HIV

Question 1

HIV-1 replication cycle

Answer 1

1. Binds CD4 via gp120 and gp41 on T cells, CD4+ monocytes and DCs
2. Binds CCR5/CXCR4 chemokine receptor
3. Replicates with reverse transcriptase enzyme to convert RNA into DNA which can be integrated into host genome
4. Hijacks host cell machinery to make viral proteins
5. Viral proteins packaged and released as mature virions

Question 2

What does Gag protein do?

Answer 2

provides intrastructural support for HIV

Question 3

How does HIV damage the immune response

Answer 3

Domino effect from CD4+ T helper cell deactivation due to infection

Question 4

Key features of HIV-1 infection

Answer 4

Question 5

3 stages of HIV

Answer 5

Acute → asymptomatic → AIDS

Question 6

Important CD4 count thresholds for other diseases

Answer 6

75 - mycobacterium avium complex
150 Pneumocystis jirovecii
300-350 pulmonary TB
400 Kaposi’s sarcoma

Question 7

Diagnosis of HIV

Answer 7

Screening - ELISA
Confirmation - Western Blot

Question 8

When are positive HIV tests possible?

Answer 8

After 10 weeks (seroconversion)

Question 9

What markers are monitored after diagnosis?

Answer 9

Viral load
CD4 count - AIDS (<200)

Question 10

How is resistance tested for?

Answer 10

Phenotypic - cell cultures + antivirals
Genotypic - HIV genome amplified

Question 11

What is the HAART regimen

Answer 11

2 NRTIs + PI (or NNRTI)

Question 12

How is HIV in pregnancy managed?

Answer 12

Antepartum - PO ziduvodine
Delivery - IV ziduvodine
Newborn - PO ziduvodine 6/52

Question 13

What to monitor in HIV?

Answer 13

HIV-1 viral load
CD4 if <350
CVS, osteoporosis risk
liver/renal/bone/lipid toxicity

Question 14

How does treatment relate to the HIV life cycle?

Answer 14