Human Immunodeficiency Virus

Question 1

What is the Human Immunodeficiency Virus?

Answer 1

• Retrovirus that infects and replicates in human lymphocytes and macrophages, resulting in immunodeficiency
• Replicates primarily in human CD4+ T cells and macrophages

Question 2

What causes HIV to spread?

Answer 2

Transmitted Via → sexual fluids (majority of cases), blood (IV drug users sharing contaminated needles or blood transfusions/ organ transplantations), breast milk

Question 3

What are the risk factors for HIV?

Answer 3

• HIV-infected blood transfusion
• IV drug use
• unprotected sexual intercourse
• percutaneous needle prick injury
• Increasing incidence in Africa and Asia

Question 4

What are the presenting symptoms/ signs of HIV?

Answer 4

HIV seroconversion is symptomatic in 60-80% of patients and typically presents as a glandular fever type illness. Typically occurs 3-12 weeks after infection.
- Fevers, Night Sweats, Weight Loss
- Skin Rashes → maculopapular rash
- Lymphadenopathy
- Sore Throat
- Oral Ulcers
- Diarrhoea
- TB
- Genital STIs
- Candidiasis → recurrent infections
- Shingles

Question 5

Describe the pathophysiolpgy of HIV

Answer 5

o HIV enters CD4+ lymphocytes by binding to their gp120 receptors
o Reverse transcriptase allows the incorporation of HIV genetic material into the host genome
o This leads to dissemination of HIV, cell death and eventual T-cell depletion

Question 6

Summarise the epidemiology of HIV

Answer 6

● Increasing in incidence in Africa and Asia

Question 7

What investigations are used to diagnose/ monitor HIV?

Answer 7

1. Combination Test (standard for diagnosis and screening) → HIV p24 Antigen + HIV antibody Test
   - the median window period for this test is 17.8 days (ranging from 13-26 days).
   - p24 Antigen → viral core protein that appears early in the blood as the viral RNA levels rise (positive earlier than antibodies)
2. Serum HIV Enzyme-Linked Immunosorbent Assay (ELISA) → positive for HIV antibodies (however antibodies may not be present in early infection)
3. CD4 Count → indicates immune status and helps in staging process.

Question 8

How is HIV managed?

Answer 8

1. 1st Line → antiretroviral therapy (ART) = two NRTIs and one PI/NNRTI (should be started as soon as HIV diagnosed)
   - NRTI’s ⇒ zidovudine, abacavir, tenofovir
   - NNRTI’s ⇒ nevirapine, efavirenz
   - Protease Inhibitors ⇒ indinavir, nelfinavir, ritonavir (end in -navir)
2. Prevention → HIV Preexposure Prophylaxis (PrEP) for individuals at high risk of contracting HIV or HIV Postexposure Prophylaxis (PEP) which is a short course of ART taken by patients after potential exposure to HIV (needs to be started 72 hrs after exposure)
   - PEP ⇒ oral antiretroviral therapy for 4 weeks
3. If CD4 count <200/mm3 → give co-trimoxazole as prophylaxis against Pneumocystis jiroveci pneumonia