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Immunology > Lytic Viruses > Flashcards

Lytic Viruses Flashcards

1
Q

Lytic viruses

A

Viruses that induce destruction of a cell

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2
Q

Picornavirus Physical Properties

Size:

Morphology:

Nucleic Acid:

Lipid Envelope:

Tegument:

pH stability:

A

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

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3
Q

Diseases associated with these simple viruses

Enteroviruses:

Rhinoviruses:

Hepatoviruses:

Parechovirus:

Kobuvirus:

A

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

Rhinoviruses: common cold

Hepatoviruses: hepatitis

Parechovirus: gastroenteritis, myocarditis, encephalitis

Kobuvirus: gastroenteritis

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4
Q

Enterovirus pathway

A

Fecal/oral pathway

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5
Q

Polio - Infection vs. Disease

A
  • 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
      *
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6
Q

Paralytic poliomyelitis (0.1-2%)

A
  • 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
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7
Q

How does infection happen

A

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

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8
Q

Picornavirus - Diagnosis

A
  • Virus isolation
    • Stool specimens and throat washings
    • Cerebrospinal fluid
    • Specific cell culture
  • Serology
    • 4 fold greater rise in titer
    • neutralization
  • PCR (multiplex)
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9
Q

Polio epidemiology

A
  • An ancient disease
  • Exclusively a human disease
  • fecal - oral transmission
  • Transmission enhanced by persons with sub-clinical infections
  • Summer epidemics in temperate climates
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10
Q

Three major epidemiological phases: Endemic

A
  • Children encounter virus at an early age
  • Maternal antibody offers protection
  • High rate of subclinical infections
  • Very low incidence of paralytic disease
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11
Q

Three major epidemiological phases: Epidemic

A
  • 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)
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12
Q

Three major epidemiological phases: Post-vaccine

A
  • Small number of cases
  • Most all cases are vaccine related
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13
Q

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

A

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

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14
Q

Poliovirus entry and genome release

A

Requires receptor interaction and injection of RNA genome into cytoplasm

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15
Q

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

A

Translation

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16
Q

Picornavirus prevention and control

A
  • Virus attachment
    • block receptors (antibody or chemicals)
  • Virus entry and genome release
  • Protease processing
  • RNA-dependent RNA polymerase inhibitors
17
Q

Polio - Public Health success

A

1955 - Inactivated virus vaccine (Salk)

1962 - Live attenuated virus vaccine (Sabin)

18
Q

Other RNA viruses - Different challenges

A

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
Q

Adenovirus

A
  • 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
Q

The adenovirus particle is much more ______ than the picornavirus particle

A

complicated

21
Q

Adenovirus disease

A
  • 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
Q

Adenovirus infectious progression

A

Eye, Upper respiratory, Gastrointestinal

23
Q

Adenovirus attachment and entry

A
  1. Viral surfing
  2. Clathrin mediated endocytosis
  3. Viral fusion pore control
24
Q

Production and Release of Adenovirus from epithelial cells

A

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
Q

Where in the cell does adenovirus undergo intracellular production

A

Nucleus

26
Q

How is adenovirus gene expression complex

A
  • Not simple partitioning into early and late segments
  • Clusters of genes are expressed from a limited number of shared promoters
27
Q

Adenovirus vaccine

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

Immunology (17 decks)

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