DNA Virus

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Author:
emm64
ID:
142983
Filename:
DNA Virus
Updated:
2012-03-21 18:03:06
Tags:
DNA Virus Micro
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Description:
DNA Virus Micro
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  1. DNA Viral Replication
    • genomes are transported into nucleus.
    • ¤Viral gene transcription is temporally regulated.
    • early genes – replication proteins, transcription factors
    • late genes – structural proteins
    • ¤Carried out by

    • cellular
    • DNA polymerase – parvo, papova
    • viral DNA polymerase – pox (cytoplasm),
    • herpes, adeno
    • (exception viral reverse transcriptase – hepadna)
  2. Parvoviruses
    • Non-enveloped
    • icosahedral capsid
    • Linear ssDNA
    • Require active cell growth to replicate
    • Fifth Disease (Slapped Cheek)
    • B19: bone marrow infects erythroid -->erythrocytes
  3. Polyomaviruses
    • Non-enveloped
    • icosahedral capsid
    • Circular dsDNA
    • T antigens – promote growth DNA replication
    • VP– capsid proteins
    • BK and JC viruses rarely cause diseases
  4. Papillomaviruses
    • Non-enveloped
    • icosahedral capsid
    • Circular, dsDNA
    • E5/E6/E7 – promote growth L– capsid proteins
    • >100 types
    • HPV16/18 – cervical cancers
  5. Adenoviruses
    • Non-enveloped
    • icosahedral capsid
    • Linear dsDNA (36kb)
    • E2 –DNA polymerase
    • E1A/E1B –deregulate cell growth and apoptosis
    • L genes- capsid proteins
    • Respiratory(10-15% of common colds)
    • GI(15% gastroenteritis)
    • Conjuctivitis
  6. Herpesviruses
    • Enveloped
    • icosahedral capsid
    • Linear, dsDNA virus (100-235kb)
    • own DNA polymerase
    • Invariable life-long persistent infection
    • Latent, reactivating infection
    • most adults infected
    • alpha type affect neuron
    • gamma type (4,8) are tumorgenic
  7. Chickenpox (Varicella)
    • Herpesvirus
    • Varicella-Zoster
    • Only herpes vaccine
    • respiratory droplets
    • No resolution,life-time infection
  8. Poxviruses
    • Enveloped
    • complex capsid
    • Liner, dsDNA, fused ends
    • Replicate exclusively in cytoplasm
    • viral DNA polymerase and RNA polymerase
    • Molluscum contagiosum
    • Cowpox
    • Smallpox
    • Orf(sheep, goat)
  9. Smallpox (Variola)
    • poxvirus
    • eradicated by vaccination
    • major-higher fatality than minor form
    • respiratory route->lymph and blood
  10. Hepadnavirus
    • Enveloped
    • icosahedral
    • Circular, partly dsDNA
    • ¤Genome replication
    • dsDNA -> RNA ->(reverse transcription) dsDNA
    • ¤Hepatitis B virus (sub-unit vaccine)
    • Reverse Transciptase is target for drugs
  11. Hep B Replication
  12. Hepatitis B Infections
    • 10% with weak
    • Fulminant hepatitis-too strong immune response ->death
    • some babies have chronic liver complications
    • oncogenic-
    • increased proliferation after lysis
    • integration of viral DNA to chromosome-disrupt tumor suppressor, upreg proto-onco
    • viral gene products act as transcriptional activators
  13. RNA Viruses
    • Genome replication RNA -> RNA
    • genome polarity
    • (+) sense vs (-) sense
    • + RNA genome DIRECTLY used for TRANSLATION
    • if not eithere - or dsRNA
    • Quasispecies (Diversity of the population

    • Replication:
  14. RNA Genome Polarity
    • dsRNA and -RNA must package Viral RNA polymerase
  15. Retrovirus Replication
    • package Reverse Transcriptase and Integrase
  16. Quasispecies
    • Diversity
    • Error-prone (no proof-reading)
    • RNA Polymerase 1/10 genomes
    • Reverse Transcritase 1/1700 nucleotides
    • Consequence: diverse pool of genomes, fast adaptation, drug/vaccine resistance
  17. Picornavirus
    • (+)RNA
    • IRES (internal ribosomal entry site), no 5' cap, goes directly into ribosome to be translated into single polyprotein then processed by protease
    • Cap blocking viral protease->disrupt host protein synthesis
  18. Enteroviruses
    • Picornavirus
    • (major cause for non-bacterial meningitis) >70 types
    • fecal-oral route
    • Poliovirus(V) encephalitis/meningitis
    • Coxsackie A - vesicular lesions (herpangina) +
    • Coxsackie B - muscle (myocarditis) +
    • Enterovirus 71 (deadly encephalitis)
  19. Rhino
    • common colds (50%)
    • aerosol
    • no vaccine
  20. Heparnavirus
    • Picornavirus
    • HEP A-hepatitis
  21. Calicivirus
    • Non-enveloped
    • (+)RNA genome
    • fecal-oral
    • Norwalk agent- (50%)GE in adults (cruiselines)
  22. Togavirus/Flavivirus
    • Enveloped
    • (+)RNA
    • Most Arboviruses (arthropod borne)
    • – transmitted from blood-sucking arthropods to humans
  23. Togavirus disease
    • Equine Encephalitis (birds->mosquitoes) Encephalitis (3/35% fatal)
    • Rubella (humans) German measles (MMR)
  24. Flavivirus Disease
    • West Nile (birds->mosquitoes) encephalitis (2-5%)
    • Dengue (monkey->mosquitoes) hemorrhagic fevers
    • Yellow Fever(monkey->mosquitoes) hemorrhagic (20-50% fatal, vaccine available)
    • Hepatitis C (humans) Hepatitis
  25. Rubella
    • Shed in oropharyngeal secretions spread by the respiratory route
    • Viremia →multiple organs
    • §Rash (German measles) 14-25 d after infection but not always
    • Severe Congenital Defects
  26. Hepatitis C
    • no vaccine, 170 million
  27. Coronavirus
    • Enveloped, (+) RNA
    • 2nd common cold cause
    • SARS-severe acute respiratory syndrome
  28. (-)RNA Replication

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