Lecture 14: HIV Part 2

Question 1

How does HIV cause illness?

Answer 1

Loss of CD4 T helper cell function deminishes the ability of the body to respond to infection and consequently depending on WBC numbers the patient will be more vulnerable to diseases. Common ones include;

• Oral thrush (commensual infection)
• Karposi sarcoma
• Toxiplasmi cysts

Question 2

Describe again the infection of CD4 cells by HIV;

Answer 2

1) Mature HIV particle binds the CD4 receptor using its gp120 surface antigen (GP120= weight in daltons).
2) CCR5 or CXCR4 (CD4 co-receptor) is required for binding. (some people lack CCR5 thus infection is limited)
3) Conformational change of receptor allows virus envelope to fuse with lymphocyte
4) Caspid and RNA enter cell.
5) inside the lymphocyte the caspid is digested (by cytoplasm enzymes)
6) Reverse transcriptase (from virion) makes a DNA copy of RNA
7) Viral DNA is removed from RNA by RNAseH and enters the nucelus
8) Integrase, opens host DNA and integrates viral DNA into host genome
9) Viral DNA in host genome is transcribed into viral proteins i.e gp120, caspid, reverse transcriptase
10) Virus assembles and buds off t cell.
11) Protease trims and organises other enzymes i.e reverse transcriptase (inside new virus, makes it functional)

= New HIV virus

Question 3

What are the four targets of anti-retroviral drugs? and an example

Answer 3

1. Fusion - enfurvitide
2. Reverse transcriptase - tenofovir
3. Integrase - raltegravir
4. Protease - atazanavir

Question 4

What are the outcomes of HIV infection and replication?

Answer 4

1. Depletion of T helper cells
2. Immune system activation
   - bone loss
   - CV disease
   - Neurological deficits and others

Question 5

Describe HIV over time and illness;

Answer 5

Following infection; HIV seroconversion illness, High viral load and rapid decrease of CD4 cells

Asymptomatic HIV; CD4 cells rise after their initial drop. but they continue to decline, viral load also falls and stablises in this time

Late stage HIV; Rise in Viral load, CD4 depletes. Illness is frequency all depends on CD4 number.

Question 6

Whats in the management of HIV?

Answer 6

1. Maintenance of health

2. Preventing transmission i.e Safe(r) sex, condoms and stopping HIV replication

Question 7

What things boost CD4 count slightly?

Answer 7

Exercise
Sleep
Weight
Eating well
Reduced alcohol intake
Stop smoking
Living circumstances etc

Question 8

Whats the current treatment regime?

Answer 8

3 drugs. 2 targets.

Reduces viral load = reduced change of transmission