The influenza virus PB1-F2 protein has interferon antagonistic activity

2011 ◽  
Vol 392 (12) ◽  
pp. 1135-1144 ◽  
Author(s):  
Sabine E. Dudek ◽  
Ludmilla Wixler ◽  
Carolin Nordhoff ◽  
Alexandra Nordmann ◽  
Darisuren Anhlan ◽  
...  
Keyword(s):  
Influenza A ◽  
Molecular Mechanisms ◽  
Nonstructural Protein ◽  
Gene Segment ◽  
Antagonistic Activity ◽  
Influenza Viruses ◽  
Type I ◽  
Influenza A Viruses ◽  
Reading Frame

Abstract PB1-F2 is a nonstructural protein of influenza viruses encoded by the PB1 gene segment from a +1 open reading frame. It has been shown that PB1-F2 contributes to viral pathogenicity, although the underlying mechanisms are still unclear. Induction of type I interferon (IFN) and the innate immune response are the first line of defense against viral infection. Here we show that influenza A viruses (IAVs) lacking the PB1-F2 protein induce an enhanced expression of IFN-β and IFN-stimulated genes in infected epithelial cells. Studying molecular mechanisms underlying the PB1-F2-mediated IFN antagonistic activity showed that PB1-F2 interferes with the RIG-I/MAVS protein complex thereby inhibiting the activation of the downstream transcription factor IFN regulatory factor 3. These findings were also reflected in in vivo studies demonstrating that infection with PR8 wild-type (wt) virus resulted in higher lung titers and a more severe onset of disease compared with infection with its PB1-F2-deficient counterpart. Accordingly, a much more pronounced infiltration of lungs with immune cells was detected in mice infected with the PB1-F2 wt virus. In summary, we demonstrate that the PB1-F2 protein of IAVs exhibits a type I IFN-antagonistic function by interfering with the RIG-I/MAVS complex, which contributes to an enhanced pathogenicity in vivo.

scholarly journals Non-Uniform and Non-Random Binding of Nucleoprotein to Influenza A and B Viral RNA

Viruses ◽  
2018 ◽  
Vol 10 (10) ◽  
pp. 522 ◽  
Author(s):  
Valerie Le Sage ◽  
Adalena Nanni ◽  
Amar Bhagwat ◽  
Dan Snyder ◽  
Vaughn Cooper ◽  
...  
Keyword(s):  
Influenza A ◽  
Gene Segment ◽  
Influenza Viruses ◽  
Viral Rna ◽  
Influenza B Virus ◽  
Viral Gene ◽  
Influenza B ◽  
Influenza A Viruses ◽  
Binding Profile ◽  
Random Manner

The genomes of influenza A and B viruses have eight, single-stranded RNA segments that exist in the form of a viral ribonucleoprotein complex in association with nucleoprotein (NP) and an RNA-dependent RNA polymerase complex. We previously used high-throughput RNA sequencing coupled with crosslinking immunoprecipitation (HITS-CLIP) to examine where NP binds to the viral RNA (vRNA) and demonstrated for two H1N1 strains that NP binds vRNA in a non-uniform, non-random manner. In this study, we expand on those initial observations and describe the NP-vRNA binding profile for a seasonal H3N2 and influenza B virus. We show that, similar to H1N1 strains, NP binds vRNA in a non-uniform and non-random manner. Each viral gene segment has a unique NP binding profile with areas that are enriched for NP association as well as free of NP-binding. Interestingly, NP-vRNA binding profiles have some conservation between influenza A viruses, H1N1 and H3N2, but no correlation was observed between influenza A and B viruses. Our study demonstrates the conserved nature of non-uniform NP binding within influenza viruses. Mapping of the NP-bound vRNA segments provides information on the flexible NP regions that may be involved in facilitating assembly.

scholarly journals Influenza A Virus Inhibits RSV Infection via a Two-Wave Expression of IFIT Proteins

