Flavivirus and Pestivirus Genus Quiz
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Flavivirus and Pestivirus Genus Quiz

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Questions and Answers

What is the diameter of the spherical nucleocapsid of the Flavivirus virion?

  • 180nm
  • 39nm
  • 50nm
  • 250nm (correct)

    • How are the envelope glycoproteins arranged in the Flavivirus virion?

  • With icosahedral symmetry (correct)
  • With irregular symmetry
  • In a linear pattern
  • In a helical pattern

    • Which genus contains a virus that only infects humans via blood transfusion, IV needles, and sexual contact?

  • Flavivirus
  • Arbovirus
  • Hepacivirus (correct)
  • Pestivirus

    • What is the arrangement of envelope proteins in mature Flavivirus particles?

    <p>&quot;Golf ball&quot; like appearance</p> Signup and view all the answers

    What is the function of the prM protein in Flavivirus?

    <p>It binds to E glycoprotein and inhibits membrane fusion during transmission through Golgi</p> Signup and view all the answers

    What is the role of NS3 protein in Flavivirus?

    <p>Viral serine proteinase involved in polyprotein cleavage; RNA replicase component; nucleoside triphosphatase and helicase activities</p> Signup and view all the answers

    How is the entry of Flavivirus into cells mediated?

    <p>Endocytosis within clathrin-coated vesicles</p> Signup and view all the answers

    What happens to the genome once it is in the cytosol?

    <p>It is bound by ribosomes and translated to produce polyprotein, which is then cleaved to produce precursor/functional proteins</p> Signup and view all the answers

    What is the role of prM protein in Flavivirus?

    <p>It binds to E glycoprotein and inhibits membrane fusion during transmission through Golgi.</p> Signup and view all the answers

    What does the flavivirus E protein do?

    <p>Directs receptor binding and membrane fusion.</p> Signup and view all the answers

    What happens once virus assembly takes place at intracellular membranes?

    <p>Virus is ready for exit by exocytosis.</p> Signup and view all the answers

    How does flavivirus entry differ under antibody-dependent enhancement (ADE)?

    <p>Virus bound by antibody can enter cells that express Immunoglobulin Fe receptors on their surface.</p> Signup and view all the answers

    What happens just before virion release by cellular furin?

    <p>Cleavage of prM occurs, converting immature particle to mature particle.</p> Signup and view all the answers

    What type of fusion protein is flavivirus E protein?

    <p>Class I type fusion protein.</p> Signup and view all the answers

    What is the diameter of the spherical nucleocapsid of the Flavivirus virion?

    <p>50nm</p> Signup and view all the answers

    What is the arrangement of envelope proteins in mature Flavivirus particles?

    <p>Golf ball-like appearance</p> Signup and view all the answers

    How many copies of M and E (envelope protein heterodimers) are present in the flavivirus virion?

    <p>180 copies</p> Signup and view all the answers

    Which genus contains a virus that only infects humans via blood transfusion, IV needles, and sexual contact?

    <p>Hepacivirus</p> Signup and view all the answers

    What is the role of prM protein in Flavivirus?

    <p>It associates with E protein in the endoplasmic reticulum to protect E from premature conformational change</p> Signup and view all the answers

    What is the function of NS2B protein in Flavivirus?

    <p>It is part of the viral proteinase that cleaves the viral polyprotein</p> Signup and view all the answers

    What happens to the genome once it is in the cytosol?

    <p>It is bound by ribosomes and translated to produce a polyprotein</p> Signup and view all the answers

    What type of fusion protein is flavivirus E protein?

    <p>Type I membrane protein</p> Signup and view all the answers

    What happens just before virion release by cellular furin?

    <p>Cleavage of prM occurs, converting immature particle to mature particle.</p> Signup and view all the answers

    How does flavivirus entry differ under antibody-dependent enhancement (ADE)?

    <p>It can enter cells that express Immunoglobulin Fc receptors on their surface.</p> Signup and view all the answers

    What is the arrangement of envelope proteins in mature Flavivirus particles?

    <p>M and E are present as heterodimers.</p> Signup and view all the answers

    What is the arrangement of envelope glycoproteins in the Flavivirus virion?

    <p>They are arranged as dimers parallel to the lipid bilayer.</p> Signup and view all the answers

    What is the diameter of the spherical nucleocapsid of the Flavivirus virion?

    <p>25-30 nm</p> Signup and view all the answers

    Which genus causes economically important diseases of cattle and sheep, without insect vectors and no human infection?

