Innate immune responses against viruses

Question 1

What are the four lines of defense against viruses?

Answer 1

1. Anatomical and chemical barriers
2. Intrinsic Immunity
3. Innate Immunity
4. Acquired Immunity

Question 2

What are the examples of Anatomical and chemical barriers?

Answer 2

Skin, mucus, saliva, tears, stomach acid

Question 3

Three processes steps of Intrinsic Immunity.

Answer 3

1. Autophagy
2. Apoptosis
3. Antiviral restriction factors

Question 4

What is the ancient greek meaning of autophagy? Virophagy? what happens during autophagy?

Answer 4

“self-devouring”
The digestion of viral particles of autophagosome.

First the virus particle is engulfed by a double-membrane structure called autophagosome after which it fuses with lysosome to form autolysosome. This in turn digests the virus.

Question 5

What are antiviral restriction factors?

Answer 5

Functionally and structurally diverse effectors that target viruses at every stage of their replication cycle.

Question 6

What is the first line of antiviral cellular defence? Is it active even in the absence of viral infection?

Answer 6

Antiviral restriction factors
Yes

Question 7

What causes the further upregulation of antiviral restriction factors?

Answer 7

Interferons

Question 8

What kind of viral features or replication events are targeted by the antiviral restriction factors?

Answer 8

evolutionarily conserved

Question 9

Viruses have evolved mechanisms to escape antiviral restriction factors?

Answer 9

1. they produce proteins that inhibit ARFs activities
2. they mutate proteins that cannot be recognized by ARFs

Question 10

“Due to the ongoing evolutionary virus–host arms race, antiviral restriction factors are often under positive selection”

Answer 10

Antiviral restriction factors are subject to positive selection pressure, meaning that beneficial mutations that enhance their antiviral activity are favored and spread within the host population over time.

Question 11

• Tetherin is type-1 protein which is induced by ____ and is under ___ selection.
• How does it inhibit the growth of viruses?
• What two other proteins/cells are activated by tetherin?
• Example of virus that can antagonize tetherin?

Answer 11

1. IFN, positive
2. by causing the newly produced virus particles to get stuck to the cell surface.
3. NF-Kb protein and NK cells
4. HIV

Question 12

• ZAP?
• Type 1 protein which is induced by ___
• found in ___ and ____
• recognize which sequence?
• strategy adopted by viruses to escape ZAP?

Answer 12

• zinc finger antiviral protein
• IFN
• cytoplasm and cell membrane
• CPG- dinucleotide sequence
• they reduce the number of CPG so that that ZAP cannot prevent their replication

Question 13

• APOBEC3 proteins are type 1 ___ inducible proteins under __ selection

-another name? why?

• viruses which have found ways to counteract APOBEC3
• these proteins also play an important role in ____

Answer 13

• IFN, positive
• cytidine deaminases, replaces cytidine of ssDNA to uridine
• HIV using rif
• evolution

Question 14

Apoptosis

Answer 14

Programmes cell death, falling off

Question 15

How is apoptosis initiated?

Ways in which viruses activate apoptosis?

Answer 15

• intrinsic; it is initiated by cellular stress
• extrinisically: tnf
• receptor binding
• mhc binding
• interact with PKR
• P53

Question 16

1. Pyrotopsis
2. mediated by ____ which is initiated by ____ that respond to ____ and ____
3. overactivated and dysregulation of inflammasome is associated with ______

Answer 16

• programmed cell death which is associated with inflammation
• inflammasome, PRR, PAMPs and DAMPs
• inflammatory disorders and pathogenesis

Question 17

What activates the innate immunity?

Answer 17

• IFNs
• antiviral cytokines

Question 18

• what is the definition of IFN?
• their effects?
• which types of IFN do humans encode?
• __ and __ are expressed in all cell types
• ___ is expressed in only in APCs

Answer 18

• cytokines that interfere with viral replication, they “alarm” the body of the antiviral responses
• they activate intrinsic immunity by activating immune cells and by increasing antigen presentation of cells
• type 1, 2 and 3
• 1 and 3
• 2 - NKC and T cells

Question 19

Which immune cells (innate) play the most active role in viral infection?

Answer 19

• macrophages
• monocytes
• nkc
• dendritic cells

Question 20

1. which compartment does macrophage form to engulf materials and what does it fuse it with?
2. What cells are APCs and which receptors do they have?
3. What activates them and which cells further activate the adaptive immunity?
4. they contain ____ to recognize various viruses and produce ____ such as ___
5. ___ migrate to infection sites and differentiate into ___
6. HIV replicates in ___ and can bind to ___ then travel to lymph nodes and they are targeted by ____

Answer 20

1. phagosome, lysosome containing hydrolytic enzymes
2. macrophages and DCs, MHC-2
3. interferons, DCs - lymph nodes
4. PRRs, cytokines such as interferons
5. monocytes, macrophages and DCs
6. macrophages, DCs, CD4 plus cells

Question 21

____ are specialized cells that kill self-infected cells by recognizing the decrease in ___

NKs are activated in response to ___
and they can produce ___

NKCs release enzymes ____ and can kill cells by ___ or ____

Answer 21

1. Cytotoxic lymphocytes, MHC class 1
2. interferons, Type 2 IFNs
3. that cause pores in the membrane and apoptosis or osmotic cell lysis