HIV Flashcards
HIV
lentivirus (retroviridae family)
enveloppes virus
2ssRNA + made of a icosahedral capsid of around 80-130 nm (small genome)
there are 9 genes in total that can cleave off 15 proteins
the main genes are GAG - core proteins,, POL - viral enzymes and Env - envelope proteins gp 120 and gp41
viral enzyme includes protease, reverse transcriptase and integrase
Replication cycle
interact with the cells
fuse with membrane and genome release in cytoplasm
genome transcribed by RT in DNA, which forms proviral dDNA
gets integrate into cell genome
transcription and translation - assembly of viral particles and release
HIV entry cycle
at the visions surface there are spikes made of two gp (trimers) called gp120 and gp41
they need to interact with CD4 receptors to induce exposure and a conformational change, which flip two regions aside, making a new region available = the co receptor binding side
after exposure of the coreceptor binding site
binding of gp120 to the cellular chemokine receptor CCR5 and CXCR4 (in function if X4 or R5 virus)
it leads to the exposure of gp41 fusion peptide, which loves hydrophobic regions and therefore has a high affitionity to go in the membrane of the host cells.
it brings the two membrane very close together which makes them permanently attached, they collapse and then fuse
CD4 receptors
it is made of 4 extracellular IgG like domain D1 to D4, with 3 disulfide bridge.
It can be used for activating the Immune response, as it is required to activate the T cell by APC
it has a hydrophobic transmembrane region and a short intracellular region of 35 aa that enable intracellular signalling
the receptors exist in 3 different formes:
oxidized
Reduced - the most relevant form for HIV entry is like this it does not have disulfide bridge, which make it flexible to interact and bind to the D1 region, which will brind the virus particles closest to the cell membrane
disulfide linker dimer
it is typically expressed on CD4 th cells ( lot)
monocyte and macrophage and B cells, but way less
targeting the attachment of gp120 with CD4 receptor variants (4)
soluble CD4 with D1 - the theory was that it would be in competition with cd4 membrane bound however it was a big fail as it was very unstable and with a very short half life. Also fears that it would help the virus to get in.
PRO542 - soluble CD4-IgG2 basically an antibody that had both D1 and D2 by changing the light chain of the AB/ It increase half life a lot and neutralized the virus way better. However it require daily injections.
sCD4-17b - D1D2 of sCD4 linked to a 17b mAB, which helps to interact and bind to the co receptor binding site. However, that site is a hidden region so it is difficult to reach it as the conformational change goes very very fast
CD4M33 - a 27 aa CD4 mimic that is a derived from a scorpion toxin. block gp120 structure on virions
CD4_binding agents
TNX-355 - humanized non repressive anti-CD4 monoclonal antibody.
it binds to D2 region (not involved in MHC2 binding) - the virus can still attach but CD4 is not flexible anymore so it cannot bend and leads to fusion
PRO-2000 this one is non specific but it is a synthetic naphtalene sulfuric acid that binds to CD3,CD4,CD48. Used as a vagina fuel as preventive drugs for contracting HIV
CD4 down modulator of HIV inhibitor
CADA - syntehtic macrocycle that specifically down modulate the CD4 receptors at the cell surface. It inhibits the pre protein translocation by targeting the CD4 signal peptide. It down modulate without preventing immunological function
PMA - phoràbol myristate acetate which activate the signal transduction of enzyme protein kinase C. By activating this, it phosphorylate S408 which enhance the internalization and lysosomal degradation off CD4
HIV induced down modulation of CD4
after infections, HIV has mechanism to decrease CD4 concentration at the cell surface
it required coordinated action of 3 HIV protein
Nef which is a negative factors and a small proteins that is expressed very early in the life cycle. I down modulate CD4 to evade the immune system and promote infectivity by promoting new visions release
Env is a surface proteins hat is present on the outer membrane that composed of two subunit Gp41 and gp120. the pre protein 160 basically retain cd4 in the ER
VpU - virus protein U is expressed later in the cell cycle but play a role in down modulating CD4 and promotes newly formed virions release. It can also inhibit Tetherin, which helps to anchor newly formed virus at the cell surface
nef role in CD downmodulation
Nef competes with p56ick binding site on the intracellular tail of CD4
nef has a high affinity of adaptor AP2 (which activate endcytoses), which is their recruited and this leads to internalization of CD4, lysosomal activation and then degradation
env role in cD4 downmodulation
Encore and CD4 both have to enter the endoplasmic reticulum to arrive at the cell membrane
fowveer they have a high affinity for each other with leads to the retention of of this complex in the ER
Vpu rol in CD4 downmodulation
viral protein U also has a high affinity for intracellular CD4 tail. which degrade CD4 I the ER by ubiquitin proteasome degradation.
vau is made off three helixes - 1 transmembrane in ER, 2 - CD4 binding main and 3 cytosol which is located in the ER
there is a ubiquitin ligase complex present in the ER
E1 ubiquitin activating enzyme
E2 ubiquitin conjugation enzyme
E3 ubiquitin liagase - everything that bind to E2 gets ubiquinated and degraded
vpU is a substrate for E3 so after formation with CD4 complex they both get ubiquinated and degrade and let gp160 to go the he membrane
CCR5 and CXCR4
chemokine receptors which act as co receptors for HIV
they are GPCR made of a N terminal domain, 7 transimemrabne domain and c terminal membrane which is the binding G protein.
CXCR4 is used by T tropic HIV strains, it is a syncytium inducing virus and more pathogenic
CCR5 is used by M trop strains
CCR5 antagonist
TAK-779 first antagonist described
PRO140 is as humanized anti-CCR5 mAB but it has to be injected
RANTES
APLAVIROC very potent but hepatotoxic
VICRIVIROC very potent and decrease viral loads significantly in CD4 cell
MARAVIROC potent activity against R5 and aproved
CXCR4 receptors antagonist
ANORMED - AMD3100
The molecule is a becyclam to two monocyclam connected by aromatic linkers
very potent in different cell line and work well for CXCR4
works really well and can be used for a synergistic effect in combination treatment in vitro
it is safe and well tolerated in phase 1
phase 2 study proved the efficacy
it is know used as a stem cell mobilizing agent in non Hodgkins lymphoma and is now called mozobil
dual antagonist
R5 strains are mostly responsible for transmission of HIV via sexual intercours
X4 strain appears lated and responsible for a rapid progression toward AIDS disease
many patients harbor dual tropic strains so you would need a dual antagonist that is able to block R5, x4 and dual tropic strains
they tried AMD3451 which block SDF1 and MIP1B induced calcium flux. By binding to the natural ligand , it blocks the intracellular mobilization of CA from outside the cells and from intracellular cell organelles
