scholarly journals Key Role of the Influenza A Virus PA Gene Segment in the Emergence of Pandemic Viruses

Viruses ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 365 ◽  
Author(s):  
Michael M. Lutz ◽  
Megan M. Dunagan ◽  
Yuki Kurebayashi ◽  
Toru Takimoto
Keyword(s):  
Mammalian Cells ◽  
Influenza A ◽  
Gene Segment ◽  
Polymerase Activity ◽  
Influenza A Viruses ◽  
Adaptive Mutations ◽  
Natural Reservoir ◽  
Wide Range ◽  
Seasonal Epidemics

Influenza A viruses (IAVs) are a significant human pathogen that cause seasonal epidemics and occasional pandemics. Avian waterfowl are the natural reservoir of IAVs, but a wide range of species can serve as hosts. Most IAV strains are adapted to one host species and avian strains of IAV replicate poorly in most mammalian hosts. Importantly, IAV polymerases from avian strains function poorly in mammalian cells but host adaptive mutations can restore activity. The 2009 pandemic H1N1 (H1N1pdm09) virus acquired multiple mutations in the PA gene that activated polymerase activity in mammalian cells, even in the absence of previously identified host adaptive mutations in other polymerase genes. These mutations in PA localize within different regions of the protein suggesting multiple mechanisms exist to activate polymerase activity. Additionally, an immunomodulatory protein, PA-X, is expressed from the PA gene segment. PA-X expression is conserved amongst many IAV strains but activity varies between viruses specific for different hosts, suggesting that PA-X also plays a role in host adaptation. Here, we review the role of PA in the emergence of currently circulating H1N1pdm09 viruses and the most recent studies of host adaptive mutations in the PA gene that modulate polymerase activity and PA-X function.

scholarly journals PB2 Residue 271 Plays a Key Role in Enhanced Polymerase Activity of Influenza A Viruses in Mammalian Host Cells

2010 ◽  
Vol 84 (9) ◽  
pp. 4395-4406 ◽  
Author(s):  
Kendra A. Bussey ◽  
Tatiana L. Bousse ◽  
Emily A. Desmet ◽  
Baek Kim ◽  
Toru Takimoto
Keyword(s):  
Mammalian Cells ◽  
Influenza A ◽  
Virus Titer ◽  
Polymerase Activity ◽  
Influenza Viruses ◽  
Host Cells ◽  
Mammalian Host ◽  
Influenza A Viruses ◽  
H5n1 Influenza ◽  
Avian Viruses

ABSTRACT The direct infection of humans with highly pathogenic avian H5N1 influenza viruses has suggested viral mutation as one mechanism for the emergence of novel human influenza A viruses. Although the polymerase complex is known to be a key component in host adaptation, mutations that enhance the polymerase activity of avian viruses in mammalian hosts are not fully characterized. The genomic comparison of influenza A virus isolates has identified highly conserved residues in influenza proteins that are specific to either human or avian viruses, including 10 residues in PB2. We characterized the activity of avian polymerase complexes containing avian-to-human mutations at these conserved PB2 residues and found that, in addition to the E627K mutation, the PB2 mutation T271A enhances polymerase activity in human cells. We confirmed the effects of the T271A mutation using recombinant WSN viruses containing avian NP and polymerase genes with wild-type (WT) or mutant PB2. The 271A virus showed enhanced growth compared to that of the WT in mammalian cells in vitro. The 271A mutant did not increase viral pathogenicity significantly in mice compared to that of the 627K mutant, but it did enhance the lung virus titer. Also, cell infiltration was more evident in lungs of 271A-infected mice than in those of the WT. Interestingly, the avian-derived PB2 of the 2009 pandemic H1N1 influenza virus has 271A. The characterization of the polymerase activity of A/California/04/2009 (H1N1) and corresponding PB2 mutants indicates that the high polymerase activity of the pandemic strain in mammalian cells is, in part, dependent on 271A. Our results clearly indicate the contribution of PB2 amino acid 271 to enhanced polymerase activity and viral growth in mammalian hosts.

scholarly journals Adaptive Mutations in Influenza A/California/07/2009 Enhance Polymerase Activity and Infectious Virion Production

2018 ◽  
Author(s):  
Patrick D. Slaine ◽  
Cara MacRae ◽  
Mariel Kleer ◽  
Emily Lamoureux ◽  
Sarah McAlpine ◽  
...  
Keyword(s):  
Influenza A ◽  
Serial Passage ◽  
Polymerase Activity ◽  
Influenza A Viruses ◽  
Adaptation Studies ◽  
Adaptive Mutations ◽  
Susceptibility To Infection ◽  
Natural Hosts ◽  
2009 H1n1 ◽  
Polymerase Basic 1

