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Flashcards in Retroviruses Deck (35)
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1

What was the first virus to be discovered that could be responsible for cancer by Peyton Rous? (Nobel Prize winner 1966)

Rous sarcoma virus

2

How many molecules of RNA are contained in a retrovirus' genome?

2

3

What is the difference between positive sense and negative sense RNA viruses?

Positive sense are in the form of mRNA whereas negative sense are not and therefore need to bring their own polymerase which converts the virus' RNA into mRNA

4

Give an example of a double-stranded positive sense RNA virus

Rotavirus

5

Give an example of a single-stranded positive sense RNA virus

Polio

6

Give examples of a single-stranded negative sense RNA virus

- Influenza
- Rabies

7

What are retroviruses? (in terms of positive or negative sense and single vs double stranded)

Diploid positive sense RNA viruses (uses the host cells transcription machinary after incorporating into the genome through reverse transcriptase)

8

Structure of a retrovirus

- Surface envelope glycoprotein
- Transmembrane envelope glycoprotein
- Lipid envelope
- Matrix (holds virus shape)
- Protease
Nucleocapsid
- Capsid (holds RNA)
- Viral RNA genome
- Integrase
- Reverse transcriptase

9

What is gag?

- Group specific antigen gene encodes the viral matrix (MA) capsid (CA) and nucleoproteins (NC)

10

What is pol?

Gene that encodes for reverse transcriptase

11

What is env?

Gene that encodes for the envelope protein

12

What genes are present in the retrovirus genome?

- Structural genes flanking LTRs and Gag, pol and env
- Accessory genes (interact with host immune response)
- Regulatory genes

13

How does the immature HIV become mature?

- Protease envolved
- Gag and pol is cleaved into a structure called a capsid which holds the viral genome
- This stage is a target for anti-retroviral therapy target

14

What are the key enzymes in retroviruses?

- Reverse transcriptase
- Integrase
- Protease

15

What does reverse transcriptase do?

Transcribes the viral genome RNA into DNA

16

What does integrase do?

Integrates the double stranded DNA into the host genome to form a provirus

17

What does protease do?

Following release of the new virion, cleavage of certain proteins is required for viral maturation and infectivity

18

What are 2 main classes of retroviruses?

- Oncovirinae (e.g RSV, HTLV-1and2)
- Lentivirinae (HIV)

19

How many human t cell leukemia viruses are there?

4

20

How many people are infected with each HTLV type?

- HTLV-1 ~ 22million
- HTLV-2 ~ 7 million
- HTLV-3 = 4 cases
- HTLV-4 = 1 case

21

What percentage of people infected with HTLV are asymptomatic?

90%

22

How long is the latency period of HTLV?

20 - 30 years

23

What does HTLV-1 cause?

- Adult T cell leukemia
- HTLV-1 Associated Myelopathy
- Tropical Spastic Paraperesis

24

How can HTLV-1 associated myelopathy be treated?

- IV methylprednisolone once daily for 3 days
- Daily prednisolone

25

What cells are affected by adult T-cell leukemia?

CD4+ T lymphocytes (flower cells on histography)

26

What percentage of adult T-cell leukemia cases have skin involvement?

60%

27

What diseases are associated with HTLV-2?

- Sporadic cases of myelopathy and TSP like HTLV-1
- Also hairy cell leukemia

28

What organ does hairy cell leukemia (HTLV-2 associated) affect?

Spleen (causes enlargement) and then bone marrow (causing decreased resistance to infections)

29

What does HIV require in order to infect target cells?

CD4 and a chemokine receptor

30

When do AIDS (oppurtunistic infections) come?

Usually around 4-5 years

31

Name some oppurtunistic HIV infections

- Kaposi-Sarkoma (Human herpesvirus 8)
- CMV retinitis
- Interstitial pneumonia (pneumocystis carinii)
- Oral leukoplakia (EBV)
- Oral candidiasis (candida albicans)

32

Why is it difficult to develo a vaccine for HIV?

Great diversity in the genome (heavily mutated)

33

What are the most common clades of HIV?

- C
- A
- AG

34

How does the serum concentration of HIV vary over time?

High viral load at the beginning then drops then rises overtime, CD4+ cells do similar except more gradual in both aspects

35

When was HAART treatment usually started and when is it now?

When Viral load started to rise and CD4+ cells began to fall, just before opportunistic infections would arise, would cause the viral load to decrease once more
- It is no used immediately