Lecture 3

Question 1

Why should you care about virus replication strategies?

Answer 1

Studying virus lifecycles exposes vulnerabilities that may be exploited in the treatment of diseae

Question 2

Why is the fact that viruses are obligate intracellular parasites which rely on the host cells biosynthetic machinery a proble,

Answer 2

This makes it harder to find drugs that are effective at blocking virus replication without being toxic to host cells

Question 3

Name 2 ways to protect against viral infection

Answer 3

1) Identify important virus specific activities and devise ways to interfere with these through the development of antiviral drugs
2) Develop vaccines that protect against viral infection

Question 4

Why should you use drugs that target multiple virus properties?

Answer 4

Viruses accumulate mutations very quickly and can survive antibiotic by natural selection. Targeting many properties at once helps to avoid this.

Question 5

Single - Step Growth Curve for Adenovirus
What is it (basic definition)?

Answer 5

Single - Step Growth Curve for Adenovirus
= homogeneous system for studying virus replication

Question 6

Single - Step Growth Curve for Adenovirus
- What type of cells are used

Answer 6

performed on cultured cells

Question 7

What does a MOI of 10 mean

Answer 7

MOI = 10
Means there are 10 infectious viruses per cell

Question 8

Growth Curve:
At what temperature is a virus absorbed?
At what temp does a virus penetrate the cell?

Answer 8

4C
37C

Question 9

What can’t a virus penetrate a cell at 4C?

Answer 9

Penetration is an energy dependent process, thus it requires a higher temperature

Question 10

Define - Eclipse period

Answer 10

Eclipse Period: The time between absorption of a virus to the cell and the appearance of infectious virus

Question 11

Define - Latent Period

Answer 11

Latent Period: time between absorption of virus and release of new infectious viruses from the cell

Question 12

Can the eclipse period = the latent period?

Answer 12

Yes
Ex. Viruses whose maturation and release form the cell coincide

Question 13

Do viruses grow exponentially?

Answer 13

NO - viruses are release as a burst due to the fact that they are assembled from preformed components

Question 14

What are the steps of the latent period?

Answer 14

1) Attachment/absorption of virus to the cell
2) Penetration of virus into the cell
3) Uncoating of the viral genome
4) Viral gene expression
5) Virus genome replication
6) Assembly of new viruses and egress or release from the cell

Question 15

An “anti-receptor” is another name for?

Answer 15

Anti-receptor = virus attachment protein

Question 16

Does Virus attachment require energy?

Answer 16

No - virus attachment is an energy-independent process
- think about how on the growth curve they can attach at 4C

Question 17

Describe - “Attachment” in the latent period

Answer 17

Consists of specific binding of a virus-attachment protein (sometimes called “anti-receptor”) with a cellular receptor molecule

Question 18

What can target receptors for attachment be?

Answer 18

• Proteins (usually glycoproteins)
• Carbohydrates ( found on glycoproteins or glycolipids)

Question 19

Which type of receptor is more specific:
- Protein
- or
- Carbohydrate?

Answer 19

Protein = more specific
Carbohydrate receptors are less specific than protein receptors bc the same configuration of carbohydrate side-chains may occur on many different glycosylated membrane bound molecules

Question 20

What was the name of the terminal sugar mentioned in lecture that influenza binds to?

Answer 20

Sialic acid is a terminal sugar that influenza likes to bind to

Question 21

Many viruses use multiple receptors … Why?
(2 reasons)

Answer 21

1) Either multiple receptors exist for the virus that may be used to gain access into different tissue types
2) Sometimes multiple receptors are utilized for the entry of a virus into a single cell i.e co-receptors

Question 22

Can different viruses use the same cellular receptor?

Answer 22

yes

Question 23

What did HIV attachment and fusion example demonstrate?

Answer 23

HIV attachment and fusion was an example of multicellular receptor use
- binding of one glycoprotein caused conformational changes allowing for more binding then the fusion protein could interact

Question 24

Does viral penetration require energy?

Answer 24

Yep - thus the cell must be metabolically active for this to occur

Question 25

What are the 2 mechanisms of penetration?

Answer 25

1) Endocytosis of the virus into intracellular vesicles (endosomes)
- Common

2) Fusion of the virus envelope with a cellular membrane
- Only applicable to enveloped viruses
- Requires the presence of a specific fusion protein in the virus envelope

Question 26

What are the 2 types of virus-driven membrane fusion?

Answer 26

• pH independent = can occur at cell surface or within an endosome
• pH dependent = occurs within an acidified endosome

Question 27

Define - Uncoating

Answer 27

§ Uncoating occurs after penetration, where the virus capsid is completely or partially removed and the virus genome is exposed

Question 28

What are the 3 general strategies for uncoating?

Answer 28

1) Uncoating at the plasma membrane
2) Uncoating within endosomes
3) Uncoating at the nuclear membrane

Question 29

Which direction do - motors move particles

Answer 29

• end motors = dynein = more towards centromere

Question 30

Which direction do + motors move particles

Answer 30

+ end motors = kynesin = more towards outside of cell