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Latest Articles on Influenza

  • A multiplex real-time reverse transcription polymerase chain reaction assay for differentiation of classical and variant II strains of avian infectious bronchitis virus Thu, 29 Sep 2022 06:00:00 -0400
    Identification of avian infectious bronchitis virus (IBV) genotypes is essential for controlling infectious bronchitis (IB) disease, because vaccines that differ from the circulating strains might not provide efficient cross-protection. In Egypt, IBV strain typing is a difficult process, due to the widespread distribution of four genotype lineages (GI-13, GI-23, GI-1, and GI-16), which may contribute to IBV vaccination failure. In this study, we developed a multiplex real-time quantitative...
  • Influenza A Virus Neuraminidase Inhibitors Thu, 29 Sep 2022 06:00:00 -0400
    Depending on the strain, influenza A virus causes animal, zoonotic, pandemic, or seasonal influenza with varying degrees of severity. Two surface glycoprotein spikes, hemagglutinin (HA) and neuraminidase (NA), are the most important influenza A virus antigens. NA plays an important role in the propagation of influenza virus by removing terminal sialic acid from sialyl decoy receptors and thereby facilitating the release of viruses from traps such as in mucus and on infected cells. Some NA...
  • Synthesis and Neuraminidase Inhibitory Activity of Sialic Acid Analogues with Fluoro, Phosphono, and Sulfo Functionalities Thu, 29 Sep 2022 06:00:00 -0400
    Methods to synthesize influenza virus inhibitors with fluoro, phosphono, and/or sulfo functional groups are described. The resulting sialic acid analogues are produced from the natural substrate N-acetylneuraminic acid as starting material. Fluorescent assay methods for inhibition of influenza neuraminidase and virus proliferation are also provided.
  • Assays for Determining the Sialidase Activity of Influenza Viruses and Monitoring Influenza Virus Susceptibility to Neuraminidase Inhibitors Thu, 29 Sep 2022 06:00:00 -0400
    Three types of assays--colorimetric, fluorescent, and chemiluminescent--are used to determine the sialidase (neuraminidase: NA) activity of influenza viruses. The fluorescent assay is cost-effective and applicable for many laboratories and is, therefore, commonly used for global monitoring of the NA inhibitor susceptibility of influenza viruses. Here, I describe, in detail, protocols for the fluorescence-based NA activity assay and the NA inhibition assay, which are used to determine the NA...
  • Enzymatic Substrates and Fluorescence Imaging of Influenza Virus Sialidase Thu, 29 Sep 2022 06:00:00 -0400
    Immunostaining with an antiviral antibody is usually performed to visualize virus-infected cells. In contrast, this study established an easy method for fluorescence (FL) imaging of cells infected with influenza A and B viruses and some paramyxoviruses without the need for cell fixation and an antiviral antibody. These viruses and the cells they have infected express the viral surface enzymes "neuraminidase" or "hemagglutinin-neuraminidase," which show sialidase activity. Sialidase activity is...
  • Roles of Glycans and Non-glycans on the Epithelium and in the Immune System in H1-H18 Influenza A Virus Infections Thu, 29 Sep 2022 06:00:00 -0400
    The large variation of influenza A viruses (IAVs) in various susceptible hosts and their rapid evolution, which allows host/tissue switching, host immune escape, vaccine escape, and drug resistance, are difficult challenges for influenza control in all countries worldwide. Access and binding of the IAV to actual receptors at endocytic sites is critical for the establishment of influenza infection. In this chapter, the progress in identification of and roles of glycans and non-glycans on the...
  • Evaluation of the Glycan-Binding and Esterase Activities of Hemagglutinin-Esterase-Fusion Glycoprotein from Influenza D Virus Thu, 29 Sep 2022 06:00:00 -0400
    Influenza D virus (IDV) is a new member of influenza virus that uses cattle as the primary reservoir and infects multiple agricultural animals. Similar to influenza C virus (ICV), IDV also has seven segments in its genome and has only one major surface glycoprotein, called the hemagglutinin-esterase-fusion (HEF) protein, for receptor-binding, receptor-destroying, and membrane fusion. HEF utilizes 9-O-acetylated sialic acids as its receptor and has both receptor binding and esterase activities,...
  • Characterization of Influenza Virus Binding to Receptors on Isolated Cell Membranes Thu, 29 Sep 2022 06:00:00 -0400
    An interplay between receptor-binding properties of influenza viruses (IVs) and spectrum of sialic acid-containing receptors on target cells in birds and mammals determine viral host range, tissue tropism, and pathogenicity. Here, we describe method that allows to characterize binding of IVs to biologically relevant cellular receptors using a conventional solid-phase enzyme-linked assay. In this method, we isolate plasma membranes from respiratory and intestinal epithelial cells of animal origin...
  • Receptor-Binding Assay for Avian Influenza Viruses Thu, 29 Sep 2022 06:00:00 -0400
    It is well known that influenza viruses utilize host cell glycans for virus attachment factors via their major glycoprotein, hemagglutinin (HA), to initiate their invasion to host cells. Unlike well-known theories in human and avian influenza viruses, barriers laying between interspecies transmission of influenza viruses among bird species are not well understood. Recently, it was speculated that glycan binding of the HA to fucosylated Siaα2-3Gal is related to the expansion in the host range of...
  • Quantification of Receptor Association, Dissociation, and NA-Dependent Motility of Influenza A Particles by Biolayer Interferometry Thu, 29 Sep 2022 06:00:00 -0400
    We describe a method for real-time analysis and quantification of influenza A virus (IAV)-receptor interactions by biolayer interferometry (BLI). Biotinylated synthetic sialoglycans or sialoglycoproteins (biotinylated or Fc-tagged) were immobilized on the tip of biosensors (coated with streptavidin or protein A) that were subsequently dipped into IAV particle solutions in 96-well plates. Association and/or dissociation of IAV particles was recorded in consecutive steps in buffers of choice. From...