Vaccination Flashcards
Immunisation: explain the difference between active and passive immunisation Vaccines: explain the meaning of the following types of vaccine, giving a specific example of each; live attenuated, inactivated, subunit, toxoid, conjugate List examples of bacterial and viral infections for which vaccination can be a successful strategy Explain the eradication of smallpox and similar efforts to control other viral diseases Medical microbiology: recall the basic principles of medical microbiology a
What is prophylaxis?
Preventing the disease before you catch it. E.g. vaccination.
What is the immunological basis of protection after vaccination?
Antibody levels decrease over time. Memory is laid down, so if pathogen re-encountered, fast and effective response.
Explain how smallpox vaccine was discovered.
Vaccines invented from Edward Jenner. Noticed milk maids didn’t get smallpox because they were exposed to a similar virus found in cows – cowpox – which gave them some immunity to smallpox. At the time, this was done by variolation (scraping a pox virus sore onto someone’s arm to give them a mild infection that would protect them against anything worse).
Explain the eradication of smallpox. When?
1977 No animal reservoir for smallpox. There are no animals with it. No latent/persistent infection – it’s an ACUTE infection so doesn’t stay with you. Easily recognised – so easy to know where smallpox remained, and ring vaccinate the last few. Vaccine was against all strains. Vaccine properties: low cost, could make a lot, heat stability, easy to administer. WHO determination and lots of money put in.
What are the three constituent parts of a vaccine?
Antigen – stimulates the immune response to target the disease. Adjuvant – enhances and regulate immune response. Also helps deliver antigen to target area. Excipients – buffer, salts… to maintain pH, osmolarity and vaccine stability.
What is a live attenuated vaccine?
Infect person with a virus. An attenuated vaccine is a vaccine altering so that it becomes harmless or less virulent, but it is kept viable.
Example of live attenuated vaccine? (x3)
Smallpox, polio (IPV vaccine – in DTaP-Hib-IPV), influenza – all viral.
What is an inactivated virus vaccine?
The actual virus but killed so it has no pathogenic effect. It cannot replicate.
Example of an inactivated vaccine?
Example of an inactivated vaccine? [DT]aP – aP part is an inactivated BACTERIUM for Whooping Cough. (OR, in the DtaP-Hib-IPV vaccine) Hepatitis A (virus)
What is a subunit vaccination?
Virus is fractionated so that it cannot replicate, but looks the same to the immune system. Components are purified and free from viral nucleic acid. Contains only specific protein subunits e.g. antigenic parts of the pathogen.
Example of subunit vaccine?
Hepatitis B (virus)
What is a toxoid vaccine?
Toxins released by bacteria are sometimes what’s mainly responsible for the disease. Toxoid vaccines use the toxin to create immunity to that toxin. This means that the body is immune against the parts of the pathogen that cause the disease (the toxin)m instead of the whole pathogen. Therefore, toxoid vaccines do not confer immunity when the bacteria are responsible for the disease. The toxin is treated to render it a harmless toxoid e.g. chemicals or heat.
Example of toxoid vaccine?
DTaP vaccine – Tetanus and Diphtheria (both bacterial) (aP is not a toxoid – it’s an inactivated BACTERIUM for Whooping Cough).
Example of conjugate vaccine?
Hib vaccine (included in DtaP-Hib-IPV vaccine). Protects against Haemophilus influenza type b. MenC conjugate (given as Hib-MenC) and protects against meningitis C. BOTH NEED BOOSTERS.
How do you make an attenuated vaccine? What is process called?
Vaccines evolve to fit best where they are found. They are really good at evolution. SO… Grow virus in different cell culture to human cells e.g. monkey cells – acquire mutations which make it adapted to function in monkey cells, sometimes sacrificing the benefits it had in human cells. When reintroduced to human cells, mismatch means virus doesn’t work very well. So can be used as a vaccine. FORWARD GENETICS.
What is a conjugate vaccine?
Most conjugate vaccines use a polysaccharide as the disease antigen.
The antigen stimulates B cells by binding to Immunoglobulin receptors, so B cells make more IgM. The antigen is WEAK, so B cells are the only cells it stimulates.
Because it doesn’t involve T cells, there is poor memory effect.
The antibodies also have low avidity because they didn’t undergo affinity maturation.
In biochemistry, avidity refers to the accumulated strength of multiple affinities of individual non-covalent binding interactions, such as between a protein receptor and its ligand, and is commonly referred to as functional affinity. As such, avidity is distinct from affinity, which describes the strength of a single interaction. However, because individual binding events increase the likelihood of other interactions to occur, avidity should not be thought of as the mere sum of its constituent affinities but as the combined effect of all affinities participating in the biomolecular interaction.
The antigen of some bacteria does not elicit a strong immunological response; so, vaccine provides limited protection in later life.
Weak, polysaccharide antigen is therefore CONJUGATED (combined) to an immunological protein (a stronger antigen) in the vaccine, thereby eliciting a stronger immunological response to the weak antigen.
Antigen-presenting cells finally pick-up the antigen in the vaccine. Naïve T cells are primed by interacting with the APC.
This stimulates T cells so that when human is infected again, stimulated B cells will quickly get T cell help too. [photo].
