HIV Flashcards
Where is HIV most prevalent
Sub Saharan Africa
How does PCP present?
Pneumocystis pneumonia - often associated with hiv - reasonably unwell for sometime - then suddenly well
What type of infections are lies to be seen late on in someone who is immunosupressed
Fungal eg yeast mould
What is teh likely outcome of HIV
Death is probably if diagnoses lat/untreated
In ppl diagnosed early - can live a normal life with period of chronic infection
Which group is HIV most oprevelant
Men who have sex with men • 101,000 total – Men 69%, Women 31% • UK – 1.1/1,000 • Leicester – 3.8/1,000 • MSM – 46% (58/1000) • Heterosexuals – 54% – Overall UK rate: 1/1000 – >1/2 are black African HIV acquisition by risk group (2014) • Men: 22/1000 • Women: 42/1000 • People who inject drugs (PWID) – 3.8/1000
Describe viral structure
1) Genome - RNA or DNA • Single-stranded (ss) • Double-stranded (ds) 2) Capsid – protein shell, protects the genome • Helical (rod-shaped or coiled) • Icosahedral (spherical or symmetric) 3) Lipid envelope – present or absent • Derived from host cell membranes • Contains virus-specific proteins (antigens) 4) Replication strategy
What are the properties of HIV?
• Human Immunodeficiency Virus – discovered in 1984 • Retrovirus (“backwards”) – ssRNA -> DNA -> ssRNA • Infects cells with CD4 surface receptor – T-helper lymphocytes (predominant) – (Monocytes / macrophages) • HIV replicates inside cells Destroys the cell Causes inflammation Spreads to / infects more cells
Describe HIV reproduction
1) free virus
2) binding and fusion - virus binds to a CD4 molecule and one of 2 coreceptos (CCR5 or CXCR4) receptor molecules are common on cell surface. Virus then fuses with cell
3) infection - virus penetrates cell. Contents emptied into cell
4) reverse transcription - single strands of viral RNA are converted into dsDNA by the reverse transcriptase enzyme
5) Integration - Viral DNA is combines with the cells own DNA by the integrate enzyme
6) Transcription - when the DNA in infected cll divides, the viral dna is read and long protein chains are made
7) Assembly - sets of viral proteins chains come together
8) Budding - immature virus pushes out o the cell, taking come cell membranes with it
9) immature virus breaks fre of the infected cell
10) maturation - protein chains in the new viral particle are cut bu the protease enzyme into individual roteins that combine to make a working virus
How is HIV transmitted
Contact of infected bodily
fluids with mucosal tissue / blood / broken skin
Sexual contact, transfusion, contaminated needles, peripheral transmission (transplacental, delivery through an infected birth canal, breast milk)
*Medical procedures
• Blood/blood-products, skin grafts,
organ donation
Describe thr progression of the viral load and CD4 count
Primary infecton/seroconversion - viral load high, CD4 count starts to recover - May have symptoms but they settle down, antibodies produced and viral load decreases a lot but infection not cleared from blood
Latent infection - viral gradually increase, cd4 slowly go down
Symptomatic infection - C44 count decreasing, viral load high
Sever infection/AIDS - Viral load high,cd4 very low, risk of PCP, fungal, viral infections
See slide
What does HIv have similar presentation to
Glandular fever - HIV in early stages may not be identified
What actors affect HIV transmission
• Type of exposure
– type of sexual act
– transfusion vs needlestick (healthcare worker accidentally pricks with infected needle) vs mucous membrane
• Viral level (viral load) in blood
– Transmission unlikely if undetectable VL
• Condom use
• Breaks in skin or mucosa
– other STI (Inflammation of genital tract)
– sexual assault
How can HIv be lived with
• Life expectancy and quality of life now excellent • General pop: 80yrs (approx) • HIV +ve: 78yrs – Early detection / good CD4 – Treatment – Adherence- take treatment (ppl might struggle with dealing with diagnosis or stigma – Healthy living • Smoking, alcohol, metabolic problems • Late detection = worse prognosis (x10 Increase risk death in 1st year)
What are diagnostic tests for HIV
• Blood tests - Serology – HIV antigen (Ag) – viral protein – HIV antibody (Ab) – immunoglobulin; immune response to antigen – Current test: detects both Ag and Ab – +ve in 4 weeks – Result on same day – May get false negative result
• Blood tests – PCR: – Polymerase chain reaction – Detects HIV nucleic acid – Highly sensitive – Detects very early infection (few days) – Expensive; results slow (up to 1 week) – Not used for initial HIV testing – Used for follow-up / treatment response
What are other “rapid” diagnostic tests for HIV
• “Rapid” tests – low cost, <1hr – Usually detect HIV antibody – Blood test (finger-prick) – Oral (saliva) – In-Home tests – Postal testing
• If negative – accurate
• May get false positive result
– Need to confirm with serology
