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ELM2 - infection & immunity > lecture 4 - HIV > Flashcards

lecture 4 - HIV Flashcards

1
Q

What type of infection did HIV originate as?

A

Zoonotic

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2
Q

What is a zoonotic infection?

A

An infection in humans caused by a pathogen originating in animals

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3
Q

What are the 3 key groups of HIV-1?

A

HIV-1 M group, HIV-1 O group, HIV-1 N group

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4
Q

What type of virus is HIV?

A

Retrovirus, lentovirus

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5
Q

Is HIV a RNA or DNA virus?

A

RNA

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6
Q

How many copies of its RNA genome does HIV have?

A

2

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7
Q

Is HIV a ds-RNA or ss-RNA virus?

A

ss-RNA

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8
Q

What make up the envelope of HIV?

A

envelope glycoproteins (gp120 +gp41)

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9
Q

What surrounds the HIV genome?

A

Nucleocapsid

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10
Q

What are the essential enzymes in HIV replication and invasion into host DNA?

A

integrase, protease, reverse transcriptase

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11
Q

What is the process of HIV replication within a host cell?

A

Attachment, Fusion, Uncoating, Reverse transcription, Nuclear Import, Integration into host DNA, transcription, nuclear export, translation, assembly, budding, release, maturation

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12
Q

What cells does HIV bind to and destroy?

A

CD4 T cells/ T lympocytes

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13
Q

What is the purpose of reverse transcription when HIV enters a host cell?

A

Makes a DNA copy of the viral RNA genome which can then be integrated into the host genome for transcription & translation

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14
Q

What is the product of reverse transcription?

A

cDNA - complementary DNA

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15
Q

What enzyme is required for the integration of HIV cDNA into the host genome?

A

Integrase

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16
Q

What state must a host CD4 T cell be in to allow the transcription of HIV genes?

A

Activated

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17
Q

What transcription machinery is used for the transcription of HIV genes in a host T cell?

A

host machinery - RNA Polymerase II

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18
Q

What are the 4 key modes of HIV transmission?

A

sexual transmission, injection drug use, blood/blood products via transfusion, vertical transmission from mother to infant

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19
Q

What is the most common route of HIV transmission?

A

sexual transmission

20
Q

Where is HIV found in the initial host when passed on sexually?

A

semen or mucosal surfaces

21
Q

What type of sexual intercourse has the highest risk of HIV transmission?

A

receptive anal intercourse

22
Q

Why do STIs enhance HIV transmission in a potential host?

A

Inflammation of mucosal surfaces results in increased recruitment of T cells so increased targets, ulceration allows HIV to get in more easily

23
Q

What barrier does HIV cross to infect in sexual transmission?

A

mucosal barriers

24
Q

What is the process of local amplification of HIV after crossing a mucosal barrier?

A

Sub-mucosal CD4+ T cells, macrophages & dendritic cells are infected

25
Q

After local amplification of HIV occurs at the submucosa, how does HIV spread to the rest of the body?

A

Via the lymphoid tissue by infected CD4+ T cells and dendritic cells

26
Q

What is the trend in CD4 T cell count from infection to 10+ years (assuming no treatment)?

A

Rapid decrease in early weeks of infection, before slight increase again until approx. a year where this is steady decrease over several years until death

27
Q

What is the trend in HIV viral load from infection to 10+ years (assuming untreated)?

A

Dramatic increase in first few weeks before decrease again until approx. 1 year when there is a slow increase over clinical latency period until huge increase during AIDS development after ~8years

28
Q

What is the observation of HIV infection in the intestine, and why?

A

Loss of lymphoid aggregates (intestine appears smooth), due to loss of memory CD4+ T cells

29
Q

Why is there a drop in viral load, and increase in CD4+ T cell count after approx. 6 weeks of HIV infection?

A

Anti-HIV immune system can control viral replication to recover CD4+ cell count

30
Q

What immune cells are particularly involved in the early anti-HIV immune response?

A

CD8+ T cells

31
Q

Why do HIV-specific CD8+ T cells fail to effectively control HIV infection?

A

HIV is able to rapidly mutate, meaning mutants will no longer bind to the MHC class 1 on CD8 T cells, meaning they cannot be recognised and eliminated

32
Q

Why does HIV have a high rate of mutation (3 reasons)?

A

1.) Reverse transcriptase & host RNA polymerase II both have poor proof reading ability
2.) High rate of viral turnover
3.) high intra-individual diversity

33
Q

How does CD4+ HIV infection impair other immune processes?

A

CD4+ T cells need to help CD8+ T cell and B cell responses

34
Q

What are the broadly conserved epitopes in HIV?

A

Epitopes that are conserved across strains so can be detected by the body and will not then mutate, allowing antibodies to develop

35
Q

Is it possible for broadly neutralising antibodies for HIV to develop?

A

Yes, in 20% of patients, few conserved broadly neutralising epitopes exist and can be targeted by antibodies, however these antibodies fail to alter disease progression

36
Q

What are the 2 key cellular reservoirs of HIV infection?

A

1.) latently infected CD4+ T cells
2.) Macrophages & dendritic cells

37
Q

Why are latently infected CD4 T cells a cellular reservoir of HIV?

A

They are not activated so will not express antigen and are therefore invisible to the immune system. They do not transcript the integrated HIV genome so HIV will not replicate, until the T cell is activated

38
Q

What are the 3 key reasons HIV infection is persistent despite immune response?

A

1.) high rate of mutation
2.) loss of CD4+ T cell help for CD8+ T cells & B cells
3.) latent infected cell reservoir

39
Q

What factor leads to the development of AIDS, during HIV infection?

A

Depletion of CD4+ T cells, below 200 count

40
Q

What does AIDS stand for?

A

Acquired ImmunoDeficiency Syndrome

41
Q

What are the 3 periods of HIV infection?

A

Primary infection, Clinical latency, AIDS

42
Q

Why does loss of CD4+ T cells lead to immunodeficiency & AIDS?

A

Loss of help to CD8+ T cells & B cells leads to increased susceptibility to infections and cancer

43
Q

What cancer is common in AIDS?

A

Kaposi’s Sarcoma

44
Q

What virus causes Kaposi’s sarcoma?

A

Herpes virus

45
Q

What types of infections/disease are common in AIDS due to reduced CD8+ T cell function?

A

Intracellular infections (viral, protozoan), cancer

46
Q

What CD4+ T cell count indicates AIDS?

A

<200cells/mm^3

ELM2 - infection & immunity (22 decks)

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