HIV Flashcards
What kind of virus is HIV?
retrovirus
What does HIV cause?
Acquired Immunodeficiency Syndrome (AIDS)
Target sites for HIV?
CD4+ receptors
What is CD4?
CD4 (Cluster of Differentiation) is a glycoprotein found on the surface of a range of cells including:
T helper lymphocytes (“CD4+ cells”)
Dentritic cells
Macrophages
Microglial cells
What do CD4+ Th lymphocytes do?
Essential for induction of adaptive immune response
Recognition of MHC2 antigen-presenting cell
Activation of B-cells
Activation of cytotoxic T-cells (CD8+)
Cytokine release
What effect does HIV infection have on immune response?
Sequestration of cells in lymphoid tissues
- Reduced circulating CD4+ cells
Reduced proliferation of CD4+ cells
Reduction CD8+ (cytotoxic) T cell activation
- Dysregulated expression of cytokines
- Increasing susceptibility to viral infections (including HIV!)
Reduction in antibody class switching - Reduced affinity of antibodies produced
Chronic Immune Activation (microbial translocation)
HIV makes you susceptible to?
Viral infections
Fungal infections
Mycobacterial infections
Infection-induced cancers
CD4+ Th cell count for risk of opportunistic infection?
<200 cells/mm3
Primary infection symptoms?
Combination of Fever Rash (maculopapular) Myalgia Pharyngitis Headache/aseptic meningitis
Note: Up to 80% present with symptoms
Onset of primary infection?
2-4 weeks after infection
What happens in the asymptomatic phase of HIV infection?
Ongoing viral replication
Ongoing CD4 count depletion
Ongoing immune activation
Risk of onward transmission if remains undiagnosed
What is an opportunistic infection?
An infection caused by a pathogen that does not normally produce disease in a healthy individual.
It uses the “opportunity” afforded by a weakened immune system to cause disease
Signs and symptoms on pneumocystis jiroveci?
Symptoms: insidious onset
SOB
Dry cough
Signs: exercise desaturation
CXR for pneumocystis jiroveci?
May be normal
Interstitial infiltrates, reticulonodular markings
Diagnosis of pneumocystis jiroveci?
BAL and immunofluorescence +/- PCR
Treatment of pneumocystis jiroveci?
Treatment: high dose co-trimoxazole (+/- steroid)
Prophylaxis: low dose co-trimoxazole
Which organism causes cerebral toxoplasmosis?
Toxoplasma gondii
CD4 threshold for cerebral toxoplasmosis?
<150
What does cerebral toxoplasmosis cause?
Multiple cerebral abscess
Chorioretinitis
Signs and symptoms of cerebral toxoplasmosis?
Headache Fever Focal neurology Seizures Reduced consciousness Raised intracranial pressure
CD4 threshold for Cytomegalovirus?
<50
Symptoms during primary HIV infection?
Fever Rash (maculopapular) Myalgia Pharyngitis Headache/aseptic meningitis
Presentation of cytomegalovirus ?
Reduced visual acuity
Floaters
Abdo pain, diarrhoea, PR bleeding
What kind of screening should all individuals with a CD4 <50 get?
Ophthalmic screening
