Types of Vaccines and their Application in Veterinary Medicine Flashcards
describe active versus passive immunization
passive: transient, given to recipient, who does not need to mount their own response
active: need to mount your own immune response and make your self
what makes a good vaccine? (6)
- safe: minimal side effects; does not cause illness or death in even a small percentage of recipients
- protective: prevents or reduces illnesses caused by pathogen, ideally in the fetus as well, and prevents transmission
- long-lasting: sustained resistance
- elicits B cell responses: stimulates production of antibodies reactive with appropriate antigenic epitopes
- elicits T cells responses: stimulates production of cellular immunity
- others: low cost, stable, easy to administer, good for the masses, elicits an immune response distinguishable from that of the natural infection to be able to carry out immunization and eradication simultaneously
list and generally describe the 4 not-live vaccines and the 2 live vaccines
not live:
1. killed/inactivated: via heat, formalin, or other chemical treatment
- recombinant protein/subunit: specific antigens (immunogens) are expressed and purified OR pathogen is inactivated, disrupted, and at least partially purified
- DNA/RNA: plasmid/mRNA encoding antigen expresses protein upon immunization
- conjugate: attach a poor immunogen to a strong immunogen
live:
1. attenuated: pathogen is rationally or blindly rendered avirulent; use of different species’ viruses (not natural host, may elicit immunity without disease)
- vectored: an attenuated virus/bacteria encodes the antigen, which is expressed upon immunization/infection; recombinant virus-vectored
describe the difference between killed, split, and subunit vaccines
killed: whole inactivated virus; works well but stronger reaction in host (sore, fever, etc.) (reactogenic)
split: pathogen is grown and killed, then disrupted and antigen enriched (less reactogenic)
subunit: specific antigens are expressed and purified (least reactogenic)
describe DNA/plasmid vaccines (strengths and weaknesses) (3)
- potentially very safe, but some concerns about integration or anti-DNA immune responses (not fully researched yet)
- put DNA into a plasmid, infect bacteria, have them make a whole lot of the vaccine and then inject that
- concerns of poor immunogenicity in humans, but potentially fast and inexpensive to produce
describe mRNA vaccines (strengths and weaknesses) (5)
- inject mRNA; potentially very safe (no DNA concerns about integration)
- potentially reactogenic
- potentally fast and inexpensive to produce
- storage challenges
- clearly effective, but still may be hurdles for widespread or veterinary use
describe conjugate vaccines (2)
- purify polysaccharides from bacteria and attach these poor immunogens to a highly immunogenic protein carrier (allows access to cells with specific receptors for the polysaccharide to then stimulate a response to for T and B cells)
- safe but expensive
list the pros and cons of killed/non-replicating vaccines
pros:
1. no residual virulence
2. easy to store and handle
cons: may need adjuvants, more expensive to produce, may not mimic actual infection so adjuvant and immunization route become critical
-mRNA may be best of both worlds but will take some time before widespread!
describe blind attenuation
- pathogen isolated from a diseased individual
- pathogen serially passaged in different substrates (cells, eggs, animals), resulting in mutations attenuating the vaccine
- attenuation is confirmed in challenge models
- varying conditions can rationall (but still blindly) attenuate (cold adaptation in temps lower than host body temp )
- mutations are identified and tested for potential for reversion
describe blind attenuation
- if a virulence determinant is known, it can be removed, rendering the pathogen avirulent or attenuated
- the virulence factors may be mutated to be non-functional or completely removed
- must be tested for potential for reversion
describe virus-vectored vaccines
- similar to plasmid vaccines; the gene of interest is inserted into a vaccine virus vector (which is attenuated in the host)
- when the recombinant virus infects the host, the antigen is expressed, eliciting immunity
example: sticking rabies into a poxvirus to vaccinate against rabies
give pros and cons of live-attenuated, recombinant, and virus-vectored vaccines
pros:
1. replicate infection without adjuvants to elicit IFNs and other cytokines
2. cheap production (post development)
3. lower doses needed to get immune response
cons:
1. may have residual virulence
2. may shed live microorganisms
3. vector-immunity concerns
4. require refrigeration
5. potential reversion
what are the 4 types of adjuvants for vaccines?
- depot: doing something to keep vaccine around in injection site for longer (historically an oil/water slurry to increase time for macrophages and other innate to come in and see vx and initiate response)
- particulate: improve antigen presentation; attach antigen to a particle that macrophages will see better to enhance cell-mediated immunity
- immunostimulatory: stimulate TLRs and other PRRs (LPS, flagellin, etc to nonspecifically activate innate response to drive a more robust adaptive response for enhanced antibody production)
- combinations: combo of any of the above
describe how veterinary vaccines are approved for use
- all vaccines checked for safety, potency, and presence of organism: free from extraneous organisms, toxicity (none), sterile (unless live vx)
- potency: still effective after storage, potency before and after accelerated aging, evidence of protection
- exception!!: conditionally licensed vaccines; used to meet an emergency condition, limited market local situation, etc., more common in food animals, generally effective for a year, but still issued based on full safety, purity, testing, and expectation of efficacy (SHOULD NOT HAVE LABEL CLAIMS)
how do we determine vaccine efficacy/
- field trials: HIGHEST STAKES; animals in natural setting, want at least on vaccine group and one control group; not challenging, just looking for incidence of disease for months post-vx
- experimental challenge studies: tests ability of vaccinated animal to resist experimentally induced disease; shows if animals protected from challenge
- laboratory measures of immunity: animals experimentally vaccinated, samples are collected, and antibody or other immune responses to agents in vaccine measured; does NOT demonstrate protection from disease
