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I&I - M1T1 > Retroviruses > Flashcards

Retroviruses Flashcards

1
Q

What are the general characteristics of all retroviruses?

A

Enveloped, 2 complete copies of +ssRNA, encode RNA-dependent DNA polymerase, replication via a DNA intermediate

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2
Q

What retroviruses can immortalize and transform cells leading to lymphomas?

A

Human T-Cell Lymphotropic Virus - HTLV-1 & HTLV-2

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3
Q

How is HTLV spread?

A

IV drug use, sexual contact, breast milk, transfusions

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4
Q

What HTLV is most common in the United States? How is it spread?

A

HTLV-2, spread via IV drug use

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5
Q

What cells are targeted for infection by HTLV-1 & HTLV-2?

A

HTLV-1 targets CD4+ T Cells
HTLV-2 targets CD8+ T Cells

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6
Q

How does HTLV-1 manifest clinically?

A

T-cell leukemia/lymphoma - lymphadenopathy, skin lesions, bone lesions, hepatosplenomegaly, death

Tropical spastic paraparesis - spinal cord atrophy, leg weakness, gait disturbances, incontinence

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7
Q

How does HTLV-2 manifest clincally?

A

Generally asymptomatic. In rare situations, may cause tropical spastic paraparesis-like syndrom

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8
Q

How does HTLV-1 cause a transformation infection?

A

The tax protein activates cellular and viral RNA synthesis in CD4 T cells. This activates synthesis of IL-2 and its receptor, which promotes rapid T cell growth and may lead to transformation.

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9
Q

What regulatory proteins are ended by HTLV-1? What are their functions?

A

Tax gene - transcriptional activator
Rex gene - mRNA processing and export

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10
Q

What are the two strains of HIV? How do their origins differ?

A

HIV-1 derived from chimpanzees
HIV-2 derived from sooty mangabey

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11
Q

What are the subgroups of HIV-1?

A

M, N, O, P.

M responsible for AIDS epidemic

N, P emerged more recently

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12
Q

What strain of HIV is responsible for the majority of AIDS cases?

A

HIV-1

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13
Q

HIV-1, subgroup M is seen in the United States. What clade predominates in the country?

A

Clade B

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14
Q

HIV-2 is most prevalent in West Africa. What clades are responsible for human-human transmission?

A

Clades A & B

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15
Q

What virion gene in HIV codes for group-specific antigen proteins, such as p24?

A

gag

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16
Q

What virion gene in HIV codes for the reverse transcriptase and other enzymes?

A

pol

17
Q

What virion gene in HIV codes for envelope glycoproteins?

A

env

18
Q

What HIV gene regulates viral transcription?

A

tat

19
Q

What is the function of the HIV rev gene?

A

Promotes export of viral RNA from the nucleus

20
Q

What major core protein is used for diagnosis of HIV-1?

A

p24

21
Q

What glycoproteins make up the HIV envelope? How are they derived?

A

gp41 & gp120 - translated as gp160 and cleaved by proteases to form separate proteins

22
Q

What is the function of Long Terminal Repeats (LTR) in the HIV genome?

A

Contains promoters & sequences for the binding of transcription factors

23
Q

True/False. Resting T cells are not productively infected by HIV.

A

True. Resting T cells contain incomplete viral cDNA or proviral DNA that is not integrated into the host chromosome. This is referred to as pre-integration latency.

24
Q

Generally describe how HIV replicates in a host.

A

The virus binds to and enters the host cell via fusion. The genomic RNA is transcribed into cDNA using an RNA-dependent DNA polymerase. The cDNA enters the nucleus and integrates into host chromosomes. From here, viral genes are transcribed and translated and new particles are produced. New viral particles bud through the cell membrane to acquire their envelope and undergo maturation.

25
Q

How does HIV bind and enter host cells? Be specific.

A

HIV binds to the CD4 receptor and CCR5 / CXCR4 co-receptor via gp120. This causes a conformational change that exposes gp41 and enables the viral and cell membranes to fuse. The viral genome is then released into the cell.

26
Q

How do new HIV particles mature? What is the importance of this process?

A

HIV proteases cleave gag and gag-pol polyproteins into individual proteins to form a mature HIV particle. This process is required in order for the particle to be infectious.

27
Q

What is considered the gold-standard for HIV testing? What is the target of detection for this test?

A

Fourth generation EIA targetting IgM, IgG and p24

28
Q

How does the use of nucleic acid testing and RT-PCR for HIV differ?

A

Nucleic acid testing provided qualitative results used in screening of blood.

RT-PCR provided quantitative results that can be used to monitor progression of infection.

29
Q

How does viral load differ from CD4 T cell counts?

A

Viral load indicates plasma HIV RNA levels and monitors the rate of disease progression. CD4 T cell counts monitor impairment of the immune system and define stages of clinical disease.

30
Q

What three genes are included in all retroviruses?

A

gag, pol, env

I&I - M1T1 (36 decks)

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