Blood and immune 5 Flashcards
(28 cards)
Lentivirus
HIV
Long incubation period
How long does it take for HIV symptoms to occur?
5-10 years after infection
How is HIV transmitted?
By body fluid Aka Blood (dirty needles) Semen (sexually transmitted) Milk (breastfeeding, hence how babies get infected)
Is persone still infectious after drugs
YES
AZT
Reduced the probability of mothers infecting their children
HAART
It keeps the virus levels low enough so there’s enough T cells to keep the immune system going. Basically you don’t die if you can keep taking the drug
HIV
100nm diameter membrane virus
• A retrovirus – the particle contains an RNA genome
• After infection the RNA is converted to DNA by a viral enzyme called the reverse transcriptase
• The DNA is then incorporated into the cells nuclear DNA by a viral enzyme called the integrase
• DNA then makes mRNA and proteins – there are 9 genes (ie 9 mRNAs) and 19 proteins
What is a membrane virus?
A virus that fuses with host cell membrane
What is a retrovirus?
So the particle contains an RNA genome, which inserts a DNA copy of their genomes into the host
Gene order lef to right
GAG Pol Env
GAG
MA
CA
NC
Pol
PR = proteinase RT = reverse transcriptase IN = Integrase - incorporates viral DNA into the cell's nuclear DNA
Env
SU = gp120 binds CD4 TM = gp41 fusion
HIV Proteins
- There are 9 genes and 19 proteins
* Some proteins are made from genes as polyproteins and cut into smaller functional proteins by the viral proteinase
What are the main structural components of the HIV1 virion?
Gp120 and gp41 (surface proteins) Lipid membran Capsid (protein) Matrix (protein) 2copies of RNA and reverse transcriptase protein
Explain the process of creating the pol protiens
There’s a gag, pol and env open reading frame
RNA turns this into a long protein/amino acid chain
This is cleaved by viral proteinase chain (another protein) into three proteins/pieces
Why so many more proteins than genes?
Because the virus makes polyprotein which are chopped up into more proteins
gp41 and gp120
• Made by proteolysis of the env gene
• gp41 and gp120 are joined
• gp120 is on the outside of the particle
• gp41 is embedded in the viral membrane and forms a stalk for gp120
• gp120 attaches the human protein CD4, which occurs on T-cells and macrophages
• This binding is the reason why HIV attacks the immune system
they form in triplets
AIDS treatment
Treatment with a combination of reverse transcriptase and proteinase inhibitor drugs delays AIDS deaths
Outline the part 1 virus life cycle
- Gp120 attaches to CD4; stalk turns into a machine and fuses viral envelope to cell membrane
- Virus release RNA into cell
- Reverse transcriptase copies viral RNA into hybrid DNA then double stranded cDNA
- This then incorporates into DNA of the host (provirus)
What is the virus life cycle part 2?
New HIV production occurs when an infected T cell is activated
- The same normal signal activates the infected T cell
- HIV DNA is transcribed
- Tat and rev transcribed
- Tat amplies transcription of viral DNA
- Rev increases transport of singly sliced RNA
- other proteins
- Assembled and leaves by exocytosis, cell lysis occurs
CD4
CD4 is part of the MHCII-TCR receptor complex
HIV combat
A Normal immune response occurs soon after initial infection, and HIV is neutralised or tagged for destruction by antibodies. Virus levels (‘viral load’) drops.
However some viral DNA survives incorporated into the T cell DNA – this produces virus whenever T cells are activated.
3 stages of infection
Stage1 – the immune response diminishes the viral load, but HIV continues to replicate in lymphatic tissue
Stage 2 - viral load gradually rises as HIV is released from lymph nodes and helper T- cells decrease
Stage3 – AIDS extensive loss of antibody and cell-mediated immune responses, because of a lack of T cells.
