HIV Flashcards
What does HIV cause?
The Acquired Immunodeficiency Syndrome (AIDS)
+ Opportunistic infections
+ AIDS-related cancers
What is the single highest predictor of mortality in AIDS?
AIDS-related conditions
What proportion of deaths in AIDS are caused by a late diagnosis?
1/4
People with HIV have a ‘near-normal’ life expectancy
TRUE
HIV infection is not preventable
FALSE - it is preventable
What type of virus is HIV?
A retrovirus
Where did HIV 2 originate?
West Africa – Sootey mangabey (simian immunodeficiency virus)
Is HIV 1 or 2 less virulent?
2
Where did HIV 1 originate?
Central/West African chimpanzees
What was responsible for the global pandemic starting in 1981?
HIV 1 group M
What are the target site for HIV?
CD4+.
CD4 (Cluster of Differentiation) is a glycoprotein found on the surface of a range of cells. Give examples of such cells.
- T helper lymphocytes (“CD4+ cells”)
- Dentritic cells
- Macrophages
- Microglial cells
What are CD4+ Th Lymphocytes essential for?
The induction of the adaptive immune response.
What roles in particular do CD4+ Th Lymphocytes carry out to achieve their aim of adaptive immune response induction?
- Recognition of MHC2 antigen-presenting cell
- Activation of B-cells
- Activation of cytotoxic T-cells (CD8+)
- Cytokine release
List conditions that people with HIV have susceptibility to.
- Viral infections
- Fungal infections
- Mycobacteria infections
- Infection induced cancers
What effect does HIV infection have on immune response?
- Cessation of cells in lymphoid tissue
- Reduced proliferation of CD4+ cells
- Reduction of CD8+ T cell activation
- Reduction in antibody class switching
- Chronic immune activation
What happens to CD4+ cells in AIDS?
They essentially just stop replicating and die.
Describe microbial translocation.
Because the gut is full of lymphoid tissue, it is attacked first.
It can then no longer protect itself, and bits of bacterial cells leak across the gut.
this leads to chronic immune activation.
What are the normal parameters for CD4+ Th cells?
500-1600 cells/mm3.
What level of CD4+ Th cells confers risk for opportunistic infections?
<200 cells/mm3.
When does rapid replication of the HIV virus occur?
In very early and very late infection
How often is there a new generation?
Every 6-12 hours
What is the average time to death without treatment?
9-11 years
Outline how infection goes from initial infection to dissemination.
- Infection of mucosal CD4 cell.
- Transport to regional lymph nodes.
- Infection established within 3 days of entry.
- Dissemination of virus.
Name 2 examples of mucosal CD4+ cells.
Langerhans and dendritic cells.
Up to what % present with symptoms?
80%
When is the average onset of sx of primary HIV infection?
2-4 weeks after infection
What are the primary symptoms of a HIV infection?
- Fever.
- Rash (maculopapular).
- Myalgia.
- Pharyngitis.
- Headache/aseptic meningitis.
What can a primary HIV infection often be mistaken for?
Glandular fever
What is the danger with primary HIV infection?
There is a very high risk of transmission
What happens during the asymptomatic phase of HIV infection?
- Ongoing viral replication.
- Ongoing CD4 count depletion.
- Ongoing immune activation.
What is there a risk of during the asymptomatic stage of HIV?
Onward transmission if remains undiagnosed.
What is the definition of ‘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.
What is the causative organism in Pneumocystis Pneumonia?
Pneumocystis jiroveci
What is the causative organism in Pneumocystis Pneumonia?
Pneumocystis jiroveci
What symptoms are associated with Pneumocystis Pneumonia?
- Insidious onset.
- SOB.
- Dry cough.
What symptoms are associated with Pneumocystis Pneumonia?
- Insidious onset.
- SOB.
- Dry cough.
What is the MAIN sign associated with Pneumocystis Pneumonia?
Exercise desaturation.
How may Pneumocystis Pneumonia appear on CXR?
- May be normal.
- Interstitial infiltrates, reticulonodular markings.
(looks a bit like cardiac failure, but without cardiac enlargement)
What methods are used to diagnose Pneumocystis Pneumonia?
BAL and immunofluorescence +/- PCR.
How is Pneumocystis Pneumonia treated?
With high dose co-trimoxazole (+/- steroid).
What is the prophylactic treatment of Pneumocystis Pneumonia?
Low dose co-trimoxazole.
Describe the relationship between HIV and TB.
EPIDEMIOLOGICAL SYNERGY!
People who are HIV + are more likely to get TB
What organism is associated with cerebral toxoplasmosis?
Toxoplasma gondii (associated with cat litter)
What is the CD4 threshold for cerebral toxoplasmosis?
<150
Outline 2 important features of cerebral toxoplasmosis in HIV.
- REACTIVATION OF LATENT INFECTION
- MULTIPLE CEREBRAL ABSCESSES (chorioretinitis)
Outline the signs and symptoms of cerebral toxoplasmosis.
- Headache.
- Fever.
- Focal neurology.
- Seizures.
- Reduced consciousness.
- Raised intracranial pressure.
What organism is responsible for cyclomegalovirus?
CMV
What is the CD4 threshold for Cyclomegalovirus?
<50
What can CMV virus also cause?
- Retinitis
- Colitis
- Oesophagitis
How may CMV infection present?
- Reduced visual acuity
- Floaters
- Abdo pain, diarrhoea, PR bleeding
What is therefore mandatory for all individuals with CD4<50?
Ophthalamic screening
Herpes zoster is _____ dermatomal and _________
Multi
Recurrent
Herpes simplex is hypertrophic
TRUE
Herpes simplex is resistant to acyclovir
TRUE
What organism is responsible for HIV associated neurocognitive impairment?
HIV - 1
What is the CD4 threshold for HIV associated neurocognitive impairment?
Any
Increased incidence with increased immunosuppression though
What does HIV associated neurocognitive impairment present with?
Reduced short term memory +/- motor dysfunction
What is the causative organism in Progressive Multifocal Leukoencephalopathy?
JC virus
What is the CD4 threshold for the development of Progressive Multifocal Leukoencephalopathy?
<100
How does Progressive Multifocal Leukoencephalopathy present?
- Rapidly progressing focal neurology.
- Confusion.
- Personality change. (causes demyelination)
What is cachexia in HIV known as?
‘Slims’ disease
Slims disease has multiple causes, list some of these.
- Metabolic – chronic immune activation.
- Anorexia – multifactorial.
- Malabsorption/diarrhoea.
- Hypogonadism.