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Infection and Immunity > New Vaccine Development > Flashcards

New Vaccine Development Flashcards

1
Q

What are the criteria of a good vaccine?

A

Safe, effective
Delivery method and vaccination schedule
Affordable and quick to make
Easy to store and transport

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2
Q

What is empiricism?

A

Knowledge obtained by direct or indirect observation or experience

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3
Q

What is rational design?

A

Creating new molecules with certain functionality - custom made

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4
Q

What are the components of vaccine formulation?

A

Antigens
Adjuvants
Delivery systems

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5
Q

What are the types of antigens for vaccines?

A

Live
Attenuated/inactivated
Subunit
VLPs
Glycoconjugate
DNA/mRNA vaccine

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6
Q

What do adjuvants do?

A

Help to generate strong, long-lasting protective immune response
The combat low immune response to non-living vaccines and have oral tolerance

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7
Q

What are advantages of adjuvants?

A

Dose sparing
More rapid immune response
Antibody response broadening

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8
Q

What are the types of adjuvants?

A

Empirical - alum
Immunostimulants - interact with specific receptors
Delivery systems can also be adjuvating

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9
Q

What are the types of immunostimulants?

A

TLR agonists - PAMPs, e.g. MPL, CpG DNA
Derivatives of bacterial enterotoxins - e.g. cholera toxin subunit B (CTB); used in mucosal vaccines to recruit e.g. M cells
Cytokines and chemokines - e.g. IL-12

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10
Q

What are methods for needle-free immunisation?

A

Electroporation
Microneedles
Oral vaccines
Chemical nanoparticles

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11
Q

Give some examples of chemical nanoparticles

A

Liposomes - act as carriers
Immune stimulating complexes - act as carriers and adjuvants
Nanogels - act as carriers and adjuvants
Nanoemulsion - act as immunostimulants
They can act as vaccine carriers or delivery vehicles or can be immunostimulants themselves

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12
Q

What is used for delivery of DNA vaccines?

A

Viral vectors

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13
Q

What do DNA and mRNA vaccines activate?

A

Cellular and humoral responses

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14
Q

What is the function of the viral envelope for DNA vaccines?

A

The protective layer of the viral envelope has the capability of delivering DNA to the host cells like a normal virus and inducing an immune response
Must be heavily modified to remove infectious components of the virus as the viral vectors are live attenuated viruses

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15
Q

How are viral vectors made safe?

A

Host-restricted - will not replicate itself within the tissues of a host e.g. Oxford/AstraZeneca SARS-CoV-2 vaccine
Self-replicating, attenuated - will not shed from host e.g. Ebola vaccine

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16
Q

How can the safety of viral vectors be increased?

A

Continuous passaging e.g. modified vaccine ankara
Non-selective in types of viral genes lost or altered
Packaging constructs and cell lines
Pseudotyping for modified efficiency and cell tropism

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17
Q

How are viral vectors made using packing constructs?

A

Put what you want to pack inside the viral envelope between the encapsidation signal - for example, can be genes of a DNA vaccine for the viral vector to deliver
Packaging construct codes for the genes of the viral envelope and do not have encapsidation signals
When both genes inserted, mammalian cells will make more of the encapsidated DNA but do not translate them into proteins
Genes that are not encapsidated are translated into structural proteins of the viral vector
Structural proteins and encapsidated DNA vaccine genes combined together in mammalian cells and viral vector can be purified out

18
Q

How are live attenuated vaccines made in the empirical era?

A

Sample of the pathogen obtained (seed virus)
Inoculate seed virus sample into production platform e.g. mammalian cells more recently being used
Virus will replicate in production platform
Virus purified
Chemicals used to inactivate the virus before formulating in a vaccine for further testing

19
Q

How are protein-based vaccines made?

A

Take DNA from protein of interest
Promoters and terminators that flank the gene of interest need to be related to the organism we want the protein to be produced in i.e. for mammalian cell platforms, mammalian promoters and terminators are used
DNA plasmid can be introduced into the manufacturing platform (plant, bacteria, mammalian) by chemical means or by viral vectors or by bacteria that naturally infect plants
In host platforms, there is already machinery in place to transcribe the DNA and translate them into recombinant proteins that can then be purified and used as a vaccine

20
Q

How are DNA/RNA vaccines made?

A

Similar to protein vaccines however the difference is that the vaccinees are the manufacturing platforms - they make the proteins themselves

21
Q

How is the SARS-CoV-2 DNA vaccine made?

A

Spike protein has all the criteria to generate a good immune response so this was chosen as the vaccine antigen
To generate DNA vaccine, the DNA coding for the spike protein is inserted into a plasmid which can be injected into the patient directly
Otherwise can be packaged into a viral vector

22
Q

How is the SARS-CoV-2 RNA vaccine made?

