HIV (1) Flashcards
What is HIV?
Retrovirus
- Uses reverse transcriptase enzyme to make a second RNA strand
What are other retorviruses?
HepB
What is HIV-2?
less virulent than HIV-1
Doesn’t necessarily result in AIDS
What is HIV-1?
Group M- Responsible for the AIDS pandemic
Significance of CD4 in HVI
CD4+ receptors are the target site for HIV
CD4 (Cluster of Differentiation) is a glycoprotein found on the surface of a range of cells including:
- T helper lymphocytes (“CD4+ cells”)
- Dendritic cells
- Macrophages
- Microglial cells
What is the function of CD4+ Th lymphocytes?
Messenger cells
Communicate cytokine release for inducing inflammation
Recognition of MHC2 antigen-presenting cell
Activation of B-cells
Activation of cytotoxic T-cells (CD8+)
Cytokine release
Effect of HIV infection 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)
All the above lead to increased susceptibility to infections (viral, fungal and mycobacterial) and infection induced cancers
What are the CD4+ Th cell parameters?
Normal: 500-1600 cells/mm3
Risk of opportunistic infections: <200 cells/mm3
What is the avg time to death without treatment?
9-11 yrs
Describe the infection of HIV
Infection of mucosal CD4 cell (Langerhans and Dendritic cells)
Transport to regional lymph nodes
Infection established within 3 days of entry
- this is why there is a 72hr window to initiate prophylaxis
Dissemination of virus
Onset and symptoms of primary HIV infection
80% are symptomatic
Onset average 2-4 weeks after infection
Combination of flu-ey symptoms and/or glandular fever: Fever Rash (maculopapular) Myalgia Pharyngitis Headache/aseptic meningitis
Very high risk of transmission
What occurs during asymptomatic HIV infection?
Ongoing viral replication
Ongoing CD4 count depletion
Ongoing immune activation
Risk of onward transmission if remains undiagnosed
What are opportunistic infections?
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
What is the most common opportunistic infection in HIV AIDS? What is the CD4 threshold? **
Pneumocystis Pneumonia
CD4 threshold < 200
What is the organism behind pneumocystis pneumonia?
Pneumocystis jiroveci
What are the symptoms and signs of pneumocystis pneumonia
Symptoms: insidious onset
SOB
Dry cough (most likely presentation)
Signs: exercise desaturation -
CXR: May be normal
Interstitial infiltrates, reticulonodular markings
Diagnosis of Pneumocysts pneumonia
BAL and immunofluorescence
+/- PCR
Treatment and prophylaxis of P pneumonia
Treatment: high dose co-trimoxazole (+/- steroid)
Prophylaxis: low dose co-trimoxazole
Tuberculosis and HIV
Epidemiological synergy
The following are more common in HIV+ than HIV- individuals
Symptomatic primary infection Reactivation of latent TB Lymphadenopathies Miliary TB Extrapulmonary TB Multi-drug resistant TB Immune reconstitution syndrome
Beware of drug-drug interactions
Symptoms/signs of Cerebral Toxoplasmosis in HIV
Symptoms/signs
Headache Fever Focal neurology Seizures Reduced consciousness Raised intracranial pressure
Neurological presentations of HIV
Presentation:
Reduced visual acuity
Floaters
Abdo pain, diarrhoea, PR bleeding
Ophthalmic screening for all individuals CD4 <50
List the skin infections associated with HIV
Herpes Zoster
- Multidermatomal
- Recurrent
Herpes Simplex
- Extensive
- Hypertrophic
- Aciclovir resistant
Human papilloma virus
- Extensive
- Recalcitrant
- Dysplastic - women need regular cervical screening
Weird/wonderful
- Penicilliosis
- Histoplasmosis
Neuro-cognitive impairment with HIV
Organism: HIV-1
CD4 threshold: Any. ↑ incidence with ↑ immunosuppression
Presentation:
Reduced short term memory
+/- motor dysfunction
Progressive multifocal leukoencephalopathy with HIV
Organism: JC virus
Reactivation of latent infection
CD4 threshold: <100
Presentation: Rapidly progressing Focal neurology Confusion Personality change
