Comparative Analyses of N-Glycosylation Profiles of Influenza A Viruses Grown in Different Host Cells

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.

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Influenza Hemagglutinin (HA) Stem Region Mutations That Stabilize or Destabilize the Structure of Multiple HA Subtypes

Journal of Virology ◽

10.1128/jvi.00057-15 ◽

2015 ◽

Vol 89 (8) ◽

pp. 4504-4516 ◽

Cited By ~ 26

Author(s):

Lauren Byrd-Leotis ◽

Summer E. Galloway ◽

Evangeline Agbogu ◽

David A. Steinhauer

Keyword(s):

Membrane Fusion ◽

Receptor Binding ◽

Conformational Changes ◽

Influenza A ◽

Mutational Analysis ◽

Host Cells ◽

Influenza A Viruses ◽

Pathogenic Potential ◽

Additional Tool ◽

Improved Stability

ABSTRACTInfluenza A viruses enter host cells through endosomes, where acidification induces irreversible conformational changes of the viral hemagglutinin (HA) that drive the membrane fusion process. The prefusion conformation of the HA is metastable, and the pH of fusion can vary significantly among HA strains and subtypes. Furthermore, an accumulating body of evidence implicates HA stability properties as partial determinants of influenza host range, transmission phenotype, and pathogenic potential. Although previous studies have identified HA mutations that can affect HA stability, these have been limited to a small selection of HA strains and subtypes. Here we report a mutational analysis of HA stability utilizing a panel of expressed HAs representing a broad range of HA subtypes and strains, including avian representatives across the phylogenetic spectrum and several human strains. We focused on two highly conserved residues in the HA stem region: HA2 position 58, located at the membrane distal tip of the short helix of the hairpin loop structure, and HA2 position 112, located in the long helix in proximity to the fusion peptide. We demonstrate that a K58I mutation confers an acid-stable phenotype for nearly all HAs examined, whereas a D112G mutation consistently leads to elevated fusion pH. The results enhance our understanding of HA stability across multiple subtypes and provide an additional tool for risk assessment for circulating strains that may have other hallmarks of human adaptation. Furthermore, the K58I mutants, in particular, may be of interest for potential use in the development of vaccines with improved stability profiles.IMPORTANCEThe influenza A hemagglutinin glycoprotein (HA) mediates the receptor binding and membrane fusion functions that are essential for virus entry into host cells. While receptor binding has long been recognized for its role in host species specificity and transmission, membrane fusion and associated properties of HA stability have only recently been appreciated as potential determinants. We show here that mutations can be introduced at highly conserved positions to stabilize or destabilize the HA structure of multiple HA subtypes, expanding our knowledge base for this important phenotype. The practical implications of these findings extend to the field of vaccine design, since the HA mutations characterized here could potentially be utilized across a broad spectrum of influenza virus subtypes to improve the stability of vaccine strains or components.

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Faculty Opinions recommendation of The epidermal growth factor receptor (EGFR) promotes uptake of influenza A viruses (IAV) into host cells.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.5680961.5653074 ◽

2010 ◽

Author(s):

Jeffrey Bergelson

Keyword(s):

Epidermal Growth Factor Receptor ◽

Growth Factor ◽

Epidermal Growth Factor ◽

Influenza A ◽

Growth Factor Receptor ◽

Host Cells ◽

Influenza A Viruses ◽

Epidermal Growth

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The epidermal growth factor receptor (EGFR) contributes to efficient entry of influenza A viruses into host cells

Cell Communication and Signaling ◽

10.1186/1478-811x-7-s1-a14 ◽

2009 ◽

Vol 7 (S1) ◽

Cited By ~ 2

Author(s):

T Eierhoff ◽

ER Hrincius ◽

U Rescher ◽

S Ludwig ◽

C Ehrhardt

Keyword(s):

Epidermal Growth Factor Receptor ◽

Growth Factor ◽

Epidermal Growth Factor ◽

Influenza A ◽

Growth Factor Receptor ◽

Host Cells ◽

Influenza A Viruses ◽

Epidermal Growth

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Ode to Oseltamivir and Amantadine?

