VIRUSES and prions

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VIRUSES and prions

• CHAPTER 10 part 2

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Viruses part II - Animals and Plants
Unique challenges. Must evade immune systems
and must cross 2 lipid bilayer barriers. (ie
cross into nucleus)
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Viral Replication Animal Viruses
insert Viral_Rep_Animal.jpg
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RNA Virus Families

• 11 RNA virus families
• Picornaviridae (fmdv, polio)
• Togaviridae (rubella)
• Flaviviridae (hep C, west nile, yellow fever)
• Orthomyxoviridae (flu, influenza)

RNA viruses more prone to mutation
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RNA Virus Families (cont.)

• Retroviridae (hep B, htlv, HIV)-retrovirus
• reverse transcriptase used to make DNA
• from RNA
• Paramyxoviridae (measles, mumps, pneumonia) -
  ss strand

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RNA Virus Families (cont.)

• Rhabdoviridae (rabies)

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RNA Virus Families (cont.)

• Orthomyxoviridae (all influenza)

Hemaglutinnin H Neuraminidase N
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DNA Virus Families

• Adenoviridae (colds)
• Herpesviridae (varicellovirus, simplex virus)
• affinity for nervous tissue
• Poxviridae (smallpox)

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DNA Virus Families (cont.)

• Papovaviridae (HPV)
• Hepadnaviridae (Hep B virus)

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Viral Replication

• Activities
• Adsorption
• Penetration (virus or chromosome)
• Synthesis
• Maturation
• Release

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Animal Viruses

• DNA viruses

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Viruslike Agents

• Prions

Kuru Creutzfeld-Jacob BSE Scrapie
Alpha helix
B-pleated sheet
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Prions Characteristics
insert Prions_Character.jpg
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The PrP protein function in mammals is believed
to ________.

• assist proteins in forming alpha helices.
• assist proteins in forming beta-pleated sheets.
• assist in normal synaptic development and
  function.
• assist in normal membrane development and
  function.

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Which mammals code for PrP?

• humans
• cows
• sheep
• all mammals
• Mammals are not affected by prions.

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Why is the term reproduction not appropriate in
prion multiplication?

• Prions occur only in mammals, so reproduction is
  a misnomer.
• All mammals have PrP, so no reproduction is
  involved.
• Prions are acquired only through ingestion, not
  by reproduction.
• Prions transform normal proteins into the
  misfolded configuration therefore, prions
  multiply by conversion.

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Prions Overview
insert Prions_Overview.jpg
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How do prions replicate?

• binary fission
• They cause normal proteins to misfold into
  infectious proteins.
• mitosis
• via DNA replication

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How are prions different from other infectious
agents?

• They cause neurological disease.
• They lack protein.
• They lack nucleic acid.
• They cannot replicate.

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Why are the beta-pleated multimers of PrP
potentially pathogenic?

• They are not detected by other organisms.
• They repress the immune system.
• They are more stable as multimers and resistant
  to proteases.
• They are found on the surface of immune cells,
  resulting in destruction of the immune system.

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Prion Reproduction Diseases
insert Prions_Diseases.jpg
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What is the incubation period of BSE?

• 4 to 5 years
• 3 days
• 6 weeks
• 7 months

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Which of the following human prion diseases is
related to mad cow disease?

• fatal familial insomnia
• variant Creutzfeldt-Jakob disease
• kuru
• Gerstmann-Straussler-Scheinker syndrome

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Viruses and Cancer

• Mechanism of cancer causation
• HPV

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Viruses and Cancer

• Oncogenes/proto-oncogenes
• V-myc V-ras mimic our cells own control
  proteins

Rous Sarcoma Virus RSV
Kaposis sarcoma - appears when immune system
depressed probably by herpes virus 8
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Viruses to know something about
HPV (DNA) HIV (RNA) Flu (RNA)
Adenovirus(DNA) Herpes(DNA)
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Herpes Simplex
After initial infection, the viruses move to
sensory nerves, where they reside as life-long,
latent viruses.
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HPV human papilloma virus
Causes warts and some strains cause cervical
cancer teratogenic
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Viral Replication Temperate Bacteriophages
insert Viral_Rep_Temperate.jpg
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HIV human immunodeficiency virus
RNA retrovirus T-cell host (CD4 T-killer
cells) needs protease to replicate binds to
CCR5 and CD4 receptors
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Adenovirus
Common cold Usually affects respiratory
tract. sometimes engineered for gene therapy
DS DNA virus
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Influenza
H hemaglutinin N neuraminidase
RNA virus mutates rapidly animal
reservoirs can cross species lines