecipitation studies revealed NS1 and NP as direct interaction partners of DDX3. Stress granules (SGs) are known to be antiviral and do form in influenza virus-infected cells expressing defective NS1 protein. Additionally, a recent study showed that DDX3 is an important SG-nucleating factor. We thus explored whether DDX3 plays a role in influenza virus infection through regulation of SGs. Our results showed that SGs were formed in infected cells upon infection with a mutant influenza virus lacking functional NS1 (del NS1) protein, and DDX3 colocalized with NP in SGs. We further determined that the DDX3 helicase domain did not interact with NS1 and NP; however, it was essential for DDX3 localization in virus-induced SGs. Knockdown of DDX3 resulted in impaired SG formation and led to increased virus titers. Taken together, our results identified DDX3 as an antiviral protein with a role in virus-induced SG formation.IMPORTANCEDDX3 is a multifunctional RNA helicase and has been reported to be involved in regulating various virus life cycles. However, its function during influenza A virus infection remains unknown. In this study, we demonstrated that DDX3 is capable of interacting with influenza virus NS1 and NP proteins; DDX3 and NP colocalize in the del NS1 virus-induced SGs. Furthermore, knockdown of DDX3 impaired SG formation and led to a decreased virus titer. Thus, we provided evidence that DDX3 is an antiviral protein during influenza virus infection and its antiviral activity is through regulation of SG formation. Our findings provide knowledge about the function of DDX3 in the influenza virus life cycle and information for future work on manipulating the SG pathway and its components to fight influenza virus infection.

scholarly journals Human Staufen1 Protein Interacts with Influenza Virus Ribonucleoproteins and Is Required for Efficient Virus Multiplication

2010 ◽  
Vol 84 (15) ◽  
pp. 7603-7612 ◽  
Author(s):  
Susana de Lucas ◽  
Joan Peredo ◽  
Rosa María Marión ◽  
Carmen Sánchez ◽  
Juan Ortín
Keyword(s):  
Influenza Virus ◽  
Virus Infection ◽  
Influenza A ◽  
Particle Production ◽  
Nonstructural Protein ◽  
A549 Cells ◽  
Influenza Virus Infection ◽  
Ns1 Protein ◽  
Infected Cells

ABSTRACT The influenza A virus genome consists of 8 negative-stranded RNA segments. NS1 is a nonstructural protein that participates in different steps of the virus infectious cycle, including transcription, replication, and morphogenesis, and acts as a virulence factor. Human Staufen1 (hStau1), a protein involved in the transport and regulated translation of cellular mRNAs, was previously identified as a NS1-interacting factor. To investigate the possible role of hStau1 in the influenza virus infection, we characterized the composition of hStau1-containing granules isolated from virus-infected cells. Viral NS1 protein and ribonucleoproteins (RNPs) were identified in these complexes by Western blotting, and viral mRNAs and viral RNAs (vRNAs) were detected by reverse transcription (RT)-PCR. Also, colocalization of hStau1 with NS1, nucleoprotein (NP), and PA in the cytosol of virus-infected cells was shown by immunofluorescence. To analyze the role of hStau1 in the infection, we downregulated its expression by gene silencing. Human HEK293T cells or A549 cells were silenced using either short hairpin RNAs (shRNAs) or small interfering RNAs (siRNAs) targeting four independent sites in the hStau1 mRNA. The yield of influenza virus was reduced 5 to 10 times in the various hStau1-silenced cells compared to that in control silenced cells. The expression levels of viral proteins and their nucleocytoplasmic localization were not affected upon hStau1 silencing, but virus particle production, as determined by purification of virions from supernatants, was reduced. These results indicate a role for hStau1 in late events of the influenza virus infection, possibly during virus morphogenesis.

scholarly journals Protein Synthesis Shut-Off Induced by Influenza Virus Infection Is Independent of PKR Activity

2000 ◽  
Vol 74 (18) ◽  
pp. 8781-8784 ◽  
Author(s):  
Thomas Zürcher ◽  
Rosa María Marión ◽  
Juan Ortín
Keyword(s):  
Protein Synthesis ◽  
Influenza Virus ◽  
Influenza Virus Infection ◽  
Nucleocytoplasmic Transport ◽  
Cellular Protein ◽  
Metabolic Labeling ◽  
Ns1 Protein ◽  
Wild Type ◽  
Mrna Polyadenylation

ABSTRACT The role of PKR activity in influenza virus-induced cell shut-off was studied by infection of PKR+ or PKR− cell cultures and metabolic labeling in vivo. No differences in the synthesis of viral proteins or the decay of cellular protein synthesis were observed. To investigate the relevance of the inhibition of cellular pre-mRNA polyadenylation and nucleocytoplasmic transport in virus-induced shut-off, we carried out similar experiments with mutant viruses lacking C-terminal sequences of NS1 protein. No differences in the shut-off induced by mutant versus wild-type viruses were observed, indicating that these nuclear events are not relevant for shut-off. The analysis of cytoplasmic mRNA stability indicated that the accumulation of viral mRNA during the infection correlated with the progressive decay of cellular mRNA, in both the wild type and an NS1 deletion mutant.

scholarly journals Amelioration of Influenza Virus Pathogenesis in Chickens Attributed to the Enhanced Interferon-Inducing Capacity of a Virus with a Truncated NS1 Gene

