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Path - Immunology > HIV Infection > Flashcards

HIV Infection Flashcards

1
Q

What type of virus is HIV?

A

Retrovirus

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2
Q

describe HIV1 genome

A

Genome is diploid, ssRNA
contains 9 genes
encodes 15 structural, regulatory and auxiliary proteins

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3
Q

Which host cells does HIV use to replicate and move from cell to cell?

A

CD4+ T helper cells

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4
Q

Which two major surface proteins does HIV use?

A

GP120 and GP41

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5
Q

What happens to CD4+ T helper cells after infection?

A

They change function

They are depleted

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6
Q

Which two things does effective immunity from HIV require?

A

Antibodies (B cells) to prevent infection and neutralise the virus

Enough CD8+ cells to eliminate latent infection

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7
Q

What are co-receptor molecules required for HIV to enter?

A

CCR5 or CXCR4

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8
Q

How is HIV transmitted?

A
  • Sexual: enters through mucosal surfaces; transmission is increased by activities that damage these surfaces like anal. sex. CD4+ cells and dendritic cells in the mucosa bind to the virus and carry it to the lymph nodes, where it spreads
  • Infected blood (transfusion, sharing needles)
  • Mother to child (before/during birth, breastfeeding)
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9
Q

What should you do with a pregnant lady with high viral count?

A

Schedule C section
Tell mother not to breastfeed

= this drives down rate of transmission to almost 0

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10
Q

What is the process for natural immunity in HIV?

A 
Mobilised within hours of infection. 
It involves: 
- inflammation 
- Macrophage + NK cells + complement activation 
- release of cytokines, chemokine
- stimulation of dendritic cells by TLR
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11
Q

What antibodies are produced for acquired immunity in HIV,?

A

anti-GP120 and anti-gp41

anti-p24 gag IgG

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12
Q

Is HIV neutralised once coated in antibodies?

A

NO, it remains infectious

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13
Q

What is the process for acquired immunity in HIV, in terms of CD4+ T cells?

A

CD4+ T cells recognise processed antigens (esp gag p24 peptides) on MHC class II

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14
Q

What is the process for acquired immunity in HIV, in terms of CD8+ T cells?

A

CD8+ kill cells that are infected with HIV and are able to suppress viral repliacation+
They recognise HIV antigens on MHC Class I
They secrete chemokine and cytokines that block virus entry onto CD4, preventing infection

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15
Q

Explain the life cycle of HIV

A
  1. HIV attaches to cell and fuses
    Proteins on outer surface of HIV (GP120, GP41) bind to CD4 cell receptor (CXCR4, CCR5)
  2. Reverse transcription (via reverse transcripase) and DNA synthesis
  3. Integration - HIV DNA is integrated into host DNA via integrase
  4. Viral transcription
  5. viral protein synthesis - CD4 nucleus produces raw material to make new HIV . Long strands need to be cut by protease
  6. Assembly of virus, release of virus
  7. Maturation
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16
Q

What are the 4 categories of drugs and which steps do they attack?

A
  1. Attachment / fusion inhibitors
  2. Reverse transcriptase inhibitors (NNRTI/NRTI, nucleoside analogues)
  3. integrase inhibitors
  4. protease inhibitors
17
Q

What is the median time for HIV infection to develop to AIRD?

A

8-10 years

18
Q

How does HIV infection present time-wise in specific categories of people?

A
  • Rapid Progressors (10%) take 2-3 years to develop AIDS
  • Long term non-progressors (<5%) have stable CD4 counts, vigorous CD4/CD8 response, take >10-15 years to develop aids
  • Exposed seronegatives are repeatedly exposed to HIV but do not convert
19
Q

How can we detect HIV presence?

A
  • anti-HIV antibodies (ELISA)
  • anti-HIV antibody Western blog (confirmatory test)
  • viral load (PCR - detects viral DNA)
20
Q

What technique is used to monitor CD4 count?

A

flow cytoometry

21
Q

What CD4 range indicates HIGHLY IMMUNOCOMPROMISED?

A

CD4 <200

22
Q

What viral load indicated that the virus is undetectable?

A

VL<20

23
Q

Why do we need to genotype the HIV sequence of all infected patients?

A

To ensure a response to treatment

Check for resistance to antiretroviral drugs

24
Q

What are the two ways we can test for viral resistance?

A
  • Phenotypic (measure viral replication in cell cultures under selective pressures of increasing concentrations of drugs)
  • Genotypic (mutations detected by direct sequencing of amplifier HIV genome)
25
Q

What are typical HAART regimes composed of?

A

2NRTI+ PI/NNRTI/II

26
Q

When should you start HIV treatment ?

A

All individuals should be started on IMMEDIATE tx

Path - Immunology (11 decks)

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