HIV AND AIDS Flashcards
how did HIV1 first come about?
its a zoonosis so it came from animals- chimpanzees and gorillas in cameroon
when was the onset of epidemic transmission of HIV-1 in IUDs and gay men recognised?
1977
describe the 2 types of HIV?
HIV-1 is the most common and HIV-2 is less common and less infectious- HIV2 is much more prevalent in Western Africa
describe the structure of HIV-1 virion?
A sperical, enveloped virus with a lipid bilayer and a capside inside containing 2 copies of the RNA genome, reverse transcriptase, integrase and protease. it has 12-14 gp120 spikes which can bind to human CD4+ and CCR5 to allow for virus-lymphocyte fusion
describe the HIV life cycle?
HIV binds to CD4+ and CCR5 receptors on the surface of CD4 cells
HIV envelope and CD4 cell membrane fuse to allow HIV entry into the cell
HIV releases and uses reverse transcriptase to convert HIV RNA to DNA
HIV enters the nucleus and release integrate which inserts viral DNA into cells DNA
HIV replicates using cells machinery
New HIV proteins and RNA move to the cell surface and synthesise into immature HIV
budding releases HIV and protease which breaks up the immature HIV to create mature HIV
describe the HIV life cycle?
HIV gp120 binds to CD4+ and CCR5 receptors on the surface of CD4 cells= conformational changes
HIV envelope and CD4 cell membrane fuse to allow HIV entry into the cell
HIV releases and uses reverse transcriptase to convert HIV RNA to DNA - meanwhile capsid uncoats = proviral DNA
HIV enters the nucleus and release integrate which inserts viral DNA into cells DNA
HIV replicates using cells machinery = viral RNA
New HIV proteins and RNA move to the cell surface and synthesise into immature HIV
budding releases HIV and protease which breaks up the immature HIV to create mature HIV
what are the most common ways of transmitting HIV?
anal or vaginal sex, sharing needles/syringes, breast feeding, blood products
outline the pathophysiology of the acute HIV syndrome stage?
Acute infection- HIV enters body and establish infections (typically flu symptoms but sometimes no symptoms)- CD4+ loss is huge in the first few weeks and these t cells are typically lost from intestinal mucosa.
meanwhile, HIV replication is huge and viral particles increase = acute viremia
This causes an immune system response which causes viral load to decrease a little and CD4+ t cell numbers to increase a little
what does AIDS stand for? what are the requirements to be classified as havign AIDS?
acquired immunodeficiency syndrome
CD4+ T cell count below 200 cells/mm cubed
or having HIV and one other opportunistic infection (only a problem because of the immunodeficiency)
what type of virus is HIV?
a single stranded positive sense enveloped retrovirus
what is CD4+ co-receptor?
CCR5 or CXCR4 (only T cells)
what are the 3 stages of HIV disease progression?
acute HIV syndrome
clinical latency
AIDS
what is viral tropism?
viral preference for particular coreceptors
e.g. HIV needs CCR5
outline the pathophysiology of the clinical latency stage of HIV?
a small viral load is detectable in peripheral blood but HIV continues to replicate as immune response is not long enough
infected macrophages serve as long-term reservoirs of HIV
= slow decline in T cell numbers
describe the pathophysiology of AIDS, the final stage of HIV?
after latency, there is a loss in normal lymph node architecture = generalise lymphadenopathy
opportunistic infections become common here:
weight loss, chills, fever, diarrhea, fatigue, recurring pneumonia and fungal infections, rare cancers etc
these infections kill the patient because of the low CD4+ count
