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Poxviruses Overview
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Poxviruses Overview

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Questions and Answers

What type of viruses resemble the cowpox virus?

  • Orthomyxoviruses
  • Picornaviruses
  • Poxviruses (correct)
  • Herpesviruses

    • What is the approximate size of the cowpox virus?

  • 230 nm by 330 nm (correct)
  • 200 nm by 250 nm
  • 300 nm by 450 nm
  • 150 nm by 200 nm

    • What kind of lesions are characteristic of cowpox infections?

  • Large, red, raised bumps
  • Flat, brown, scaly patches
  • Small, pink, wart-like tumors (correct)
  • Small, purple, blister-like sores

    • How many genes are contained in the cowpox virus genome?

    <p>163 genes</p> Signup and view all the answers

    In which animal language is the cowpox virus primarily studied?

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

    Where are cowpox lesions rarely found on the body?

    <p>Palms and soles</p> Signup and view all the answers

    What is the genome type contained in parapoxviruses?

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

    Which of the following is a characteristic of the parapoxvirus genome compared to orthopoxviruses?

    <p>Higher guanine plus cytosine content</p> Signup and view all the answers

    What is the approximate size of parapoxviruses?

    <p>260 × 160 nm</p> Signup and view all the answers

    Which of the following statements is true regarding the composition of poxviruses?

    <p>They contain more protein than DNA</p> Signup and view all the answers

    What structure is unique to the uncoating step of poxviruses?

    <p>It requires a newly synthesized, virus-encoded protein</p> Signup and view all the answers

    Which characteristic differentiates parapoxviruses from other animal viruses?

    <p>Uncoating requires a virus-encoded protein</p> Signup and view all the answers

    What pattern is exhibited on the surface of parapoxviruses?

    <p>Crisscross pattern</p> Signup and view all the answers

    How do virus particles typically establish contact with a host cell?

    <p>By fusing with the cell membrane</p> Signup and view all the answers

    What role do inverted terminal repeats play in the genome of poxviruses?

    <p>They connect the ends of the viral DNA strands</p> Signup and view all the answers

    What governs the distribution, synthesis, and handling of variola virus DNA?

    <p>Recommendations from the World Health Organization</p> Signup and view all the answers

    What pathological alteration occurs in epidermal cells infected by variola virus?

    <p>Ballooning degeneration</p> Signup and view all the answers

    Which virus is primarily used for smallpox vaccination?

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

    What is a key histopathological finding in both variola and vaccinia infections?

    <p>Formation of vesicles filled with white cells and debris</p> Signup and view all the answers

    What is the typical incubation period for variola (smallpox)?

    <p>10–14 days</p> Signup and view all the answers

    What occurs to the skin as a result of variola infection?

    <p>Scarring due to dermal necrosis</p> Signup and view all the answers

    How does vaccinia virus differ from cowpox virus?

    <p>It has distinct restriction endonuclease maps</p> Signup and view all the answers

    What outcome is typically seen at the site of inoculation with vaccinia virus?

    <p>Localized pustular lesions</p> Signup and view all the answers

    What occurs to the cell membranes of infected epidermal cells?

    <p>They break down and coalesce with neighboring cells</p> Signup and view all the answers

    Which statement about variola virus host range is correct?

    <p>It has a narrow host range limited to humans</p> Signup and view all the answers

    What is the primary reservoir host for cowpox virus?

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

    In which year was monkeypox first recognized in captive monkeys?

    <p>1958</p> Signup and view all the answers

    Which disease features pronounced lymphadenopathy, a symptom not seen in smallpox?

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

    How is cowpox typically acquired by humans?

    <p>By direct contact with wild animals</p> Signup and view all the answers

    Which of the following statements about cowpox is true?

    <p>Feline cowpox cases are sporadic.</p> Signup and view all the answers

    What clinical features do human infections with monkeypox have compared to smallpox?

    <p>Less severe symptoms than smallpox</p> Signup and view all the answers

    In which regions are human monkeypox infections primarily detected?

    <p>Remote villages in tropical rain forests</p> Signup and view all the answers

    What is the common outcome after exposure to a cowpox virus?

    <p>Potential zoonotic disease transmission</p> Signup and view all the answers

    Which of these is a symptom of human monkeypox?

    <p>Hemorrhagic skin lesions</p> Signup and view all the answers

    What is the status of cowpox in domestic cattle today?

    <p>It is no longer enzootic in cattle.</p> Signup and view all the answers

    What type of proteins do poxviruses contain that help evade the host immune defense system?

