Introduction to Vaccines Flashcards
Define a vaccine
Something that stimulates the immune system without causing harm or side effects
What is the aim of vaccines
To provoke immunological memory to protect individual against a particular disease
What is the difference between something that is immunogenic and reactogenic
Immunogenic - ability to start an immune response
Reactogenic - ability to cause reaction
Define an antigen
Anything that causes an immune response
What is in a vaccine?
- Antigen
- Adjuvant (normally alum)
- Stabilisers (PBS)
- Water
What types of antigen can you use in a vaccine (5)
- Inactivated Protein
- Tetanus toxoid
- Recombinant protein
- Hep B
- Live attenuated pathogen
- Polio/BCG
- Dead pathogen
- Split flu vaccine
- Carbohydrates
- S. pneumoniae
What is the MOA of inactivated toxoid vaccines
Inactivated toxin induces antibodies which block toxin binding to nerves
What are some advantages of Inactivated toxoid vaccines
- Cheap
- Well characterised
- Safe
What are some disadvantages of Inactivated toxoid vaccines
- Requires understanding of toxin moa
- Not all organisms encode toxins
- Small risk of failure to inactivate (some impurities)
How are recombinant protein vaccines made
- Surface antigen gene isolated
- Gene inserted into yeast
- Modified Yeast cells produce sAg
- Purified into vaccine
What is the MOA for recombinant protein vaccines
Induces classic neutralising antibodies
What are the advantages of recombinant protein vaccines
- Pure
- Useful if we know surface antigen
- Safe
- Low strain variation
What are some disadvantages of recombinant protein vaccines
- Relatively expensive
- Doesn’t work for everything
How are dead pathogen vaccines made
Whole pathogen can be chemically killed
These are innoculated into eggs
Vaccine purified from eggs
What is the MOA for dead pathogen vaccines
Induces antibody and T cell response
What are the advantages of dead pathogen vaccines
- Antigenic components are intact
- Therefore, more immunogenic as other components are included
What are some disadvantages of dead pathogen vaccines
- Fixing/killing can alter chemical structure of antigen
- Requires capacity to grow the pathogen (H5N1)
- Vaccine induced pathogenicity
- Risk of contamination with live pathogen (polio)
- ‘Dirty’
How are live attenuated vaccines made
- Attenuation by serial passage
- Comparison of end virus with orginical virus
- Loss of virulence factors
What is the MOA of Live attenuated vaccines
- They replicate in situ
- Trigger innate response and boost immune response
What are the advantages of live atteniated vaccines
- Induce strong immune response
What are the disadvantages of live attenuated vaccines
- Can revert to virulence
- Can infect immunocompormised (BCG/HIV)
- Attenuation may lose key antigens
How are conjugate vaccines made
Polysaccharide coat component is coupled to an immunogenic carrier protein
What is the MOA for conjugate vaccines
- T cells only recognise peptides
- B cells recognise conjugate (polysaccharide + carrier protein)
- Processes and presents peptide antigen to CD4 cells
- CD4 T cell releases mediators which elicit memory in B cells
What are the advantages of conjugate vaccines
- Improved immunogenicity
- Highly effective at controlling bacterial infeciton
What are the disadvantages of conjugate vaccines
- Expensive
- Strain specific
- Carrier protein interference
- Polysaccharide alone is poorly immunogenic
Once the adaptive immune response is activated, what are the mechanisms in which they control the infection
- Prevention of entry
- Antibody blockade
- Opsonisation -> phagocytosis
- Boost T/B cell immunity
- B cells activate T cells, T cells release mediators to boost B cell function
- B cell produces Antibodies
- Kill Infected Cells
- CD8 cells recognise stressed cells
What is meant by R0
The number of cases one case generates on average over the course of their infection period
How can vaccines reduce R0
Herd immunity allows for transmission termination
Higher the R0, the higher the number of people you need to vaccinate
What are some barriers to the development or compliance of vaccines
- Development issues
- Takes a long time to get from bench to bedside
- Cost of product
- Vaccine scares - anti-Vaxx
What are the 2 areas of concern for vaccine complications
- Acute responses
- Fluvax
- High cytokine release
- Fluvax
- Chronic complication
- Pandemrix (?H1N1)
- Narcolepsy
- Pandemrix (?H1N1)
What has stopped us from developing more effective vaccines?
- High variation of target organism
- Classic immune will only recognise one variant
- HIV
- Classic immune will only recognise one variant
- Strain Replacement
- One strain vaccinated, decrease in incidence, other strains increase in incidence
- Natural infection can sometimes not be protective
- HIV, CMV, TB
- BEcause antigens are changing or hidden as in HIV
- HIV, CMV, TB
- Flawed translation from animal models
Vaccinations can increase the transfer of antibodies across the placenta to the baby. What time should the mother be vaccinated for flu or pertussis?
2nd or 3rd trimester
With regards to flu vaccine, what is a novel approach for this therapy
Influenza changes all the time, the head portion changes
The stem of the haemagluttinin molecule remains more constant than the head
Could be potential target
