Retroviruses

Question 1

Which of the following statements about retroviruses is TRUE?

A. Most retroviruses cause cell death by spontaneously bursting.

B. Retroviruses rely on the host cells RDDP (reverse transcriptase) to transcribe their genome into dsDNA.

C. Sumaviruses are cause high mortality disease in humans

D. Oncoretroviruses affect vertebrates and cause various sarcomas and leukemias

E. HIV is a subgroup of the lentiviruses, with HIV-2 of West African origin being more virulent than HIV-1

Answer 1

D.

A is incorrect because retroviruses don’t usualy cause cell death - they are sneaky. B is incorrect because the viruses package their own RDDP in their virions, as the host cell does not have reverse transcriptase. C is incorrect - sumaviruses cause no known clinical disease. E is incorrect because HIV-1 is more virulent than HIV-2.

Question 2

Which of these proteins are NOT an important component of attachment/entry of HIV to the host cell?

A. CD4

B. gp120

C. p24

D. CCR5

E. gp41

Answer 2

C.

p24 is a product of the cleaved gag gene, which forms the viral capsid.

Question 3

HIV virions become infectious when a virally encoded protease cleaves what gene in one of two possible ways?

Answer 3

gag/pol gene

Question 4

Which of the following is NOT a quality that contributes to HIV diversity?

A. It has its own promoter LTR region that is able to be transcribed wherever it is inserted in the host genome

B. Its genome is segmented allowing for recombination

C. Mutations arise every time reverse transcription occurs due to error-prone RT.

D. It has high replication rate and short replication time

E. The immune system and the cellular mileu select for the most “fit” virus quasispecies

Answer 4

B.

Altough its genome is non-segmented, HIVs RNA is spliced to encode different viral messages.

Question 5

a mutation in what protein has been proposed as a possible “cure” for HIV infection?

Answer 5

CCR5.

The CCR5-delta32 mutation results in a smaller protein that isn’t on the outside of the cell anymore. Most forms of HIV cannot infect cells if there is no CCR5 on the surface, and people who are homozygous for this mutation are virtually immune to HIV (~1% of caucasians). People who are heterozygous for delta32 mutation show some resistance to infection.

Question 6

this virus is:

• located mostly in tropical regions
• endemic in Southern Japanese isles and the Caribbean
• transmitted through breast feeding and other blood/fluid mediums
• causes adult t cell leukemia and tropical spastic paraparesis (TSP)

Answer 6

HTLV-1

Question 7

What is the prevailing thought about what causes CD4 depletion in HIV-infected individuals?

Answer 7

Depletion is thought to be due to HIV-induced chronic immune activation