L23 - HIV Flashcards
what is HIV
positive sense ssRNA retrovirus
what are endogenous retroviruses (HERVs)
ancient infections with retroviruses have implemnetd viral DNA into human genome
8% of human genome accounts for viral DNA
= most are inactive
what does HIV cause and which strain causes the most infections of this
AIDs
= Aquired Immunodefieiciency syndrome
HIV-1 - 40 milllion infected worldwide
what have we not been able to do to HIV
break the chain of transmission
= 40 million people living with HIV worldwide in 2021 - global pandemic
= 1.5 million new
where is HIV concentrated globally
South Africa
what is HIV split into
hierachical ranking
high abiulity to mutate = lots of strains/sub-types
source/ orogin of HIV-1 and HIV-2
HIV-1:
Simian Immunodefiecny virus (SIV) in primates recmobined to infect chimps
= SIVcpz
had the ability to infect humans
HIV-2:
SIV in ‘Sooty mangebey’ - SIVsmm
what was HIV orignally
Zoonotic infection
= primates harbor species specific SIVs
corss species transmission from hunting/butchering with blood contact
route of group M infection over history- HIV-1
originated in Congo
travelled to Haiti –> europe + America
= once it hit big cites like NYC and LA was hard to control
common fetsaures of retroviruses
Lipid envelope derived from host cell with glycoprteins imbeded
inner glycoprotein capsid maintains integrity
ssRNA —> placed in nucleus after retrotranscribing
3 defining enzymes of HIV/retroviruses
reverse transcriptase:
ssRNA —> dsRNA —dsDNA
integrase:
allows genteic material to be inserted into genome of host
protease:
cleaves transcibed viral proteins to mature them into functional proteins
simple replicative cyclke of HIV
binding to CD4 receptor by HIV on T-cells
chemokine receptor binds = comfrmational change and entry of virus
virus sheds shell and capsid
reverse transcriuptase –> ssRNA —> ssDNA
integrase places it within genome = cuts hsot DNA and inserts
viral proteins matured by protease and viral proteins bud and leave host cell
3 main regions of HIV genome
Pol (polymerase):
codes for enzymes
Gag (antigen):
codes for structural proteins to form viral particle
Env (envelope):
codes for envelope proteins involved in adhesion and entry
how does HIV spread round body
HIV invades and undegroes first repliaction
spreads to lymph nodes and invades immine cells
= used as ‘Trojan horses’ to get round body
relationship between CD4 t cell count over course of infection and HIV copies - AIDs
- HIV invades CD4 cells and numbers of them decline
- decline in hosts causes copies of HIV to decrease
- over course of years T-cell count gets lower and lower as HIV increases
= eventaul death due to opportunistic disease
dynamics of HIV replication on T cells
high tunover state leading to immune exhasution
= T-cells continously destroyed,produced and activated
= less effective over time
body is weakened when attacked by another infection = coesnt have the ability to fight it off
AIDs vs HIV
condition vs prescence of pathogen
which chemokine receptor does HIV bind to on T cells
CCR5
what can affect a persons succeptibility to AIDs
genetic variations
= some people are immune
CCR5 variations can affect binding to HIV
= depending on the mofifcations a person may have to CCR5
antiretroviral therapy (ART)
target steps in HIVs life cycle
- entry inhibitor
reverse tarnscriptase inhibitor - integrase
- protease
= combinations of these drugs can block progression
timeline of proper ART prescription
1-6 months
= achieve undectable viral load
6 months +
= maintain undectable load
= No risk to transmitting to sexaul partner
ARTs: PrEP vs PEP
PrEP:
Pre-Exposure Prophylaxis
= taking ARTs before being inected to prevent infection
PEP:
Post-exposure prophylaxis
= taking ARts after being exposed to HIV to prevent infection
why is there no HIV vaccine yet
Suraface glycoproteins are variable and envelope constantly changes
High rate of mutation = tolerance for genetic diversity
lack of understanding what the ‘desired’ immune response is dfue to lack of people who survive
= elite controllers do not represent norm
what are ‘elite controllers’ in terms of HIV
people who are able to control HIV infection without ART help
= we dont know why and this doesnt represent the norm
disadvantages of ART
doesnt eliminate the virus just keeps it under control
expensive