Viruses ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 1171
Author(s):  
Yaron Drori ◽  
Jasmine Jacob-Hirsch ◽  
Rakefet Pando ◽  
Aharona Glatman-Freedman ◽  
Nehemya Friedman ◽  
...  
Keyword(s):  
Influenza A Virus ◽  
Influenza A ◽  
Influenza Viruses ◽  
Mass Spectrometry Analysis ◽  
Influenza A Viruses ◽  
Rsv Infection ◽  
Syncytial Virus ◽  
Mouse Lungs

Influenza viruses and respiratory syncytial virus (RSV) are respiratory viruses that primarily circulate worldwide during the autumn and winter seasons. Seasonal surveillance has shown that RSV infection generally precedes influenza. However, in the last four winter seasons (2016–2020) an overlap of the morbidity peaks of both viruses was observed in Israel, and was paralleled by significantly lower RSV infection rates. To investigate whether the influenza A virus inhibits RSV, human cervical carcinoma (HEp2) cells or mice were co-infected with influenza A and RSV. Influenza A inhibited RSV growth, both in vitro and in vivo. Mass spectrometry analysis of mouse lungs infected with influenza A identified a two-wave pattern of protein expression upregulation, which included members of the interferon-induced protein with the tetratricopeptide (IFITs) family. Interestingly, in the second wave, influenza A viruses were no longer detectable in mouse lungs. In addition, knockdown and overexpression of IFITs in HEp2 cells affected RSV multiplicity. In conclusion, influenza A infection inhibits RSV infectivity via upregulation of IFIT proteins in a two-wave modality. Understanding the immune system involvement in the interaction between influenza A and RSV viruses will contribute to the development of future treatment strategies against these viruses.

IFN-κ suppresses the replication of influenza A viruses through the IFNAR-MAPK-Fos-CHD6 axis

2020 ◽  
Vol 13 (626) ◽  
pp. eaaz3381 ◽  
Author(s):  
Yongquan He ◽  
Weihui Fu ◽  
Kangli Cao ◽  
Qian He ◽  
Xiangqing Ding ◽  
...  
Keyword(s):  
Influenza A Virus ◽  
Influenza A ◽  
Influenza Viruses ◽  
Mitogen Activated Protein Kinase ◽  
Type I Interferons ◽  
Type I ◽  
Influenza A Viruses ◽  
Human Lung Cells ◽  
Avian Influenza A Virus ◽  
Factor C

Type I interferons (IFNs) are the first line of defense against viral infection. Using a mouse model of influenza A virus infection, we found that IFN-κ was one of the earliest responding type I IFNs after infection with H9N2, a low-pathogenic avian influenza A virus, whereas this early induction did not occur upon infection with the epidemic-causing H7N9 virus. IFN-κ efficiently suppressed the replication of various influenza viruses in cultured human lung cells, and chromodomain helicase DNA binding protein 6 (CHD6) was the major effector for the antiviral activity of IFN-κ, but not for that of IFN-α or IFN-β. The induction of CHD6 required both of the type I IFN receptor subunits IFNAR1 and IFNAR2, the mitogen-activated protein kinase (MAPK) p38, and the transcription factor c-Fos but was independent of signal transducer and activator of transcription 1 (STAT1) activity. In addition, we showed that pretreatment with IFN-κ protected mice from lethal influenza viral challenge. Together, our findings identify an IFN-κ–specific pathway that constrains influenza A virus and provide evidence that IFN-κ may have potential as a preventative and therapeutic agent against influenza A virus.

scholarly journals Molecular basis of mammalian transmissibility of avian H1N1 influenza viruses and their pandemic potential

2017 ◽  
Vol 114 (42) ◽  
pp. 11217-11222 ◽  
Author(s):  
Mark Zanin ◽  
Sook-San Wong ◽  
Subrata Barman ◽  
Challika Kaewborisuth ◽  
Peter Vogel ◽  
...  
Keyword(s):  
Genetic Markers ◽  
Nuclear Export ◽  
Influenza A ◽  
Nonstructural Protein ◽  
H1n1 Influenza ◽  
Influenza Viruses ◽  
Upper Respiratory Tract ◽  
Influenza A Viruses ◽  
Airborne Transmission ◽  
Nonstructural Protein 1

