Microbiology and Host Defense: DNA Viruses Overview
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Questions and Answers

What characteristic feature gives the name to Poxviruses?

  • Their DNA structure
  • Their vesicular skin lesions (correct)
  • Their infection method
  • Their pathogenic potential

    • Which of the following statements about smallpox virus is true?

  • It is primarily spread through waterborne transmission.
  • Its fatality rate is identical for both variola major and minor strains.
  • It has a known animal reservoir that contributes to its spread.
  • It is caused by variola major and variola minor but is indistinguishable antigenically. (correct)

    • What was a major reason for the WHO's campaign to eradicate smallpox?

  • The virus could mutate rapidly.
  • There was no known extra-human reservoir for the virus. (correct)
  • Asymptomatic carriage of the virus was common.
  • The existence of multiple animal reservoirs.

    • Where is the smallpox virus currently secured?

    <p>In two WHO-restricted laboratories.</p> Signup and view all the answers

    What type of genome do Poxviruses possess?

    <p>Linear, double-stranded DNA</p> Signup and view all the answers

    What is the primary health condition associated with the JC virus?

    <p>Progressive multifocal leukoencephalopathy</p> Signup and view all the answers

    Which of the following viruses is associated with Kaposi sarcoma?

    <p>Human herpesvirus 8</p> Signup and view all the answers

    What structure characterizes the herpesvirus genome?

    <p>Linear double-stranded DNA</p> Signup and view all the answers

    What is the size range of hepadnaviruses?

    <p>40-48 nm</p> Signup and view all the answers

    What type of nucleic acids do poxviruses contain?

    <p>Double-stranded DNA</p> Signup and view all the answers

    Which type of infections can hepadnaviruses cause?

    <p>Both acute and chronic hepatitis</p> Signup and view all the answers

    What is the composition of the vaccinia virus primarily made up of?

    <p>Protein, lipid, and DNA</p> Signup and view all the answers

    In which cells do herpesviruses typically establish latent infections?

    <p>Ganglial or lymphoblastoid cells</p> Signup and view all the answers

    Which virus family is characterized by non-enveloped, icosahedral, double-stranded linear DNA and is associated with pharyngitis?

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

    Which clinical symptom is primarily associated with Human Papilloma Virus (HPV)?

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

    What condition is caused by the BK virus and primarily affects transplant patients?

    <p>Kidney complications</p> Signup and view all the answers

    Which of the following viruses is NOT a DNA virus family mentioned above?

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

    Which virus is known to cause chicken pox and can also reactivate to cause zoster?

    <p>Varicella-Zoster virus</p> Signup and view all the answers

    Which of the following is a clinical manifestation of Cytomegalovirus infection?

    <p>Congenital abnormalities</p> Signup and view all the answers

    What is the main structural characteristic of poxviruses compared to other families mentioned?

    <p>Complex structure</p> Signup and view all the answers

    What virus is associated with causing oral lesions and is primarily transmitted through sexual contact?

    <p>Herpes simplex virus type 1</p> Signup and view all the answers

    What is one reason why smallpox is considered a significant threat for bioterrorism?

    <p>It can remain stable for a long time when freeze-dried.</p> Signup and view all the answers

    Which clinical manifestation typically occurs after a 4 to 5 day incubation period of smallpox?

    <p>A uniform papulovesicular rash that evolves to pustules.</p> Signup and view all the answers

    What is the incubation period for the smallpox virus?

    <p>12 to 14 days.</p> Signup and view all the answers

    What type of body inclusions are associated with the smallpox virus?

    <p>Guarnieri bodies.</p> Signup and view all the answers

    How does the smallpox virus affect host immunity?

    <p>It interferes with host defenses, depressing cell-mediated immunity.</p> Signup and view all the answers

    What is a significant risk factor regarding the recognition of smallpox cases by healthcare providers?

    <p>Healthcare providers may not promptly recognize or respond to early cases.</p> Signup and view all the answers

    What is one consequence of the inflammatory responses caused by the smallpox virus?

    <p>Death from overwhelming primary viral infection or bacterial superinfection.</p> Signup and view all the answers

    How long can scab forms of the smallpox virus remain stable at room temperature?

    <p>Up to 1 year.</p> Signup and view all the answers

    What is the size range of adenoviruses?

    <p>26–48 kb</p> Signup and view all the answers

    Which diseases can be caused by adenoviruses?