    <p>Pestivirus</p> Signup and view all the answers

    What is the diameter of the spherical enveloped particle of the Flavivirus virion?

    <p>~50nm</p> Signup and view all the answers

    Which genus contains a single virus that only infects humans via blood transfusion, IV needles, and sexual contact?

    <p>Hepacivirus</p> Signup and view all the answers

    What is the arrangement of envelope glycoproteins in mature Flavivirus particles?

    <p>Golf ball-like appearance</p> Signup and view all the answers

    What is the size of the linear ‘+’ sense ssRNA genome of Flavivirus?

    <p>10-11kb</p> Signup and view all the answers

    Which enzyme is involved in the cleavage of the Flavivirus polyprotein?

    <p>Viral proteinase (NS2B/NS3A)</p> Signup and view all the answers

    What is the function of the precursor membrane protein (prM) in Flavivirus?

    <p>It associates with E protein to form a heterodimer and protects E from premature conformational change</p> Signup and view all the answers

    What is the role of NS3 protein in Flavivirus?

    <p>Viral serine proteinase involved in polyprotein cleavage; RNA replicase component; nucleoside triphosphatase and helicase activities</p> Signup and view all the answers

    What occurs just before virion release by cellular furin?

    <p>Cleavage of prM (membrane anchor)</p> Signup and view all the answers

    What is the synthesis location of non-structural proteins in Flavivirus?

    <p>On membranes in the cytoplasm</p> Signup and view all the answers

    What happens to the flavivirus RNA once it is in the cytosol?

    <p>It is bound by ribosomes and translated to produce polyprotein, which is then cleaved to produce precursor/functional proteins</p> Signup and view all the answers

    What is the arrangement of domain II in flavivirus E protein?

    <p>Forms dimer interface and contains the hydrophobic fusion peptide, protected from the aqueous environment by neighboring E in the dimer</p> Signup and view all the answers

    What type of fusion protein is flavivirus E protein?

    <p>Class II type fusion protein</p> Signup and view all the answers

    How does entry of flavivirus differ under antibody-dependent enhancement (ADE)?

    <p>Virus bound by antibody can enter cells that express Immunoglobulin Fe receptors on their surface, causing more severe disease like dengue hemorrhagic fever.</p> Signup and view all the answers

    Study Notes

    Flavivirus Structure and Composition

    • Diameter of the spherical nucleocapsid is approximately 40-50 nm.
    • Flavivirus virion has an envelope consisting of glycoproteins arranged in a specific pattern; the E (envelope) proteins form dimers.
    • Mature Flavivirus particles feature envelope proteins (M and E) arranged in a heterodimer structure, with about 180 copies of each protein in a typical virion.

    Infection and Transmission

    • The genus Hepacivirus contains a virus that infects humans primarily through blood transfusions, intravenous needles, and sexual contact.
    • The genus Pestivirus is associated with economically significant diseases of cattle and sheep, transmitted without insect vectors and is not pathogenic to humans.

    Protein Functions and Mechanisms

    • The prM protein protects the E protein during transport and maturation; it is cleaved to form the M protein upon viral maturation to facilitate membrane fusion.
    • NS3 protein acts as a protease and is involved in viral genome replication; it plays critical roles in viral lifecycle processes.
    • NS2B protein functions alongside NS3 as a co-factor essential for the proteolytic cleavage of the Flavivirus polyprotein.

    Viral Entry and Genome Processing

    • Flavivirus entry into host cells is mediated by receptor-mediated endocytosis; E protein facilitates fusion with the endosomal membrane.
    • Once in the cytosol, the flavivirus RNA genome is translated into proteins and serves as a template for further replication.

    Assembly and Release

    • After virus assembly at intracellular membranes, the newly formed virion is transported to the plasma membrane for release.
    • Just before virion release, furin, a host cell protease, cleaves the prM protein to activate the virus and facilitate release.
    • Under antibody-dependent enhancement (ADE), flavivirus entry can be facilitated by antibodies, leading to increased viral uptake.

    Additional Structural Characteristics

    • The flavivirus E protein is a class II fusion protein, functioning in membrane fusion during entry.
    • The arrangement of domain II in the flavivirus E protein is crucial for its fusion activity and structural stability.

    Genome Size

    • The linear ‘+’ sense ssRNA genome of Flavivirus is approximately 10,700 nucleotides in length.

    These notes summarize the key aspects of flavivirus structure, infection mechanisms, and the roles of specific proteins essential for its lifecycle and pathogenicity.

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    Test your knowledge about Flavivirus and Pestivirus genus, including their characteristics, transmission, and impact on human and animal health.

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