Scientific Basis Of Vaccines

Question 1

What is a prophylactic vaccine?

Answer 1

A biological substance that does not cause disease, which when administered to the recipient, produces an adaptive immune response which provides protection against future disease

Question 2

What is the function of MHC class 1 + MHC class 2?

Answer 2

MHC 2 - B cell maturation

MHC 1 - memory cytotoxic T cell

Question 3

What scientific concepts came from Jenners experiments?

Answer 3

1. Challange dose - provides protection from infection
2. Concept of attenation
3. Concept that prior exposure to agent boosts protective response
4. Cross species protection - antigenic similarity

Question 4

What is Herd immmunity?

Answer 4

When a significant portion of a population becomes immune to a infectious disease the ri of spread from person to person decreases

Question 5

What are the 3 rationale for vaccines?

Answer 5

Protection of the induvidual

Protection of population - herd immunity

Eradication of disease

Question 6

What boosts herd immunity?

Answer 6

Periodic outbreaks of disease in community

Vaccines

When there is no natural boosting (disease rates decline) =. Increases importance of vaccination up rates

Question 7

What occurs during primary exposure of the immune response too an antigen?

Answer 7

5-7 days - antibody response

2 weeks for a full response

IgM produced

Class switching of IgM to IgG

Memory T and B cells from

Question 8

What occurs during the secondary exposure of the imune response to a ntigen?

Answer 8

< 7 days for full protective response

Question 9

what are the general principles of vaccines?

Answer 9

1. Induce the correct type of response
   - antibodies = polio virus
   - cell mediated immunity = tuberculosis
   - usually depends on the type of disease were trying to protect against
2. Induce response in the right place
   - mucosal = influenza
   - systemic = yellow fever
3. Duration of protection
   - short term = antibody sufficient
   - long term = memory essential
   - boosters = natural or vaccines
   - type of infection = incubation type long or short
4. Age of vaccination
   - maternal igG antibodies through placenta = may interfere with the vaccine
   - sigA in breast milk
   - onset of infection = eg. Only present in children under 3

Question 10

What is a Monotypic pathogen?

Answer 10

Surfacce antigens have remained the same to date

Vaccination or infection gives life long immunity

Eg. Measles

Question 11

What is a polytypic pathogen?

Answer 11

Surface antigens change and immunity is readily overcome

Eg. Influenza

Question 12

What is a live attenuated vaccine?

Answer 12

Eg. BCG, MMR, Yellow fever

Serial culture in forgein host “passage”

Chemical mutagenesis and selection of phenotypes

Genetic engineering to create knockouts lacking genes for virulence

Question 13

What are the limitations of a live attenuated vaccine?

Answer 13

Eg. Polio vaccine caused by reversion to virulence

Will require cold chain refrigeration to keep them alive - Adds to vaccine costs - difficult in come parts of the world

Question 14

What are the benefits of using live attenuated vaccines?

Answer 14

Useful for producing CTL memory cells as they can infect APCs

Question 15

What is a killed/inactivated whole organism vaccine?

Answer 15

Killed with heat or chemical

Eg. Influenza, cholera

Question 16

What are the limitations of inactivated whole organism vaccine?

Answer 16

Boosting often required

Question 17

What is a sub-unit vaccine (individual components)?

Answer 17

• proteins (often surface antigen, eg Hep B)
• toxoids (tetanus) = inactivated toxins using formaldehyde
• peptides
• polysaccharide (poor antigens so often conjugated with other component)

Question 18

What is the problem with using polysaccharides as vaccines?

Answer 18

Poor antigens

• short term memory
• no T cell immunity

Muscle less immunogenicity in children <2 yr

ENHANCE IMMUNOGENICITY BY PROTEIN CONJUGATION

Question 19

How can polysaccharides be conjugated?

Answer 19

Polysaccharide is linked to carrier protein

Question 20

What are vaccine adjuvants?

Answer 20

Chemicals we can add to vaccines to make them more immunogenic

Question 21

Why was smallpox able to be eradicated?

Answer 21

No sub-clinical infections

After recovery, the virus was eliminated - no carrier states

No animal reservoir

Effective vaccine slow spread, poor transmission

Question 22

Why is it difficult to produce a vaccine fr HIV/AIDS?

Answer 22

High mutation rate

On average each HIV vision produced by a infected cell differes fro the original infecting virus by 1 mutation atleast

Immunity against one strain will be ineffective against others

A effective vaccine would probably have to induce memory CTLs to kill virus infected cells - BUT DANGER OF REVERSION TO VIRULENCE

Question 23

What are passive treatments?

Answer 23

Doesn’t activate the immune system

• Maternal transfer
  — Treatment with antibody from another source
• rapid short effect

Eg. Rabies - following a bite from a suspected rabid animal