7. HIV and Viruses Flashcards
What is HIV?
Human immunodeficiency virus
It affects human immune system.
Leads to AIDS - acquired immune deficiency syndrome.
What is AIDS?
Immune system deteriorates and fails.
More vulnerable to infections
HIV host cells
It infects& eventually kills helper T cells.
Helper T cells act as host cell for the virus.
Why are T cells so important?
They send chemical signals that activate phagocytes / cytotoxic T-cells and B-Cells.
Without them helper T cells the immune system unable to mount an effective response to infections as eventually helper T cells will reach low level.
The initial infection of HIV
HIV replicated rapidly and infected person may experience severe flu Symptoms.
After, HIV replication drops to lower level = latency period.
During this period (lasts for years) the infected person wont experience any symptoms.
Why does the initial stage of HIV causes flu like symptoms?
The immune system mounts a response to the virus.
Unable to festive all virus so small amount remains in cells and continues to replicate
When do people go from having HIV to AIDs?
When Symptoms of failing immune system start to appear and their helper T cell count drops below a very low level.
How long does it take for HIV to Develop into AIDs?
10 years roughly , without treatment.
Initial stage of AIDS?
Minor infections of mucous membranes
Inside nose/ ears/ genital
Respiratory infections
More susceptible to serious infections like chronic diarrhoea / TB
During late stages of AIDs
Very low number of immune system cells
Serious infections just as toxoplasmosis of the brain - parasite infection
It’s these serious infections that kill the patient not HIV itself
Survival rate with AIDS
Varies a lot
Depends on;
Existing infections / strain of HIV infection / age / healthcare
Antiviral drugs delay time between HIV developing into AIDs
HIV structure
Spherical structure.
Core - genetic material RNA and proteins including reverse transcriptase.
Outer coating of protein called a capsid.
Outer layer called envelope which is made up of the membrane stole from cell membrane of a previous host cells.
Attachment proteins that help HIV attach to host helper T cell
What is significant about the HIV attachment proteins ?
They’re foreign antigens that can be recognised by immune system.
During replication however the virus can change parts of the structure of its attachment proteins - antigenic variation which helps HIV evade destruction of IS
Where does HIV replicate ?
Inside the helper T cells of the host
It doesn’t have the equipment ( enzymes & ribosomes ) to replicate on its own so it uses those of the host cell
Stage 1 of hiv replication
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Attachment protein attached to receptor molecule on the cell membrane of the host helper T cell
