Viruses and Prions Overview
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Questions and Answers

How do nonenveloped viruses typically attach to host cells?

  • Through lipid bilayer interactions
  • Via protein spikes
  • Through endocytosis directly
  • By using their capsid proteins (correct)

    • What method do enveloped viruses use to enter a host cell?

  • Cell lysis
  • Direct injection of nucleic acid
  • Endocytosis or membrane fusion (correct)
  • None of the above

    • What occurs during the uncoating phase of viral infection?

  • The host immune response is activated
  • Viral proteins are transported out of the nucleus
  • Virions are assembled
  • The capsid disassembles and is digested (correct)

    • How are new virions released from enveloped viruses?

    <p>Through budding</p> Signup and view all the answers

    What characterizes a chronic persistent viral infection?

    <p>Continuous release of virions over time</p> Signup and view all the answers

    Which method is primarily used to cultivate most animal viruses?

    <p>Tissue culture technique</p> Signup and view all the answers

    What is a major limitation of the ELISA test?

    <p>Samples must be in liquid form</p> Signup and view all the answers

    Which technique is commonly used to detect viral genetic material?

    <p>Polymerase chain reaction (PCR)</p> Signup and view all the answers

    What is required for reverse transcriptase (RT) in RT-qPCR?

    <p>Viral RNA to be converted into cDNA</p> Signup and view all the answers

    What triggers flare-ups in latent persistent infections?

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

    What is the primary role of leukocytes in the immune response?

    <p>To modulate inflammation and clear pathogens</p> Signup and view all the answers

    Which of the following structures is primarily responsible for filtering lymph?

    <p>Lymph nodes</p> Signup and view all the answers

    Which type of leukocyte is known for its role in fighting parasites and causing allergies?

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

    What class of antimicrobial peptides rapidly kill invaders by disrupting cell membranes?

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

    Where does the maturation of T cells occur?

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

    What condition indicates an increase in leukocytes in the blood?

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

    What is the main physical barrier to pathogens in the human body?

    <p>Epithelial tissue</p> Signup and view all the answers

    What happens to lymph nodes when they detect an invading microbe?

    <p>They become swollen and inflamed</p> Signup and view all the answers

    What is indicated by a high cycle threshold (Ct) value in a PCR test?

    <p>Low concentrations of the DNA sample</p> Signup and view all the answers

    Which characteristic makes designing antiviral drugs challenging?

    <p>Antivirals must be selectively toxic to host cells</p> Signup and view all the answers

    What is the role of interferons in the immune response?

    <p>Signal to neighboring cells to enhance their defenses</p> Signup and view all the answers

    Which of the following is NOT a mechanism of innate immunity?

    <p>Memory response</p> Signup and view all the answers

    Which drug is known to inhibit viral DNA replication?

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

    What do nucleoside reverse transcriptase inhibitors (NTRIs) target?

    <p>Reverse transcriptase enzymes</p> Signup and view all the answers

    What happens when prions are ingested?

    <p>They induce normal proteins to misfold</p> Signup and view all the answers

    Which physiological barrier helps to trap pathogens that enter the respiratory system?

    <p>Mucociliary escalator</p> Signup and view all the answers

    How do antimicrobial peptides (AMPs) function?

    <p>Destroy a wide spectrum of pathogens</p> Signup and view all the answers

    What concept does the hygiene hypothesis suggest?

    <p>Increased diversity in microbiota supports immune health</p> Signup and view all the answers

    Which of the following is an example of adaptive immunity?

    <p>Vaccination response</p> Signup and view all the answers

    Which antiviral drug is used as a preventive measure shortly after suspected exposure to rabies?

    <p>An injectable antibody mixture</p> Signup and view all the answers

    What property of viruses poses a challenge for antiviral drug development?

    <p>They are obligate intracellular pathogens.</p> Signup and view all the answers

    Which of the following statements is true regarding innate immunity?

    <p>It includes physical and chemical barriers.</p> Signup and view all the answers

    What type of viruses are obligate intracellular pathogens and cannot survive outside of a host cell?

    <p>Nonliving pathogens</p> Signup and view all the answers

    Which of the following is NOT a feature of viral capsids?

    <p>They are composed entirely of lipids.</p> Signup and view all the answers

    What distinguishes enveloped viruses from naked viruses?

    <p>Enveloped viruses have a phospholipid bilayer.</p> Signup and view all the answers

    Which viral genome type is directly translated by host cell ribosomes?

    <p>Single-stranded positive RNA</p> Signup and view all the answers

    What is the primary reason that RNA viruses mutate more frequently than DNA viruses?

    <p>DNA polymerases have proofreading capabilities.</p> Signup and view all the answers

    What is antigenic drift?

    <p>Frequent minor changes to viral surface proteins.</p> Signup and view all the answers

    How does antigenic shift occur?

