Human Immunodeficiency Virus (HIV)

Question 1

What is HIV and what does it do in the human body?

Answer 1

A retrovirus acting on CD4+ receptors found on immune cells. It damages these cells and reduces the circulating levels of CD4+ cells which disrupts the immune system.

Question 2

What does HIV infection predispose people to?

Answer 2

Opportunistic infections

Cancers

Question 3

What is the normal circulating level of CD4+ cells?

Answer 3

500-1600cells/mm^3

Question 4

What CD4+ level predisposes people to opportunistic infection?

Answer 4

<200cells/mm^3

Question 5

How does HIV infection establish itself?

Answer 5

Mucosal CD4+ cells (Langerhans/dendritic) are infected by the virus and travel to the regional lymph nodes where the virus spreads from.

Question 6

Describe the stages of HIV infection.

Answer 6

1) Primary infection: Symptomatic with classical viral symptoms. Rapid virus replication and highly contagious.
2) Asymptomatic infection: Virus still replicating but not as fast as in the primary infection.
3) AIDS: Virus rapidly replicates again. CD4+ numbers depleted so far that patient gets opportunistic infections which eventually kill the patient.

Question 7

Name opportunistic infections important in HIV infection affecting the respiratory system.

Answer 7

Pneumocystic pneumonia

Tuberculosis

Question 8

Name opportunistic infections important in HIV infection affecting the nervous system and how they present.

Answer 8

Cerebral toxoplasmosis: focal neurological signs, seizures, reduced conscious level, raised ICP, headache, fever

HIV-associated neurocognitive impairment (HIV-1 infection): short term memory loss and motor dysfunction

Progressive multifocal leukoencephalopathy (JC infection): rapidly progressive confusion, personality change, focal neurology

Question 9

Name opportunistic infections important in HIV infection affecting the eyes and how they present

Answer 9

Cytomegalovirus: reduced visual acuity

Give all patients with a CD4+ count below 50 ophthalmic screening

Question 10

What organs does cytomegalovirus infect in HIV patients?

Answer 10

Eyes

Bowel

Question 11

What is Slim’s disease and what causes it?

Answer 11

HIV associated wasting

Anorexia
High metabolic rate from chronic immune activation
Diarrhoea
Hypogonadiam

Question 12

Name some AIDS related cancers.

Answer 12

Kaposi’s sarcoma (vascular tumour of mucosa/skin including lungs and gut)

Non-Hodgkin’s lymphoma

Cervical cancer (test HIV in all complicated HPV disease)

Question 13

How can HIV present haematologically?

Answer 13

Anaemia (90%)

Thrombocytopenia

Question 14

How can HIV be transmitted?

Answer 14

Sexual (anoreceptive)
Parental (injection)
Mother to child (placental/delivery/breast feeding)

Question 15

Which populations are at a higher risk of HIV?

Answer 15

MSM
Black Africans
PWID

Question 16

What tests are available for HIV?

Answer 16

4th generation HIV test - tests for the HIV antibody and p24 protein. shortens the time between infection and getting positive result

Rapid HIV tests (POCT) - fingerprick test with result in 30 minutes

Recent infection testing algorithm - used to identify if infected within last 4-6 months, used of epidemiology

Question 17

Describe the HIV life cycle.

Answer 17

Virus attaches to CD4 cell receptor via CCR5 co-receptor and enters cell.

Virus uses reverse transcriptase to change shape and integrase to enter human DNA

Human cell uses protease to replicate viral DNA

Question 18

What are the 6 antiretroviral drug classes and what do they act on and what do they prevent?

Answer 18

Nucleotide reverse transcriptase inhibitors (NRTI) - act on reverse transcriptase to prevent the virus’ DNA changing shape to fit into human DNA

Non-nucleotide reverse transciptase inhibitors (NNRTI) - act on reverse transcriptase to prevent the virus’ DNA changing shape to fit into human DNA

Protease inhibitor - act on protease to prevent the human cell replicating viral dna

Integrase inhibitor - act on integrase to prevent viral DNA entering human DNA

CCR5 inhibitor - at on CCR5 to prevent virus entering the cell (“entry inhibitor”)

Monoclonal antibody (mAbs) - prevent virus entering cell (“entry inhibitor”)

Question 19

How do you treat HIV?

Answer 19

Highly active anti-retroviral therapy (HAART): combination of 3 drugs from 2 different antiretroviral drug classes. This prevents resistance. Can be in a single tablet formation.

Question 20

What is the most important factor in preventing drug resistance in HIV?

Answer 20

Drug adherence

Question 21

Why is viral load measured?

Answer 21

High viral load means hgh risk of sexual transmission.

Undetectable viral load means 0 risk of sexual transmission.

Question 22

How can you prevent mother-child transmission.

Answer 22

Placental: HAART during pregnancy

Birth: if detectable viral load, do c-section. if undetectable do vaginal delivery

Milk: exclusively formula fed

Pre-exposure prophlaxis for baby

Question 23

What is PrEP?

Answer 23

Pre-exposure prophlaxis

Once daily medication (truvada) to prevent HIV infection in high risk patients

Question 24

Name one drug regimen used to treat HIV.

Answer 24

Bictegravir (integrase inhibitor) + emtricitabine (NRTI) + tenofovir (NRTI)