Human Immunodeficiency Virus (HIV) Flashcards
What is HIV and what does it do in the human body?
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.
What does HIV infection predispose people to?
Opportunistic infections
Cancers
What is the normal circulating level of CD4+ cells?
500-1600cells/mm^3
What CD4+ level predisposes people to opportunistic infection?
<200cells/mm^3
How does HIV infection establish itself?
Mucosal CD4+ cells (Langerhans/dendritic) are infected by the virus and travel to the regional lymph nodes where the virus spreads from.
Describe the stages of HIV infection.
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.
Name opportunistic infections important in HIV infection affecting the respiratory system.
Pneumocystic pneumonia
Tuberculosis
Name opportunistic infections important in HIV infection affecting the nervous system and how they present.
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
Name opportunistic infections important in HIV infection affecting the eyes and how they present
Cytomegalovirus: reduced visual acuity
Give all patients with a CD4+ count below 50 ophthalmic screening
What organs does cytomegalovirus infect in HIV patients?
Eyes
Bowel
What is Slim’s disease and what causes it?
HIV associated wasting
Anorexia
High metabolic rate from chronic immune activation
Diarrhoea
Hypogonadiam
Name some AIDS related cancers.
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)
How can HIV present haematologically?
Anaemia (90%)
Thrombocytopenia
How can HIV be transmitted?
Sexual (anoreceptive)
Parental (injection)
Mother to child (placental/delivery/breast feeding)
Which populations are at a higher risk of HIV?
MSM
Black Africans
PWID
What tests are available for HIV?
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
Describe the HIV life cycle.
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
What are the 6 antiretroviral drug classes and what do they act on and what do they prevent?
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”)
How do you treat HIV?
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.
What is the most important factor in preventing drug resistance in HIV?
Drug adherence
Why is viral load measured?
High viral load means hgh risk of sexual transmission.
Undetectable viral load means 0 risk of sexual transmission.
How can you prevent mother-child transmission.
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
What is PrEP?
Pre-exposure prophlaxis
Once daily medication (truvada) to prevent HIV infection in high risk patients
Name one drug regimen used to treat HIV.
Bictegravir (integrase inhibitor) + emtricitabine (NRTI) + tenofovir (NRTI)
