Lecture 14 The Micobial World VIRUSES

Question 0

What is the major target for Ab’s on viruses?

Answer 0

The viral spikes present of the viruses.

*We can stop infections from occurring if Abs are made to that spike this = neutralization.

Question 1

How are viruses neutralized?

Answer 1

T cytotoxic cells can react with cell surface complexes and destroy the viral factories. At the same time Ab’s will intercept the newly produced “messages in bottle” and stop new cells from being infected by binding the viruses and blocking their ability to bind.

Question 2

How are new viruses of recent times infecting new hosts?

Answer 2

Spike (*glycoprotein) modifications and/or because of more efficient transport from region to region in the world.

Question 3

What are viruses?

Answer 3

Viruses are genes (Nucleic acids genome) packaged in protein bottles. They can be either ss DNA/RNA or ds DNA/RNA

Question 4

What are the possible shapes for the capsids (“protein bottles”) ?

Answer 4

1) icosahedral 2) helical

Question 5

what are the two ways viruses can be released?

Answer 5

1) Budding process

2) Lysis

Question 6

What is the budding process?

Answer 6

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 7

What is lysis?

Answer 7

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

-Cytolysis= no envelope

Question 8

What are the five cellular outcomes of viral infections?

Answer 8

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

Question 9

What is lytic?

Answer 9

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

Question 10

What is Chronic, non-lytic viral infection?

Answer 10

Infected cells slowly release viral progeny without cell death.

Question 11

What is latent infection?

Answer 11

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

Question 12

What is viral transformation?

Answer 12

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

Question 13

Where is the genetic material stored in viruses?

Answer 13

Enclosed within the capsid.

Question 14

What is the + sense strand?

What is the - antisense strand?

Answer 14

Same orientation as mRNA

opposite orientation as mRNA

Question 15

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

Answer 15

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

Question 16

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

Answer 16

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 17

What is the growth curve like for a single cell infected with a single virus particle?

Answer 17

Most viral infections follow a simple one=step growth curve.

Question 18

What does the eclipse period represent>?

Answer 18

The period of time during which the virus uncoats and begins replicating its individual constituents.

*Total number = yield

Question 19

What do all viruses need to be able to synthesize to effectively carryout their replication in a cell? and Why?

Answer 19

positive-strand + mRNA

Because viruses hijack a cells normal mechanisms for translation of + mRNA into proteins.

Question 20

What is viremia?

Answer 20

The release of viral agent into the blood.

Question 21

What are viroids?

Answer 21

Infectious nucleic acid polymers that lack capsids, infect plants.

Question 22

What are prions?

Answer 22

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

Question 23

How are diseases spread horizontally?

Answer 23

from individual to individual.

-This is spread by air, water, food, contact, insects, trauma to barriers, or from normal flora in immunosuppresed hosts.

Question 24

How are diseases spread vertically?

Answer 24

from mother to neonate, or both.

Question 25

what is the iceberg effect?

Answer 25

Many infections that occur with little or no obvious symptoms and are followed by immune memory.

Question 26

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

Answer 26

The number of microorganisms present in a patient must exceed a certain “threshold” to cause disease.

Question 27

Is the threshold of overt disease fixed?

Answer 27

No it is not, it varies with physical state, genetics, immunological status etc, of the host.

Question 28

a) Will a viral ssDNA(single strand) need to code for NA-polymerase?
b) Also will it need to bring in a NA- polymerase?

Answer 28

a) - NO

b) - NO

Question 29

a) Will a viral dsDNA(double strand) need to code for NA-polymerase?
b) Also will it need to bring in a NA- polymerase?

Answer 29

a) - NO

b) - NO

Question 30

a) Will a viral (+ )ssRNA (single strand) need to code for NA-polymerase?
b) Also will it need to bring in a NA- polymerase?

Answer 30

a) + Yes

b) - No (will use hosts cell ribosomes)

Question 31

a) Will a viral (-) ssRNA (single strand) need to code for NA-polymerase?
b) Also will it need to bring in a NA- polymerase?

Answer 31

a) + Yes

b) + Yes

Question 32

a) Will a viral dsDNA(double strand) need to code for NA-polymerase?
b) Also will it need to bring in a NA- polymerase?

Answer 32

a) + YES

b) + YES

Question 33

What are the 4 types of replication discussed in class specific to DNA/DNA dependent RNA/DNA polymerase (Hint: charts he drew)

Answer 33

1) DNA dependent, DNA polymerase
2) DNA dependent, RNA polymerase
3) RNA dependent, RNA polymerase
4) RNA dependent, DNA polymerase