Canadian Journal of Infectious Diseases and Medical Microbiology ◽

10.1155/2006/106989 ◽

2006 ◽

Vol 17 (1) ◽

pp. 11-14 ◽

Cited By ~ 5

Author(s):

JM Conly ◽

BL Johnston

Keyword(s):

Influenza A ◽

Antigenic Variation ◽

Interleukin 1 ◽

Influenza Viruses ◽

Host Cells ◽

Surface Glycoprotein ◽

Influenza B ◽

Influenza A Viruses ◽

Epidemic Disease ◽

Specific Antigens

Influenza A and B viruses are the two major types of influenza viruses that cause human epidemic disease. Influenza A viruses are further categorized into subtypes based on two surface antigens: hemagglutinin (H) and neuraminidase (N). Influenza B viruses are not categorized into subtypes (1). Influenza A viruses are found in many animal species, including humans, ducks, chickens, pigs, whales, horses and seals, whereas influenza B viruses circulate only among humans. The H antigen contains common and strain-specific antigens, demonstrates antigenic variation, and acts as a site of attachment of the virus to host cells to initiate infection (1). The N antigen contains subtype-specific antigens and also demonstrates antigenic variation between subtypes. It is a surface glycoprotein possessing enzymatic activity essential for viral replication in both influenza A and B viruses. The N antigen allows the release of newly produced virions from infected host cells, prevents the formation of viral aggregates after release from the host cells, and prevents viral inactivation by respiratory mucous (2,3). It is thought that this enzyme may also promote viral penetration into respiratory epithelial cells and may contribute to the pathogenicity of the virus by promoting production of proinflammatory cytokines such as interleukin-1 and tumour necrosis factor from macrophages (4-6).

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Influenza–Host Interplay and Strategies for Universal Vaccine Development

Vaccines ◽

10.3390/vaccines8030548 ◽

2020 ◽

Vol 8 (3) ◽

pp. 548

Author(s):

Hye Suk Hwang ◽

Mincheol Chang ◽

Yoong Ahm Kim

Keyword(s):

Influenza Virus ◽

Influenza A ◽

Vaccine Development ◽

Current Knowledge ◽

Host Cells ◽

Influenza A Viruses ◽

Universal Vaccine ◽

Lectin Receptors ◽

Endosomal Membrane ◽

Influenza Virus Hemagglutinin

Influenza is an annual epidemic and an occasional pandemic caused by pathogens that are responsible for infectious respiratory disease. Humans are highly susceptible to the infection mediated by influenza A viruses (IAV). The entry of the virus is mediated by the influenza virus hemagglutinin (HA) glycoprotein that binds to the cellular sialic acid receptors and facilitates the fusion of the viral membrane with the endosomal membrane. During IAV infection, virus-derived pathogen-associated molecular patterns (PAMPs) are recognized by host intracellular specific sensors including toll-like receptors (TLRs), C-type lectin receptors, retinoic acid-inducible gene-I (RIG-I)-like receptors (RLRs), and nucleotide-binding oligomerization domain (NOD)-like receptors (NLRs) either on the cell surface or intracellularly in endosomes. Herein, we comprehensively review the current knowledge available on the entry of the influenza virus into host cells and the molecular details of the influenza virus–host interface. We also highlight certain strategies for the development of universal influenza vaccines.

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Influenza’s Newest Trick

mBio ◽

10.1128/mbio.02854-19 ◽

2019 ◽

Vol 10 (6) ◽

Author(s):

Jeffery K. Taubenberger

Keyword(s):

Influenza A ◽

Rna Virus ◽

Surface Proteins ◽

Host Cells ◽

Influenza A Viruses ◽

Protease Activation ◽

Major Surface Proteins ◽

Major Surface ◽

Cleavage Motif

ABSTRACT Influenza A viruses are important pathogens for humans and for many birds and mammals. Hemagglutinin and neuraminidase are the major surface proteins of this enveloped RNA virus. Hemagglutinin requires proteolytic cleavage for activation, but because the viral genome does not encode its own protease, an exogenous serine protease must be provided by host cells. A novel, neuraminidase-dependent mechanism for hemagglutinin activation was described, in which a thrombin-like protease allows an influenza A/H7N6 virus, isolated from a mallard duck, to replicate systemically and induce enhanced disease in avian and mammalian model animals and to replicate in vitro in the absence of trypsin. Thrombin-like protease activation required the N6 neuraminidase, but also required the presence of a thrombin-like cleavage motif in the H7 hemagglutinin. This novel example of neuraminidase-dependent hemagglutinin activation demonstrates the extraordinary evolutionary flexibility of influenza A viruses and is a fascinating example of epistasis between the hemagglutinin and neuraminidase genes.