A

mRNA from spike protein obtained
For RNA vaccines, some form of packaging will be needed to protect the more fragile mRNA and deliver it to the cell - nanoparticle usually used is a form of lipid bilayer that engulfs millions of copies of mRNA coding for the spike protein in its cavity
The whole thing is then injected into the patient and the patient’s cells will use the mRNA to make the spike protein to trigger an immune response

23
Q

How do DNA and mRNA vaccines work?

A

Have the DNA/RNA coding for the spike protein protected by viral vector (DNA) or nanoparticle (mRNA)
When injected into cells of vaccinee, the DNA/mRNA uncoats and cells recognise this and make the spike proteins
These proteins trigger an immune response that produce antibodies that neutralise the spike protein

24
Q

What are some rational design strategies?

A

Synthetic vaccine
Reverse vaccinology
Structural vaccinology
pDNA or mRNA vaccine

25
Q

What was the traditional vaccine method?

A

Wai weeks/months for virus sample to arrive
Grow the virus in eggs
Inactivate/attenuate the virus
Prepare vaccine

26
Q

What is the new vaccine method?

A

Sequence virus genome, published online
Use only spike sequence, find consensus spike sequence of several samples
Modify spike sequence to be more effective
mRNA/DNA/recombinant vaccine

27
Q

Describe synthetic vaccines

A

Use published sequence of antigens to manufacture vaccines
No need for growing the actual virus, can manipulate DNA digitally before production based on prior experience with similar pathogens
These techniques can accelerate vaccine availability in pandemics
e.g. H7N9 avian influenza virus, SARS-CoV-2

28
Q

Describe reverse vaccinology

A

Identifies new antigens based on the genome sequence of microorganisms - genome based antigen discovery
Requires sequencing of viral genome
e.g. meningococcus serogroups B, SARS-CoV-2

29
Q

How are the best antigens chosen to trigger an immune response with reverse vaccinology?

A

First must identify what variants or strains to target and find the consensus sequence to target that variant or strain
Benefit of consensus sequence is that can target multiple strains/variants at once because vaccine is being created with a genome sequence that is the same across different variants or strains

30
Q

What are consensus sequences?

A

Consensus sequences are regions of the genome that are the same or similar in a sample of different variants or strains

31
Q

How is the consensus sequence obtained?

A

Isolate the pathogen sample from different patients and sequence the genome
The figure out which proteins are the best to generate antigens using different plots e.g. antigenicity plot
Consensus sequence then must be found in the regions of interest by using the sequences of the variants/strains obtained from different patient populations

32
Q

What are the benefits of reverse vaccinology?

A

Most powerful antigen discovery tool currently available
Provides access to the entire antigen repertoire of bacteria and parasites - even those not cultivable under lab conditions
Can screen for the most conserved protective antigens by choosing the consensus sequence for the entire pathogen population

33
Q

What are the limitations of reverse vaccinology?

A

Data overload - millions and millions of genome sequences from individual microorganisms
This method can only be used for protein antigens, not carbohydrate antigens bc proteins coded for by DNA/RNA and carbohydrates are not
Method is not suitable for antigens in the wrong conformation

34
Q

Describe structural vaccinology

A

Uses atomic level information about key antigens and their epitopes to rationally modify antigens
3D structure of proteins determined by X-ray crystallography, NMR, electron microscopy
e.g. RSV, SARS-CoV-2

35
Q

How are structural biology techniques used to make the correct form of the F protein of RSV?

A

F protein similar to SARS-CoV-2 spike protein as RSV uses this protein to enter the cell
When the F protein is on the virus it has a tightly coiled structure
However when the F protein is expressed on its own to make a safer subunit vaccine, it will adopt a different conformation so the immune system can make antibodies against this structure instead of the structure on the virus

36
Q

How do DNA/mRNA vaccines induce both humoral and cellular immunity?

A

If the DNA/RNA is introduced into the APCs of a healthy individual they will be presented on the surface of the cells and activate the immune system
They then shed subunit antigens to be processed by other APCs
The vaccine DNA/mRNA can also go into healthy muscle cells - these also make the antigen subunit which can be shed and recognised by APCs

37
Q

What are benefits of using pDNA/mRNA vaccines?

A

Mimics true infection as it induces both cellular and humoral immunity
Cheap and fast to produce, does not require a cold chain for DNA vaccines

38
Q

What are limitations of using pDNA/mRNA vaccines?

A

Limited to protein-based antigens
mRNA is unstable so requires cold chain and must be stored in a deep freezer so may cause problems when transporting

39
Q

What type of vaccine is the BioNTech/Pfizer?

A

mRNA vaccine - mRNA + lipid nanoparticle wall (lipid bilayer)

40
Q

What made production of the BioNTech/Pfizer vaccine possible?

A

New technologies:
- Rationally designed mutated spike protein
- Pseudo-uracil
- Versatile plug and play vaccine manufacturing system

41
Q

Why is pseudo-uracil required in the mRNA vaccine?

A

mRNA with normal uracil will trigger an immune response
mRNA with pseudo-uracil can escape the immune response while still being translated

Infection and Immunity (33 decks)

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