#7 Retro II Flashcards
For complex retro virus we see 6 accessory proteins of HIV
Vif, Vpr, Vpu, Nef, Tat, Rev
***key for pathogenesisi
Regulatory Proteins =
crucial for viral replication and are good targets for therapy
Tat and Rev
Accessory protein thats the transactivator of transcription—absolutely necessary for transcription
Tat:
Regulator of Virion expression—allows structural gene expression by promoting transport of unspliced RNA from nucleus to cytoplasm
Rev
Rev does:
Regulator of Virion expression—allows gene expression by promoting transport of unspliced RNA from nucleus to cytoplasm
“rev like reverend… promotes the ‘unholy (unspliced) RNA out of nucleus.. GET THEE OUT of the hold nucleus! !!
Tat does:
Accessory protein thats the transactivator of transcription—absolutely necessary for transcription
“i’ll buy tat and tat and tat (think transactions!)
Restriction Factor—viral proteins that overcome cell defenses or ‘restrictions’
Vif
Vpu
: promotes virion release from cells.. .inhibits host protein ‘tetherin’ that inhbits viral release from cell
Vpu
“viron promotor usher” because he ushers people out
causes cellular antiviral protein (deoxycytidine deanimase) to be degraded
Vif: Virion Infectivity Factor
inhibits host protein ‘tetherin’ that inhbits viral relesase from cell
Vpu
Why does Vif destory deoxycytidine deanimase
otherwise it’s encorporated into new virions where bock RT in next cell by inducing massive mutations in viral dsDNA
Vif does:
destroys deoxycytidine deanimase bc when if its incorporated into new virions it blocks the RT~~ get bunch of mutations
IG retroviruses have 1 receptor for HIV ______which is the initial receptor present on immune cells
—CD4
main population depleated in AIDS
CD4T helpers
Role of DC cells in HIV
can they bind?
are they infected?
DC can bind HIV but aren’t productivey infected; instead assist with viral dissemination (bring virus back to lymph node where there’s high populatuion of CD4 cells)
These can be ________infected but not efficiently killed and serve as a reservior of virus produciotn
Macrophages
***for HIV, CD4 binding is required but NOT sufficient to cause membrane fusion bc
NEED a co-R
Infection of _______ in the brain infection~contribution to AIDS dementia
Microglia
see these infect primarily T cells and macrophages but NOT T-cell lines
M-tropic
a. responsible for initial infection, transmission, and predominates in Asymptomatic ind
M-tropic
M-tropic infect
T cells and macros but NOT Tcell lines
cause initial infection/transmission/seen in asympotomatic ind
infects primary T cells and T-cell lines, NOT macrophages
T-Tropic
associated with disease progression, arise in AIDS stage of infection
T-Tropic
T-tropic infects which cells
predominates when
primary T cells AND tcell lines but NOT macrohpages
disesease progression… seen during AIDS
co-recpeotor for M-tropic HIV
CCR5
CCR5 receptor for chemokines: (name 3) can specifically inhibit M-tropic HIV by occupying the receptor
RANTES, MIP-1α, MIPβ—these chemokines
RANTES, MIP-1a, MIPB chemokines work to slow progression of HIV by
inhibiting M-tropic binding to CCR5 co receptor (they bind it themselves
co-receptor for T-Tropic
CXCR4:
natural ligand is cytokine stromal derived factor 1 (SDF-1) that can
block T-tropic HIV infection
What can block T-Tropic infection by competinv for CXCR4
cytokine stromal dereived factor
SDF-1
Basis for strain tropisms
a. Envelope sequence of di HIV types have preference for dif co-receptors
b. Most concern is for M-tropic virus bt it is source of person-person transmission
Most concern is for ______ virus bt it is source of person-person transmission
M-tropic
rare ind remain seronegative despite high-risk behavior and presumed viral exposure dt
b. 32bp-depletion of CCR5 gene ∆32
–see non-funx CCR5 (~10% of caucasions heterozygous and 1%homo)
c. WT: WT
—get infected and progress to disease normally
d. WT:∆32:
get infected and progress to disease more slowly (express ½ as much normal)
e. ∆32:∆32—
highly resistant to infection.. people are normal but don’t have CCR5 expressed on cells
Fusion Process—
- Env initially contacts_____ and induce a conformation change in Evn
- Change will cause exposure of the____
- _____ ‘fusion domains’ are exposed and fuse
CD4
co-receptor binding site
gp41
______ peptides form and instert into cell
Fusion
Co-R engagement triggers a _______ of the N and C terminal helical regions of gp41 which brings membrane together and fuses them
‘snapback’
Fusion process overview
- Env initially contacts CD4 and induce a conformation change in Evn
- Change will exposure the co-receptor binding site
- gp41 ‘fusion domains’ are exposed and fuse
- Fusion peptides form and inster into cell
- Co-R engagement triggers a ‘snapback’ of the N and C terminal helical regions of gp41 which brings membrane together and fuses them
How does snapback happen and what is it’s purpose
Co-R engagement triggers a ‘snapback’ of the N and C terminal helical regions of gp41 which brings membrane together and fuses them
**like chinese finger trap!!
Can we block this Snapback mechanism?
