General Characteristics of Viruses

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General Characteristics of Viruses
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• HIV ! Avian Flu !
• SARS ! Ebola !
• West Nile ! Smallpox !
• Hepatitis A,B,C,D,E !
• Polio ! HPV !

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Viruses infect all living things

• Animal kingdom
• Plant kingdom
• Microbes

• Specificity/selectivity for host

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Manifestations of Viral Infections

• Asymptomatic
• Acute viral syndrome (influenza, rhinovirus, etc)
• Persistent viral syndrome (EBV)
• Chronic infection
• Reactivating (HSV-1/2, VZV (chicken
  pox/shingles))
• Progressive (HBV, HCV, HIV)
• Cancer (EBV, HPV-16, HBV, HCV, KSHV)
• Death (HIV, et al)
• Acute death (smallpox, Ebola, SARS)

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Viral pathogenesis --- disease

• Virus replication
• Targeted cells
• Host response

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What is a virus?

• What are the essential characteristics of a
  virus?
• Physical
• Biological

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What is a virus?

• Physical Characteristics
• Genetic Material
• Nucleic acid
• RNA (ssRNA, dsRNA, segmented)
• DNA (ssDNA, dsDNA)
• Protein coat (subunit structure)
• Nucleoprotein
• Capsid
• Capsomeres, Geometrical constraints
• Envelope (some)

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Adenoviruses
Rhabdoviruses (rabies)
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Size of Viruses
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What is a virus?

• Genetic material limited
• 103 to 105 bases long
• Codes for unique proteins
• Polymerases RNA replication
• Kinases
• Proteases
• Structural proteins
• Accessory proteins

Targets for antiviral agents - limited
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What is a virus?

• Biological Charateristics
• Viruses as parasites
• Parasites
• Not capable of independently completing a full
  replication cycle
• Cellular parasites
• Subcellular parasites
• Viruses
• Viroids
• Prions

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What is a virus?

• Are viruses alive?
• Characteristics of living organisms?

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What is a virus?

• Biological Characteristics
• Viral replication strategies
• Viral replication cycles
• Binding/entry
• Uncoating
• Genome replication (w/wo integration)
• Protein production
• Assembly
• Budding
• Host cell tropism (receptors)
• Lytic vs. non-lytic infection

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Vaccinia Poliovirus
Adenovirus Herpesvirus
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Morphological Assays

• Electron microscopy
• Isolated virus or infected cells
• Nonenveloped or enveloped (alternate method to
  determine if an envelope is present?)
• Core structure

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Epidemiology

• Tracking prevalence of viruses in host
  populations
• Blood components and tissue samples
• Virus culture
• In vitro (tissue culture)
• In vivo (susceptible animal model)
• Molecular testing
• PCR methods
• Southern blot
• ELISA (enzyme linked immunosorbent assay)
• Assay for antigen (viral protein)
• Assay for antibody directed against virus