Lec 5 - Vaccines

Question 1

What disease was used to eradicate smallpox and how did this happnen?

Answer 1

cowpox antigens similar to smallpox. infection generated immune response that was effective against smallpox infection

Question 2

What is the main function of vaccines?

Answer 2

stimulate an adaptive response so on infection, 2ndry response occurs

Question 3

Describe the 2 aims of vaccines

Answer 3

1. long lasting immunity
2. preventing transmission w/in populations

Question 4

Describe some factors that favour the global eradication of a disease

Answer 4

• cost effective eradication scheme; programme more likely to be followed
• lack of animal carriers; prevents reinvasion of pathogen from animals
• lack of host long-term carriers; prevents reinvasion of pathogen from carriers
• lack of serovars of pathogen; one vaccine is effective
• effective & cheap vaccine available; worldwide programme possible

Question 5

Why does herd immunity matter?

Answer 5

chance of transmission of a disease onto an unvaccinated person is greatly reduced if 2/3 of community is vaccinated

Question 6

Give examples of available vaccines

Answer 6

• japanese encephalitis
• tetanus
• rabies
• anthrax

Question 7

Give some features of an effective vaccie

Answer 7

• practical considerations; cost per dosage is low, effective
• induces T cell response (especally important in viral infections)
• induces neutralising antibody
• safe; will not give rise to infection
• long lasting

Question 8

Describe briefly the 3 main types of vaccine

Answer 8

• subunit - parts of the pathogen
• attenuated - most effective. live pathogen in which strain has been weakened so will not cause disease, low virulence
• killed - does not replicate

Question 9

Give the 4 methods of obtaining an attenuated strain for a vaccine

Answer 9

• bacteria - serial passage in vitro (BCG vaccine for M. tuberculosis)
• virus - serial passage through cell culutre in vitro (polio)
• adapted to low temps (viruses)
• genetically altered (cholera - removal of the A subunit)

Question 10

how are killed vaccines killed?

Answer 10

heat / chemical treatment

Question 11

For the table below, describe both LIVING and NON LIVING in terms of the definitions here

Answer 11

Question 12

Even though subunit vaccines are regarded as the most effective (safest & few side effects) what are some of the downsides related to them?

Answer 12

require adjuvant, multiple injections, shortwr lived

Question 13

Give 3 examples of subunit vaccines

Answer 13

• toxoid - inactivated toxin eg Diptheria
• subcellular fractions eg polysaccharide coat
• recombinant proteins - eg Hep B outer surface structure expressed in yeast

Question 14

What is a conjugate vaccine and state why it is useful?

Answer 14

conjugatevaccine may be a polysaccharide coat linked to carrier protein - stimulates both a B and T cell response

Question 15

what is the peptide vaccine for HPV designed to stimulate ?

hint; killed vaccines do not stimulate these

Answer 15

cytotoxic T cells

Question 16

What are recombinant expression vaccines?

Answer 16

eg vaccinia virus used to express a HepB antigen

Question 17

What is a DNA vaccine?

Answer 17

DNA inserted into an expresion vector and transfected into muscle cell (Eg) . expression can then be from when DNA inserts into chromosome / episomal

Question 18

What are some of the barriers against creating an effective vaccine?

Answer 18

• cost
• high mutation rates of viruses eg/large no. serotypes
• lack of adequate medical infrastructure
• personal/religous reasons
• fake news eg decline of B. pertussis vaccines (USA - 80s/90s) leading to rise in Whooping Cough incidence