Introduction to Vaccines

Question 1

Define a vaccine

Answer 1

Something that stimulates the immune system without causing harm or side effects

Question 2

What is the aim of vaccines

Answer 2

To provoke immunological memory to protect individual against a particular disease

Question 3

What is the difference between something that is immunogenic and reactogenic

Answer 3

Immunogenic - ability to start an immune response

Reactogenic - ability to cause reaction

Question 4

Define an antigen

Answer 4

Anything that causes an immune response

Question 5

What is in a vaccine?

Answer 5

• Antigen
• Adjuvant (normally alum)
• Stabilisers (PBS)
• Water

Question 6

What types of antigen can you use in a vaccine (5)

Answer 6

• Inactivated Protein
  
  • Tetanus toxoid
• Recombinant protein
  
  • Hep B
• Live attenuated pathogen
  
  • Polio/BCG
• Dead pathogen
  
  • Split flu vaccine
• Carbohydrates
  
  • S. pneumoniae

Question 7

What is the MOA of inactivated toxoid vaccines

Answer 7

Inactivated toxin induces antibodies which block toxin binding to nerves

Question 8

What are some advantages of Inactivated toxoid vaccines

Answer 8

• Cheap
• Well characterised
• Safe

Question 9

What are some disadvantages of Inactivated toxoid vaccines

Answer 9

• Requires understanding of toxin moa
• Not all organisms encode toxins
• Small risk of failure to inactivate (some impurities)

Question 10

How are recombinant protein vaccines made

Answer 10

• Surface antigen gene isolated
• Gene inserted into yeast
• Modified Yeast cells produce sAg
• Purified into vaccine

Question 11

What is the MOA for recombinant protein vaccines

Answer 11

Induces classic neutralising antibodies

Question 12

What are the advantages of recombinant protein vaccines

Answer 12

• Pure
  
  • Useful if we know surface antigen
• Safe
  
  • Low strain variation

Question 13

What are some disadvantages of recombinant protein vaccines

Answer 13

• Relatively expensive
• Doesn’t work for everything

Question 14

How are dead pathogen vaccines made

Answer 14

Whole pathogen can be chemically killed

These are innoculated into eggs

Vaccine purified from eggs

Question 15

What is the MOA for dead pathogen vaccines

Answer 15

Induces antibody and T cell response

Question 16

What are the advantages of dead pathogen vaccines

Answer 16

• Antigenic components are intact
  
  • Therefore, more immunogenic as other components are included

Question 17

What are some disadvantages of dead pathogen vaccines

Answer 17

• Fixing/killing can alter chemical structure of antigen
• Requires capacity to grow the pathogen (H5N1)
• Vaccine induced pathogenicity
• Risk of contamination with live pathogen (polio)
• ‘Dirty’

Question 18

How are live attenuated vaccines made

Answer 18

• Attenuation by serial passage
  
  • Comparison of end virus with orginical virus
• Loss of virulence factors

Question 19

What is the MOA of Live attenuated vaccines

Answer 19

• They replicate in situ
• Trigger innate response and boost immune response

Question 20

What are the advantages of live atteniated vaccines

Answer 20

• Induce strong immune response

Question 21

What are the disadvantages of live attenuated vaccines

Answer 21

• Can revert to virulence
• Can infect immunocompormised (BCG/HIV)
• Attenuation may lose key antigens

Question 22

How are conjugate vaccines made

Answer 22

Polysaccharide coat component is coupled to an immunogenic carrier protein

Question 23

What is the MOA for conjugate vaccines

Answer 23

• T cells only recognise peptides
• B cells recognise conjugate (polysaccharide + carrier protein)
• Processes and presents peptide antigen to CD4 cells
• CD4 T cell releases mediators which elicit memory in B cells

Question 24

What are the advantages of conjugate vaccines

Answer 24

• Improved immunogenicity
• Highly effective at controlling bacterial infeciton

Question 25

What are the disadvantages of conjugate vaccines

Answer 25

* Expensive * Strain specific * Carrier protein interference * Polysaccharide alone is poorly immunogenic

Question 26

Once the adaptive immune response is activated, what are the mechanisms in which they control the infection

Answer 26

* Prevention of entry * Antibody blockade * Opsonisation -\> phagocytosis * Boost T/B cell immunity * B cells activate T cells, T cells release mediators to boost B cell function * B cell produces Antibodies * Kill Infected Cells * CD8 cells recognise stressed cells

Question 27

What is meant by R₀

Answer 27

The number of cases one case generates on average over the course of their infection period

Question 28

How can vaccines reduce R₀

Answer 28

Herd immunity allows for transmission termination Higher the R₀, the higher the number of people you need to vaccinate

Question 29

What are some barriers to the development or compliance of vaccines

Answer 29

* Development issues * Takes a long time to get from bench to bedside * Cost of product * Vaccine scares - anti-Vaxx

Question 30

What are the 2 areas of concern for vaccine complications

Answer 30

* Acute responses * Fluvax * High cytokine release * Chronic complication * Pandemrix (?H1N1) * Narcolepsy

Question 31

What has stopped us from developing more effective vaccines?

Answer 31

* High variation of target organism * Classic immune will only recognise one variant * HIV * Strain Replacement * One strain vaccinated, decrease in incidence, other strains increase in incidence * Natural infection can sometimes not be protective * HIV, CMV, TB * BEcause antigens are changing or hidden as in HIV * Flawed translation from animal models

Question 32

Vaccinations can increase the transfer of antibodies across the placenta to the baby. What time should the mother be vaccinated for flu or pertussis?

Answer 32

2nd or 3rd trimester

Question 33

With regards to flu vaccine, what is a novel approach for this therapy

Answer 33

Influenza changes all the time, the head portion changes The stem of the haemagluttinin molecule remains more constant than the head Could be potential target