WE. LOVE. HIV.

Question 1

What does Rb stand for?

Answer 1

retinoblastoma protein

Question 2

Draw and label cell proliferation blocking!

Answer 2

Retinoblastoma protein binds cell proliferation factor. This leaves t inactive. Also, the p53 protein (which activates Rb to bond). This means cell proliferation is blocked - NO tumor

Question 3

Draw and label cell proliferation activation!

Answer 3

Viral proteins (E7 and E6) sequester Rb protein and p53, meaning gene transcription continues as cell proliferation factor remains active! CANCER.

Question 4

What is p53?

Answer 4

It is a tumor suppressor that regulates the cell cycle

Question 5

Describe and doodle the retroviral cycle.

Answer 5

Entry into cell and loss of capsid envelope. Then reverse transcriptase makes RNA/DNA double helix THEN DNA/DNA double helix THEN integration into the host genome THEN transcription making lots of RNA copies THEN translation into viral proteins and assembly of many new virions.

Question 6

What is the HIV 3 stage battle plan headings?

Answer 6

1) recognise and attach to host cell 2) delivery of viral nucleic acid into host 3) mutate and reproduce to survive

Question 7

Deets about step 1 of the HIV battle plan:

Answer 7

1) recognise and attach to host cell - HIV recognises a receptor on the host cells leading to ineffective immune system and eventual DEATH - hence immunideficiencies and a terminal susceptibility to otherwise compatible diseases.

Question 8

Deets about step 2 of the HIV battle plan:

Answer 8

2) delivery of viral nucleic acid into host: HIV is a retrovirus, it carries ssRNA and enzymes necessary for production of HIV DNA and incorporati0on into host chromosome

Question 9

DEETs about step 3 of the HIV battle plan:

Answer 9

3) Mutate and reproduce to survive: mutation rate 65x that of influenza. HIV is a moving target. dies w/host and cannot be transmitted by normal means so must rely on sexual urge to survive!!

Question 10

Doodle a quick HIV structure poster

Answer 10

go girl g g go go go

Question 11

What does the variable loop V3 in the HIV gp120 interact with? And what does this interaction follow?

Answer 11

Co-receptor, eg CCR5 on macro/mono and CXCR4 on t-cells eventually. Follows binding to CD4.

Question 12

What is CD4 in relation to HIV virions?

Answer 12

PRIMARY RECEPTOR - but a co-receptor is also required.

Question 13

What is CD4 recognised by?

Answer 13

gp120 V1/V2 loop region

Question 14

What is the change required for variants to recognise CXCR4?

Answer 14

Maybe only 1aa change in gp120 V3 loop region.

Question 15

Quickly recap the process of cell-mediated adaptive immunity that generally works for the body:

Answer 15

All cells (inc Thelper) have on their surface a number of peptides derived from digestion of proteins in their cytosol. These are bound to class 1 MHC proteins. Cyt Tcells scan the surface of all cells and KILL those that exhibit foreign markers on their MHCs via the recognition of MHC1-peptide complex by tcell receptor and co-receptor CD8. TCR binds to MHC-peptide complex and concommitent binding of CD8 from t cell activates t cell, leading to death of target cell via apoptosis.

Question 16

Why does the cell mediated adaptive immunity thang not work for HIV infected celles?

Answer 16

Because HIV inhibits expression of MHC1 on the surface of the cells they inhabit, so they are not picked up by cyt t cells!

Question 17

Why does the innate immune system offer a litte more help than the adaptive for fighting HIV?

Answer 17

Because it recognisesthe LACK of MHC1 on the surface of the cells.

Question 18

Which cell monitors the amound of MHC1 on the immune cells? And how is that cells activity changed by this?

Answer 18

Natural killer (NK) cells, and their activity is inhibited by high levels of MHC1. They selectively kill cells expressing low levels of MHC1

Question 19

How does HIV respond to NK cells?

Answer 19

Responds by aquiring mechanisms to inhibit apop.

Question 20

What are some of the strategies used to combat HIV? 5 of them

Answer 20

Inhibiting integrase, inhibit reverse transtcription or transcriptase, inhibit entry (receptors or gp120/41), inhibit protease or vaccines.

Question 21

How does the inhibiting protease method work?

Answer 21

HIV protease cleaves multidomain viral proteins into the active subunits. It is a dimer of 99aa, with active aspartates in the binding pockets and a flap which closes on the peptide. DRUGS such as crixivan which mimics peptide substrate bus is uncleavable and nelfanavir which is the most popular.

Question 22

How does antibodies to HIV protease work?

Answer 22

HIV protease peptide and anti-protease fab fragment

Question 23

How does inhibition of RT work?

Answer 23

Drugs such as zidovudine which is a nucleoside RT inhibitor, works by being a nuceoside analogue that is modified to be recognised by HIV RT and link into growing DNA but without the OH required for further transcription.

Question 24

What is the current inhibitor therapy being used?

Answer 24

1+ protease inhibitor (potent but side effects), RT inhibitor with 2 nucleoside inhibitors. combos combat resistance.

Question 25

Why is the body bad at getting an antbody to work against gp120?

Answer 25

Because the CD4 binding site on gp120 is narrow and restricted, difficult for Fab to penetrate and bind. Mutations around the site also prevent recognition. However chimerus vaccines have worked!

Question 26

DNA vaccines?

Answer 26

DNA vaccines designed to raise CD8 T cells and abs to HIV proteins are under development. Vaccine DNA delivered either as packaged DNA or modified ‘live’ viruses eg: adenovirus or vaccina ankara. BOTH types contain HIV protein coding sequences that has been modified to prevent self-replication. The results show control not cure.
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Question 27

What is a difficulty in making a vaccine for HIV?

Answer 27

The mutation rate, the RT of HIV is very error prone.

Question 28

Microbicides?

Answer 28

This is the inhibition of co-receptor CCR5. CCR5 normally responds to beta chemokines. PSC-RANTES is a modified version of RANTES, which recognises CCR5, and it BLOCKS ccr5! WORKDS.

Question 29

What availability do we have of looking at gp120?

Answer 29

NO CD4 free HIV gp120 is available even now.

Question 30

Describe the CD4-gp120 interaction

Answer 30

Mainly through the MAIN CHAIN of gp120, suggests that even with high mutation it will still recognise CD4. There are large conformational changes in gp120 on CD4 binding to facilitate V3+coreceptor binding.

Question 31

What is IgG b12?

Answer 31

An antibody to CD4 site. It has a Trp100 that protrudes, allowing it to reach into the recessed CD4 binding site!

Question 32

More binding shenanigans:

Answer 32

gp41 interacts with gp120 and C termini to generate a functional oligomer. V1/V2 partially occludes CD4 binding site. After CD4 binding, there is a conformational change with the formation of Phe43 cavity. Chemokine receptor binds to bridging sheet and V3 loop - causing an orientational shift of core gp120 relative to the oligomer - triggers further changes, leading to the fusion of viral and target membranes.

Question 33

What is Phe43?

Answer 33

It is involved in the binding shit of gp120/CD4, it becmes a cavity after CD4 binding.

Question 34

Is the conformation change in gp120 required to reveal the CD4 binding site?

Answer 34

NO, the change locks CD4 into place.