3.2.4 HIV Flashcards
What is HIV?
Virus that affects immune system
What is AIDS?
Disease where immune system deteriorates & eventually fails
What cells do HIV infect and use as a host?
helper T-cells
When are people said to have developed AIDS?
When there’s less than 200 mm-3 helper T-cells numbers so body can’t fight usual harmless pathogens (e.g. flu)
HIV has a ______ structure
Spherical
What does HIV’s core contain
RNA & proteins
e.g. enzymes: reverse transcriptase, integrase, and protease
What is HIV’s outer coating of protein called?
Caspid
HIV has a ___ layer called an ______
HIV has a outer layer called an envelope
What is the envelope made out of?
Membrane stolen from cell membrane of previous host cell
What are sticking from the envelope?
Attachment proteins
(Contains glycoproteins)
What do attachment proteins help HIV to do?
To attach to host helper T-cell
What is a retrovirus (e.g. HIV)?
Use reverse transcriptase & RNA method
Describe how HIV replicates
- Attachment protein attaches to CD4 cell-surface antigen on host helper T-cell
- Capsid is released into cell, where it uncoats and releases genetic material (viral RNA) & core proteins into cytoplasm
- Inside cell, reverse transcriptase is used to make complementary strand of DNA from viral RNA template
- From this, double-stranded viral DNA is made & inserted into human DNA
- Host cell enzymes are used to make viral proteins from viral DNA found within human DNA
- Viral proteins are assembled into new viruses (made by host cell), which bud from cell & go infect other cells
What happens during the initial infection period?
HIV replicates rapidly & infected person may experience severe flu-like symptoms
What happens after the initial infection period?
HIV replication drops to a lower level = latency period
What occurs during the latency period (which can last for years)?
Infected person won’t experience any symptoms
What is the effect of AIDS?
Develop diseases that wouldn’t cause serious problems in people with healthy immune system
Name 4 factors that affect the progression of HIV to AIDS & survival time with AIDS
- Existing infections
- Strain of HIV
- Age
- Access to healthcare
Describe the initial symptoms of AIDS
Minor infection of mucous membranes (e.g. inside of nose, ears) & recurring respiratory infections
Describe the symptoms of as AIDS progress & as no. of immune system cells decrease
Patients become susceptible to more serious infections
e.g. chronic diarrhoea, severe bacterial infections, tuberculosis
Describe the symptoms during the late stages of AIDS
- Can develop range of serious infections
- These kill AIDS patients not HIV itself
Name an issue when trying diagnose HIV
Symptoms are non-specific
Name 2 ways of testing HIV
Blood tests
- Antibodies to HIV
- Looking for HIV specific protein - P24
When diagnosing AIDS, what do you need to look at? (2)
- AIDS related symptoms
- No. of helper T cells
Name 2 examples of treatments for HIV
- Antiviral drugs
- Enzyme inhibitors
What do antiviral drugs do?
Slow down the progression of HIV infection and AIDS in an infected person
Describe what an integrase inhibitor does
Binds to integrase so viral DNA can’t be transcribed so viral RNA and proteins cannot be produced
Describe what an attachment and entry inhibitor does
- During attachment, protein on HIV binds to CD4 receptors
- Attachment and entry inhibitors bind to these attachment points
Describe what a protease inhibitor does
Prevents protease catalysing the assembly of viral proteins in cytoplasm of host
Name 3 reasons why HIV vaccinations are considered unsafe (3)
- Inactive virus may become active
- Protein from HIV may harm cells
- People may test HIV positive after vaccine used
How do antibiotics kill bacteria?
- Interfer with their metabolic reactions
- Target bacterial enzymes and ribosomes used in these reactions
Why can antibiotics only target bacterial enzymes & ribosomes, and thus not damage human cells?
Bacterial enzymes & ribosomes are different from human enzymes & ribosomes
Why can’t antibiotics be used to cure viruses?
Don’t have their own enzymes & ribosomes (use host cells’ ones)
What do most antiviral drugs do?
Target few virus-specific enzymes
e.g. HIV uses revere transcriptase to replicate ∴ prevented by using reverse-transcriptase inhibitors
Name 3 ways HIV spreads
- Unprotected sexual intercourse
- Infected bodily fluids
- (e.g. like blood from sharing contaminated needles)
- From HIV-postive mother to her fetus
Not all babies are born infected with HIV & taking ____ _____ during pregnancy can reduce chance of baby being HIV-positive
antiviral drugs
Why is HIV testing, based on HIV antibody detection, before a baby is 18 months inaccurate?
∵ baby of HIV-positive mother may have some HIV antibodies in their blood regardless of whether or not they’re infected
When can a virus be described as inactive?
When it’s not replicating