North American wild birds are an important reservoir of influenza A viruses, yet the potential of viruses in this reservoir to transmit and cause disease in mammals is not well understood. Our surveillance of avian influenza viruses (AIVs) at Delaware Bay, USA, revealed a group of similar H1N1 AIVs isolated in 2009, some of which were airborne-transmissible in the ferret model without prior adaptation. Comparison of the genomes of these viruses revealed genetic markers of airborne transmissibility in the Polymerase Basic 2 (PB2), PB1, PB1-F2, Polymerase Acidic-X (PA-X), Nonstructural Protein 1 (NS1), and Nuclear Export Protein (NEP) genes. We studied the role of NS1 in airborne transmission and found that NS1 mutants that were not airborne-transmissible caused limited tissue pathology in the upper respiratory tract (URT). Viral maturation was also delayed, evident as strong intranuclear staining and little virus at the mucosa. Our study of this naturally occurring constellation of genetic markers has provided insights into the poorly understood phenomenon of AIV airborne transmissibility by revealing a role for NS1 and characteristics of viral replication in the URT that were associated with airborne transmission. The transmissibility of these viruses further highlights the pandemic potential of AIVs in the wild bird reservoir and the need to maintain surveillance.

scholarly journals Defective interfering influenza A virus protects in vivo against disease caused by a heterologous influenza B virus

2011 ◽  
Vol 92 (9) ◽  
pp. 2122-2132 ◽  
Author(s):  
Paul D. Scott ◽  
Bo Meng ◽  
Anthony C. Marriott ◽  
Andrew J. Easton ◽  
Nigel J. Dimmock
Keyword(s):  
Influenza A Virus ◽  
Influenza A ◽  
Influenza Viruses ◽  
Influenza B Virus ◽  
Influenza B ◽  
Type I ◽  
Type I Ifn ◽  
B Virus ◽  
The Family

Influenza A and B viruses are major human respiratory pathogens that contribute to the burden of seasonal influenza. They are both members of the family Orthomyxoviridae but do not interact genetically and are classified in different genera. Defective interfering (DI) influenza viruses have a major deletion of one or more of their eight genome segments, which renders them both non-infectious and able to interfere in cell culture with the production of infectious progeny by a genetically compatible, homologous virus. It has been shown previously that intranasal administration of a cloned DI influenza A virus, 244/PR8, protects mice from various homologous influenza A virus subtypes and that it also protects mice from respiratory disease caused by a heterologous virus belonging to the family Paramyxoviridae. The mechanisms of action in vivo differ, with homologous and heterologous protection being mediated by probable genome competition and type I interferon (IFN), respectively. In the current study, it was shown that 244/PR8 also protects against disease caused by a heterologous influenza B virus (B/Lee/40). Protection from B/Lee/40 challenge was partially eliminated in mice that did not express a functional type I IFN receptor, suggesting that innate immunity, and type I IFN in particular, are important in mediating protection against this virus. It was concluded that 244/PR8 has the ability to protect in vivo against heterologous IFN-sensitive respiratory viruses, in addition to homologous influenza A viruses, and that it acts by fundamentally different mechanisms.

scholarly journals Attenuation and immunogenicity in mice of temperature-sensitive influenza viruses expressing truncated NS1 proteins

2005 ◽  
Vol 86 (10) ◽  
pp. 2817-2821 ◽  
Author(s):  
Ana M. Falcón ◽  
Ana Fernandez-Sesma ◽  
Yurie Nakaya ◽  
Thomas M. Moran ◽  
Juan Ortín ◽  
...  
Keyword(s):  
Influenza A ◽  
Influenza Viruses ◽  
Wild Type Virus ◽  
Temperature Sensitive ◽  
Ns1 Protein ◽  
Wild Type ◽  
Influenza A Viruses ◽  
Lethal Challenge

