Lecture 3 Flashcards
Why should you care about virus replication strategies?
Studying virus lifecycles exposes vulnerabilities that may be exploited in the treatment of diseae
Why is the fact that viruses are obligate intracellular parasites which rely on the host cells biosynthetic machinery a proble,
This makes it harder to find drugs that are effective at blocking virus replication without being toxic to host cells
Name 2 ways to protect against viral infection
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
Why should you use drugs that target multiple virus properties?
Viruses accumulate mutations very quickly and can survive antibiotic by natural selection. Targeting many properties at once helps to avoid this.
Single - Step Growth Curve for Adenovirus
What is it (basic definition)?
Single - Step Growth Curve for Adenovirus
= homogeneous system for studying virus replication
Single - Step Growth Curve for Adenovirus
- What type of cells are used
performed on cultured cells
What does a MOI of 10 mean
MOI = 10
Means there are 10 infectious viruses per cell
Growth Curve:
At what temperature is a virus absorbed?
At what temp does a virus penetrate the cell?
4C
37C
What can’t a virus penetrate a cell at 4C?
Penetration is an energy dependent process, thus it requires a higher temperature
Define - Eclipse period
Eclipse Period: The time between absorption of a virus to the cell and the appearance of infectious virus
Define - Latent Period
Latent Period: time between absorption of virus and release of new infectious viruses from the cell
Can the eclipse period = the latent period?
Yes
Ex. Viruses whose maturation and release form the cell coincide
Do viruses grow exponentially?
NO - viruses are release as a burst due to the fact that they are assembled from preformed components
What are the steps of the latent period?
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
An “anti-receptor” is another name for?
Anti-receptor = virus attachment protein
Does Virus attachment require energy?
No - virus attachment is an energy-independent process
- think about how on the growth curve they can attach at 4C
Describe - “Attachment” in the latent period
Consists of specific binding of a virus-attachment protein (sometimes called “anti-receptor”) with a cellular receptor molecule
What can target receptors for attachment be?
- Proteins (usually glycoproteins)
- Carbohydrates ( found on glycoproteins or glycolipids)
Which type of receptor is more specific:
- Protein
- or
- Carbohydrate?
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
What was the name of the terminal sugar mentioned in lecture that influenza binds to?
Sialic acid is a terminal sugar that influenza likes to bind to
Many viruses use multiple receptors … Why?
(2 reasons)
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
Can different viruses use the same cellular receptor?
yes
What did HIV attachment and fusion example demonstrate?
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
Does viral penetration require energy?
Yep - thus the cell must be metabolically active for this to occur
What are the 2 mechanisms of penetration?
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
What are the 2 types of virus-driven membrane fusion?
- pH independent = can occur at cell surface or within an endosome
- pH dependent = occurs within an acidified endosome
Define - Uncoating
§ Uncoating occurs after penetration, where the virus capsid is completely or partially removed and the virus genome is exposed
What are the 3 general strategies for uncoating?
1) Uncoating at the plasma membrane
2) Uncoating within endosomes
3) Uncoating at the nuclear membrane
Which direction do - motors move particles
- end motors = dynein = more towards centromere
Which direction do + motors move particles
+ end motors = kynesin = more towards outside of cell