YES! T20 (Fuzeon) can bind the N-term helical region to block snap-back
T20 (Fuzeon) can
bind the N-term helical region to block snap-back
HIV is IG at the mucosal surface or by blood products and is spread to lymph node via
DC cells biding and carrying HIV there
Once virus infects T cells in lymph nodes (thanks a lot DC cells.. ya fuckers) and spills into circulation causing
viremia
During asymptomatic phase, FCD traps virus, keeps viremia ____ but nodes (especially _____) are major site of replications
low
GALT
deteriorates in late infection
~~ GALT
What traps our virus in asymptomatic phase to viremia low
FCD
Direct killing of CD4 T by HIV is due to
massive reproduction =
mmb leakage and death
Whats the bystander effect to kill cells during HIV
c. Apoptosis induced by infection—some evidence that cells undergo apoptosis even if infection is unproductive
Syncytia (fuse cells) induced by fusion of infected cell w/ unifected cells
-via Env or infected cell interacts with CD4/CCR5 on unifected cell); cells usually die and could kill uninfected cells
_____ (fuse cells) induced by fusion of infected cell w/ unifected cells
-via Env or infected cell interacts with ______ on unifected cell); cells usually die and could kill uninfected cells
Syncytia
CD4/CCR5
Indirect effects on infected CD4 cells
–immune response
kills infected cells, important for clearing initial viremia
INdirect effects on infected CD4 cells
________ may bind uninfected cells, now susceptible to ADCC
soluble gp120
Impairment of immune system fnx
CD4 T cell fnx altered, loss of CD4 and T cell help, leads to
severly compromised immune system
What happens to infected macrophages with HIV and ability to work effectively
b. Infected macrophages dysfunctional→ aberrant immune fnx
Acute infection and seroconversion
-initially we see burst of virus production coinciding with:
a. Initial burst of virus production coincides w/ decreased CD4T cells
Acute infection:
Early vigorous CTL, subsequent humoral response with FCD help, clears viremia… immune response only ‘appears’ to control infection because
; high level of virus production persists in lymph/GALT
Asymptomatic phase:
contineud strong immune response, gradual decline in ______
CD4 counts
progression measured by CD4 counts and CD4:CD8 ratio
‘vial load’ by measuring _____ by PCR and pts with lower set point have better prognosis
RNA
a lower viral set point of RNA means patient has:
better outcome
Symptomatic/AID phase: late in infection
CD4 cells depleted below _____and immune system begins to fail
~~viremia increases, pts suseptible to many opportunisti infections
200
Point of tests to detect HIV
indentify infected person to start tx
identify carriers
follow course of ts
Serology cannot detct newly infected until
4-6 weeks post infection
Seriology inclucdes
Ab Elisa:
Ag Elisa
Western blot
Ab Elisa~ initial screeing, detect Ab to virus
Ag ELISA: detects p24 capside antigen earlier then Ab
Western blot: confimation test
Ag ELISA: detects _______earlier then Ab
p24 capside antigen
detects virus in blood
RNA RT-PCR
Use of reat time PCR
quantitateve virus in blood
VERY sensitive and detects virus before seroconversion (for high risk/newborns)
gauges viral load in asymptomatics at low titers
quantitateve virus in blood
VERY sensitive and detects virus before seroconversion (for high risk/newborns)
gauges viral load in asymptomatics at low titers
RT-PCR
RT inhibitor: nucleoside/nonnucleoside analogs:
(AZT ect >16 drugs)
a. effective but drug resistant strains appear rapidly (billion virus replication per/day so they are prone to RT errors at 5errors/genome)
Protease inhibotors (>11 drugs):
exteremly effective, reduce viral load by 30-100 x alone, but still see resist.
Fusion inhibitors (T-20) aviable but
$$$$ and must be injected
Entry inhibitors:
Maraviroc—CCR5 co-R antagonist
Raltegravir
Integrase inhibitor
HAART is
Highly Active Anti-Retroviral Therapy
Considereable success of cocktails of triple therapy
a. viritually eliminates virus production in some ind for years w/ undetectable viral load, increase CD4 count and lots of clinical benefit
~~ long term its toxic
HAART
HAART helped us discover replication dynamics of HIV and HIV ½ life
estimate time to clear free virus and infected T cells=
other ‘compartments’ w/ longer ½ lives like Macrophage or FDC =
2 months (infected T cells)
1-2 years (macrophage of FCD)
Infected memory T cell: long lived, can detect virus from those on HAART for more then
5 years and would need 75 years to clear them!
Issues with HAART
a. not all pts respond to HAART
drug regimen is hard to follow (but getting easiert w/ once a day pills)
toxic effects seen in long term HAART users
‘inaccessbible’ pool of virus
Effort to devo drugs with less toxicity in the pipeline
New attacment inhibitors or anti-CD4 antibody
New CXCR4 and ‘dual receptor’ inhibitors and anti-CCR5 antibody
RT inhibitors to common drug resistant viruses
New integrase inhibitors
Maturation inhibitors that work on gag and gag-pol proteins
Vaccine for HIV
Saw a ‘prime boost’ approach… in thialand~ 30% less liekly to HIV/AIDS (51 if the 8,000) people given the vaccine and 74 of them received dummy shots
–responders had a novel, broadly neutralizing antibody; hope is finely tuned vaccine can elicit it
