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Virology > Lecture 4 > Flashcards

Lecture 4 Flashcards

1
Q

How do viruses compete with host for translation machinery?

A

Shut off host translation
-Viruses do not have a cap and use IRES instead
-IRES recruits 40s ribosomal without using eIF4E
-eIF4E gets degraded–>blocks host translation for host while still translating for virus

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2
Q

Between icosahedral and helical capsids which is more likely to assemble without a genome inside?

A

Icosahedral
-helical capsids require genome

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3
Q

What 2 ways can envelope be acquired and released?

A
  1. Sequential
  2. Concerted
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4
Q

How do enveloped viruses enter and exit cells?

A

Enter:
1. Fusion
2. Endocytosis
Exit
1. Budding
2. Exocytosis

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5
Q

How do non-enveloped viruses enter and exit cells

A

Enter:
1. Form a hole–>penetrate membrane
2. Endocytosis
Exit
1. Cell lysis
2. pore forming
3. exosomes

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6
Q

Characteristics of cell intrinsic immunity

A

-present in ALL cells
-fast to respond
-Hard coded in genome
-detects molecular patterns

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7
Q

Characteristics of cellular innate immunity

A

-Requires SPECIALIZED CELLS
-Fast to respond
-Hard coded in genome
-Detects molecular patterns

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8
Q

Characteristics of Adaptive immune response

A

-Requires SPECIALIZED CELLS
-SLOW to respond
-Adapts to pathogens
-detects very SPECIFIC molecular patterns
-Changes/evolves over time–>NOT hard coded

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9
Q

Which immune system cannot adapt to pathogens during infection?

A
  1. Cell intrinsic immunity
  2. Cellular Innate Immunity
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10
Q

Which imune system requires specialized cells?

A
  1. Cellular innate immunity
  2. Adaptive Immunity
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11
Q

True or false: Not all animals have an innate immune system

A

False
All animals have an innate immune system

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12
Q

What is the key signaling molecule in cell intrinsic immune system

A

Interferon (IFN)

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13
Q

What triggers the cell intrinsic innate response?

A

The presence of viral nucleic acid

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14
Q

What is a PAMP

A

Pathigen Associated Molecular Pattern
-Nucleic acid for viruses

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15
Q

What is PRR?

A

Pattern recognition receptor

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16
Q

What does the PRR RIG-I recognize?

A

Short dsRNA

17
Q

What does the PRR MDA-5 recognize?

A

Long dsRNA

18
Q

What does the PRR cGAS recognize?

A

dsDNA

19
Q

Where does the dsDNA in the cytoplasm that cGAS recognizes come from?

A

When mitochondria is under stress by RNA viruses it makes it leak dsDNA

20
Q

What is the pathway for RIG-I and MDA-5?

A
  1. Adaptor: MAVS
  2. Protein kinase: TBK1
  3. Transcription factors: IRF3 and IRF7
  4. Product: Type I IFN alpha and beta
21
Q

What is the pathway for cGAS?

A
  1. Adaptor: STING
  2. Protein kinase: TBK1
  3. Transcription factors: IRF3 and IRF7
  4. Product: Type I IFN alpha and beta
22
Q

What are ISGs

A

Interferon stimulated genes
-can singularly block any step in viral infection

23
Q

How are ISGs made?

A

IFN will bind to receptor IFNAR which activates protein kinase
-Transcription factors STAT1 and STAT2 are phosphorylated
-translocated into nucleus
-ISGs are made

24
Q

What is autocrine signaling?

A

IFN binds to receptors on the SAME cell that made the IFN & activates transcription on that cell

25
Q

What is paracrine signaling?

A

IFN binds to receptors on NEIGHBORING cells and activates transcription on those cells

26
Q

How are uninfected cell be warned & prevent infection?

A

Paracrine signaling from infected cell

27
Q

What is an example of a specific ISG and how does it work?

A

TRIM5alpha–>specific HIV restriction factor
-binds to HIV capsids & forces them to uncoat quickly–>disrupts reverse transcription

28
Q

How can viruses evolve around TRIM5alpha?

A

Viruses can change its sequences of their core proteins so TRIM5alpha cannot bind

29
Q

What is an example of a general ISG and how does it work?

A

Protein kinase R (PKR)–>general mRNA translation inhibitory factor
-activated by dsRNA
-phosphorylates eIF2alpha–>prevents cap dependent mRNA translation

30
Q

How can viruses evolve around PKR?

A

Cap independent mRNA translation

31
Q

What are the 2 cell death pathways?

A
  1. Apoptosis
  2. Pyroptosis
32
Q

How does apoptosis work and what signals it?

A

Cell death is caused by caspases 3 and 7
External signal: TNFalpha
Internal signal: Cell stress (mitochondrial damage)

33
Q

How does pyroptosis work and what signals it?

A

Cell death is caused by inflammasome and caspase 1
-IL-1beta and IL-18 causes inflammation and cell death

34
Q

What can repress gene expression?

A

Small RNA molecules (siRNAs)

35
Q

How does RNAi work?

A

Perfect complementary to target leads to cleavage
-important in plants and eukaryotes

36
Q

How do microRNAs work?

A

Imperfect complementarily to target leads to mRNA translation repression

Virology (19 decks)

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