It was previously shown that two mutant influenza A viruses expressing C-terminally truncated forms of the NS1 protein (NS1-81 and NS1-110) were temperature sensitive in vitro. These viruses contain HA, NA and M genes derived from influenza A/WSN/33 H1N1 virus (mouse-adapted), and the remaining five genes from human influenza A/Victoria/3/75 virus. Mice intranasally infected with the NS1 mutant viruses showed undetectable levels of virus in lungs at day 3, whereas those infected with the NS1 wild-type control virus still had detectable levels of virus at this time. Nevertheless, the temperature-sensitive mutant viruses induced specific cellular and humoral immune responses similar to those induced by the wild-type virus. Mice immunized with the NS1 mutant viruses were protected against a lethal challenge with influenza A/WSN/33 virus. These results indicate that truncations in the NS1 protein resulting in temperature-sensitive phenotypes in vitro correlate with attenuation in vivo without compromising viral immunogenicity, an ideal characteristic for live attenuated viral vaccines.

scholarly journals Targeting host calpain proteases decreases influenza A virus infection

2016 ◽  
Vol 310 (7) ◽  
pp. L689-L699 ◽  
Author(s):  
Fany Blanc ◽  
Laetitia Furio ◽  
Dorothée Moisy ◽  
Hui-Ling Yen ◽  
Michel Chignard ◽  
...  
Keyword(s):  
Influenza A ◽  
Molecular Mechanisms ◽  
Influenza A Viruses ◽  
Host Immune Responses ◽  
Proinflammatory Mediators ◽  
Acute Respiratory Diseases ◽  
Calpain Inhibition ◽  
Interfering Rna

Influenza A viruses (IAV) trigger contagious acute respiratory diseases. A better understanding of the molecular mechanisms of IAV pathogenesis and host immune responses is required for the development of more efficient treatments of severe influenza. Calpains are intracellular proteases that participate in diverse cellular responses, including inflammation. Here, we used in vitro and in vivo approaches to investigate the role of calpain signaling in IAV pathogenesis. Calpain expression and activity were found altered in IAV-infected bronchial epithelial cells. With the use of small-interfering RNA (siRNA) gene silencing, specific synthetic inhibitors of calpains, and mice overexpressing calpastatin, we found that calpain inhibition dampens IAV replication and IAV-triggered secretion of proinflammatory mediators and leukocyte infiltration. Remarkably, calpain inhibition has a protective impact in IAV infection, since it significantly reduced mortality of mice challenged not only by seasonal H3N2- but also by hypervirulent H5N1 IAV strains. Hence, our study suggests that calpains are promising therapeutic targets for treating IAV acute pneumonia.

scholarly journals Genotypic Variants of Pandemic H1N1 Influenza A Viruses Isolated from Severe Acute Respiratory Infections in Ukraine during the 2015/16 Influenza Season

Viruses ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 2125
Author(s):  
Oksana Zolotarova ◽  
Anna Fesenko ◽  
Olga Holubka ◽  
Larysa Radchenko ◽  
Eric Bortz ◽  
...  
Keyword(s):  
Influenza A ◽  
Rna Binding ◽  
Respiratory Infections ◽  
Nonstructural Protein ◽  
Antigenic Site ◽  
Influenza Viruses ◽  
Influenza A Viruses ◽  
Epidemic Season ◽  
Nonstructural Protein 1 ◽  
Increased Risk

Human type A influenza viruses A(H1N1)pdm09 have caused seasonal epidemics of influenza since the 2009–2010 pandemic. A(H1N1)pdm09 viruses had a leading role in the severe epidemic season of 2015/16 in the Northern Hemisphere and caused a high incidence of acute respiratory infection (ARI) in Ukraine. Serious complications of influenza-associated severe ARI (SARI) were observed in the very young and individuals at increased risk, and 391 fatal cases occurred in the 2015/16 epidemic season. We analyzed the genetic changes in the genomes of A(H1N1)pdm09 influenza viruses isolated from SARI cases in Ukraine during the 2015/16 season. The viral hemagglutinin (HA) fell in H1 group 6B.1 for all but four isolates, with known mutations affecting glycosylation, the Sa antigenic site (S162N in all 6B.1 isolates), or virulence (D222G/N in two isolates). Other mutations occurred in antigenic site Ca (A141P and S236P), and a subgroup of four strains were in group 6B.2, with potential alterations to antigenicity in A(H1N1)pdm09 viruses circulating in 2015/16 in Ukraine. A cluster of Ukrainian isolates exhibited novel D2E and N48S mutations in the RNA binding domain, and E125D in the effector domain, of immune evasion nonstructural protein 1 (NS1). The diverse spectrum of amino-acid substitutions in HA, NS1, and other viral proteins including nucleoprotein (NP) and the polymerase complex suggested the concurrent circulation of multiple lineages of A(H1N1)pdm09 influenza viruses in the human population in Ukraine, a country with low vaccination coverage, complicating public health measures against influenza.

