Introduction to Virology

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Introduction to Virology
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I. Objectives

• What is a virus
• How do viruses multiply
• How are viruses classified
• (What are some of the diseases viruses cause)

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II. Historical Perspective

• A. Ancient times
• 1. poliovirus
• 2. smallpox
• B. More recent history
• 1. 1790s
• Iwanowski
• 2. 1890s
• Jenner

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III. What is a virus?

• A. Characteristics

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B. Comparison to bacteria 1. overall

• Bacteria Virus
• Intracellular parasite (no) yes
• Plasma membrane yes no
• Binary fission yes
  no
• Filterable no
  yes
• Possess DNA RNA yes no
• ATP production yes no
• Ribosomes yes no
• Antibiotic sensitive yes no

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• 2. Growth comparison
• 3. Size comparison
• 4. Genome size comparison

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IV. Nucleocapsid morphology
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• A. Helical
• B. Polyhedral
• C. Complex

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V. How viruses multiply (13.10)

• 1. Basic strategy
• Attachment
• Penetration
• Synthesis of viral proteins and nucleic acids
• Maturation
• Release

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2. Bacterial viruses Fig 13.12

• Lytic vs lysogenic cycle

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3. General Animal Virus Multiplication
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a.Virus Budding Fig 13.20
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4. Differences in lab culture of viruses

• a. bacteriophage
• b. animal viruses

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VI. Differences in multiplication due to
differences in genome organization

• A. Genome organization

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B. DNA Viruses Life Cycle Fig 13.17
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C. Replication of RNA viruses Fig 13.17
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VI. Classification schemes

• A. Formal taxonomies
• B. Baltimore Classification

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C. Nucleic acid type --gt Baltimore classification

• Class I
• ds DNA
• Class II
• ssDNA (positive and negative)
• Class III
• dsRNA
• Class IV
• ssRNA (positive)

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• Class V
• ssRNA (negative)
• Class VI
• ssRNA (positive, replication intermediate DNA)

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1. Class I dsDNA Viruses

• Bacterial
• Bacteriophage
• Plant
• Caulomoviridae

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• Human
• Herpesviridae
• Adenoviridae
• Poxviridae
• Papovaviridae
• Papillomavirus
• Polyomavirus
• Vacuolating agent

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• Hepadnaviridae
• After protein synthesis, DNA replicated through
  RNA intermediate

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2. Class II ssDNA viruses

• Bacteria
• Plant
• Animal

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3. Class III dsRNA viruses

• Reoviridae

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4. Class IV ss () RNA viruses

• Picornaviridae
• Togaviridae
• Flaviviridae
• Coronaviridae
• Calciviridae

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5. Class V ss (-) RNA viruses

• Rhabdoviridae
• Filoviridae
• Paramyxoviridae
• Orthomyxoviridae
• Bunyaviridae
• Deltaviridae
• Arenaviridae

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Retrovirus Life Cycle Fig 13.19
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6. Class VI ss () viruses (dsDNA intermediate)

• Retroviridae
• Oncoviruses
• Lentivirus

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D. Review of Replication Strategies
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VII. Effects of Viral Infection on Cell
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VIII. Oncogenic Viruses
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IX. Plant viruses

• Morphologically similar to animal viruses
• Enter through wounds or parasites
• Some multiply in insects

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X. Viroids

• Plant pathogens
• infectious naked RNA
• 20-25 identified so far
• ss covalent circle

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XI. Prions

• A. Fig 13.21
• B. PrPC vs PrPSc
• Structural differences
• Detergent solubility differences
• Differences in susceptibility to protein
  degrading enzymes

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Prion diseases of humans and animals