Scientific Bases of vaccines

Question 1

Define vaccine?

Answer 1

Biological substance that does not cause disease and when administered to patient , an adaptive immune response is produced providing protection against future diseases

Question 2

What is the overall immune response from MHC class 2?

Answer 2

Antigen taken in by endocytosis, peptide presented and naive CD4+ T cell binds to peptide MHc complex. CD4+ T cell becomes mature helper T cell (Th1 or Th2) and goes onto activate B cells to produce antibodies, or become memory helper T cell

Question 3

What is the overall immune response from MHC class 1?

Answer 3

Antigen already inside cell (infection) , peptide presented and naive CD8+ T cell binds to peptide MHc complex. CD8+ T cell becomes mature CYTOTOXIC T cell (CTL) which kill infected cells using perforin+granzymes or become memory cytotoxic T cells

Question 4

Define variolation?

Answer 4

Deliberate infection with smallpox - Jenner did with cowpox

Question 5

What is the purpose of vaccinations?

Answer 5

Protect individual
Protect population - herd immunity
Eradicate disease (e.g. smallpox and almost polio)

Question 6

What things in a vaccination need to be tested when being developed?

Answer 6

Challenge dose - prove protection from infection
Attenuation (reduced effect)
Prior exposure
Cross-species protection - antigenic similarity

Question 7

What is the vaccine paradox?

Answer 7

Herd immunity = memory boosted. Used to be natural boosting by outbreaks f disease. Disease rates decline due to vaccinations but no more natural boosting so important of vaccine uptake increases

Question 8

Why are vaccines taken despite side effects in some cases?

Answer 8

Better than acc infection conseqeunces

Question 9

What is the immune response to a vaccination step by step?

Answer 9

Primary exposure - vaccination - antibody response, takes almost 2 weeks for class switching from IgM to IgG to take place. Memory B cells and Memory T cells made

Secondary exposure - real life - less than 7 days for response due to priot exposure

Question 10

Why can all vaccines not be made in similair way? e.g.oral vaccine

Answer 10

Vaccine must induce correct TYPE of response e.g. antibodies, or cell medaited immunity, as well as in the RIGHT PLACE e.g. sIgA in mucosal membrane against influenza

Question 11

How do duration of protection of vaccines cary?

Answer 11

Antibodies made are enough for short term

If long term, need memory, boosters needed (either naturally or via vaccine)

Question 12

What is a incubation time and how does it vary?

Answer 12

Incubation time is how long it takes until you are actually protected from a disease due to pathogen after taking the vaccine - not immediately immune to pathoegen

Long incubation time - measles vaccine
Short incubation time - cholera vaccine

Question 13

Why are vaccinations not given to neonates?

Answer 13

Already have maternal IgG antibodies through placenta and sIgA from breast milk. These antibodies might interfere with vaccine effects

• timings for diff vaccine vary

Question 14

What is monotypic? and why is this important in vaccinations?

Answer 14

Surface antigens of pathogens stay unchanged e.g. measles virus
- only need one vaccine/infection - gives life long immunity

Question 15

What is polytypic and how does this factor affect vaccinations?

Answer 15

Surface antigens change so immunity is readily overcome e.g. inflienza virus
need more than one vaccine

Question 16

Define antigenic drift?

Answer 16

Accumulation of mutations in genes that code for surface proteins change with time

Question 17

What is antigenic shift?

Answer 17

Recombination of several viral strains to produce a different subtype with a mixture of surface antigens from the original strains

Question 18

What are the 3 types of vaccines?

Answer 18

live attenuated
Killed, whole organisms
Sub unity vaccine (individual components)

Question 19

Give a examples of live attenuated vaccines?

Answer 19

Polio, MMR, yellow fever

Question 20

How are attentuated forms of viruses/bacteria created? 3 ways

Answer 20

• Serial culture of host who had wild virus ages ago and carried attenuated version (measles)
• Chemical mutagenesis and selection of phenotypes
• genetic engineering to create knockouts lacking genes of virulence

Question 21

Which cells are produced after live attentuated vaccine is administered?

Answer 21

Cytotoxic memory cells that can infect APCs

Question 22

How are live attentuated vaccines stored?

Answer 22

Cold chain (refridgeration) to keep them alive- costs high

Question 23

How are organisms killed for killed (inactivated) whole organisms vaccines?

Answer 23

using heat or chemicals e.g. formalin or B propiolactone used to inactivate influenza or pertussis

Question 24

What is a requirement of killed whole organisms vaccine administrations?

Answer 24

Multiple doses to keep immunity at protective levels

Question 25

Why does live attentuated vaccine not need multiple doses?

Answer 25

Natural boosting +much stronger responses so multiple doses not needed

Question 26

What can be used for sub unit vaccines?

Answer 26

Protein e.g. surface antigens
Toxoids e.g for diptheria
Synthetic peptides
Polysaccharides (poor antigens) so conjugated to toxoids or outer membrane protein for strong enough response

Question 27

How are toxoids made?

Answer 27

Inactivate toxins using formaldeyde

Question 28

How do bacterial toxins provide immunity step wise?

Answer 28

Toxin inactivate into otxoids and used as vaccine allows cells to produce antibodies without tissue damage or disease from direct toxin itself

• antibodies produced = protection

Question 29

How are bacterial capsular polysaccharides used as vaccines?

Answer 29

Much less immunogenic in children under 2 since they are poor antigens, have short term memory and have no T cell immunity

Question 30

How are bacterial capsular polysaccharides made to be better vaccines?

Answer 30

Since they are short lasting, enhance immunogenicitiy via protein conjugation allowing long lasting immunity and response in children

Question 31

Why do conjugated polysaccharides produce stronger immune response in children?

Answer 31

Not only do conjugated polysaccharides allow antibody production but the entire complex is taken up by cell (due to the protein) and presented on MHC class 2 of B CELLS allowing stronger immune response as well as antibody response

Question 32

What are vaccine adjuvants?

Answer 32

Chemicals added to make vaccine more immunogenic

Question 33

What is the purpose of vaccine adjuvants?

Answer 33

Enhance immune response to antigen (more antibodies produced)
promote uptake and antigen presentation
stimulate correct cytokine profile

Question 34

Give an example of a vaccine adjuvant? and how does it work)

Answer 34

Aluminium salts (allow slow release of antigen)

Question 35

What are the difficulties in producing vaccine against HIV?

Answer 35

High mutation rate - immunity against one strain would be ineffective
Effective vaccine also needs to induce memory CTLs so needs to be live attentuated vaccine - danger of reversion to virulence!!! esp due to the high mutation rate

Question 36

Why are live attentuated vaccine used?

Answer 36

Strong response and long term since produces CYTOTXIC CTL MEMORY CELLS

Question 37

Why can’t some viruses be given as live attenutated vaccines + example?

Answer 37

Polio - can revert back to virulence

Question 38

Disadvantages of live attentuated?

Answer 38

Cost for refridgeration

Possibiloty of conversion back to virulence

Question 39

What is a passive immunity?

Answer 39

Treatment with antibody from another source e.g. serum

Question 40

Give example of passive immunity?

Answer 40

maternal transfer

prophylaxis

Question 41

Whatis the point of passive treatment?

Answer 41

Rapid short effect