HIV and viruses Flashcards
What does HIV stand for?
Human immunodeficiency virus
What does HIV lead to?
Acquired immune deficiency system (AIDS)
What does HIV do to helper T-cells?
Infects and kills them
What do the helper T-cells act as for the virus?
Host cells
What is the effect of not having enough helper T-cells?
They send chemical signals that activate phagocytes, cytotoxic t-cells and b-cells so without enough the body is not able to develop an effective response to infections
When does someone with HIV develop AIDS?
When the number of helper T-cells in the body reach a critically low level
What is the latency period?
When HIV replicate slows after replication is rapid after initial infection.
What happens during the latency period?
It can last for years and the infected person won’t experience any symptoms so they won’t know the have it
What is the average time between infection with HIV and development of AIDS without treatment?
10 years
What are initial symptoms of AIDS?
Minor infections of mucous membranes and recurring respiratory infections
What are some symptoms as AIDS progresses?
They become more susceptible to more serious infections including chronic diarrhoea, severe bacterial infections and tuberculosis
What happens during the late stages of AIDS?
Patients have a very low number of immune system cells and can develop a range of serious infections such as toxoplasmosis of the brain and candidiasis of the respiratory system
What are the components of a virus particle?
Core
Envelope
Capsid
Attachment proteins
What does the core contain?
Genetic material in the form of RNA
Enzyme reverse transcriptase
What are attachment proteins used for?
Helping the HIV attach to the host helper T-cell
When can HIV only reproduce?
When inside the cells of the organism it has infected
What is the first stage in HIV replication?
The attachment protein attaches to a receptor molecule on the cell membrane of the host helper T-cell
What is the second stage in HIV replication?
The capsid is released into the cell where it uncoats and releases genetic material (RNA) into the cell’s cytoplasm
What is the third stage in HIV replication?
In the cell, reverse transcriptase is used to make a complimentary strand of DNA from the viral RNA template
What is the fourth stage in HIV replication?
Double stranded DNA is made and inserted into the human DNA
What is the fifth stage in HIV replication?
Host cell enzymes are used to make viral proteins from the viral DNA found within the human DNA
What is the last stage in HIV replication?
The viral proteins are assembled into new viruses, which bud from the cell and go on to infect other cells
Why dont antibiotics work on viruses?
Antibiotics target the bacterial enzymes and ribosomes but viruses dont have their own enzymes and ribosomes, only the ones from the host cell
What are anti-viral drugs?
They are designed to target the few virus-specific enzymes that exist
What is the best way to control HIV?
Reducing its spread
How is HIV spread?
Through unprotected sex, through infected bodily fluids, to a baby from a HIV-positive mother whilst pregnant
