Scientific Basis of Vaccines

Question 1

What do vaccine adjuvants do?

Answer 1

enhance immune response to antigen
promote uptake and antigen presentation
stimulate correct cytokine profiles

Question 2

What types of vaccines are there?

Answer 2

1.Live, attenuated organism
by:- serial passage,
low temperature adaptation,
recombinant genetics ( S.typhi Ty21a; galE + aroA/B/C mutant)
selection of natural attenuated strains

2.. Killed, whole organism
e.g. pertussis, flu (old type)
polio (Salk type), cholera, HepA
reactogenicity
boosting required

3. Sub-unit vaccines (individual components)
   
   • proteins
   • toxoids (diphtheria; tetanus)
   • peptides (synthetic)
   • polysaccharide - poor antigens
     - conjugated to toxoid + outer membrane protein (e.g. MenC; Hib;)
   • recombinant proteins
   • sub-cellular fractions
   • surface antigens
     e. g. Hepatitis B; influenza haemagglutinins; menB
   • virulence determinant
     e. g. aP-pertussis:- adhesin + toxoid + OMP

Question 3

What is conjugation and how does conjugation work?

Answer 3

Conjugation links polysaccharide antigen to protein carrier (e.g. diphtheria or tetanus) that the infant’s immune system already recognises in order to provoke an immune response

eg a protein can act as a conjugate and the B cell recognises the protein and presents it to a T cell that will recruit cytokines that encourage B cell to make more potent high affinity antibodies all because of the protein conjugate recruiting more T cell help

Question 4

What is a toxoid?

Answer 4

a chemically modified toxin from a pathogenic microorganism, which is no longer toxic but is still antigenic and can be used as a vaccine.