Infection - HIV Flashcards

1
Q

Which is more common in the UK - HIV, Hep B or Hep C?

A

Hep C (1 in 200 people), then HIV (roughly 100,000 people), then hep B (1 in 1000 people)

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2
Q

Why is HIV called a ‘retrovirus’?

A

It travels ‘backwards’ from ssRNA to DNA to ssRNA

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3
Q

How does HIV cause symptoms?

A

It replicates inside body cells, destroying the cell and causing inflammation. It then spreads to/infects more cells

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4
Q

How does HIV replicate inside the cell?

A
  • virus binds to CD4 molecule and a co-receptor, then fuses with cell
  • contents of virus are emptied into the cell
  • ssRNA from virus converted into DNA by reverse transcriptase
  • viral DNA combined with cell’s DNA by integrase, so when when infected cell divides, viral proteins are made too
  • viral chains come together and immature virus breaks free of the infected cell
  • protein chains in new viral particle are cut by protease into individual proteins to make a working virus
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5
Q

How is HIV transmitted?

A

Contact of infected bodily fluids with mucosal tissue/blood/broken skin. Can be through sexual contact, transfusion, contaminated needles or perinatal transmission

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6
Q

Why is there an initial drop in CD4 cell count after HIV infection which then recovers?

A

The viral load increases dramatically after infection, but the immune system then kicks in and begins to decrease the viral load and CD4 count recovers

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7
Q

What happens when the CD4 count of a HIV-sufferer drops below 200?

A

They develop AIDS and have severe symptoms

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8
Q

What are the factors that affect how easy it is to transmit HIV between people?

A
  • type of exposure (type of sexual act, transfusion/needle stick/mucous membrane)
  • viral load in blood
  • condom use
  • breaks in skin/mucosa
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9
Q

What is the difference in life expectancy between that of the general population and someone with HIV?

A

As long as they have early detection, adhere to treatment and live healthily (no smoking, alcohol or metabolic problems) then they should have same life expectancy (77 years)

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10
Q

How is serology used to detect HIV?

A
  • shows HIV antigen (Ag) which indicates whether viral protein is present
  • shows HIV antibody (Ab) which indicates immune response to antigen
  • result can be given on same day
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11
Q

How can PCR be used to diagnose HIV?

A
  • detects HIV nucleic acid
  • very highly sensitive, detects early infection
  • disadvantages: expensive, results slow
  • used more to test the follow-up response to treatment rather than initial test
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12
Q

What are the aims of HIV treatment?

A
  • to have an undetectable HIV viral load
  • reconstitute CD4 count
  • reduce general inflammation
  • reduce transmission risk
  • good quality of life
  • normalise lifespan
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13
Q

How are people with HIV treated?

A

They are given two nucleoside reverse transcriptase inhibitors, and a non-nucleoside reverse transcriptase inhibitor/ protease inhibitor/ integrase inhibitor = 3 in total

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14
Q

Why do we give three anti-retrovirals?

A

There are millions of rounds of viral replication every day and the virus mutates every 2-3 rounds, so resistance to drugs can develop in days. This is harder with 3 drugs

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15
Q

How can HIV spread be prevented?

A
  • increase condom usage
  • prevent mother-child transmission
  • ARV treatment as prevention
  • medical circumcision
  • post-exposure prophylaxis
  • pre-exposure prophylaxis
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