Scientific Basis of Vaccines Flashcards
What is a 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 are some consideration taken in vaccine development
- What kind of protection is needed for this disease
- When is the protection needed
- Are memory cells required and what type
- Where should the immune response take place
- What kind of vaccine is neccesary
What are the main concepts of Jenners’s experiments
- Challenge dose - proves protection from infection
- Concept of attenuation
- Concepts that prior exposure to agents boost protective response
- Cross-species protection - antigenic similarity
What are the main aims for vaccination
- Protection of the individual
- Protection of the population - herd immunity
- Eradication of Disease
Describe the vaccine paradox
- The more we vaccinate the more dependant we are in reaching 95% vaccination for herd immunity
- There is a lack of natural immune boosting
How long does it take for a primary response against an antigen to take place
- 5-7 days for antibody response
- 2 weeks for a full response
- IgM to IgG switching memory B and T cells
How long does it take for a secondary response against an antigen to take place
With prior expose it takes around 7 days or less for a full protective response
What are the general principle with vaccines
- Induce the correct type of response
- Induce response in the right place
- Duration of protection
What affect the vaccination protection duration
- Is it needed for a short or long-term purpose
- Are boosters needed for seasonal response
- What type of infection is it
When should we vaccinate for infections
- Vaccinate before 5 years for most vaccines
- Maternal IgG antibodies from the placenta and IgA from breast milk may interfere with vaccines
- Optimum timing for vaccination needs to be determined by experimentation
What are monotypic pathogens
- Measles is serologically monotypic. Surface antigens have remained the same to date.
- Vaccination or infection gives lifelong immunity.
What are polytypic pathogens
e.g. Influenza. Surface antigens change and immunity is readily overcome
What is antigenic drift
accumulation of mutations in genes that code for virus surface proteins with time
What is antigenic shift
Recombination of viral strains to produce a different subtype with a mixture of surface antigens from the original strains
Describe live attenuated organism type vaccines
- BCG vaccine, Polio, MMR, Yellow fever
- Live organisms which have had their virulence reduced
- May require a cold chain (keep it cold) which may add to the cost
- Concern of reversion to virulent state
- Useful in inducing a CTL memory cell response
Describe inactiavted whole organism type vaccines
- Influenza, Polio, Cholera, Hep A
- Boosting is often required
- Limited lifespan of vaccine
Describe Sub-unit type vaccines
- Present individual components of pathogens
- Generally safer but can be hard to give an adequate response
- Proteins, Toxoids, Peptides, Polysaccharides, Proteins
How can we use bacterial toxins as vaccines
- take toxins and inactivate with formaldehyde
- Use it as a toxoid vaccine
- Toxoid triggers immune response and produces antibodies
How can we use bacterial capsular polysaccharides as vaccines
- Tend to be poor antigens and they are short term and have no T cell response
- Enhanced by using conjugation by attaching different components to the polysaccharides
How do polysaccharide vaccines for
- Provides B cell receptor with polysaccharide and induce a enhanced response
- Activates T cell for an enhanced response
What is the role of adjuvants in vaccines
- enhance immune response to antigen
- promote uptake and antigen presentation
- stimulate correct cytokine profiles
How was the eradication of small pox possible
- 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 hard to produce vaccines for some infection such as HIV/AIDS
- There is a high mutation rate
- Danger of reversion to virulence with live attenuated vaccine
What are some examples of passive treatments
- Passive immunity: maternal transfer
- Treatment with antibody from another source: serum - Prophylaxis and/or treatment Rapid Short effect
