PI2 Virus Structure and Replication

Question 1

What are the two main components of a virus?

Answer 1

• DNA or RNA genome
• Protein coat

Question 2

Viruses that only have a nucleocapsid are termed what?

Answer 2

Non-enveloped

Question 3

What are the properties of non-enveloped viruses?

Answer 3

• Environmentally stable
• resistant to temp, acids, proteases, detergents, drying, and harsh conditions of GI tract

Question 4

How do non-enveloped viruses spread?

Answer 4

• Does NOT require close person-to-person contact
• May spread through infected water, sewage, and other infected materials

Question 5

Viruses that have a lipid bilayer surrounding the nucleocapsid are termed what?

Answer 5

Enveloped

Question 6

Where is the envelope derived from?

Answer 6

the host cell membrane during release (budding)

Kind of similar to exocytosis

Question 7

What are the properties of an enveloped virus?

Answer 7

• Environmentally labile - sensitive to acid, detergents, drying, heat, difficulty surviving GI tract

Question 8

How are enveloped viruses generally spread?

Answer 8

close person-to-person contact through droplets, secretions, blood, transplants, injection

Question 9

What are the 3 steps of virus entry into a cell?

Answer 9

1. Cell recognition and attachment (adsorption)
2. Penetration
3. Uncoating

Question 10

How do viruses ensure delivery to appropriate cell types for efficient viral replication?

Answer 10

Viruses have attachment proteins that recognize the correct cell receptors

Question 11

How do entry inhibitors work?

Answer 11

“wedge” themselves into the viral glycoproteins and prevent fusion with the host cell

Question 12

How do positive sense RNA viruses replicate within the host cell?

Answer 12

• positive sense is essentially mRNA
• can use the host cell ribosomes to directly translate
• synthesizes viral encoded RNA-dep RNA polymerase

Question 13

How to negative sense RNA viruses replicate within the cell?

Answer 13

• Viral RdRp must be included within the virion
• RdRp copies the genomic RNA into the complementary + sense strand that can then use the host cell ribosomes

Question 14

Which RNA virus does NOT replicate in the cytoplasm?

Answer 14

Influenza

Question 15

How does Xofluza work?

Answer 15

Blocks the viral endonuclease cleavage of host cell mRNA that steals the 5’ cap and puts it on the viral RNA essentially prohibiting viral replication

Question 16

What must RNA viruses encode?

Answer 16

RNA-dependent RNA Polymerase

Question 17

What is the only DNA virus that does not replicate in the nucleus?

Answer 17

Poxviruses

Question 18

What enzyme do retroviruses include in the virion?

Answer 18

Reverse Transcriptase

Question 19

What 3 enzymes do retroviruses encode?

Answer 19

1. Reverse Transcriptase
2. Integrase
3. Viral protease

All are drug targets

Question 20

What kind of PCR is used to detect RNA viruses?

Answer 20

RT-PCR (reverse transcription)