HIV

Question 1

What are some symptoms of HIV?

Answer 1

Immunocompromised

Fever, dry cough for 3 weeks, weight loss, skin lesions, sore mouth.

Anything that isn’t usually a problem but now is because patients are now immunocompromised.

Fungal and Parasitic infections as these are usually uncommon but common in HIV as immunocompromised.

Question 2

What is the structure and behavior of a virus?

Answer 2

• Genome - RNA or DNA
  
  • Single-stranded
  • Double-stranded
• Capsid - protein shell, protects the genome
  
  • Helical (rod-shaped or coiled)
  • Icosahedral (spherical or symmetric)
• Lipid envelope - present or absent
  
  • Derived from host cell membranes
  • Contains virus-specifc proteins (antigens)
• Replication strategy

Question 3

What is HIV?

Answer 3

• Human Immunodeficiency Virus - discovered in 1984
• Retrovirus “backwards” - ssRNA to DNA to ssRNA
• Infects cells with CD4 surface receptor
• T-helper lymphocytes and monocytes / macrophages
• HIV replicates inside cells
  
  • Destroys the cell
  • Causes inflammation
  • Spreads to / infects more cells.

Question 4

How does HIV infect cells?

Answer 4

1. Free virus
2. Binding and fusion
3. Infection
4. Reverse Transcription
5. Integration
6. Transcription
7. Assembly
8. Budding
9. Break free
10. Maturation

Question 5

How is HIV transmitted?

Answer 5

Contact of infected bodily fluids with mucosal tissue / blood / broken skin

• 95% is sexually transmitted.
• Blood transfusions (very very rare in UK) -
• Some haemophilia have HIV because blood didn’t used to be screened.
• Contaminated needles
• Perinatal transmission (rare in UK as can have treatment - only 1-2%) -Transplacental, During delivery through an infected birth canal, As a result of ingestion of breast milk carrying virus.

Question 6

How do people get infected with HIV? How does the disease progress?

Answer 6

Infected.

Viral infection / load increases and CD4 count decreases - unwell.

Then, CD4 increases again and virus load drops.

BUT, virus then slowly increases and CD4 count decreases. (Below 500, start to notice symptoms)

If CD4 count is below 200 then they have severe, AIDS defining -In hospital.

Question 7

How does an acute HIV infection present?

Answer 7

Similar symptoms to a glandular fever. (List)

Question 8

What infections can you get as HIV progresses?

Answer 8

Question 9

What factors affect HIV transmission?

Answer 9

• Type of exposure
  
  • Type of sexual act
  • Transfusion vs needle stick vs mucous membrane
• Viral level (viral load) in blood
  
  • Transmission unlikely if undetectable VL
• Condom use
• Breaks in skin or mucusa
  
  • Other STI (inflammation of genital tract)
  • Sexual assault

Question 10

What is the risk of HIV transmission?

Answer 10

It is 90-100% if its a blood transfusion.

Question 11

What is the life expectancy of HIV patients?

Answer 11

• Life expectancy and quality of life now excellent
• General population lives to about 80
• HIV positive: 70yrs
• Early detection / good CD4
  
  • Treatment
  • Adherence
  • Healthy living -
    
    • Smoking, alcohol, metabolic problems.
• Late detection = worse prognosis (10x risk of death in 1st year)

Question 12

What diagnostic tests can be done for HIV?

Answer 12

• Blood tests - serology
  
  • HIV antigen (Ag) - viral protein
  • HIV antibody (Ab) - immunoglobulin; immune response to antigen.
  • The current test detects both Ag and Ab
  • You become HIV positive within 4 weeks of infection
  • You can get results of the test on the same day
  • May get false negative result.
• PCR - Once got serology then do PCR.
  
  • Detects HIV nucleic acid
  • Highly sensitive but expensive so not used for initial HIV testing (used for follow-up / treatment response)
  • Detects early infection (few days)
• “Rapid tests” - low costs and results in under an hour. If negative then can rule it out. BUT, can get a false positive.
  
  • These detect HIV antibody.
  • Can be a blood test (finger prick), oral (saliva)
  • In-home or postal testing.

Question 13

Who should be tested?

Answer 13

• Everyone if the rate is over 2 in 1000 in popuation
• If getting recurrent severe infections
• Resp: Bacterial pneumonia / TB
• Neuro: Meningitis / dementia
• Derm: Severe psoriasis. Recurrent / multi-dermal shingles
• Gatro: chronic diarrhoea / weightloss (maybe)
• Haem: any unexplained blood abnormality
• Onc: Lymphoma, anal cancer
• Gynae: Cervical intrapithelial neoplasia (CIN)
• Any STI / Hep B / Hep C

Question 14

What strategies would be used to treat and reduce the prevalence of HIV?

Answer 14

Anti-retro viral drugs (ARVs)

Question 15

What are the aims of HIV treatment?

Answer 15

• Undetectable HIV viral load
• Reconstitute CD4 count / Immune system
• Reduce general inflammation
• Reduce risk of transmission
• Good quality of like
• Normalise lifespan.

Question 16

What does treatment target?

Answer 16

• CD4 receptors
• Reverse Transcriptase
• Maturation

Question 17

When should you start treatment for HIV?

Answer 17

Straight away!

Question 18

Why do we give 3 ARVs to treat HIV?

Answer 18

• Millions of rounds of viral replication each day
• Virus mutates (changes / adapts) every 2-3 rounds
• Resistance to drugs develops in days
• 1 drug - develops resistance quickly
• 3 drugs - harder to develop resistance
• Patient must keep taking drugs.

Question 19

What strategies would you use to treat and reduce the prevalence of HIV?

Answer 19

• Increase condom usage
• Prevention of mother-to-child transmission
• AVR treatment as prevention
• Medical circumcision
• Post-exposure prophylaxis
• Pre-exposure prophylaxis
• Combine the above
• Future Vaccine??

Question 20

How can HIV cause ethical dilemmas?

Answer 20

• Psychological impact of diagnosis
• Dealing with stigma
• Patient confidentiality vs:
  
  • Health of mother
  • Health of unborn child
  • Health of sexual contact (husband)
  • Health of older child
  • Risk to patients / staff at workplace