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Microbiology > Viral Replication & Pathogenesis > Flashcards

Viral Replication & Pathogenesis Flashcards

1
Q

Mention the stages of viral replication

A
  1. Recognition
  2. Attachment
  3. Penetration/Uncoating
  4. Early expression of viral genes
  5. Replication of viral nucleic acid
  6. Synthesis of new viral components
  7. Assembly and packaging of new virions
  8. Exit from cell
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2
Q

Which one of the steps of viral replication is an energy-dependent step❓

A

Penetration

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3
Q

Describe the process of uncoating

A

Separation of viral nucleic acid from outer structural components

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4
Q

After the process of uncoating, how are viruses released❓

A

As free n.a eg picornavirus

Nucleocapsid eg reovirus

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5
Q

Naked viruses accumulate in the cytoplasm and are released during lysis

True or false

A

True

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6
Q

Enveloped viruses are released gradually by budding or exocytosis

True or false

A

True

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7
Q

List the factors in viral pathogenesis

A 
Virulence of virus 
Effects of viral infection 
Entry into host 
Course of infection 
Cell tropism
Cell damage 
Host immune response
Virus persistence
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8
Q

The course of a viral infection would go as follows…

A

•Primary replication
Where virus replicates after gaining initial entry into the host

•Systemic spread
Virus many spread via blood stream

•Secondary replication
Takes place at susceptible tissues following systemic spread

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9
Q

Viral virulence depend on what factors❓

A

Dose

Virus strain

Inoculation route

Host factors

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10
Q

Viral affinity for specific body tissues is determined by❓

A

Cell receptors for virus

Ability of cell to support viral replication

Physical barriers

Temperature, pH, oxygen tension

Digestive enzymes and bile

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11
Q

Retroviruses do not generally cause cell death. Why❓

A

They are released from the cell by budding rather than by cell lysis and cause persistent infections

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12
Q

Mention a few viruses that cause lysis and death of the cells in which they replicate

A

Picornavirus

Rhinovirus (fever, ⬆️mucus secretion)

Poliovirus (paralysis or death due to respiratory failure)

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13
Q

Immune response to a virus has the greatest impact on the outcome of infection

True or false

A

True

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14
Q

Cellular immunity plays the major role in clearing virus infection whereas humoral immunity protects against reinfection

True or false

A

True

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15
Q

Enhanced viral injury could be due to what mechanisms❓

A

⬆️secondary response to Tc cells eg HBV

Complement mediated cell lysis

Binding of unneutralized virus complexes to cell-surface Fc receptors, thus ⬆️no of affected cells eg Dengue haemorrhagic fever, HIV

Immune complex deposition in organs eg rash of rubella and measles

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16
Q

What are the two types of chronic persistent infections❓

A
  1. True latency-
    •Complete latency after infection eg HSV, VSV
    •Genome maybe integrated into cellular genome or exist as episome
  2. Persistence-
    •replication is continuous at a very low level eg HIV, HBV, CMV, EBV
17
Q

What are the mechanisms of viral persistence❓

A

Antigenic variation

Immune tolerance due to genetics, pre-natal infection, molecular mimicry

Restricted gene expression

⬇️regulation of MCH1
🚫recognition of infected cells
Eg adenovirus

⬇️regulation of molecules involved in immune recognition eg LFA-3 and ICAM-1 by EBV

Infection of immunopriviliged sites within the body eg HSV in sensory ganglia in the CNS

Direct infection of cells of immune system itself eg Herpes virus and HIV

18
Q

Which virus causes a down regulation of LFA-3 and ICAM-1❓

A

EBV

19
Q

Which virus causes a direct infection of cells of immune system itself❓

A

Herpes virus

HIV

20
Q

Adenovirus causes a ⬇️regulation of MHC_2

True or false

A

False, MHC_1

21
Q

How would

  1. DNA genomes undergo replication❓
  2. +ssRNA genomes undergo replication❓
  3. -ssRNA genomes undergo replication❓
A
  1. Similar to cellular replication; transcription, translation
  2. Either translation/reverse transcribed to DNA first
  3. Used as template to make +ssRNA first, then continues like no.3
22
Q

HSV causes an infection of immunopriviliged sites (CNS) in the body

True or false

A

True

Microbiology (11 decks)

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