Lecture 34 - Vaccines Flashcards
Difference between an antigen and an immunogen
An antigen is defined as ANtibody GENerating
An immunogen elicits an immune response (is more general)
Passive vaccination sources
1)
2)
3)
1) Human Ig preparations from pooled human sera
2) Specific human Ig from pooled human serum
3) Animal-derived serum antibodies or antitoxins
When are passive vaccines useful?
When there is no time for the body to mount an immune response (EG: snake bite)
Broad definition of a vaccine
Elicit an immune response to protect form infectious disease
Experimental vaccine approaches 1) 2) 3) 4)
1) Cure existing disease (therapeutic)
2) Block physiology (hormones, fertility)
3) Prevent, cure cancers
4) Prevent, cure autoimmune disorders (EG: allergies)
Requirements for a vaccine
1)
2)
3)
1) Efficacious
2) Safe
3) Affordable
Do vaccinations prevent infections?
No. They shorten the exponential phase of replication, resulting in a subclinical infection
Things to consider when designing a vaccine 1) 2) 3) 4) 5)
1) Where does the body first encounter the pathogen
2) Which parts of the body does the pathogen encounter
3) Virulence factors produced by pathogen
4) Extent of antigenic variation of virulence factor
5) How is antigen to be presented to the immune system
Vaccine approach for toxin-secreting bacteria
Give multiple vaccines, to ensure that antibody titre is high enough to neutralise toxin
Vaccine design consideration for antigenic diversity of virulence determinant
Include all virulence determinants, or just the dominant ones?
How to enhance vaccine immunogenicity 1) 2) 3) 4)
1) Elicit the correct type of immune response (Th1 or Th2 mediated)
2) Adjuvants
3) Target innate immunity (DCs) to program adaptive immunity
4) Target the correct branch of the immune system(mucosal immunity versus tissue immunity)
Bordatella pertussis 1) 2) 3) 4)
1) Gram -, small coccobacillus
2) Spread by aerosols
3) PTX, AC toxins
4) P69, fim, FHA adhesins
How can vaccine efficacy be tested?
Kendrick test
Kendrick test
1)
2)
3)
1) Administer vaccine to animal intraperitoneally
2) Challenge animal with intracranial antigen
3) If vaccine works, mice don’t die
Old pertussis vaccine
Whole cell killed vaccine
Problems with old pertussis vaccine
Very immunogenic, as contains LPS
Tetanus vaccine 1) 2) 3) 4) 5)
1) Old vaccine
2) Over 95% effective
3) Inactivated tetanospasmin toxoid
4) Induces toxin-neutralising antibodies
5) Inhibits disease, not infection
Proportion of neonatal deaths due to tetanus in 1993 compared to now
14% versus 5%
Name for an inactivated toxin
Toxoid
Can clostridium tetani be eradicated?
No.
Ubiquitous in soil
Most common cause of meningitis in children
Haemophilus influenzae
When does immunity to H influenzae develop?
10-16 years of age
Consequence of H influenzae capsule inhibiting C3b binding
1)
2)
1) Not opsonised, evades phagocytosis
2) Growth is uncontrolled, causes septic shock
T-dependent B cell antibody pathway
1)
2)
3)
1) T cell binds cognate antigen presented on MHCII by B cell
2) CD4+ releases IL-2, IL-4, IL-5
3) B cell is activated, proliferates, matures
