Virology (Thiele)

Question 1

Which viruses can Slip through memb without binding receptors?

Answer 1

1) Parvovirus
2) Rhinovirus
- both small and it happens by chance

Question 2

How do most viruses enter a cell?

Answer 2

Receptor mediated endocytosis

-Viral Receptor and a VAP(on virus)

Question 3

Uncoating

Answer 3

DNA Virus- endocytosed, capsid travels to nucleus where it releases DNA. Capsid uncoating
RNA Virus- uncoating done more rapidly, RNA released into the cytosol. Nucleoprotein uncoating

Question 4

Monocystronic

Answer 4

Each mRNA produces one specific protein

Question 5

Polycistronic

Answer 5

• Each MRNA produces multiple proteins on THE SAME poly peptide chain
• Cleave large protein into smaller proteins

Question 6

Monopartite

Answer 6

All genes are found on single strand of DNA or RNA

Question 7

Multipartitie

Answer 7

Virlar genes are distributed between several strands of DNA or RNA
-Together=GENOME

Question 8

Positive Strand

Answer 8

can be read by host ribosomes

Question 9

negative strand

Answer 9

can NOT be read by host genomes

• packaged in capsid with its own RNA dep, RNA poly
• must synthesize complementary strand before translating

Question 10

Three phases of viral proteins

Answer 10

1) Intermediate Early
2) Early
3) Late

Question 11

Intermediate Early

Answer 11

Makes proteins that allow virus to takeover cell

Question 12

Early

Answer 12

Makes enzymes to replicate and begins replication of Viral genome

Question 13

Late

Answer 13

Makes structural proteins (E.g. Capsid and Glycoproteins

-DNA is packaged at the nucleus

Question 14

Retroviruses

Answer 14

Capsid contains RNA dep DNA poly packaged with the RNA

-reverse transcribes the RNA upon uncoating

Question 15

Viral Mutations

Answer 15

1) Recombination- intramolecular genetic exchange b/w virus and host
2) Reassortment-“grab bag” all genes into a compartment and randomly selected out in groups to make new “viral strands”
3) Transcapsidation- protein capsid from virus A, genome from virus B
4) Marker Rescue- Lethal mutants recombine with helper virus to make mutant viable again

Question 16

What can happen when a virus infects a cell?

Answer 16

1) Abortive- host not permissive(no receptors, inapprop temps, not right enz)
2) Lytic- not what viruses want to do (CPEs-holes in memb, degrading nuclear mater and proteins)

3)Persistent Infections (Chronic, Latent, Recurring)-cells replicate for generations with releasing much virus
-patching, capping, shedding
-Latent infections
- Transformation- removal of “brakes from cell cycle”
-

Question 17

What is an inclusion body?

Answer 17

aggregate of VIRAL proteins, RNA, or DNA

• used diagnostically
  - -> Cowdry type inclusion body=HSV
• SEEN IN LYTIC INFECTION

Question 18

What is a synctia?

Answer 18

Result of cell fusion.
VAPs bind and form Multinucleated Giant Cell
-SEEN OFTEN in RSV
-Lytic infection

Question 19

Main ways virus evades immune system?

Answer 19

1) Patching- aggregates MHC in clumps
2) Capping-aggregates MHC on one end of cell
3) Shedding- Makes tons of MHC and sheds receptors to prevent immune cells from binding to virally infected cell

Question 20

Latent Virus

Answer 20

not multiplying , Hiding from immune system

-Source of recurrent infections

Question 21

How does interferon help viral infections?

Answer 21

Decrease infection to surrounding cells

Question 22

Incubation Period

Answer 22

Period of time between exposure to symptoms

- a virus gains access to cell and is starting to produce more virus

Question 23

Prodrome

Answer 23

Non-Specific symptoms prior to the presentation of the disease

Question 24

Drome

Answer 24

Clinical illness (Chicken pox symptoms)

Question 25

Methods of Transmission

Answer 25

1) Direct Contact
2) Injection/Transfusion/Transplantation
3) Fecal-oral
4) Respiratory

Question 26

Enveloped or Non enveloped easier to kill?

Answer 26

Enveloped

Non-Enveloped can withstand drying, detergeants, extreme pH and Temps

Question 27

Who is most susceptible to viral infection?

Answer 27

Infants/Children and the Elderly

-Generally more severe disease on first exposure

Question 28

General seasonal virus trends

Answer 28

Winter/Fall- Respiratory

Spring/Summer- Enteric

Question 29

Outbreak

Answer 29

A new virus in NEW location

Question 30

Epidemic

Answer 30

Over large geographical area resulting in the introduction of a new strain of virus.

Question 31

Pandemic

Answer 31

World Wide Epidemic. Approx every 5 years