New vaccine development

Question 1

Criteria of a good vaccine?

Answer 1

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

Question 2

Empiricism vs Rational design?

Answer 2

• Empiricism: Knowledge obtained by direct or indirect observation or experience
• Rational design: Creating new molecules with certain functionality –custom made
• Know what it looks like, how it behaves
• Tools in molecular biology, gene synthesis, structural biology

Question 3

Components of a vaccine?

Answer 3

1. Antigens
2. Adjuvants
3. Delivery systems

Question 4

Types of antigens for vaccines?

Answer 4

*Live
*Attenuated/Inactivated
*Subunit
*VLPs
*Glycoconjugate
*Bacteria with capsule
*DNA/mRNA vaccine

Question 5

Describe Adjuvants and their advantages

Answer 5

*Adjuvants help generate strong, long-lasting protective immune response
– combat low immune response to non-living vaccines
– oral tolerance

*Advantages
– dose sparing
– more rapid immune response
– antibody response broadening

Question 6

Types of adjuvants?

Answer 6

*Empirical era: Alum
*Immunostimulants - interact with specifi receptors
– TLR agonist
– 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
*Delivery systems can also be adjuvating (natural or designed)
*Unmethylated CpG (TLR-9)
– only found in bacteria and viruses
*MPL (TLR-4)
– from bacterial endotoxin (modified)

Question 7

Methods for needle-free immunization

Answer 7

Physical:
Electroporation
Microneedles
Oral vaccines

Nanoparticles:
Nanogels
Nanoemulsion
ISCOMs
Liposomes

Question 8

Describe Viral vectors for delivery of DNA vaccines

Answer 8

g DNA or mRNA vaccine: induced humoral AND cellular immunity

g Viral envelope (for DNA vaccines): Harness ability of virus to deliver
DNA into cells; also induces immune response
– Heavily modified to make safe

g For safety, viral vectors can be
– Host-restricted (will not replicate itself within the tissues of host)
– Self-replicating, attenuated (will not shed from host)
g E.g. Host-restricted: Oxford/AstraZeneca SARS-CoV2 vaccine
g e.g. Self-replicating, attenuated: Ebola vaccine rVSVΔG-ZEBOV

Question 9

How to increase the safety of viral vectors?

Answer 9

g Empirical approach
– continuous passaging (e.g Modified Vaccine Ankara)
– non-selective in types of viral genes lost or altered

g More recent advances
– packaging constructs and cell lines
– pseudotyping for modified efficiency and cell tropism

Question 10

Making traditional vaccines?

Answer 10

Question 11

Making protein-based vaccines

Answer 11

Question 12

Making pDNA or mRNA-based vaccines

Answer 12

– DNA/mRNA vaccines’ delivery by live attenuated viral vectors (DNA) and liposomes (mRNA)

Question 13

List rational design strategies

Answer 13

g Synthetic vaccine
g Reverse vaccinology
g Structural vaccinology
g pDNA or mRNA vaccine

Question 14

Compare the Traditional method and New vaccine method

Answer 14

Traditional method:
g Wait for weeks/months for virus sample to arrive
g Grow up virus in eggs
g Inactivate/attenuate virus
g Prepare vaccine

New vaccine method:
g Sequence virus genome; published online
g Use only spike sequence (safe); find
consensus spike sequence of several
samples
g Modify spike sequence to be more effective
g mRNA vaccine/DNA vaccine/recombinant
vaccine

Question 15

Describe Synthetic vaccines

Answer 15

g Used published sequence of antigens to manufacture vaccines
g No need for growing actual virus; can manipulate DNA digitally before
production based on prior experience with similar pathogens
g Accelerate vaccine availability in pandemics
g Examples: H7N9 avian influenza virus (a.k.a. 2014 bird flu), SARS-CoV2

Question 16

Describe Reverse vaccinology

Answer 16

– Use digital genome sequence and computers to predict good candidate antigens & consensus sequence
g Identify new antigens based on the genome sequence of microorganisms
– Genome-based antigen discovery
g Examples: meningococcus serogroup B (Bexsero, GSK); SARS-CoV2

Question 17

Reverse vaccinology: benefits and limitations

Answer 17

g Most powerful antigen discovery tool currently available
g Provides access to the entire antigen repertoire of bacteria and parasites (even those not cultivable under laboratory conditions)
g Screen for the most conserved protective antigens
g Limitations: Data overload; protein antigens only; antigen in wrong conformation

Question 18

Describe Structural vaccinology

Answer 18

– Use knowledge of protein structure to make better antigens
g Use atomic-level information about key antigens and their epitopes to rationally modify antigens
g 3D structure of proteins determined by X-ray crystallography, NMR, electron microscopy
g Examples: RSV, SARS-CoV2

Question 19

pDNA/mRNA vaccines: benefits and limitations

Answer 19

g Mimics true infection – induces BOTH cellular and humoral immunity
g Cheap and fast to produce; does not require a cold chain for DNA vaccines
g Limited to protein immunogens
g Cold chain for mRNA vaccines; easily degraded if using normal mRNA

– Introduce DNA or mRNA into vaccinee instead of protein antigens. Vaccinee cell makes protein antigens from DNA/mRNA

Question 20

Describe BioNTech/Pfizer vaccine

Answer 20

g mRNA vaccine – mRNA + lipid nanoparticle wall (lipid bilayer)

g New technologies that made it possible
– Rationally designed mutated spike protein
– ‘Pseudo-uracil’
– Versatile ‘plug and play’ vaccine manufacturing system

Question 21

Describe Pseudo-uracil’ in mRNA vaccine

Answer 21

gΨ = 1-methyl-3’-pseudouridylyl/ N(1)-methylpseudouridine

g mRNA with normal uracil (U) will trigger immune response
g mRNA with ‘pseudo-uracil’ can escape immune response while still being translated

Question 22

Versatile ‘plug and play’ vaccine manufacturing

Answer 22

DNA printer

g Virus mutate – New variants/strains; e.g. Alpha, Beta, Delta, Omicron
g How to adapt your vaccine platform to new variants or strains?

Question 23

Compare VLPs vs. Synthetic vaccine vs. Viral vectors

Answer 23