8 - Defence and Vaccination against Bacteria

Question 1

What are the 2 divisions of acquired immunity?

Answer 1

HUMORAL
- directly mediated by antibodies
CELL MEDIATED
- mediated by T lymphocytes and NK cells

Question 2

What are the roles of humoral and cellular immunity?

Answer 2

antibody mediated
- toxin neutralisation
- complement binding
promoting phagocytosis through opsonisation
cell-mediated
- important in eliminating intracellular bacteria
- interaction of the reactive T lymphocytes and the macrophage is key to clearance of infection

Question 3

What are the properties of a good vaccine?

Answer 3

A GOOD VACCINE PROVIDES SUBSTANTIAL BENEFIT TO HEALTH AT LOW COST AND LOW RISK

Ideally a vaccine:
Stimulates an effective immune response
Is safe and does not cause adverse reactions
Is inexpensive to manufacture and distribute
Is stable
Is easy to administer
Should be simple for both manufacturer and regulatory authorities to control

Question 4

What is herd immunity?

Answer 4

a form of immunity that occurs the the vaccination of a significant portion of the population provides a measure of protection for individuals who have not yet developed immunity

refers to the effect of immunity within a population to reduce transmission of the infectious agent, thereby protecting those who are susceptible (i.e. not immune) to the disease.

The endemic state reflects a balance between the transmissibility of the infectious agent and the level of immunity in the population.

Question 5

During which stage of a clinical trial is vaccine efficacy determined?

Answer 5

Phase III

Question 6

How is vaccine efficacy calculated?

Answer 6

1 - ( attack rate in vaccinated group/ attack rate in unvaccinated group)

Question 7

What are the 3 main elements of vaccines?

Answer 7

ANTIGEN
ADJUVANT - to enhance and modulate the immune response
EXCIPIENTS
buffers, salts, saccharides and proteins maintain the pH, osmolality and stability of the vaccine

Question 8

What are conjugate vaccines?

Answer 8

carbohydrate chemically linked to immunogenic protein

• T cell recognition of protein carriers enhances B-cell activation
• promotes efficient antibody response to polysaccharide capsule

Question 9

What are live attenuated vaccines?

Answer 9

a vaccine prepared from live microorganisms or functional viruses whose disease-prodding ability has been weakened, but whose immunogenic properties have not

Question 10

How have pathogenic bacteria evolved to avoid host defences?

Answer 10

• resist complement
  e. g. Mycobacterium tuberculosis have a thick cell wall
• resist antibodies
  e. g. Neisseria gonorrhoea have antigenic variation
• resist phagocytosis
  e. g. Chlamydia hide inside other cells
• inhibit intracellular killing
  e. g. Mycobacterium tuberculosis block phagosome maturation