Mice are not natural hosts for influenza A viruses (IAVs), but they are useful models for studying antiviral immune responses and pathogenesis. Serial passage of IAV in mice invariably causes the emergence of adaptive mutations and increased virulence. Typically, mouse-adaptation studies are conducted in inbred laboratory strains BALB/c and C57BL/6, which have defects in the antiviral Mx1 gene that results in increased susceptibility to infection and disease severity. Here, we report the adaptation of IAV reference strain A/California/07/2009(H1N1) (a.k.a. CA/07) in outbred Swiss Webster mice. Serial passage led to increased virulence and lung titers, and dissemination of the virus to brains. We adapted a deep-sequencing protocol to identify and enumerate adaptive mutations across all genome segments. Among mutations that emerged during mouse-adaptation, we focused on amino acid substitutions in polymerase subunits: polymerase basic-1 (PB1) T156A and F740L, and polymerase acidic (PA) E349G. These mutations were evaluated singly and in combination in minigenome replicon assays, which revealed that PA E349G increased polymerase activity. By selectively engineering these three adaptive PB1 and PA mutations into the parental CA/07 strain, we demonstrated that adaptive mutations in polymerase subunits decreased the production of defective viral genome segments with internal deletions, and dramatically increased the release of infectious virions from mouse cells. Together, these findings increase our understanding of the contribution of polymerase subunits to successful host adaptation.

scholarly journals Influenza: An Emerging and Re-emerging Public Health Threat in Nepal

2018 ◽  
Vol 3 (2) ◽  
pp. 1-2
Author(s):  
Bishnu Prasad Upadhyay
Keyword(s):  
Influenza Virus ◽  
Influenza A ◽  
Winter Season ◽  
Emerging Infectious Diseases ◽  
Influenza Viruses ◽  
Influenza B ◽  
Influenza A Viruses ◽  
Influenza A H1n1 ◽  
New Variant ◽  
Seasonal Epidemics

Influenza virus type A and B are responsible for seasonal epidemics as well as pandemics in human. Influenza A viruses are further divided into two major groups namely, low pathogenic seasonal influenza (A/H1N1, A/H1N1 pdm09, A/H3N2) and highly pathogenic influenza virus (H5N1, H5N6, H7N9) on the basis of two surface antigens: hemagglutinin (HA) and neuraminidase (NA). Mutations, including substitutions, deletions, and insertions, are one of the most important mechanisms for producing new variant of influenza viruses. During the last 30 years; more than 50 viral threat has been evolved in South-East Asian countriesof them influenza is one of the major emerging and re-emerging infectious diseases of global concern. Similar to tropical and sub-tropical countries of Southeast Asia; circulation of A/H1N1 pdm09, A/H3N2 and influenza B has been circulating throughout the year with the peak during July-November in Nepal. However; the rate of infection transmission reach peak during the post-rain and winter season of Nepal.

Host-cell dependent role of phosphorylated keratin 8 during influenza A/NWS/33 virus (H1N1) infection in mammalian cells

2021 ◽  
Vol 295 ◽  
pp. 198333
Author(s):  
Flora De Conto ◽  
Francesca Conversano ◽  
Sergey V. Razin ◽  
Silvana Belletti ◽  
Maria Cristina Arcangeletti ◽  
...  
Keyword(s):  
Host Cell ◽  
Mammalian Cells ◽  
Influenza A ◽  
Virus H1n1 ◽  
H1n1 Infection ◽  
Keratin 8

scholarly journals Plasticity of the Influenza Virus H5 HA Protein

mBio ◽  
2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Huihui Kong ◽  
David F. Burke ◽  
Tiago Jose da Silva Lopes ◽  
Kosuke Takada ◽  
Masaki Imai ◽  
...  
Keyword(s):  
Influenza Virus ◽  
Amino Acid ◽  
Mammalian Cells ◽  
Influenza A ◽  
Viral Antigen ◽  
Influenza Viruses ◽  
Influenza A Viruses ◽  
Highly Pathogenic ◽  
Antigenic Properties ◽  
Ha Protein

ABSTRACT Since the emergence of highly pathogenic avian influenza viruses of the H5 subtype, the major viral antigen, hemagglutinin (HA), has undergone constant evolution, resulting in numerous genetic and antigenic (sub)clades. To explore the consequences of amino acid changes at sites that may affect the antigenicity of H5 viruses, we simultaneously mutated 17 amino acid positions of an H5 HA by using a synthetic gene library that, theoretically, encodes all combinations of the 20 amino acids at the 17 positions. All 251 mutant viruses sequenced possessed ≥13 amino acid substitutions in HA, demonstrating that the targeted sites can accommodate a substantial number of mutations. Selection with ferret sera raised against H5 viruses of different clades resulted in the isolation of 39 genotypes. Further analysis of seven variants demonstrated that they were antigenically different from the parental virus and replicated efficiently in mammalian cells. Our data demonstrate the substantial plasticity of the influenza virus H5 HA protein, which may lead to novel antigenic variants. IMPORTANCE The HA protein of influenza A viruses is the major viral antigen. In this study, we simultaneously introduced mutations at 17 amino acid positions of an H5 HA expected to affect antigenicity. Viruses with ≥13 amino acid changes in HA were viable, and some had altered antigenic properties. H5 HA can therefore accommodate many mutations in regions that affect antigenicity. The substantial plasticity of H5 HA may facilitate the emergence of novel antigenic variants.

