Retroviruses

Question 1

Define the 3 activites of Reverse transcriptase in retroviral transcription.

Answer 1

1. RNA-dependent DNA synthesis (1st strand)
2. RNAse H (degradation of RNA in hybrid)
3. DNA-dependent DNA synthesis (2nd strand = dsDNA)

Question 2

Describe the clinical significance of the high error rate in Reverse transcriptase.

Answer 2

Gives retroviruses high variability = the ability to outrun CTLs, ABs, harder to make vaccines.

Question 3

What do integrase, reverse transcriptase and protease have in common?

Answer 3

These are encoded by pol gene (enzymatic activity) in pro-virus and are both targets for anti-viral therapy.

Question 4

Describe how insertional mutagenesis of retroviral DNA can increase cancer risk.

Answer 4

HIV integration can turn on oncogenes or damage nearby cellular genes

Question 5

How do ready-made HIV envelope glycoproteins escape host immune system?

Answer 5

Envelope proteins (trimer) is extensively glycosylated in secretory pathway to protect the virus from immune system.

Question 6

Describe the spread, prevalence and diseases of: HTLV-1 infection.

Answer 6

Tsm: breast milk, cell-to-cell contact, male to female sex tsm;
Prevalence: Carribeans and Aborigines;
Diseases: chronic (autoimmune) inflammation, Adult T cell leukemia

Question 7

Describe the spread, prevalence and diseases of: ATL infection

Answer 7

Tsm: breast milk;
Prevalence: Clustering in Kyushu Japan;
Diseases: T cell leukemia with HIGH WBC (<450,000!!)