L10: Blood borne viruses-HIV Flashcards
What is HIV?
Human immunodeficiency virus
Globally are there more men or women with HIV? Why?
Globally more women
Access to healthcare unequal
Sexual abuse
Young women most vulnerable
In the UK are there more men or women with HIV?
More men
46% of cases through men sleeping with men
54% heterosexual
People who inject drugs–> small proportion HIV
How is HIV trends changing in the UK now?
Rates are falling
Sharp decrease in men sleeping with men transmission
Decrease in number of unknown infected cases
Late diagnosis remains high–> often worse outcomes
Increases in number of newly diagnosed born in the UK
What 4 things are useful to think about when considering how a virus acts?
Structure and behaviour
1) Genome DNA or RNA
- -> Double stranded or single stranded
2) Caspid- protein shell to protect genome
- -> Helical (rod or coiled shaped)
- -> Icosahedral (spherical or symmetric)
3) Lipid envelope- present or absent
- -> often derived from host
- -> contains antigens to help attach to other cells (virus specific proteins)- target for blood test
4) Replication strategy
How does HIV act?
- HIV retrovirus–> works backwards–> ssRNA–> DNA (back to ssRNA in new virus)
- Caspid protein shell
- Envelope proteins
- Antigens gp41 and gp120–> interacts with CD4 receptor predominantly on T helper cell
- Contains enzymes –> Reverse transcriptase, integrase and protease to help it work
- HIV replicates inside cells–> Destroys the cell, causes inflammation, spreads to/infects more cells
What is the mechanism of action of HIV?
Free virus interacts with CD4 cell
1- Bind to the CCR5 and CXCR4 receptors on the surface
2- Virus fuses with cell
3- Infection: penetrates cell, contents emptied into cell
4- Reverse transcriptase ssRNA–> dsDNA
5- Integrase enzyme integrates it into cells DNA
6- During transcription viral DNA copied and proteins made
7- Assembly–> viral proteins come together
8- Budding–> immature virus pushes out of cell taking cell membrane with it
9- Immature virus breaks free of infected cell
10- Maturation: protein chains are cut into individual proteins by proteases to form working virus
What are the methods of transmission of HIV between people?
Main one is sexual contact
Transfusion –> HIV infected blood transfused–> not done now since its tested first
Contaminated needles
Perinatal transmission–> vertical transmission (mother to baby)–> transplacental (across placenta), through contact with birth canal, Breast milk
Medical procedures–> blood/blood products, skin grafts, organ donation etc…
What happens to the viral cells and the CD4 cells during the course of infection?
Primary infection/ seroconversion
- -> Body fights infection (antibody production)
- -> CD4 high–> decrease–> increase–> infection not cleared
- -> Viral initially high decreases–> low - viral set point,
Latent infection (1yr, 5yrs etc)–> viral load replicates–> increases, CD4 cells decrease
Symptomatic infection–> Viral cells increased, CD4 cells <350 cell/microlitre
Severe infection/ AIDS–> Viral cell high, CD4 <200
What are the acute symptoms of HIV?
Systemic--> fever, weight loss etc Central--> malaise (general feeling unwell), headache, neuropathy Skin--> rash Gastric--> nausea, vomiting Liver and spleen--> enlargement Mouth--> sores thrush Muscles--> myalgia
Pt may not go to Dr but highly infectious
What are some of the symptoms associated with severe HIV?
Menigitis Toxoplasmosis AIDs Hyperglyceamia Unexplained anaemia TB HIV wasting syndrome Pelvic inflammatory disease Hepatitis etc...
What factors affect HIV transmission after exposure?
Type of exposure–> types of sexual act (not all cause transmission), transfusion, needle stick, mucous membrane etc…
Viral levels in blood (viral load)–> if undetectable in HIV +ve patient transmission unlikely
Condom use
Breaks in skin or mucosa–> STI (inflammation of genital tract), sexual assult–> risk of damage, more likely to get transmission
What transmission route has the highest risk of transmission?
Blood transfusion 90-100% chance
Rest is actually relatively small
What is it like living with HIV in the UK? (life expectancy etc)
LE and quality of life good
90:90:90–> 90% diagnosed, 90% treated, 90% undercontrol
LE–> 78yrs–> early detection, treatment, adherence to treatment, healthy living (smoking, alcohol, metabolic problems)
Late detection- worse prognosis
What test are done for HIV detection?
Blood test (serology)
- -> look for protein antigen
- -> look for antibody to fight antigen –> Ig
- -> HIV for 4 weeks result shown –> false negative if done before this time
- -> result on same day as test
PCR
- -> detect nucleic acids
- -> highly sensitive
- -> detects early infection
- -> results slow, expensive
- -> used for follow up not initial diagnosis
Rapid test, results within minutes
- -> Oral (saliva), blood test (finger prick), home testing kits, postal kits, detects HIV antibody
- -> False negative possible
- -> Need conformation with serology
