Immunology-Vaccination

Question 1

What is the aim of vaccination?

Answer 1

prevent or curtail infection on subsequent exposure to pathogen

protect against toxic effects of microbial products

Question 2

What is the Reproductive Ratio?

Answer 2

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

Question 3

What issues influence the reproductive ratio of a pathogen?

Answer 3

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)

Question 4

What is passive vaccination?

Answer 4

administration of antibody for acute treatment

Question 5

What are the risks of passive vaccination?

Answer 5

Subsequent admin of antitoxin can create Type III hypersensitivity (serum sickness)

subsequent inefficient active vaccination

Question 6

What are the uses of passive vaccination?

Answer 6

post-exposure tx for tetanus and rabies

antitoxin admin for snake bites

prophylaxis of hemolytic disease of newborn

Question 7

What is active vaccination

Answer 7

admin of antigen

Question 8

What are the three types of active vaccination?

Answer 8

Killed or inactivated vaccines

Subunit vaccines

Live-attenuated vaccines

Question 9

What are killed or inactivated vaccines?

Answer 9

pathogenic organisms that have been inactivated by tx with heat or formalin

Question 10

What needs to be balanced in any vaccination?

Answer 10

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

Question 11

Why are there few effective killed viral vaccines?

Answer 11

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

Question 12

What are the advantages of killed or inactivated vaccines?

Answer 12

Cheap to develop
safe
efficacious

Question 13

What are the disadvantages of killed or inactivated vaccines?

Answer 13

limited shelf life or require cold chain
limited immunogenicity (require 2nd injection soon after first or annual booster)
usually need an adjuvant

Question 14

What is a subunit vaccine?

Answer 14

do not contain the whole organism

Question 15

What are the advantages of subunit vaccines?

Answer 15

no potentially infectious particles present

storage is usually not a problem

Question 16

What are the disadvantages of subunit vaccines?

Answer 16

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

Question 17

What is an adjuvant?

Answer 17

substance used to increase non-specific immune response to a vaccine

Question 18

What are the three major mechanism of adjuvants?

Answer 18

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

Question 19

What adjuvants are typically used?

Answer 19

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

Question 20

What are live attenuated vaccines?

Answer 20

live organisms that have lost some of their virulence or grow slowly

Question 21

How is attenuation achieved?

Answer 21

1. growing pathogens in different host
2. passaging pathogens through eggs or tissue culture cells
3. isolating temperature sensitive mutants that grow at temps above or below host temp
4. genetic manipulation
5. recombinant viruses

Question 22

What are advantages of live attenuated vaccines?

Answer 22

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

Question 23

What are disadvantages of live attenuated vaccines?

Answer 23

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