Lecture 4 Part 4: Retroviruses

Question 1

What type of genome do retroviruses have

Answer 1

ssRNA(+) virus

Question 2

Are retroviruses enveloped or non-enveloped?

Answer 2

enveloped

Question 3

How many RNA strands are present in the retrovirus genome?

Answer 3

Two identical strands of RNA(+)

Question 4

How do retroviruses replicate?

Answer 4

Replicates through DNA intermediate

Question 5

What is reverse transcriptase?

Answer 5

An RNA-dependent DNA polymerase that converts viral RNA into DNA

Question 6

Which cells are commonly infected by retroviruses?

Answer 6

Dendritic cells, macrophages, and CD4+ T cells

Question 7

Retroviruses

Answer 7

• Error prone
• Induces genetic instability, generates variants
• Escapes immune recognition
• Vaccine design difficult

Question 8

How many subfamilies of human retroviruses are there?

Answer 8

3

Question 9

Name two examples of oncoviruses

Answer 9

1. HTLV-1 (Human T-lymphotropic virus type 1)
2. HTLV-2 (Human T-lymphotropic virus type 2)

Question 10

Name two examples of lentiviruses

Answer 10

1. HIV-1 (Human Immunodeficiency Virus type 1)
2. HIV-2 (Human Immunodeficiency Virus type 2)

Question 11

slide 28

Question 12

What are the two key HIV envelope glycoproteins?

Answer 12

gp120 and gp41

Question 13

What is the function of gp120 in HIV?

Answer 13

Determines tissue tropism; Initially binds CD4 & CCR5

Question 14

Why is gp120 considered highly variable?

Answer 14

Because it undergoes antigenic drift, variable

Question 15

Which cells are targeted when gp120 binds to CD4 and CCR5?

Answer 15

Macrophages, dendritic cells, activated T cells, and microglia

Question 16

Which cells are targeted when gp120 binds to CD4 and CXCR4?

Answer 16

Naïve and helper T cells.

Question 17

What is the function of gp41 in HIV infection?

Answer 17

facilitates cell-cell fusion between viral envelope and host cell membrane

Question 18

What enters the cytoplasm during HIV infection?

Answer 18

Viral RNA and reverse transcriptase (RT)

Question 19

What does reverse transcriptase (RT) do in HIV?

Answer 19

It synthesizes cDNA from viral RNA, often with errors

Question 20

How is viral cDNA incorporated into the host genome?

Answer 20

By the enzyme integrase

Question 21

What is the integrated form of HIV DNA called?

Answer 21

integrated provirus

Question 22

What happens after the provirus is integrated?

Answer 22

Host transcribes viral genes or latent integration

Question 23

Can latent HIV be reactivated?

Answer 23

yes it can be reactivated (signals unknown)

Question 24

Which cells often have persistent HIV infection?

Answer 24

macrophages

Question 25

What can Env mutation cause in HIV?

Answer 25

Env mutation can shift tropism to T cells (M-tropic vs. T-tropic)

Question 26

Where does HIV proliferate, and what does it lead to?

Answer 26

Proliferates in lymph nodes leading to viremia

Question 27

What is the result of HIV infection on CD4+ T cells?

Answer 27

Results in depletion of CD4+ T cells

Question 28

How does HIV disease progress?

Answer 28

Disease progresses from asymptomatic disease to severe immunosuppression