Lecture 3 - Vaccines Flashcards
Examples of live attenuated virus vaccine 1) 2) 3) 4)
1) Sabin polio vaccine
2) MMR
3) Varicella
4) Yellow fever
Examples of inactivated virus vaccine
1)
2)
1) Salk polio
2) Tick-borne encephalitis
Examples of protein subunit vaccines
1)
2)
3)
1) Hepatits B
2) HPV
3) Seasonal flu
HIV cell entry process
1)
2)
3)
1) gp120 binds to CD4. This exposes the coreceptor binding site on gp120 for CCR5
2) gp41 inserts fusion peptides (HR1, HR2) into the cell membrane
3) 6-helix bundle formation. Membrane fusion
What are the most common targets for potential HIV vaccines?
gp120, gp41
What is an escape variant?
A mutated epitope of a virus, whose original epitope was targeted by the immune system
Failed HIV vaccines
1)
2)
3)
1) Vax04 (vaxgen)
2) STEP
3) RV144
Outcome of STEP trail
Increase in disease
Outcome of RV144 trial
~20% protection afforded
Type of vaccine that was Vax04
Recombinant monomeric env protein in alum
Type of vaccine that was STEP
Recombinant type-5 adenovirus vector with HIV-1 T cell antigens
NO ENV PROTEIN
Type of vaccine that was RV144
Recombinant poxvirus vector + booster with env protein
How does HIV evade the immune system? 1) 2) 3) 4) 5)
1) Contains regions with extreme tolerance for mutation
2) Very high mutation rate
3) Glycan shield of gp120.
4) Unstable association between gp120 and gp41 –> shedding of membrane trimers, exposure of irrelevant antigens
5) Highly conserved coreceptor binding site on gp120 is covered by glycans until binding with CD4 occurs
Number of glycans normally attached to each gp120 trimer
20-30
What is enriching for antibodies that recognise the CD4 binding site on gp120? 1) 2) 3) 4)
1) Produce a probe that mimics the CD4 binding site.
2) Produce another probe that is the CD4 binding site with a single amino acid change within the binding site.
3) Select for antibodies which bind the CD4 probe, and not the variant.
4) Using these probes, isolate B cells which produce antibodies against the Cd4 binding site.
What is large-scale isolation of bNt Mabs form memory B cells?
1) Sort individual IgG B cells that bind to a modified gp160 trimer called 2CC
2) Recover IgV genes from each cell.
3) Reexpress as recombinant, complete IgG in test tube.
How are different cell types identified?
Flow cytometry
What does bNt Mabs stand for?
Broadly-neutralising monoclonal antibodies
What is unusual about some bNt Mabs?
They don’t show evidence of coming from anti-HIV B cells
Germline antibody (without somatic hypermutation) doesn’t bind to HIV antigens.
What are ‘waves’ of antibody immunity?
As the virus mutates, antibodies are made against different, more conserved epitopes.
The virus has an increasingly narrow range of epitopes to change
Antibody response becomes more potent, greater breadth
How must broadly-neutralising antibodies be delivered to be effective at controlling HIV?
As a penta-therapy (five different kinds)
With fewer than five different types of bNt, response is too small.
Limitations to therapy with broad neutralising antibodies
When treatment with antibodies stops, virus is resurgent