2006 ◽  
Vol 81 (4) ◽  
pp. 1838-1847 ◽  
Author(s):  
Angela N. Cauthen ◽  
David E. Swayne ◽  
Margaret J. Sekellick ◽  
Philip I. Marcus ◽  
David L. Suarez
Keyword(s):  
Influenza Virus ◽  
High Titer ◽  
Kidney Tissue ◽  
Ns1 Protein ◽  
Phenotypic Differences ◽  
Embryo Cells ◽  
Ns1 Gene ◽  
Virus Strains ◽  
Lethal Doses

ABSTRACT Avian influenza virus (AIV) A/turkey/Oregon/71-SEPRL (TK/OR/71-SEPRL) (H7N3) encodes a full-length NS1 protein and is a weak inducer of interferon (IFN). A variant, TK/OR/71-delNS1 (H7N3), produces a truncated NS1 protein and is a strong inducer of IFN. These otherwise genetically related variants differ 20-fold in their capacities to induce IFN in primary chicken embryo cells but are similar in their sensitivities to the action of IFN. Furthermore, the weak IFN-inducing strain actively suppresses IFN induction in cells that are otherwise programmed to produce it. These phenotypic differences are attributed to the enhanced IFN-inducing capacity that characterizes type A influenza virus strains that produce defective NS1 protein. The pathogenesis of these two variants was evaluated in 1-day-old and 4-week-old chickens. The cell tropisms of both viruses were similar. However, the lesions in chickens produced by the weak IFN inducer were more severe and differed somewhat in character from those observed for the strong IFN inducer. Differences in lesions included the nature of inflammation, the rate of resolution of the infection, and the extent of viral replication and/or virus dissemination. The amelioration of pathogenesis is attributed to the higher levels of IFN produced by the variant encoding the truncated NS1 protein and the antiviral state subsequently induced by that IFN. The high titer of virus observed in kidney tissue (≈109 50% embryo lethal doses/g) from 1-day-old chickens infected intravenously by the weak IFN-inducing strain is attributed to the capacity of chicken kidney cells to activate the hemagglutinin fusion peptide along with their unresponsiveness to inducers of IFN as measured in vitro. Thus, the IFN-inducing capacity of AIV appears to be a significant factor in regulating the pathogenesis, virulence, and viral transmission of AIV in chickens. This suggests that the IFN-inducing and IFN induction suppression phenotypes of AIV should be considered when characterizing strains of influenza virus.

Bovine lactoferrin: involvement of metal saturation and carbohydrates in the inhibition of influenza virus infection1This article is part of a Special Issue entitled Lactoferrin and has undergone the Journal's usual peer review process.

2012 ◽  
Vol 90 (3) ◽  
pp. 442-448 ◽  
Author(s):  
Agostina Pietrantoni ◽  
Maria Grazia Ammendolia ◽  
Fabiana Superti
Keyword(s):  
Influenza Virus ◽  
Peer Review Process ◽  
Influenza Virus Infection ◽  
Respiratory Illness ◽  
Bovine Lactoferrin ◽  
Cytopathic Effects ◽  
Antiviral Compounds ◽  
Induced Apoptosis ◽  
Virus Strains ◽  
Early Phases

Influenza is a highly contagious, acute respiratory illness, which represents one of the main plagues worldwide. Even though some antiviral drugs are available, the alarming increase of virus strains resistant to them highlights the need to find new antiviral compounds. As we have recently demonstrated that bovine lactoferrin (bLf) prevents influenza virus-induced apoptosis, in the present wor,k we have attempted to investigate in depth the mechanism of the anti-influenza virus effect of this protein. To this aim, experiments have been carried out whereby different forms of bLf were added to the cells during different phases of viral infection. Results obtained showed that bLf was able to prevent influenza virus cytopathic effects when incubated with the cells after the adsorption step, independently from ion saturation or carbohydrate content. Moreover, the influence of iron saturations or sialic acid/carbohydrates removal on bLf activity on the early phases of infection has been observed. Our results provide further insights on the antiviral activity of bLf and suggest novel strategies for treatment of influenza virus infection.

scholarly journals Plasmid-only rescue of influenza A virus vaccine candidates

2001 ◽  
Vol 356 (1416) ◽  
pp. 1965-1973 ◽  
Author(s):  
J. H. Schickli ◽  
A. Flandorfer ◽  
T. Nakaya ◽  
L. Martinez-Sobrido ◽  
A. Garcia-Sastre ◽  
...  
Keyword(s):  
Influenza Virus ◽  
Influenza A ◽  
Reverse Genetics ◽  
Genetic Manipulation ◽  
Influenza Viruses ◽  
High Yield ◽  
Ns1 Protein ◽  
Potential Threat ◽  
Rescue System ◽  
Rapid Generation

The potential threat of another influenza virus pandemic stimulates discussion on how to prepare for such an event. The most reasonable prophylactic approach appears to be the use of effective vaccines. Since influenza and other negative–stranded RNA viruses are amenable to genetic manipulation using transfection by plasmids, it is possible to outline new reverse genetics–based approaches for vaccination against influenza viruses. We suggest three approaches. First, we use a plasmid–only rescue system that allows the rapid generation of high–yield recombinant vaccine strains. Second, we propose developing second–generation live influenza virus vaccines by constructing an attenuated master strain with deletions in the NS1 protein, which acts as an interferon antagonist. Third, we suggest the use of Newcastle disease virus recombinants expressing influenza virus haemagglutinin proteins of pandemic (epizootic) strains as novel vaccine vectors for use in animals and possibly humans.

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