    <p>Acute respiratory diseases, conjunctivitis, and gastroenteritis</p> Signup and view all the answers

    What distinguishes parvoviruses from adenoviruses in terms of their genome?

    <p>Parvoviruses have a single-stranded genome.</p> Signup and view all the answers

    The replication of parvoviruses occurs in which type of cells?

    <p>Only in actively dividing cells</p> Signup and view all the answers

    Which type of virus is known to cause erythema infectiosum?

    <p>Parvovirus B19</p> Signup and view all the answers

    Which characteristic is NOT true about papillomaviruses?

    <p>They are enveloped viruses.</p> Signup and view all the answers

    What size are polyomaviruses compared to other DNA viruses mentioned?

    <p>They are small at approximately 45 nm.</p> Signup and view all the answers

    What is a key difference between polyomaviruses and some other DNA viruses?

    <p>Polyomaviruses have transforming ability in vitro.</p> Signup and view all the answers

    What is the primary clinical manifestation associated with Epstein-Barr virus infection?

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

    Which DNA virus is known to be responsible for Fifth disease in children?

    <p>Parvo B19 virus</p> Signup and view all the answers

    Identify the virus associated with umbilicated warts.

    <p>Molluscum contagiosum</p> Signup and view all the answers

    Which virus is characterized by its complex structure and is known to cause smallpox?

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

    Name the virus that causes progressive multifocal leukoencephalopathy.

    <p>JC virus</p> Signup and view all the answers

    Study Notes

    DNA-Containing Viruses Overview

    • Major groups of clinically relevant DNA viruses include adenoviruses, parvoviruses, papillomaviruses, polyomaviruses, herpesviruses, hepadnaviruses, and poxviruses.
    • Key symptoms and characteristics vary widely among these virus families.

    Adenoviruses

    • Medium-sized, nonenveloped viruses (70-90 nm) with icosahedral symmetry; genome is linear dsDNA (26-48 kb).
    • Associated with acute respiratory diseases, conjunctivitis, and gastroenteritis.
    • 67 known types infect humans, primarily targeting mucous membranes.

    Parvoviruses

    • Very small (18-26 nm), nonenveloped viruses with icosahedral symmetry, possessing ssDNA (~5 kb).
    • Replicate in actively dividing cells; stable over pH range of 3-9.
    • B19 virus causes Hydrops fetalis, aplastic anemia, and Fifth disease (erythema infectiosum).

    Papillomaviruses

    • Naked icosahedral viruses (55 nm) with double-stranded supercoiled DNA.
    • Human Papillomavirus (HPV) can lead to genital cancers; associated with wart-like lesions.
    • Animal-specific papillomaviruses do not infect humans.

    Polyomaviruses

    • Small (45 nm), nonenveloped, heat-stable viruses; structurally related to HPV.
    • Notable human pathogens include JC virus linked to progressive multifocal leukoencephalopathy and BK virus causing nephropathy in transplant patients.

    Herpesviruses

    • Large viruses (150-200 nm) with a lipid-containing envelope and icosahedral nucleocapsid structure; linear dsDNA genome (120-240 kb).
    • Cause lifelong latent infections; include HSV-1 (oral lesions), HSV-2 (genital herpes), and Varicella-Zoster virus (chickenpox and shingles).
    • Epstein-Barr virus causes infectious mononucleosis, while HHV-8 is associated with Kaposi's sarcoma.

    Hepadnaviruses

    • Small (40-48 nm), enveloped viruses with partially dsDNA molecules (~3.2 kb).
    • Known for causing acute and chronic hepatitis B infections; persistent infections increase liver cancer risks.
    • Contains icosahedral nucleocapsid core within a lipid envelope.

    Poxviruses

    • Largest known viruses (220-450 nm) with complex structure; contain linear covalently closed dsDNA (130-375 kb).
    • Pathogenic types include Smallpox, Molluscum contagiosum, and Monkeypox.
    • Smallpox eradicated globally in 1980; stored in restricted laboratories.

    Variola (Smallpox) Virus

    • Two types: variola major (3-40% fatality) and variola minor (>1% fatality).
    • Highly contagious, spread via respiratory droplets; no known animal reservoir.
    • WHO-led eradication campaign in 1967 confirmed eradication by 1980; posing bioterrorism threat due to stability and high infectivity.

