Part 6: Vaccines Flashcards
Def: Active immunity
Resistance developed in response to stimulus by an antigen, characterised by host production of antibodies
Natural- immune response to pathogen
Acquired- immune response to vaccine
Def: Passive immunity
Immunity conferred by an antibody produced in another host
Natural- mother to child via breast milk or placenta
Artificial- following administration of immunoglobulin or antiserum
Briefly describe a human adaptive immune response to a virus
1) Infected/immune cells recognise and process the viral antigens, and present them on the cell surface
2) Helper T-cells recognise presented antigens and release cytokine which recruit T-cells. T-cells target and kill infected cells.
3) B-cells recognise infected cells and produce antibodies which bind to infected cell, acting as markers
What property of immune cells is important in vaccine principles
Some B and T-cells become memory cells which means they remember particular antigens, aiding the immune response upon re-exposure
Def: Vaccine
An immuno-biological substance designed to produce protection against a specific disease through active immunisation.
Describe a live (attenuated) vaccine
Uses a weakened version of the living pathogen
Describe a killed (inactivated) vaccine
Uses a dead version of the pathogen, but it remains antigenic
Describe a toxoid vaccine
Vaccine against toxin producing bacteria. The exotoxins are detoxified, rendering them not pathogenic, but antigenic so an immune response is still triggered.
Describe a sub-unit vaccine
Fragments (e.g. antigens) are extracted from the pathogen (instead of the whole pathogen) and presented to the immune system.
Can contain protein and polysaccharide molecules found on the pathogen’s surface (protein sub-unit) or just polysaccharide molecules (pure polysaccharide sub-unit)
Describe a recombinant viral vector vaccine
Harmless live replicating viruses that have the pathogen’s antigen gene inserted into it.
How does a recombinant viral vector vaccine work?
A gene is inserted into a harmless viral vector
The virus replicates inside the cell and produces the coded antigen
The antigen is recognised by the host, triggering an immune response.
Def: mRNA vaccine
Uses the hosts own cell machinery to make the antigen which is presented to the immune system
How does an mRNA vaccine work?
mRNA is encapsulated in lipid nanoparticles and injected into the host. The mRNA codes for the antigen produced by the specific pathogen.
The cell reads the mRNA, and produces millions of copies of antigens which are then recognised by the host’s immune cells, triggering an immune response.
Give some advantages of vaccine manufacture
Difficult to make in ‘generic form’ so it retains its market value more.
Innovation has led to faster robust, flexible and effective manufacturing.
Improves public health stability
Give some disadvantages to vaccine manufacture
High barriers to entry due to safety regulations and high costs
New antigens typically require new cell substrates
Vaccine development takes a long time to investment return is long-term
Vaccine uses will be lower than treatments for that disease.
Def: Spike protein
The surface protein on the Covid-19 virus which binds to the ACE-2 receptor on human cells, allowing virus entry
What type of vaccine is the Oxford-AstraZeneca vaccine and what platform does it use.
Viral vector vaccine
Chimpanzee adenovirus
How does the Oxford-AstraZeneca vaccine work?
1) The spike protein is inserted into a harmless, non-replicating chimpanzee adenovirus
2) After being injected, the host cells read the genetic code and produce millions of spike proteins
3) This triggers an immune response
What type of vaccines are the BioNTech and Moderna vaccines and what platform do they use
mRNA vaccines
Lipid nano-particle encapsulated mRNA
What type of vaccine is the Novavax vaccine and what platform does it use
Protein subunit vaccine
Synthetic nanoparticles coated with trimer spike protein, uses an immune boosting adjuvant
Def: Adjuvant
A substance used to boost the immune response to a vaccine
How is Novavax made?
1) The spike protein gene is modified and inserted into baculovirus (insect virus)
2) Modified baculovirus infects and multiplies within Sf9 cells (insect cell line)
3) Sf9 cells act as cell factories to produce large quantities of recombinant spike protein which are harvested.
4) The recombinant spike proteins are arranged around a nanoparticle core and mixed with an adjuvant.
