HIV Flashcards
(23 cards)
what is human immunodeficiency virus (HIV)?
a retrovirus/tumour virus (meaning it is associated with cancer)
why do a lot of viruses not have a vaccine?
they evolve too quickly
there are too many variants
they have a complex life cycle
what are retroviruses and lentiviruses (the same thing)?
retroviruses are viruses that convert their RNA into DNA within the host
they are also called lentiviruses because the disease progresses slowly
what is the structure of HIV particles?
they contain a protein called gp120 on their lipid envelope that acts as a receptor to bind to host cells
the contain single stranded RNA and a reverse transcriptase enzyme enclosed within a nucleocapsid
how does HIV infect a host cell?
- the virus binds to CCR5 receptor on the host cell using gp120 and the envelope fuses with the plasma membrane of the host
- the nucleocapsid enters the host’s cytoplasm and the RNA is released then converted to DNA using reverse transcription
- DNA is transported to the nucleus and integrates into the host’s genome
- when the host replicates it produces new RNA and mRNA encoding for viral proteins
- new nucleocapsids form and the virus leaves the host by budding off taking some of the host’s membrane to form its plasma membrane
what are the different stages of a retrovirus?
latent when the DNA of the virus is in the host’s genome but it isn’t replicating, it is also known as a pro-virus
permissive when they are activated
lytic when it is producing lots of viral proteins
what happens when a person is initially infected with HIV?
the virus is cleared so the antibodies might not be detected in a test and they will have no symptoms
what is seroconversion?
when antibodies are first detected in a test
what happens as a person is infected with HIV over time?
the immune system responds to the infection with cytotoxic T cells and the levels of virus particles increases
the person starts to show symptoms
the virus mutates to avoid being detected by cytotoxic T cells
how are T helper cells killed by HIV?
direct lysis
syncytium formation which is where the surrounding cells fuse and die
NK cells or apoptosis
what is the symptomatic phase?
when a person with HIV’s T helper cell count is below 200 and they are at risk of developing AIDS
where are the infected T helper cells found?
in secondary lymphoid tissue
what causes symptoms of AIDS?
the patients T helper cells are too low to fight off other infects called opportunistic infections
other infections that the person fought off in the past might be reactivated e.g. chickenpox
how is HIV transmitted?
prolonged contact of body fluids
unprotected sex, sharing needles, breast feeding and mother to foetus
how can changing behaviour prevent HIV transmission?
safe sex
testing blood before transfusions
not sharing needles
treating HIV-positive pregnant women
why is there no vaccine for HIV?
it has a rapid mutation rate and mutates within people
antibodies don’t affect the virus transmission
why is it hard to find drugs to treat HIV?
the virus has a rapid mutation rate
the drugs cause bad side effects
latent viruses aren’t affected by drugs
it is expensive
what are the 2 types of drugs used to treat HIV?
combination therapy: a cocktail of drugs that have different targets e.g. antiretroviral (AZT) drugs
preventative drugs: biyearly injections of a capsid inhibitor
how could stem cell therapy be a future treatment for HIV?
patient is given a bone marrow stem cell transplant using a donor that lacks CCR5 receptors
how could kick and kill be a future treatment for HIV?
reactivate the latent HIV virus and use immunotherapy to kill it
how could passive immunisation be a future treatment for HIV?
using human monoclonal antibodies to neutralise the virus
how could gene editing be a future treatment for HIV?
using CRISPR to remove the viral genome from the host cell
how could engineered T cell receptors be a future treatment for HIV?
recognise reservoirs of infected CD4 T cells to remove them