scholarly journals Characterization of Subtype H6 Avian Influenza A Viruses Isolated From Wild Birds in Poyang Lake, China

2021 ◽  
Vol 8 ◽  
Author(s):  
Zhimin Wan ◽  
Qiuqi Kan ◽  
Zhehong Zhao ◽  
Hongxia Shao ◽  
Thomas J. Deliberto ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Avian Influenza ◽  
Mammalian Cells ◽  
Influenza A ◽  
Poyang Lake ◽  
Wild Birds ◽  
Mouse Lung ◽  
Influenza A Viruses ◽  
Domestic Poultry ◽  
History Of

Subtype H6 avian influenza A viruses (IAVs) are enzootic and genetically diverse in both domestic poultry and wild waterfowl and may cause spillovers in both pigs and humans. Thus, it is important to understand the genetic diversity of H6 IAVs in birds and their zoonotic potential. Compared with that in domestic poultry, the genetic diversity of H6 viruses in wild birds in China has not been well-understood. In this study, five H6 viruses were isolated from wild birds in Poyang Lake, China, and genetic analyses showed that these isolates are clustered into four genotypes associated with reassortments among avian IAVs from domestic poultry and wild birds in China and those from Eurasia and North America and that these viruses exhibited distinct phenotypes in growth kinetics analyses with avian and mammalian cells lines and in mouse challenge experiments. Of interest is that two H6 isolates from the Eurasian teal replicated effectively in the mouse lung without prior adaptation, whereas the other three did not. Our study suggested that there are variations in the mammalian viral replication efficiency phenotypic among genetically diverse H6 IAVs in wild birds and that both intra- and inter-continental movements of IAVs through wild bird migration may facilitate the emergence of novel H6 IAV reassortants with the potential for replicating in mammals, including humans. Continued surveillance to monitor the diversity of H6 IAVs in wild birds is necessary to increase our understanding of the natural history of IAVs.

ViDiT–CACTUS: an inexpensive and versatile library preparation and sequence analysis method for virus discovery and other microbiology applications

2018 ◽  
Vol 64 (10) ◽  
pp. 761-773 ◽  
Author(s):  
Joost T.P. Verhoeven ◽  
Marta Canuti ◽  
Hannah J. Munro ◽  
Suzanne C. Dufour ◽  
Andrew S. Lang
Keyword(s):  
Influenza A ◽  
High Throughput Sequencing ◽  
Low Cost ◽  
Quality Data ◽  
Library Preparation ◽  
Virus Discovery ◽  
Influenza A Viruses ◽  
Wide Range ◽  
Functional Profiling ◽  
Biology Laboratory

High-throughput sequencing (HTS) technologies are becoming increasingly important within microbiology research, but aspects of library preparation, such as high cost per sample or strict input requirements, make HTS difficult to implement in some niche applications and for research groups on a budget. To answer these necessities, we developed ViDiT, a customizable, PCR-based, extremely low-cost (less than US$5 per sample), and versatile library preparation method, and CACTUS, an analysis pipeline designed to rely on cloud computing power to generate high-quality data from ViDiT-based experiments without the need of expensive servers. We demonstrate here the versatility and utility of these methods within three fields of microbiology: virus discovery, amplicon-based viral genome sequencing, and microbiome profiling. ViDiT–CACTUS allowed the identification of viral fragments from 25 different viral families from 36 oropharyngeal–cloacal swabs collected from wild birds, the sequencing of three almost complete genomes of avian influenza A viruses (>90% coverage), and the characterization and functional profiling of the complete microbial diversity (bacteria, archaea, viruses) within a deep-sea carnivorous sponge. ViDiT–CACTUS demonstrated its validity in a wide range of microbiology applications, and its simplicity and modularity make it easily implementable in any molecular biology laboratory, towards various research goals.

Characterization of proteins with Siaα2-3/6Gal-linked glycans from bovine milk and role of their glycans against influenza A virus

2018 ◽  
Vol 9 (10) ◽  
pp. 5198-5208 ◽  
Author(s):  
Hanjie Yu ◽  
Yaogang Zhong ◽  
Zhiwei Zhang ◽  
Xiawei Liu ◽  
Kun Zhang ◽  
...  
Keyword(s):  
Influenza A Virus ◽  
Influenza A ◽  
Bovine Milk ◽  
Milk Proteins ◽  
Biological Functions ◽  
Wide Range ◽  
Range Of Functions ◽  
Bovine Milk Proteins

The bovine milk proteins have a wide range of functions, but the role of the attached glycans in their biological functions has not been fully understood yet.

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.

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