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PY6010 > HIV-1 > Flashcards

HIV-1 Flashcards

1
Q

What is AIDs in relation to HIV?

A

HIV is a viral infection which, if left untreated, can lead to AIDS, which is the immunodeficient phase of the disease.

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2
Q

Which type of T lymphocyte is severely destroyed in HIV, and why?

A

CD4 T helper cells.
This is because HIV binds to the CD4 molecule of these T helper cells to replicate, eventually leading to a decline in the balance of T lymphocytes amounts.

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3
Q

What reactions occur during HIV?

A
  1. T cell suppression

2. Intense immune activation

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4
Q

Where are T cells mostly concentrated within the body, which is also where HIV reservoirs form?

A

Lymph tissues and the GIT.

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5
Q

What are the events stem from HIV?

A
  1. A fall in circulating CD4 T helper cells
  2. Vulnerability to opportunistic infections
  3. Infecting other CD expressing cells
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6
Q

When can a productive infection of CD4 T helper cells be detected?

A

Within 2 days of viral challenge.

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7
Q

How do other cells, other than CD4 T helper cells, get infected by HIV?

A

Cells travelling to the lymph nodes also become infected (since HIV first infects CD4 T helper cells in the lymph nodes), so this leads to a major loss of antigen dependent responses.

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8
Q

How does CD4 T helper cell levels decline overtime in HIV?

A

During the 1st HIV infection, there is a reduction in peripheral CD4 T helper cells (which can be detected), but these levels can fluctuate after the primary infection is resolved.

CD4 T helper cells hence decline over many years.

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9
Q

What occurs during the latent (asymptomatic) phase of HIV?

A

Specific homeostasis mechanisms control the imbalance between T helper cells and other lymphocytes.

  • Think of it like a pie; this is the T lymphocyte compartment, where the homeostasis of T cells must be maintained.
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10
Q

What makes up most of the T cell compartment of homeostasis?

A
  1. CD4 T helper cells

2. CD8 cytotoxic T cell

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11
Q

What happens if T cells are lost?

A

New or naive T cells can differentiate from bone marrow pre-cursors, or from existing pools of memory T cells.

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12
Q

How is T cell homeostasis preserved in HIV?

A

Loss of CD4 T helper cell is balanced with an increase of CD8 cytotoxic T cells.
This is shortly lived until AIDs occurs.
Eventually sources of T cells become exhausted trying to balance this, so T lymphocyte levels eventually fall.

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13
Q

What are some examples of other HIV targets?

A

Chemokine receptors, found in other WBCs to enter the host cell.
Monocytes, macrophages, and dendritic cells can also be infected.
Different variants use different receptors to infect more T helper cells.

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14
Q

What parts of the body can act as reservoirs for replication of HIV?

A
  1. Liver
  2. Spleen
  3. Bone marrow
  4. Lymph nodes
  5. GI
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15
Q

What can CD4 T helper depletion in the gut lead to?

A

Increased permeability of the intestinal lining, which can translocate bacteria leading to more immune activation.

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16
Q

Why can HIV never be eradicated from the body?

A

Because memory cells are long-lived & don’t die, so when infected with HIV it can never go away.

17
Q

How is HIV reactivated in the body after a latent period?

A

When the infected cells reappear from their reservoirs.

18
Q

What is the normal process of CD4 T helper cell activation?

A

Antigens stimulate naive CD4 T helper cells which proliferate into effector T cells to destroy the pathogen.
As the pathogen becomes weaker, T cells can either undergo apoptosis, or remain dormant until the same antigen appears.

19
Q

What can occur when HIV affects naive T cells?

A

HIV can integrate into the DNA of the host cell, and lock itself into memory cells.
If the same antigen appears, then HIV becomes reactivated again.

20
Q

What are the 3 possible outcomes if memory T cells become latently infected?

A
  1. They can reactivate & die
  2. They can release HIV
  3. They can transmit HIV to another host cell
21
Q

Why are CD8 cytotoxic T cells unusually vigorous in HIV?

A

Because it needs to help with the imbalance of CD4 T helper cells.

22
Q

How long after initial exposure of HIV to reservoirs form in the body?

A

Within 5 days.

23
Q

How can HIV block symptoms of the immune system?

A

HIV integrates its genes into chromosomes which usually modulate the killing of the host cell.
In this way, the immune system response is blocked.

24
Q

How do self-cells in the body become ‘invisible’ in the presence of HIV?

A

HIV decreases the expression of MHC I (which is a self-recognising protein), so self-cells become invisible.

25
Q

What can constant HIV mutations lead to?

A
  1. Emergence of new HIV variants in the already infected person
  2. Resist drug therapy
  3. Resisting immune attack
26
Q

Why are the lymph nodes considered a ‘sanctuary’ for harbouring HIV?

A

Because limited anti-viral drug can penetrate into the lymph nodes, and there is also limited host clearance mechanisms there.

27
Q

What occurs in a very high HIV load, high HIV load, and low HIV load?

A

Very high: CD4 T helper/CD8 cytotoxic T cells are exhausted and decreased

High: Low CD4 T helper cells

Low: Stable amounts of CD4 T helper cells and CD8 cytotoxic T cells.

28
Q

What patient factor can be shown when monitoring the viral load of HIV in an individual?

A

Viral load can show the patients adherence to the drug

29
Q

How does antiretroviral therapy (ART) help in suppressing HIV replication?

A

ART prevents new cells from becoming infected, but do not eliminate the infection once it has already integrated into the host cell.

30
Q

What is the aim of HAART intensification in HIV?

A

To achieve a complete suppression of residual virus (completely removing the reservoirs).

It is also known as a ‘cocktail’ of drugs

31
Q

How do immunosuppressants aid in eradicating HIV?

A

They decrease the activation of CD4 T helper cells, and reduce their susceptibility to viral infection + replication.

32
Q

How can the reactivation of latent reservoirs aid in the eradication of HIV?

A

Viral load stops ‘hiding’, which can then be killed in combination with HAART + other drugs.

33
Q

Why is HIV still an issue in poorer countries?

A

Because tests are expensive, slow and hard to access.

34
Q

Why are HIV patients asymptomatic to tuberculosis?

A

Because tuberculosis infects WBC’s, and since HIV patients have a low WBC count, they wont experience the symptoms of TB.

PY6010 (23 decks)

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