Lecture 5: viruses pt 2

Question 1

How do double stranded RNA enter/infect a cell?

Answer 1

dsRNA stays in the cytoplasm

• Can make -ssRNA and viral proteins
• Must encode it’s own RNA polymerase

Question 2

What is the funtion of retroviruses?

Answer 2

+ssRNA that converts to into DNA

• DNA travels to nucleus
• Makes more dsDNA and mRNA
• mRNA travels to cytoplasm to make viral proteins

Question 3

How is a virus assembled on a host?

Answer 3

• Empty capsid is laid down
• Insertion of Viral spikes into the host
• nucleic acid packaged into the capsid
• Uses host ATP energy to move viral parts around

essentially, the virus uses the host’s cells against itself

Question 4

How is the virus released?

Answer 4

• Lysis by nonenveloped viruses
• Exocytosis by enveloped viruses
• budding by enveloped viruses

Question 5

What happens when the cell undergoes lysis?

Answer 5

it kills the cell, ruptures the membrane and releases the virons
-typical of nonenveloped viruses

Question 6

What happens when the cell undergoes budding?

Answer 6

viral proteins assemble at cell membrane, capsid fuses with membrane, pinches off for release
-typical of enveloped viruses

Question 7

What happens when the cell undergoes exocytosis?

Answer 7

Virus particle enclosed in vesicle by the golgi, fuses with membrane, pinches off for release
-typical of enveloped viruses

Question 8

What type of antiviral do you give patients?

Answer 8

depends on what area of the cycle you are trying to stop

Question 9

What is the purpose of entry inhibitors? (antiviral)

Answer 9

it interferes with binding and fusion

Question 10

What is the purpose of reverse transcriptase? (antiviral)

Answer 10

it inhibits reverse transcription

Question 11

What is the purpose of integrase inhibitors? (antiviral)

Answer 11

inhibits viral DNA from host genome

Question 12

What is the purpose of protease inhibitors?(antiviral)

Answer 12

inhibits virions from budding from host cell

Question 13

What is the Acute type of infection?

Answer 13

it is the lytic stage; short term infection

• virus infects host cell
• virus multiplies
• virus lyses cell, releases

Question 14

What is the persistent/chronic type of infection?

Can infected cells divide?

Answer 14

latent; long term infection

• become integrated into the host genome
• when host cell divides all resulting cells will contain the viral genes
• Cell does not lyse and appears normal

Question 15

What are oncoviruses?

Answer 15

viruses that cause cancer

Question 16

What are good treatment tactics for viruses?

Answer 16

1. Vaccination
2. Antivirus (only lessen severity)
3. surgery

Question 17

What is the cytopathic effect (CPE)?

Answer 17

virus induced damage that alters appearance of host cell

Question 18

What are the different ways CPE could be present?

Answer 18

• Inclusion bodies
• Syncytia
• Changes in shape, size, etc

Question 19

What are inclusion bodies?

Answer 19

aggregation of viruses or damaged organelles

Question 20

What is syncytia?

Answer 20

fusion of multiple infected host cells

Question 21

What are viruses that infect bacteria?

Answer 21

bacteriaphages; only specific bacteriaphages affect specific bacteria and do not harm human cells

Question 22

What are other non-living infectious agents called?

Answer 22

Spongiform encephalopathies; tissue that looks like a sponge

Question 23

What are the effects of spongiform encephalopathies?

What are they caused by?

Answer 23

• long period of latency before clinical signs
• Range from mental derangement to loss of muscle control
• progressive, often fatal
• Caused by prions, only made of proteins, no nucleic acid

Question 24

How does (+/-) ssRNA infect a host?

Answer 24

-stays in the cytoplasm
- (-)ssRNA must be translated to (+)ssRNA
-becomes -ssRNA
most encode its own RNA polymerase

Question 25

What type of polymerase do retrograde viruses use?

Answer 25

Reverse Transcriptase polymerase

Question 26

How do oncoviruses cause cancer?

Answer 26

1) Activate proto-oncogenese
2) Viral genes that are cancerous are integrated into host genome
3) Turn off host cell tumor repressor