Scientific Basis Of Vaccines Flashcards
What is a prophylactic vaccine?
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
What is the function of MHC class 1 + MHC class 2?
MHC 2 - B cell maturation
MHC 1 - memory cytotoxic T cell
What scientific concepts came from Jenners experiments?
- Challange dose - provides protection from infection
- Concept of attenation
- Concept that prior exposure to agent boosts protective response
- Cross species protection - antigenic similarity
What is Herd immmunity?
When a significant portion of a population becomes immune to a infectious disease the ri of spread from person to person decreases
What are the 3 rationale for vaccines?
Protection of the induvidual
Protection of population - herd immunity
Eradication of disease
What boosts herd immunity?
Periodic outbreaks of disease in community
Vaccines
When there is no natural boosting (disease rates decline) =. Increases importance of vaccination up rates
What occurs during primary exposure of the immune response too an antigen?
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
What occurs during the secondary exposure of the imune response to a ntigen?
< 7 days for full protective response
what are the general principles of vaccines?
- 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 - Induce response in the right place
- mucosal = influenza
- systemic = yellow fever - Duration of protection
- short term = antibody sufficient
- long term = memory essential
- boosters = natural or vaccines
- type of infection = incubation type long or short - 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
What is a Monotypic pathogen?
Surfacce antigens have remained the same to date
Vaccination or infection gives life long immunity
Eg. Measles
What is a polytypic pathogen?
Surface antigens change and immunity is readily overcome
Eg. Influenza
What is a live attenuated vaccine?
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
What are the limitations of a live attenuated vaccine?
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
What are the benefits of using live attenuated vaccines?
Useful for producing CTL memory cells as they can infect APCs
What is a killed/inactivated whole organism vaccine?
Killed with heat or chemical
Eg. Influenza, cholera
What are the limitations of inactivated whole organism vaccine?
Boosting often required
What is a sub-unit vaccine (individual components)?
- proteins (often surface antigen, eg Hep B)
- toxoids (tetanus) = inactivated toxins using formaldehyde
- peptides
- polysaccharide (poor antigens so often conjugated with other component)
What is the problem with using polysaccharides as vaccines?
Poor antigens
- short term memory
- no T cell immunity
Muscle less immunogenicity in children <2 yr
ENHANCE IMMUNOGENICITY BY PROTEIN CONJUGATION
How can polysaccharides be conjugated?
Polysaccharide is linked to carrier protein
What are vaccine adjuvants?
Chemicals we can add to vaccines to make them more immunogenic
Why was smallpox able to be eradicated?
No sub-clinical infections
After recovery, the virus was eliminated - no carrier states
No animal reservoir
Effective vaccine slow spread, poor transmission
Why is it difficult to produce a vaccine fr HIV/AIDS?
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
What are passive treatments?
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
