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Flashcards in Lytic Viruses Deck (27):
1

Lytic viruses

Viruses that induce destruction of a cell

2

Picornavirus Physical Properties

Size:

Morphology:

Nucleic Acid:

Lipid Envelope:

Tegument:

pH stability:

Size: 22-30nm

Morphology: Icosahedral

Nucleic Acid: ssRNA (+ polarity)

Lipid Envelope: NO

Tegument: NO

pH stability: Enteroviruses stable at pH 3-9; Rhinoviruses unstable below pH 6

3

Diseases associated with these simple viruses

Enteroviruses:

Rhinoviruses:

Hepatoviruses:

Parechovirus:

Kobuvirus:

Enteroviruses: paralysis, common cold, meningitis, diarrhea, hand-foot-and-mouth disease

Rhinoviruses: common cold

Hepatoviruses: hepatitis

Parechovirus: gastroenteritis, myocarditis, encephalitis

Kobuvirus: gastroenteritis

4

Enterovirus pathway

Fecal/oral pathway

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5

Polio - Infection vs. Disease

  • Inapparent infections (90-95%)
    • Virus recoverd from throat and/or stool
    • asymptomatic
  • Mild illness (4-8%)
    • Minor undifferentiated ferbile illness
    • Influenza like
  • Asceptic meningitis (1-2%) - non paralytic
    • Minor illness progresses to CNS infasion
    • Disease lasts 2-10 days; rapid and complete recovery
    •  

6


Paralytic poliomyelitis (0.1-2%) 

 

 

 

  • Initial nonspecific febrile illness
  • Spectrum of paralytic disease is variable
  • Asymmetric flaccid paralysis
  • Lower extremeties involved more than upper
  • Large muscle groups involved more often
  • Bulbar paralysis: involvement of cranial nerves, medulla, respiratory compromise, death 5%
  • Slow recovery
  • Complications - resiudal paralysis

7

How does infection happen

Virus passes into Gastro-associated lymph tissues, then to local lymph nodes and then to the blood stream via lymphatic system

8

Picornavirus - Diagnosis

  • Virus isolation
    • Stool specimens and throat washings
    • Cerebrospinal fluid
    • Specific cell culture
  • Serology
    • 4 fold greater rise in titer
    • neutralization
  • PCR (multiplex)

9

Polio epidemiology

  • An ancient disease
  • Exclusively a human disease
  • fecal - oral transmission
  • Transmission enhanced by persons with sub-clinical infections
  • Summer epidemics in temperate climates

10

Three major epidemiological phases: Endemic

  • Children encounter virus at an early age
  • Maternal antibody offers protection
  • High rate of subclinical infections
  • Very low incidence of paralytic disease

11

Three major epidemiological phases: Epidemic

  • Late 1800s and Early 1900s in US
  • Coincides with advent of indoor plumbing
  • Patients are older when they first encounter virus
  • Higher incidence of paralytic disease in older children and adults (no longer have maternal antibody)

12

Three major epidemiological phases: Post-vaccine

  • Small number of cases
  • Most all cases are vaccine related

13

How many proteins are made by the polio virus? Why is this important?

1 protein - which uses protesases to cut itself into many smaller proteins - these proteases are a good target for treatment

14

Poliovirus entry and genome release

Requires receptor interaction and injection of RNA genome into cytoplasm

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15

Viral Effect on host cell; Inhibition of ________ plays a role in cell death

Translation

16

Picornavirus prevention and control

 

  • Virus attachment
    • block receptors (antibody or chemicals)
  • Virus entry and genome release
  • Protease processing
  • RNA-dependent RNA polymerase inhibitors

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17

Polio - Public Health success

1955 - Inactivated virus vaccine (Salk)

1962 - Live attenuated virus vaccine (Sabin)

18

Other RNA viruses - Different challenges

Negative strand RNA - can't immediatedly translate genome (Don't come with their own ribosomes)

  • Have to bring along their own protein to get to positive strand RNA

Double stranded RNA - segmented genomes with each segment transcribed separeately to produce monocistronic mRNAs

19

Adenovirus

  • Original isolate form normal adenoid tissues
  • 51 serotypes
  • Cross reactivity - family common antigen - reduces infection with other types and re-infection is rare
  • Double-stranded DNA genome not enveloped
  • Spread via fecal/oral route or respiratory
  • Frequently causes unapparent respiratory infections
  • Icosahedral capsid 

20

The adenovirus particle is much more ______ than the picornavirus particle

complicated

21

Adenovirus disease

  • Gastrointestinal in children
  • More severe in immunosuppressed
  • Enteric adenovirus infections
    • Incubation 3-10 days
    • Diarrhea lasts 6-9 days
    • May have vomiting and fever preceding diarrhea
    • More common in children than adults

22

Adenovirus infectious progression

Eye, Upper respiratory, Gastrointestinal

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23

Adenovirus attachment and entry

  1. Viral surfing
  2. Clathrin mediated endocytosis
  3. Viral fusion pore control




     

24

Production and Release of Adenovirus from epithelial cells

Virus attaches to apical surface

Virus shed into intestinal lumin

Virus released from basal surface

Excess virus penton spike fiber released from cells - disrupts adhesion junctions

25

Where in the cell does adenovirus undergo intracellular production

Nucleus

26

How is adenovirus gene expression complex

  • Not simple partitioning into early and late segments
  • Clusters of genes are expressed from a limited number of shared promoters

27

Adenovirus vaccine

  • A live adenovirus vaccine became available and is routinely administered upon entry into the armed forces
  • Prevoius vaccine was discontinued in 1999