HIV Flashcards
(17 cards)
What is HIV?
A virus which infects and kills T-helper cells, leading to the deterioration of the immune system (AIDS)
When is AIDS developed?
When T-helper cell count falls below a certain level
Stages of HIV infection —> AIDS
Initial infection means HIV replicates rapidly inside host Th cells (flu like symptoms)
Latency period lasting years where replication stops
Millions of virus is released after causing Th cell number to rapidly fall and AIDS develops
HIV structure
RNA + reverse transcriptase enclosed in a capsid
Enclosed in envelope with attachment proteins
HIV = RNA
Genetic material needed to replicate virus inside Th cells
Reverse transcriptase
An enzyme needed for dna replication inside virus
Capsid
Protein that encloses genetic material and reverse transcriptase
Envelope
Composed of phospholipids stolen from cell membrane of a T helper cell
Attachment proteins
The antigens on the virus which attaches to cell surface of Th cell
Why do virus replication take place in cells?
Has no ribosomes to synthesise protein compartments of a new virus
How does virus enter Th cell?
Attachment proteins attach to cell surface membrane of a Th cell
Capsid is released into cell’s cytoplasm and the RNA released into cytoplasm from inside capsid
Incorporation of HIV DNA into Thcell DNA
Enzyme reverse transcriptase synthesises DNA strand copy which is incorporated into human T helper cell DNA code in its chromosome
Synthesis of new viral parts
Viral DNA is transcribed into HIV mRNA at the ribosomes
HIV proteins eg capsid translated by ribosomes of the T helper cell according to HIV RNA code
Assembling of new viruses
Using synthesised virus compartments, many viruses are assembled and bud off from cell surface membrane of host cell
Development of AIDS
As more and more Th cells die, more serious infections become an issue such as tuberculosis and rare forms of cancer or parasite infections
Why does HIV have a lipid envelope?
When assembled HIV buds off from the host cell, a piece of the phospholipid bilayer is taken off the host cells membrane = lipid envelope
Why does HIV kill helper T cells ?
When infected, they interfere with the normal functioning of helper T cells so they die