    <p>Viral proteins</p> Signup and view all the answers

    What significant event occurs during the replication of poxviruses?

    <p>Formation of cytoplasmic factories</p> Signup and view all the answers

    Which enzyme is present in the core of poxvirus particles?

    <p>RNA polymerase</p> Signup and view all the answers

    How does early transcription proceed in poxviruses in the presence of inhibitors of protein synthesis?

    <p>It is not affected</p> Signup and view all the answers

    What is required for the second-stage uncoating step of poxviruses?

    <p>RNA and protein synthesis</p> Signup and view all the answers

    Which characteristic is true about smallpox in relation to poxviruses?

    <p>It is the first viral disease eradicated from the world</p> Signup and view all the answers

    What does nongenetic reactivation of poxviruses involve?

    <p>The action of the uncoating protein</p> Signup and view all the answers

    Why does immunization with the vaccinia virus offer limited protection against other genera of poxviruses?

    <p>There is limited cross-reactivity across genera</p> Signup and view all the answers

    What happens to the synthesis of host cell macromolecules during the second-stage uncoating of poxviruses?

    <p>It is inhibited</p> Signup and view all the answers

    What forms the basis of virion assembly for poxviruses?

    <p>Formation of multiple membranes</p> Signup and view all the answers

    Study Notes

    Poxviruses Overview

    • Parapoxviruses have distinctive morphology and smaller size (260 × 160 nm) compared to orthopoxviruses.
    • These viruses contain linear double-stranded DNA with genome sizes ranging from 130–375 kbp; vaccinia virus genome is approximately 135 kbp.
    • Vaccinia virus has around 185 open reading frames and a higher guanine plus cytosine (G + C) content (63%) than orthopoxviruses.

    Viral Structure and Composition

    • Poxvirus virions are complex, oval or brick-shaped, measuring 300–400 nm in length and 230 nm in diameter; they have ridged external surfaces.
    • The composition includes 3% DNA, 90% protein, and 5% lipid.
    • Virions possess more than 100 polypeptides, including essential enzymes for transcription and virion assembly.

    Replication and Uncoating

    • Replication occurs in cytoplasmic factories where virus particles attach to cell surfaces, inducing membrane fusion.
    • The initial uncoating step requires newly synthesized, virus-encoded proteins, allowing viral cores to release into the cytoplasm.
    • Early mRNA transcribes about half the viral genome using viral RNA polymerase.

    Immunological and Pathological Characteristics

    • Extensive serologic cross-reactivity exists among vertebrate poxviruses due to shared nucleoprotein antigens.
    • Poxviruses can evade host immune responses due to viral proteins, and smallpox was the first viral disease eradicated globally.
    • Histological examination during variola infection reveals cytoplasmic inclusions, mononuclear cell infiltration, and “ballooning degeneration” of epidermal cells, resulting in vesicle formation and skin scarring.

    Vaccinia vs. Variola Viruses

    • Vaccinia virus, used for smallpox vaccination, is genetically distinct from cowpox, believed to be its ancestor.
    • The incubation period for smallpox (variola) ranges from 10–14 days; symptoms appear suddenly post-exposure.
    • Smallpox has a narrow host range limited to humans, while vaccinia has different origins and genetic makeup due to possible recombination events.

    Monkeypox and Cowpox

    • Monkeypox, first identified in 1958, is a zoonotic disease primarily found in Africa, first noted in West and Central Africa after smallpox eradication.
    • Cowpox is transmitted primarily from rodents to cattle, with accidental infections reported in humans and domestic cats.
    • Cowpox virus lesions can be differentiated from vaccinia, showcasing deep red hemorrhagic characteristics.

    Buffalopox

    • Buffalopox is the sole member of the Molluscipoxvirus genus, showing lesions that are distinct and usually not transmitted to animals, highlighting its unique epidemiological profile.

    Clinical Features

    • Clinical presentations of monkeypox resemble those of smallpox but generally less severe, with notable lymphadenopathy absent in smallpox.
    • Human cases of cowpox may exhibit severe symptoms such as hemorrhagic lesions and general malaise, often without direct animal contact.

    Research and Handling Regulations

    • Distribution and handling of variola virus DNA are tightly regulated by the World Health Organization.
    • Proposals for research related to variola require strict adherence to guidelines, emphasizing safety and surveillance post-smallpox eradication.

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    Related Documents

    Jawetz Chapter 34.pdf

    Description

    Explore the unique characteristics of parapoxviruses compared to orthopoxviruses. This quiz covers their morphology, genome structure, and size differences. Test your knowledge on the viral genome of these distinctive pathogens.

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