Vaccination Flashcards
What is a vaccine?
Something that stimulates the immune system without causing serious harm or side effects
What properties would an ideal vaccine have?
Completely safe Easy to administer Single dose, needle free Cheap Stable- doesn't react inside body Active against all variants Effective- life-long protection
What can antibodies do?
- bind virus and neutralise it
- Engulf it (opsonisation)- makes pathogen more attractive to macrophage
- Antigens will be recognised by CD4 T cells in context of MHC II
What is R0?
The reproduction number
If R0<1 the infection will die out in the long run
If R0>1 the infection will continue to spread
R0=2 means infected person infects 2 people
What is herd immunity?
Transmission cases are only met by immune people (vaccination driven immunity)
The chain of transmission is broken
What forms are antigens in in a vaccine?
Inactivated protein e.g. tetanus toxoid Recombinant protein e.g. Hep B Live attenuated pathogen e.e. polio/BCG Dead pathogen e.g. split flu vaccine Carbohydrate e.g. S. Pneumonia
What makes a vaccine work better?
An adjuvant
It induces danger signals that activate dendritic cells to present antigen to T cell
Its used in combination with a specific antigen
What is found in a vaccine?
An antigen
An adjuvant
Stabilising things e.g. buffers
Water
What are inactivated protein vaccines?
E.g. Tetanus and diphtheria
Its a chemically inactive bacteria exotoxin
It stimulates production of antibody which will block action of exotoxin
Pros: cheap, safe, simple to produce, high protective efficacy
Cons: needs god understanding of biology, not all pathogens produce toxins
What are recombinant protein vaccines?
E.g. Hep B surface antigen (HBSAg)
Its a recombinant protein from antigen
Immune system will generate neutralising antibodies against antigen
Pros: pure, safe,
Cons: expensive, not very immunogenic, hasn’t proven to answer to all pathogens
What are conjugate protein vaccinations?
S. pneumonia
Polysaccharide coat is coupled to immunogenic “carrier” protein
Protein stimulates T cell response via CD4 which improves B cell immune response
Pros: improves immunogenicity, highly effective at controlling bacterial infections
Cons: expensive, strain specific
What are dead pathogen vaccines?
Influenza split vaccine
Uses a chemically killed antigen
Induces antibody and T cell response
Pros: leaves antigenic components intact, cheap, quick
Cons: killing antigen can alter structure, requires capacity to grow pathogen, vaccine induced pathogenicity is a risk, live pathogen can contaminate the vaccine
What are attenuated vaccines?
E.g. BCG, LAIV, OPV
Pathogens are attenuated by serial passage. This stops the disease causing ability but can still be recognised by an immune system as foreign.
Because they’re live they can replicate on host and trigger innate immune response
Pros: Induce strong immune response, can replicate so need low doses
Cons: may develop virulent factors, attenuation may lose key antigens, can be outcompeted by other infections
Why is protein structure critical?
Some proteins have a prefusion and post fusion structure
Some proteins fold into a different structure and antibodies are made against the wrong shape
Whats the problem with bacterial coats?
Bacteria often have a capsule made of polysaccharide
Its not very good at inducing B cell response
Alternate approaches are needed