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Virucidal Activity of Moringa a From Moringa Oleifera Seeds Against Influenza A Viruses by Regulating TFEB

10.21203/rs.3.rs-135760/v1 ◽

2020 ◽

Author(s):

Yongai Xiong ◽

Muhammad Shahid Riaz Rajoka ◽

MengXun Zhang ◽

Ning Liang ◽

Zhendan He

Keyword(s):

Antiviral Activity ◽

Inflammatory Cytokines ◽

Influenza A ◽

Moringa Oleifera ◽

Cytopathic Effect ◽

Cellular Protein ◽

Host Cells ◽

Influenza A Viruses ◽

Different Types ◽

Infected Cells

Abstract BackgroundInfluenza A viruses (IAVs) are highly contagious pathogens infecting human and numerous animals. The viruses cause millions of infection cases and thousands of deaths every year, thus making IAVs a continual threat to global health. MethodsMoringa A was isolated from Moringa oleifera seeds and tested for antiviral activity against H1N1. The antiviral activity of Moringa A was tested by checking their effect on hemagglutination and PFU activities of the studied virus, and the cytopathic effect was observed too. Additionally, the different types of treatment experiments were performed to complement the analysis of the antiviral activity of Moringa A, and the contents of inflammatory cytokines and the expression of TFEB were detected.ResultsMoringa A inhibits virus replication in host cells, and it protects infected cells from cytopathic effect induced by IAVs. The EC50 and EC90 value of Moringa A for IAVs were 1.27 and 5.30 μM, respectively. The different types of treatment experiments revealed that Moringa A has a significant inhibitory effect on the IAVs both before and after drug addition. What’s more, Moringa A was observed to decrease the levels of inflammatory cytokines TNF-α, IL-6, IL-1β and IFN-β in H1N1 infected RAW264.7 cells. Finaly, Moringa A was found to inhibit the expression and nuclear transfer of the cellular protein transcription factor EB (TFEB), and weaken the autophagy in infected cells, which could be an important antiviral mechnism of Moringa A. ConclusionsMoringa A has potent antiviral activity against IVAs, which could be due to the autophagy inhibition property.

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Prevalence of PB1-F2 of influenza A viruses

Journal of General Virology ◽

10.1099/vir.0.82378-0 ◽

2007 ◽

Vol 88 (2) ◽

pp. 536-546 ◽

Cited By ~ 103

Author(s):

Roland Zell ◽

Andi Krumbholz ◽

Annett Eitner ◽

Reimar Krieg ◽

Karl-Jürgen Halbhuber ◽

...

Keyword(s):

Influenza A ◽

Molecular Genetic ◽

Swine Influenza ◽

Influenza Viruses ◽

Host Cells ◽

Genetic Lineage ◽

Mitochondrial Localization ◽

Influenza A Viruses ◽

Stop Codons ◽

And Function

PB1-F2 is a pro-apoptotic polypeptide of many influenza A virus (FLUAV) isolates encoded by an alternative ORF of segment 2. A comprehensive GenBank search was conducted to analyse its prevalence. This search yielded 2226 entries of 80 FLUAV subtypes. Of these sequences, 87 % encode a PB1-F2 polypeptide greater than 78 aa. However, classic swine influenza viruses and human H1N1 isolates collected since 1950 harbour a truncated PB1-F2 sequence. While PB1-F2 of human H1N1 viruses terminates after 57 aa, classic swine H1N1 sequences have in-frame stop codons after 11, 25 and 34 codons. Of the avian sequences, 96 % encode a full-length PB1-F2. One genetic lineage of segment 2 sequences which is avian-like and different from the classic swine FLUAV comprises PB1-F2 sequences of porcine FLUAVs isolated in Europe (H1N1, H1N2, H3N2). Of these PB1-F2 sequences, 42 % also exhibit stop codons after 11, 25 and 34 codons. These amino acid positions are highly conserved among all FLUAV isolates irrespective of their origin. Molecular genetic analyses reveal that PB1-F2 is under constraint of the PB1 gene. The PB1-F2 polypeptide of FLUAVs isolated from European pigs is expressed in host cells as demonstrated by immunohistochemistry. Using different PB1-F2 versions fused to an enhanced GFP, mitochondrial localization is demonstrated for those PB1-F2 polypeptides which are greater than 78 aa while a truncated version (57 aa) shows a diffuse cytoplasmic distribution. This indicates similar properties and function of porcine and human FLUAV PB1-F2.

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