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Barts year 3 semester 1 > Retroviruses > Flashcards

Retroviruses Flashcards

1
Q

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

A

Rous sarcoma virus

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2
Q

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

A

2

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3
Q

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

A

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

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4
Q

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

A

Rotavirus

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5
Q

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

A

Polio

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6
Q

Give examples of a single-stranded negative sense RNA virus

A
  • Influenza

- Rabies

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7
Q

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

A

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

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8
Q

Structure of a retrovirus

A
  • Surface envelope glycoprotein
  • Transmembrane envelope glycoprotein
  • Lipid envelope
  • Matrix (holds virus shape)
  • Protease
    Nucleocapsid
  • Capsid (holds RNA)
  • Viral RNA genome
  • Integrase
  • Reverse transcriptase
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9
Q

What is gag?

A
  • Group specific antigen gene encodes the viral matrix (MA) capsid (CA) and nucleoproteins (NC)
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10
Q

What is pol?

A

Gene that encodes for reverse transcriptase

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11
Q

What is env?

A

Gene that encodes for the envelope protein

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12
Q

What genes are present in the retrovirus genome?

A
  • Structural genes flanking LTRs and Gag, pol and env
  • Accessory genes (interact with host immune response)
  • Regulatory genes
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13
Q

How does the immature HIV become mature?

A
  • 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
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14
Q

What are the key enzymes in retroviruses?

A
  • Reverse transcriptase
  • Integrase
  • Protease
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15
Q

What does reverse transcriptase do?

A

Transcribes the viral genome RNA into DNA

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16
Q

What does integrase do?

A

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

17
Q

What does protease do?

A

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

18
Q

What are 2 main classes of retroviruses?

A
  • Oncovirinae (e.g RSV, HTLV-1and2)

- Lentivirinae (HIV)

19
Q

How many human t cell leukemia viruses are there?

A

4

20
Q

How many people are infected with each HTLV type?

A
  • HTLV-1 ~ 22million
  • HTLV-2 ~ 7 million
  • HTLV-3 = 4 cases
  • HTLV-4 = 1 case
21
Q

What percentage of people infected with HTLV are asymptomatic?

A

90%

22
Q

How long is the latency period of HTLV?

A

20 - 30 years

23
Q

What does HTLV-1 cause?

A
  • Adult T cell leukemia
  • HTLV-1 Associated Myelopathy
  • Tropical Spastic Paraperesis
24
Q

How can HTLV-1 associated myelopathy be treated?

A
  • IV methylprednisolone once daily for 3 days

- Daily prednisolone

25
Q

What cells are affected by adult T-cell leukemia?

A

CD4+ T lymphocytes (flower cells on histography)

26
Q

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

A

60%

27
Q

What diseases are associated with HTLV-2?

A
  • Sporadic cases of myelopathy and TSP like HTLV-1

- Also hairy cell leukemia

28
Q

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

A

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

29
Q

What does HIV require in order to infect target cells?

A

CD4 and a chemokine receptor

30
Q

When do AIDS (oppurtunistic infections) come?

A

Usually around 4-5 years

31
Q

Name some oppurtunistic HIV infections

A
  • Kaposi-Sarkoma (Human herpesvirus 8)
  • CMV retinitis
  • Interstitial pneumonia (pneumocystis carinii)
  • Oral leukoplakia (EBV)
  • Oral candidiasis (candida albicans)
32
Q

Why is it difficult to develo a vaccine for HIV?

A

Great diversity in the genome (heavily mutated)

33
Q

What are the most common clades of HIV?

A
  • C
  • A
  • AG
34
Q

How does the serum concentration of HIV vary over time?

A

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

35
Q

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

A

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

Barts year 3 semester 1 (7 decks)

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