Viruses Lecture 5 (Test 1)

Question 1

What is Neutralization?

Answer 1

when Ab to the viral spikes bind onto a virus/bacteria and stop them from binding to the host’s cells

Question 2

Viral proteins made within the host will be what?

Answer 2

• 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

Question 3

Why are mutated spikes important?

Answer 3

• In expanding the range of potential hosts a virus might infect
• Spike modifications or efficient transport from region to region allow this!

Question 4

What are viruses?

Answer 4

Genes (nucelic acid genome) packaged in protein bottles (capsids).

-Can be ds DNA, ds RNA, ss DNA, or ss RNA

Question 5

What shapes can the capsids be?

Answer 5

1) Isosahedral

2) Helical

Question 6

How are viruses released?

Answer 6

1) A budding process

2) Lysis

Question 7

What is the budding process ?

Answer 7

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.

Question 8

What is lysis?

Answer 8

Viruses that trigger cells to break open and release naked nucleocapsids (**spike proteins are integrated directly into capsid!)

-Cytolysis= no envelope

Question 9

What are the five cellular outcomes of viral infections?

Answer 9

1. Abortive
2. Lytic
3. Chronic, non-lytic
4. Latent
5. Transformation

Question 10

What is lytic?

Answer 10

An acute process where viral progeny are released by death (lysis) of the cell.

Question 11

What is Chronic, non-lytic viral infection?

Answer 11

Infected cells slowly release viral progeny without cell death.

Question 12

What is latent infection?

Answer 12

virus genome usually becomes integrated into the cell DNA where it becomes dormant for various times.

Question 13

What is viral transformation?

Answer 13

where the virus causes the cell to proliferate in a uncontrolled manner.

Question 14

Where is the genetic material stored in viruses?

Answer 14

Enclosed within the capsid.

Question 15

What is the + sense strand?

What is the - antisense strand?

Answer 15

Same orientation as mRNA

opposite orientation as mRNA

Question 16

What are the 2 key steps for the virus to replicate and cause disease within a cell, both involving nucleic acids?

Answer 16

1) Viruses must cause the replication of their genetic material
2) Viruses must produce positive-stranded mNRA (+) [(+) RNA], to replicate their protein components.

Question 17

What are the key 6 steps of viral infection and replication?

Answer 17

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

Question 18

What is viremia?

Answer 18

The release of viral agent into the blood.

-This is followed by multiple organ infection & secondary viremia

Question 19

What are viroids?

Answer 19

Infectious nucleic acid polymers that lack capsids, infect plants.

Question 20

What are prions?

Answer 20

infectious agents that appear to be only protein, infect only humans and animals.

Question 21

How are diseases spread horizontally?

Example?

Answer 21

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”

Question 22

How are diseases spread vertically?

Example?

Answer 22

from mother to neonate, or both.

Ex: HSV-2

Question 23

what is the iceberg effect?

Example?

Answer 23

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

Question 24

What must happen with the number of microorganisms to cause clinical disease?

Answer 24

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

Question 25

Detail what happens when virus attaches to host.

Answer 25

Virus attach onto host’s cell via spikes → the envelope of the virus fuse with the cell membrane → virus penetrate the cell → uncoat the protein capsid to release genetic materials → replication of viral proteins and genomes → assemble new viruses → released