    Smallpox Pathogenesis

    • Entry through inhalation, initially infecting upper respiratory tract, followed by regional lymph nodes, leading to viremia and dissemination to organs.
    • Incubation period lasts 12-14 days; clinical symptoms include fever and malaise before papulovesicular rash appears.
    • Characteristic uniform vesicular rash forms, with lesions appearing simultaneously on face, arms, and extremities.

    Diagnosis and Pathological Features

    • Presence of eosinophilic inclusions (Guarnieri bodies) in infected cells.
    • Viral proteins may impair host immune defenses, potentially leading to severe inflammatory responses.
    • Diagnosis includes vesicular scrapings for analysis.

    DNA-Containing Viruses Overview

    • Major groups include adenoviruses, parvoviruses, papillomaviruses, herpesviruses, polyomaviruses, hepadnaviruses, and poxviruses.
    • DNA viruses can be categorized based on envelope presence and capsid symmetry.

    Clinically Important DNA Viruses

    • Adenovirus: No envelope, icosahedral, ds linear DNA. Causes pharyngitis, conjunctivitis, and UTI.
    • Parvovirus: No envelope, icosahedral, ss linear DNA. Associated with Fifth disease in children and anemia due to RBC destruction in fetuses.
    • Papillomavirus: No envelope, icosahedral, ds circular DNA. Human Papilloma Virus (HPV) linked to warts and cervical/anal squamous cell carcinoma.
    • Herpesvirus: Envelope present, icosahedral, ds linear DNA. Includes HSV-1 (oral lesions, cold sores), HSV-2 (genital herpes), Varicella-Zoster virus (chickenpox, shingles), Epstein-Barr virus (mononucleosis), and Cytomegalovirus (congenital abnormalities).
    • Polyomavirus: No envelope, icosahedral, ds circular DNA. JC virus causes progressive multifocal leukoencephalopathy; BK virus affects transplant patients.
    • Hepadnavirus: Envelope present, icosahedral, partially ds circular DNA. Hepatitis B virus leads to hepatitis.
    • Poxvirus: Envelope present, complex structure, ds linear DNA. Includes smallpox (eradicated), molluscum contagiosum (umbilicated warts), and monkeypox (similar, less deadly).

    Adenoviruses

    • Medium-sized, nonenveloped, icosahedral viruses with fiber spikes enhancing host attachment.
    • Pathogenic adenoviruses can cause vesicular skin lesions.

    Poxviruses

    • Genomes are linear, double-stranded DNA ranging from 130-375 kb.
    • Poxvirus replication occurs in the cytoplasm, with numerous enzymatic proteins, including RNA polymerase.

    Smallpox (Variola Virus)

    • Consists of variola major (3-40% fatality) and variola minor (>1% fatality).
    • Highly contagious via respiratory droplets; survives well in the environment.
    • Global eradication confirmed by WHO in 1979; now stored in secure facilities.

    Bioterrorism Concerns

    • Smallpox is stable, high infectivity, and no longer widely vaccinated against, increasing population susceptibility.
    • Response strategies are available through the CDC.

    Smallpox Pathogenesis

    • Virus enters via inhalation, replicates in the respiratory tract, and spreads through lymphatic dissemination.
    • Incubation lasts 12 to 14 days, followed by fever and a characteristic papulovesicular rash developing into pustules.
    • Guarnieri bodies are eosinophilic inclusions used for diagnosis.

    Mpox (Monkeypox)

    • Spreads through direct contact and has similar symptoms to smallpox, but lower fatality (1-10% depending on clade).
    • Vaccine (JYNNEOS) developed for mpox and smallpox; requires 2 doses for effective protection.

    Virus Replication Cycles of Major Virus Families

    • Parvoviridae: No envelope, nucleus, 24 hours replication cycle.
    • Polyomaviridae: No envelope, nucleus, 48 hours replication cycle.
    • Adenoviridae: No envelope, nucleus, 25 hours replication cycle.
    • Hepadnaviridae: Envelope present, nucleus/cytoplasm, 12-24 hours replication cycle.
    • Herpesviridae: Envelope present, nucleus, 15-72 hours replication cycle.
    • Poxviridae: Envelope present, cytoplasm, 20 hours replication cycle.

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    DNA Viruses: An Overview PDF

    Description

    This quiz covers the major groups of clinically important DNA-containing viruses. Explore the characteristics of various virus families, their envelopes, and capsids. Enhance your understanding of microbiology and the mechanisms of host defense against these pathogens.

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