Topic 2---C: Cells and The Immune System- 7. HIV and Viruses Flashcards
What does HIV stand for?
Human Immunodeficiency Virus
What does HIV affect?
HIV is a virus that affects the human immune system and it eventually leads to AIDS (acquired immune deficiency syndrome).
What is AIDS?
It’s a condition where the immune system deteriorates and eventually fails.
What does HIV infect?
HIV infects and eventually kills helper T-cells which acts as the host cells for the virus.
How does the destruction of the helper T-cells by HIV impact an infected person?
- Without helpter T-cells B cells can’t be activated to divide by mitosis to form plasma and memory cells.
- Chemical signals can’t be released to attract more phagocytes to the area.
- Signal cytotoxic T-cell can’t be released to kill the infected cell.
- Without enough helper T-cells the immune system is unable to mount an effective response to infections.
When do people infected with HIV develop AIDS?
When the helper T-cell numbers in their body reach a critically low level.
What is the initial infection of HIV?
- During the initial infection period, HIV replicates rapidly.
- Infected person may experience severe flu-like symptoms.
What happens after the initial infection of HIV?
- After this period, HIV replication drops to a lower level (latency period).
- During the latency period (which can last for years) the infected person won’t experience any symptoms.
What are the symptoms of aids?
- Initial symptoms include minor infections of mucous membranes e.g. (inside of the nose, ears) and recurring respiratory infections.
- Decrease in number of immune system cells so patients become more susceptible to more serious infections including chronic diarrhoea.
- During the late stages of AIDS, patients have a very low number of immune system cells so can develop a range of serious infections such as toxoplasmosis of the brain (parasite infection).
What are factors that affect progression of HIV to AIDS and survival time with AIDS?
- Existing infections
- Age
- Access to health care
- Strain of HIV they’re infected with
What is the HIV structure?
- The virus particle has a spherical structure.
- It’s made up of a core containing the genetic material (RNA) and some proteins (including the enzyme reverse transcriptase).
- It has an outer coating of protein called a capsid.
- It has an extra outer layer called an envelope.
- Sticking out from the envelope are loads of copies of attatchment proteins that help HIV attatch to the host helper t-cell.
How can HIV reproduce?
They can only reproduce inside the cells of the organism it has infected.
- HIV replicates inside the Helper t-cells of the host.
- It doesn’t have the equipment (such as enzymes and ribosomes) to replicate on it’s own so it uses those of the host cell.
Stages of the replication of HIV?
- The attatchment proteins on HIV attatches to a receptor molecule on the cell membrane of the host helper t-cell.
- RNA and reverse transcriptase is inserted into the host cell.
- DNA copy made of viral RNA.
- DNA joins to host cells DNA.
- DNA used to make RNA HIV copies and HIV capsid proteins.
- Host cell makes new viruses budding off from membrane of host cell.
How can the progression of HIV infection into AIDS be slowed down?
Antiviral drugs can be used which inhibit reverse transcriptase so the reproduction of HIV is slowed down.
How can HIV spread?
-It can spread via unprotected sexual intercourse through infected bodily fluid e.g. (blood from sharing contaminated needles).
