General Characteristics of Viruses
- small size (nm)
- acellular/noncellular
- single type of nucleic acid (DNA or RNA)
- protein coat
- obligate intracellular parasites
Viral Structure
- virion: fully developed virus particle, infections
- nucleic acid
* DNA or RNA
* single-stranded or double stranded (ssDNA, dsDNA, ssRNA, dsRNA)
* linear, circular & segmented
Viral Structure: Capsid
- protein nucleic acid
- made of capsomeres
- may have spikes
Viral Structure: Enzymes
- use host cell machinery
* drugs that interfere with viral reproduction also disrupt host cell function
- some package their own (viral) enzymes
* we can target these with drugs
Viral Structure: Envelope
- naked non-envelope
- enveloped viruses
* phospholipid membrane around capsid
* from host plasma or nuclear membrane
* must stay moist during spread from host to host
Viral Structure: Envelope
- viral & host specific proteins/carbs
* adsorption/attachment sites (bind host receptor)
~ naked viruses
~ enveloped viruses
* determine host range
* example: influenza & HIV
Attachment
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Hemagglutination
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Antigenic Drift
- only RNA viruses can go through this
Classification
- nucleic acid
- size & shape
- +/- envelope
- strategy for replication
Virus Taxonomy
- 6 orders -virales
- 87 families -viridae
- 19 subfamilies -
- 248 genera -virus
Growth of Viruses
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Virus Plaques
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Viral Multiplication
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Lytic Cycle
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Comparison of Bacterial & Animal Virus Replication
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Virus Entry
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Animal Viral Biosynthesis: DNA Genomes
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Animal Viral Biosynthesis: RNA Genomes
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Release By Budding or Lysis
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Influenza Virus
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Antigenic Shift
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Retrovirus: HIV Virion Structure
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HIV Lifecycle
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HIV Activation
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Inhibition of HIV
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