HIV

Question 1

Definition

Answer 1

Single stranded, positive sense enveloped RNA retrovirus.

Question 2

Two types of HIV

Answer 2

HIV 1 = more commonly associated with AIDS
in US + worldwide = more virulent
HIV 2 = rarer, restricted to Western Africa + Southern Asia = less virulent

Question 3

Risk factors

Answer 3

Sharing needles/ needle stick injury
MSM
Unprotected anal sex
High maternal viral load - mother to child transmission

Question 4

Pathophysiology

Answer 4

HIV gp120 (+ co-receptor) target CD4+ receptors on T helper cells, macrophage and dendritic cells
1. endocytosis RNA + DNA
2. reverse transcriptase transcribes complimentary double stranded proviral DNA
3. integrase: viral DNA integrated into host’s
4. protein synthesis
5. viral proteins + RNA exocytosis + take part of CD4+ cell surface membrane

Question 5

Co-receptors examples

Answer 5

• Need to bind to both to enter
• CXCR4 = found mainly on T cells
• CCR5 = found on T cells macrophages, monocytes, dendritic cells

Question 6

Replication problems

Answer 6

HIV notorious for producing errors during replication = during infection can mutate to create slightly different strains of viruses = all still HIV but target different cells = VIRAL TROPISM

Question 7

Aetiology

Answer 7

males to male transmission
male to female = MC in resource limited settings
female to male = less common - HIV present in vaginal + cervical fluids of infected women
mother to child transmission
- placenta during delivery
- breast milk
accidents on needle sticks
blood products (transfusions)

Question 8

Infection life pathway

Answer 8

1. Infection - CD4+ then “set point”
2. clinical latency (years)
3. Sx
4. AIDS: CD4+ count <200/mm2

Question 9

Signs and symptoms (acute infections)

Answer 9

Malaise
Fever
Diarrhoea
Night sweats
Sore throat
minor opportunistic infection
- oral candida
- recurrent shingles
- oral infection

Question 10

Signs and symptoms (200-500 T cells/mm3)

Answer 10

swollen lymph nodes
(lymphadenopathy)
hairy leucoplakia
- white patch on tongue
- caused by EBV
oral candidiasis
- yeast infections

Question 11

signs and symptoms <200 t cells/mm3

Answer 11

Immune system SEVERELY compromised:
- persistent fever, FATIGUE, weight loss + DIARHHOEA
AIDS defining conditions:
- CMV (e.g. colitis -> OWL EYES)
- recurrent bacterial pneumonia
- pneumocystis pneumonia
- fungal infections: candidiasis of oesophagus. cryptosporidium
- Kaposi sarcoma = skin lesions
- primary lymphomas
- TB
- toxoplasmosis

Question 12

Diagnosis

Answer 12

History
Antibody testing = ELISA - using Anti HIV Ig
P24 antigen
Negative test requires repeat 12 weeks later
Positive test = repeat combined HIV antibody + P24 antigen test or:
Western blot = detects P24 as well as GP120 + GP41 antibodies

Question 13

Treatment

Answer 13

Highly active antiretroviral therapy (HAART)
- combination of medicine = HIV regimen
- slow down HIV replication
Protease Inhibitors (PI)
Integrase Inhibitors (II)
Prophylactic co-trimoxazole (under 200)
- protect against pneumocystis jirovecii pneumonia (PCP)