Immunology-Vaccination Flashcards
What is the aim of vaccination?
prevent or curtail infection on subsequent exposure to pathogen
protect against toxic effects of microbial products
What is the Reproductive Ratio?
number of new infections in a totally susceptible population resulting from contact with an infected individual
Ro of <1=individual will infect fewer than 1 susceptible individual
What issues influence the reproductive ratio of a pathogen?
Population density-easier to spread when more people
Spatial configuration-easier to spread in large herds
Natural barriers-sea, mountains, islands, etc
Political barriers-restrictions on animal import/export
Proportion of immune individuals-herd immunity, how many people must be vaccinated to eliminate infection (1-1/Ro)
What is passive vaccination?
administration of antibody for acute treatment
What are the risks of passive vaccination?
Subsequent admin of antitoxin can create Type III hypersensitivity (serum sickness)
subsequent inefficient active vaccination
What are the uses of passive vaccination?
post-exposure tx for tetanus and rabies
antitoxin admin for snake bites
prophylaxis of hemolytic disease of newborn
What is active vaccination
admin of antigen
What are the three types of active vaccination?
Killed or inactivated vaccines
Subunit vaccines
Live-attenuated vaccines
What are killed or inactivated vaccines?
pathogenic organisms that have been inactivated by tx with heat or formalin
What needs to be balanced in any vaccination?
Inactivation and retained antigenicity
Want to treat the pathogen enough to render it harmless, but not enough that the body mounts little or no immunological response to it
Why are there few effective killed viral vaccines?
degree of immunity is proportional to the quantity of administered antigen–difficult and expensive
Good at stimulating antibody production, but don’t induce T cell immunity
What are the advantages of killed or inactivated vaccines?
Cheap to develop
safe
efficacious
What are the disadvantages of killed or inactivated vaccines?
limited shelf life or require cold chain
limited immunogenicity (require 2nd injection soon after first or annual booster)
usually need an adjuvant
What is a subunit vaccine?
do not contain the whole organism
What are the advantages of subunit vaccines?
no potentially infectious particles present
storage is usually not a problem
What are the disadvantages of subunit vaccines?
MHC restriction (may produce strong response in one animal, little or no response in another)
require adjuvants
regular booster doses necessary
balance between immunogenicity and toxicity
improper inactivation of pathogens can lead to outbreak
quality and purity often poor
induce poor immunological memory
What is an adjuvant?
substance used to increase non-specific immune response to a vaccine
What are the three major mechanism of adjuvants?
Depot effect: retain antigen at inoculation site, slowly releases over days/weeks
Non-spec irritants: induce low grade inflammation, attract macrophages
Polyclonal activation: augment specific response
What adjuvants are typically used?
Alum: adsorbs antigen to surface of particles and releases it slowly
Saponin: detergen that sets up mild inflammatory response at inoc site
Liposomes: artificial cells that can contain the vaccine
What are live attenuated vaccines?
live organisms that have lost some of their virulence or grow slowly
How is attenuation achieved?
- growing pathogens in different host
- passaging pathogens through eggs or tissue culture cells
- isolating temperature sensitive mutants that grow at temps above or below host temp
- genetic manipulation
- recombinant viruses
What are advantages of live attenuated vaccines?
often require only one inoculation
most antigens retained intact
type of immunity generated is often close to virulent pathogen
set up low grade infection which constantly stims the immune system
usually available as freeze-dried organisms and have extended shelf lives
What are disadvantages of live attenuated vaccines?
usually more expensive to develop
possibility of reversion to virulence
most are safe when delivered to adults, but can cause disease in neonates or immune-depressed animals
inverse relationship between degree of attenuation and degree of protection
