HIV Flashcards
What type of virus is HIV?
RNA retrovirus
Describe the different types of HIV
HIV1 - group M responsible from the global epidemic
HIV2 - localised to west Africa, few cases in the UK
When does replication occur in HIV?
Very late and very early infection - new generation every 6-12 hours
What cells are infected in HIV?
CD4+ cells in the mucosal tissue then transfers into the blood stream via lymphatic drainage
How soon is infection established in the body?
72 hours
What is the target site for HIV?
T helper lymphocytes
State the four functions of T helper lymphocytes
- recognise MHC2 antigen presenting cells
- activate B cells
- activate cytotoxic T cells
- cytokine release
How does HIV alter immune system?
Reduced circulation and proliferation of CD4+ T cells
Reduced CD8+ T cells
Reduced antibody affinity
Chronic immune activation (microbial translocation -GALT)
What is normal CD4 T cell count?
500-1600 cells/mm3
At what CD4 T cell level is there the highest risk fo opportunistic infections?
<200 cells/mm3
What are the four key stages in HIV infection?
Primary
Asymptomatic
Symptomatic
AIDS
With no treatment how long does HIV take to progress from primary to AIDS?
9-11 years
How many people present with HIV primary infection?
80%, 2-4 weeks after infection
How does primary HIV present?
Fever, maculopapular rash, myalgia, pharyngitis, headache, aseptic meningitis
What happens in the asymptomatic phase?
Ongoing viral replication, CD4 depletion, immune activation and risk of onward transmission
Define opportunistic infections
An infection that pathogen does not normally cause disease in a healthy individual
What infection can HIV cause in the lungs?
Pneumocystic Pneumonia
When does PCP occur and what are the signs/symptoms?
CD4 <200
Symptoms - insidious onset, SOB, dry cough
Signs - exercise oxygen desaturation (pulse up and oxygen down fast)
What will a CXR of PCP show?
Normal, interstitial infiltrates, reticulonodular markings
How is PCP diagnosed?
Broncho-alveolar lavage, PCR/immunoflorescence
How is PCP treatment?
High dose co-trimoxazole
What types of TB are more common in HIV positive patients?
Symptomatic primary infection, reactivation of latent TB, lymphadenopathies, miliary TB, extra pulmonary TB, multi-drug resistant, immune reconstitution syndrome
What organism causes cerebral toxoplasmosis?
Toxoplasma gondii
At what CD4 count can cerebral toxoplasmosis occur?
<150
What can reactivation of toxoplasma gondii cause?
Cerebral abscess
Chorioretinitis
How will cerebral toxoplasmosis present?
Headache, fever, seizures, focal neurology, reduced consciousness, raised ICP