Viruses Lecture 5 (Test 1) Flashcards
(25 cards)
What is Neutralization?
when Ab to the viral spikes bind onto a virus/bacteria and stop them from binding to the host’s cells
Viral proteins made within the host will be what?
- Sampled, cut up and peptides presented on class I HLA .
- Then passing T cytotoxic cells can react w/ these cell surface complexes and DESTROY VIRAL FACTORIES
Why are mutated spikes important?
- In expanding the range of potential hosts a virus might infect
- Spike modifications or efficient transport from region to region allow this!
What are viruses?
Genes (nucelic acid genome) packaged in protein bottles (capsids).
-Can be ds DNA, ds RNA, ss DNA, or ss RNA
What shapes can the capsids be?
1) Isosahedral
2) Helical
How are viruses released?
1) A budding process
2) Lysis
What is the budding process ?
Where each virus leaves in a membrane bubble that stays around the virus capsid, MAKING an ENVELOPE(protein +lipid).
*Envelope has hundreds of virally encoded proteins, spikes imbedded in it.
What is lysis?
Viruses that trigger cells to break open and release naked nucleocapsids (**spike proteins are integrated directly into capsid!)
-Cytolysis= no envelope
What are the five cellular outcomes of viral infections?
- Abortive
- Lytic
- Chronic, non-lytic
- Latent
- Transformation
What is lytic?
An acute process where viral progeny are released by death (lysis) of the cell.
What is Chronic, non-lytic viral infection?
Infected cells slowly release viral progeny without cell death.
What is latent infection?
virus genome usually becomes integrated into the cell DNA where it becomes dormant for various times.
What is viral transformation?
where the virus causes the cell to proliferate in a uncontrolled manner.
Where is the genetic material stored in viruses?
Enclosed within the capsid.
What is the + sense strand?
What is the - antisense strand?
Same orientation as mRNA
opposite orientation as mRNA
What are the 2 key steps for the virus to replicate and cause disease within a cell, both involving nucleic acids?
1) Viruses must cause the replication of their genetic material
2) Viruses must produce positive-stranded mNRA (+) [(+) RNA], to replicate their protein components.
What are the key 6 steps of viral infection and replication?
1) viral attachment via spikes
2) penetrate cell
3) uncoat the protein and expose viral genome
4) Replication of viral protein & viral genome
5) Assembly of new viral particles
6) Release viral particles by 1) budding(envelope) or 2) lysis (naked)
NOTE* The cell NEVER does BOTH
What is viremia?
The release of viral agent into the blood.
-This is followed by multiple organ infection & secondary viremia
What are viroids?
Infectious nucleic acid polymers that lack capsids, infect plants.
What are prions?
infectious agents that appear to be only protein, infect only humans and animals.
How are diseases spread horizontally?
Example?
from individual to individual.
-This is spread by air, water, food, contact, insects, trauma to barriers, or from normal flora in immunosuppresed hosts.
Ex: EBV “kissing disease”
How are diseases spread vertically?
Example?
from mother to neonate, or both.
Ex: HSV-2
what is the iceberg effect?
Example?
Many infections that occur with little or no obvious symptoms and are followed by immune memory.
Example: EB virus
(1-5 yr old child)
1.0 % w/ clinically apparent disease
What must happen with the number of microorganisms to cause clinical disease?
The number of microorganisms present in a patient must EXCEED a certain “threshold” to cause disease.
-Note: The threshold of disease is NOT FIXED varies w/ physical state, genetics, and immunologic state of host.
Ex: Herpes