scholarly journals In vivo evasion of MxA by avian influenza viruses requires human signature in the viral nucleoprotein

2017 ◽  
Vol 214 (5) ◽  
pp. 1239-1248 ◽  
Author(s):  
Christoph M. Deeg ◽  
Ebrahim Hassan ◽  
Pascal Mutz ◽  
Lara Rheinemann ◽  
Veronika Götz ◽  
...  
Keyword(s):  
Avian Influenza ◽  
Transgenic Mice ◽  
Influenza A ◽  
Influenza Viruses ◽  
Influenza A Viruses ◽  
Avian Influenza Viruses ◽  
Species Barrier ◽  
Human Virus ◽  
Adaptive Mutations

Zoonotic transmission of influenza A viruses can give rise to devastating pandemics, but currently it is impossible to predict the pandemic potential of circulating avian influenza viruses. Here, we describe a new mouse model suitable for such risk assessment, based on the observation that the innate restriction factor MxA represents an effective species barrier that must be overcome by zoonotic viruses. Our mouse lacks functional endogenous Mx genes but instead carries the human MX1 locus as a transgene. Such transgenic mice were largely resistant to highly pathogenic avian H5 and H7 influenza A viruses, but were almost as susceptible to infection with influenza viruses of human origin as nontransgenic littermates. Influenza A viruses that successfully established stable lineages in humans have acquired adaptive mutations which allow partial MxA escape. Accordingly, an engineered avian H7N7 influenza virus carrying a nucleoprotein with signature mutations typically found in human virus isolates was more virulent in transgenic mice than parental virus, demonstrating that a few amino acid changes in the viral target protein can mediate escape from MxA restriction in vivo. Similar mutations probably need to be acquired by emerging influenza A viruses before they can spread in the human population.

scholarly journals An influenza reassortant with polymerase of pH1N1 and NS gene of H3N2 influenza A virus is attenuated in vivo

2012 ◽  
Vol 93 (5) ◽  
pp. 998-1006 ◽  
Author(s):  
Holly Shelton ◽  
Matt Smith ◽  
Lorian Hartgroves ◽  
Peter Stilwell ◽  
Kim Roberts ◽  
...  
Keyword(s):  
Influenza A Virus ◽  
Influenza A ◽  
Mdck Cells ◽  
Gene Segment ◽  
Influenza Viruses ◽  
Interferon Response ◽  
H3n2 Virus ◽  
M Gene ◽  
Ns Gene

Influenza viruses readily mutate by accumulating point mutations and also by reassortment in which they acquire whole gene segments from another virus in a co-infected host. The NS1 gene is a major virulence factor of influenza A virus. The effects of changes in NS1 sequence depend on the influenza polymerase constellation. Here, we investigated the consequences of a virus with the polymerase of pandemic H1N1 2009 acquiring an NS gene segment derived from a seasonal influenza A H3N2 virus, a combination that might arise during natural reassortment of viruses that currently circulate in humans. We generated recombinant influenza viruses with surface HA and NA genes and matrix M gene segment from A/PR/8/34 virus, but different combinations of polymerase and NS genes. Thus, any changes in phenotype were not due to differences in receptor use, entry, uncoating or virus release. In Madin–Darby canine kidney (MDCK) cells, the virus with the NS gene from the H3N2 parent showed enhanced replication, probably a result of increased control of the interferon response. However, in mice the same virus was attenuated in comparison with the virus containing homologous pH1N1 polymerase and NS genes. Levels of viral RNA during single-cycles of replication were lower for the virus with H3N2 NS, and this virus reached lower titres in the lungs of infected mice. Thus, virus with pH1N1 polymerase genes did not increase its virulence by acquiring the H3N2 NS gene segment, and MDCK cells were a poor predictor of the outcome of infection in vivo.

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