Lecture 8- Defence and Vaccination against Bacteria

Question 1

What are the different forms of bacterial vaccines?

Answer 1

• Toxoids
• Conjugates
• Live attenuated
• Killed whole cells

Question 2

What are the two different types of immunities and briefly compare them

Answer 2

1) Innate
- first line defence
- rapid
- not very specific (molecular patterns)
- does not require previous expose
- Monocytes and PMLs
- inflammatory
2) Acquired
- takes time
- requires previous exposure
- Lymphocytes (+ other cells involved)

Question 3

What are the two subclasses of of acquired immunity?

Answer 3

1) Humoral
- antibodies
- produced by B lymphocytes
- Plasma cells secret Igs
2) Cell Mediated
- T lymphocytes and NK cells
- involvement of other cells (macrophages)

Question 4

What are the roles of antibodies?

Answer 4

• Opsonisation
• Agglutination
• Neutralisation (of toxins)
• Complement activation

Question 5

What are the roles of cell-mediated immunity?

Answer 5

• For intracellular pathogens

- Interaction of T lymphocytes and macrophages

Question 6

What are the properties of a good vaccine?

Answer 6

• stimulates an effective immune response
• safe and no adverse reaction
• inexpensive
• stable
• easy to administer

Question 7

Define the term ‘herd immunity’

Answer 7

The effect of immunity within a population where enough people are immune, protecting those who are still susceptible to the disease.

Question 8

What happens in the different phases of clinical trials?

Answer 8

PHASE 1- test for safety and immunogenicity. In a small number of healthy adults
PHASE 2- assess immune response, safety. In small target group
PHASE 3- Placebo controlled double blind trials, check effectiveness.

Question 9

How do you calculate vaccination efficacy?

Answer 9

1 - (Attack rate in vaccinated group/ attack rate in unvaccinated group)
- expressed as a %

Question 10

During which phase of the clinical trials is vaccination efficiency determined?

Answer 10

Phase III

blinded placebo controlled stage

Question 11

How do you calculate the vaccine coverage needed to achieve the herd effect?

Answer 11

(1-1/R0)/ effectiveness

Question 12

How do you calculate the herd effect?

Answer 12

1- (attack rate unvaccinated post-intro/ attack rate unvaccinated pre-intro)

Question 13

What three things do vaccines contain?

Answer 13

1) Antigen- to stimulate the immune response to the target disease
2) Adjuvant- to enhance and modulate the immune response
3) Excipients- buffer, salts, saccharides, protein to maintain pH, osmolarity and stability of the vaccine and preservatives

Question 14

How do DNA vaccines result in immunity?

Answer 14

• DNA is entered
• host expresses the desired antigen
• host mounts its own immune response

Question 15

What sort of vaccine is DTaP?

Answer 15

Tetanus and Diptheria are toxoids= chemically inactivated bacterial exotoxins

Question 16

What are the advantages of a toxoid vaccine?

Answer 16

• Simple to produce
• relatively pure
• safe
• high protective efficacy
  
  • very immunogenic
  • appropriate immune response (toxin neutralising antibodies block activity)

Question 17

What is the aP of DTaP?

Answer 17

• pertussis
• infects ciliated epithelium and releases toxins
• convulsive cough
• recovery after antibody production

Question 18

What type of vaccine is the pertussis vaccine?

What are the pros and cons of the vaccine?

Answer 18

Whole cell vaccine 
PROS: efficacy rate > 90%
CONS:
- anaphylaxis
- prolonged crying
- febrile seizures
- acute encephalopathy (caused by Na+ channel mutations)

Can also get acellular vaccine

Question 19

Which components of B. pertussis is associated with virulence?

Answer 19

1) Attachment to ciliated epithelium
2) Adherence and complement resistance
3) Toxins (pertussis toxin)

Question 20

What is His? What are its symptoms? What sort of vaccine is it?

Answer 20

H. influenza type B
- meningitis
- septicaemia
Conjugate vaccine

Question 21

What is the paediatric combination vaccine called? Which antigens does it protect against? What is it adjuvant?

Answer 21

VACCINE:
= DTaP- Hib- IPV

ANTIGEN:

• Diptheria toxoid
• Tetanus toxoid
• acellular Pertussis components ( pertussis toxoid, filamentous haemagglutinin, pert actin, fibrine t2/3)
• Hib PRP- conjugate
• Inactivated polio virus types 1,2 and 3

ADJUVANT: aluminium phosphate

Question 22

What is the structure of polysaccharide antigens?

Answer 22

• large and linear
• not readily degraded
• highly repetitive determinant

Question 23

What is the immune response to a polysaccharide antigen?

Answer 23

• predominantly IgM
• poor memory effect
• low avidity antibody
• T cell independent antigen

Question 24

What are conjugate vaccines?

Answer 24

Carbohydrate chemically linked to an immunogenic protein

Question 25

What are the pros and Cons of conjugate vaccines?

Answer 25

PROS: highly purified components= safe, simple for licensure and control, effective long-lived bootable immunity, offer herd immunity
CONS: sophisticated technology= expensive