    <p>When two different virus strains combine.</p> Signup and view all the answers

    The capsid of most animal viruses is primarily composed of what?

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

    What property is NOT used in the classification of viruses?

    <p>Molecular weight of the capsid</p> Signup and view all the answers

    Which of the following best describes a cytopathic effect of a viral infection?

    <p>Cellular changes leading to cell death.</p> Signup and view all the answers

    Which of the following viruses typically has a segmented RNA genome?

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

    What role do viral spikes (peplomers) play in the viral life cycle?

    <p>They mediate attachment to host cells.</p> Signup and view all the answers

    The process through which beneficial mutations in viruses enable them to escape host immune detection is known as what?

    <p>Selection pressure</p> Signup and view all the answers

    Which of the following is NOT a characteristic of single-stranded RNA viruses?

    <p>They are always double-stranded.</p> Signup and view all the answers

    Study Notes

    Viruses and Prions

    • Viruses are acellular obligate intracellular pathogens.
    • 70% of human viruses are zoonotic.
    • Virion: A single, infectious virus particle.
    • Capsid: Protein shell that packages and protects the genome.
    • Enveloped viruses: Have a lipid based envelope surrounding the capsid.
    • Naked/nonenveloped virus: Does not have an envelope.
    • Viral spikes: Protrude from the capsid or envelope.
    • Viral genomes can be RNA or DNA, single or double-stranded, segmented or non-segmented, linear or circular.
    • Viral genomes change over time, due to their rapid replication rate and lack of proofreading capabilities in RNA polymerases.
    • Antigenic Drift: Minor changes to the HA and NA spikes due to error-prone RNA polymerase.
    • Antigenic Shift: Major changes to genetic reassortment, usually occurs when two or more strains of a virus combine to create a new subtype.
    • Important DNA viral families:
      • Papillomaviridae (human papillomaviruses)
      • Herpesviridae (herpes, varicella-zoster virus/chickenpox)
      • Poxviridae (smallpox)
    • Important RNA viral families:
      • Coronaviridae (SARS, SARS-CoV-2, common colds)
      • Flaviviridae (Hepatitis C virus, West Nile Virus, Dengue fever virus)
      • Retroviridae (HIV)
      • Parmyxoviridae (Measles & mumps)
      • Orthomyxoviridae (Influenza)
    • Animal Virus Replication:
      • Attachment: Viral proteins bind to host cell receptors.
      • Penetration: Nonenveloped viruses enter by endocytosis; enveloped viruses enter by endocytosis or membrane fusion.
      • Uncoating: Capsid is degraded in cytoplasm, nucleus, or endocytic vesicle.
      • Replication: Genome replication and viral protein synthesis.
      • Assembly: New virions are formed.
      • Release: Enveloped viruses bud off; nonenveloped viruses kill the host cell.
    • Acute infections: Viruses infect a host cell and new virions are immediately made.
    • Persistent infections: Replication strategies allow viruses to avoid immune clearance.
      • Chronic persistent infections: Continuous release of virions over time with slow progression.
      • Latent persistent infections: Flare-ups with intermittent periods of dormancy; virions are shed during flare-ups.
    • Prions: Infectious proteins that cause transmissible spongiform encephalopathies (TSEs).
    • Misfolded proteins: Associated with neurodegenerative diseases.
    • Hygiene hypothesis: Decreases in diversity and levels of microbes in the microbiota may negatively affect immune responses.

    Innate Immunity

    • Ancient protection in all eukaryotes.
    • Generalized, lacks specificity and memory.
    • Mechanical barriers: Prevent pathogen spread by rinsing, flushing, or trapping.
    • Chemical barriers: Directly attack invaders or establish environments that limit pathogen survival.
    • Antimicrobial Peptides (AMPs): Proteins that destroy a wide spectrum of pathogens.
    • Physical barriers: Epithelial tissue lines every body cavity and entrance; skin serves as a major physical barrier.
    • Lymphoid tissues: filter lymph and screen for antigens.
      • Primary lymphoid tissues: Site of leukocyte production and maturation (thymus and bone marrow).
      • Secondary lymphoid tissues: filter lymph and sample body sites for antigens (lymph nodes, spleen, and MALT).
    • Leukocytes: White blood cells.
      • Granulocytes: cells with granules in their cytoplasm.
      • Agranulocytes: lack granules in their cytoplasm.
    • Neutrophils: Most abundant white blood cells; phagocytize foreign cells and viruses.
    • Eosinophils: Fight parasites or cause allergies.

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    Chapter 6 - Viruses and Prions PDF

    Description

    This quiz covers essential concepts related to viruses and prions, including their structures, classifications, and genetic variations. Understand the differences between enveloped and naked viruses, as well as antigenic drift and shift. Test your knowledge of viral families and their significance in human health.

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