Vaccines Flashcards
What are the most effective ways to prevent infectious diseases from spreading?
Prevent transmission
Prevent infection
Intentional exposure to pathogens in a form that cannot cause an infectious disease.
Vaccination
What is the purpose of a vaccine?
To develop long-term immune protection against the pathogen
The vaccine acts as the ______ _______ to the pathogen, to develop memory __ and __ cells.
The idea is that when the person is naturally infected with the _________ pathogen, the person will have a more _________ immunity the second time around.
primary exposure
T, B
identical
effective
Stops transmission of infectious diseases so it protects susceptible individuals.
Herd immunity
Herd immunity protects what individuals?
Susceptible individuals (the very young, old or immunocompromised)
Herd immunity is only effective when a _______ number of people ar immune
sufficient
Herd immunity needs to generally be higher for what kinds of diseases?
Those in which the pathogens have high speeds of replication
Was Andrew Wakefield’s study valid?
NO!
Is there any evidence to support the link between MRR vaccine and autism?
No
What is the correlation between immunization rates and infection rates.
Inverse
As immunization rates go down, infection rates go up.
How did Edward Jenner develop the first vaccine against smallpox?
Inoculated a boy with cowpox virus.
Why does inoculation with cowpox lead to immunity to smallpox?
Both belong to the pox family of viruses.
Because of this, they share similar antigens and will thus produce memory T and B cells that are effective against small pox.
How did Louis Pasteur develop his version of vaccines?
Used pasteurization to heat kill pathogens.
What are the different, licensed vaccines in use today?
- Live, attenuated vaccines
- Killed/inactivated vaccines
- Subunit vaccines
a) - Toxoid vaccines
b) - conjugate vaccines
Describe a live, attenuated vaccine.
Microorganism is attenuated or weakened
- still expresses surface antigens
replicates in vaccinated individual at a REDUCED or SLOWER rate
Why is it important that the inactivated pathogen replicates slower?
Replicates so slowly that it will never beat the immune system, and always gets destroyed
Live, attenuated vaccines mimic a ________ microbe, so recipients produce a ______ primary immune response.
natural
normal
What cells are developed from live, attenuated vaccines?
Long-lived PC, memory B and T cells
Attenuated microbes must do what to be effective in developing immunity?
Replicate
What are two methods of attenuating pathogens?
- Using animal viruses that are naturally attenuated for humans
- Cell culture - generate mutants of the microbe that cannot replicate competently in humans
Which attenuation method is mainly used for viruses?
Cell culture
Which of the two attentuation methods is least common?
Using naturally attenuated animal viruses.
How does the cell culture method of attenuation work?
Grow microbe in non-human cells and/or altered conditions
Select mutant microbes that replicate well in the foreign ells/conditions and replicate poorly in human cells.
Why is it more difficult to attenuate bacteria using cell culture?
Bacteria have more genes than viruses so, genes that encode for antigens can be altered
(in addition to genes important for replication)
What are the advantages of live vaccines?
Mimics natural infection
Develop T and B cell long-term protective immunity
Usually immunity is achieved with one, low dose
Raises immune response to all antigens/multiple epitopes
What are the disadvantages of live vaccines?
Usually require refrigeration (issue for developing countries)
In unlikely cases:
- could spread to susceptible persons
- cannot be used in immunodeficient or pregnant people
- may revert back to virulent form
Live vaccines are technically _________ for most vaccines under development.
unachievable
What happens if a live, attenuated vaccine is underattenuated?
Overattenuated?
Under - cause disease
over - doesn’t provoke an immune response
What is the major difference between inactivated vaccines and attenuated vaccines?
Microbes cannot replicate in inactivated vaccines
Inactivated vaccines are used with microbes with what characteristics?
1 - cannot be attenuated
2 - Have oncogenic potential
How are microbes inactivated?
Using heat, UV radiation or chemicals
What is critical in the inactivation process?
That the inactivation process DOES NOT alter antigens
What are the advantages of inactivated vaccines?
Microbe CANNOT return to a virulent form
- thus, cannot cause disease
safer than live, attenuated
can be used with immunodeficient patients
What is a small risk associated with inactivated vaccines?
That not all pathogens are inactivated during preparation
Why is it unlikely that not all microbes are inactivated for an inactivated vaccine?
There are strict criteria for approval - if even one is still alive, the vaccine does not get approved
What are subunit vaccines composed of?
Purified antigens
What are the different purified antigens used in subunit vaccines?
Proteins or toxins
Polysaccharides
How are subunit vaccines prepared?
Grow microbe in culture
Antigens are shed (in the case of bacterial toxins) or chemicals are used to break apart the microbe and release the surface antigens (proteins or polysaccharides)
Antigens are then purified and injected into host
The seasonal influenza vaccine is an example of what type of vaccine?
Subunit vaccine
What are the two important surface antigens of the influenza virus?
Hemagglutinin
Neuraminidase
How is the influenza vaccine made?
Inject chicken eggs with the influenza virus they select for the season
Replicates in the embryo
Crack egg and use detergents to break up influenza and purify H and N antigens
Why do people with allergies to eggs not get the seasonal flu shot?
Because that is where the influenza virus is grown
Toxoid subunit vaccines area against what?
Bacterial toxins
How is a toxin converted to a toxoid?
Inactivate the toxin moeity so it loses its toxicity using heat or chemicals.
What is a toxoid?
Toxin without the toxic moiety that retains its antigens but does not cause disease
Conjugate subunit vaccines are used when antigens are of what type?
Polysaccharides
How are conjugate subunit vaccines made?
Polysaccharide antigen is conjugated to a protein to make a B cell bind to a T cell
What is the polysaccharide usuallly linked to in a conjugate subunit vaccine?
diphteria or tetanus toxoid
What is important about the protein conjugates?
People must already have developed immunity to the toxoids before using them as conjugates
Why does the polysaccharide need to be conjugated?
Only protein antigens generate memory T and B cells. By providing a protein antigen, the Tfh can bind to the B cell (which presents peptides on MHC2) to release cytokines and allow class switching, along with clonal expansion.
What is the main advantage of subunit vaccines?
Zero risk of pathogenicity - safe for immunocompromised persons
What are disadvantages of inactivated and subunit vaccines?
Preparation may alter antigen’s conformation
stimulates a weaker immune response then live vaccines
- requires a larger dose adn multiple boosters to create long term immunity
- vaccine requires an adjuvant
What are adjuvants. What do they do?
Adjuvants enhance the immune response to vaccine antigens
- require a lower dose of antigens
- require fewer boosters
Adjuvants are not required for what vaccine type?
Live, attenuated
Most human vaccines use what as an adjuvant?
Alum
How does alum work?
not tested on this
Traps vaccine antigens in tissue at injection site
- leads to slow and persistent release of vaccine antigens
- allows for easier detection and prolonged uptake by dendritic cells
What is the main limitation of alumn? i.e. what types of pathogens is it not effective against?
Only generates B cell immunity
Not effective against intracellular bacteria and intracellular viruses
