14 - Vaccination

Question 1

Variolation

Answer 1

Pus taken from a smallpox blister and introduced into skin of an uninfected person to confer protection

Question 2

Who discovered vaccination

Answer 2

Edward Jenner

Question 3

Discovery of vaccination

Answer 3

Inoculation with cowpox protects against smallpox (closely related)

Question 4

First human viral disease to be eradicated by vaccination

Answer 4

Smallpox (caused by infection with variola virus) via protective immunity induced by closely related virus (vaccinia virus)

Question 5

Herd immunity

Answer 5

• Occurs when a large portion of a community becomes immune to a disease.
• The spread of disease from person to person therefore becomes unlikely, protecting susceptible individuals who cannot be vaccinated

Question 6

Passive immunity

Answer 6

• Administration of antiserum containing preformed antibodies
• Immediate protection against recent infection or ongoing disease

Question 7

Limitations of passive immunity

Answer 7

Can trigger hypersensitivity, antibodies are degraded very quickly

Question 8

Active immunity

Answer 8

• Protection induced by person’s own immune system with specificity and memory
• Both humoral and cell mediated
• Can last decades

Question 9

Types of vaccines

Answer 9

Inactivated, subunit, killed

Question 10

Passive natural immunity

Answer 10

Antibodies acquired through breast milk or placenta

Question 11

Passive artificial immunity

Answer 11

Immunity gained through antibodies harvested from another person or animal

Question 12

Active natural immunity

Answer 12

Immunity gained through illness and recovery

Question 13

Active artificial immunity

Answer 13

immunity acquired through vaccine

Question 14

Rabies

Answer 14

• Zoonotic viral disease spread to humans via bite of infected animal
• Virus travels along nerves to reach CNS
• Delay between infection and arrival in CNS means post-exposure prophylaxis can prevent disease
• Most people with symptomatic rabies do not survive

Question 15

Rabies vaccine

Answer 15

Inactivated vaccine (killed virus), or rabies immunoglobulin are offered, depending on exposure or degree of risk

Question 16

Live attenuated viral vaccines

Answer 16

• Have modified genomes and are less virulent than wild type viruses
• Antigens are similar enough to WT to induce immune response that protects against WT
• More potent than killed/inactivated/non replicative antigens as they infect target cells and induce a broad range of effect immune responses (including CD8+ T cells)

Question 17

Method for deriving live attenuated vaccines

Answer 17

• Pathogenic virus is isolated from a patient and grown in human cultured cells
• The cultured virus is used to infect monkey cells
• The virus acquires many mutations that allow it to grow well in monkey cells
• Virus no longer grows well in human cells

Question 18

Why are live attenuated replicating virus vaccines best immunogen

Answer 18

Because both T cell and B cells responses are induced

Question 19

What response is best for immunisation

Answer 19

Not just antibodies, also CD8+ T cell specific response

Question 20

Yellow fever vaccine

Answer 20

• Derived by passage thorugh mice and other lab animals
• 48 nucleotide substitutions (of ~11,000 nt) of which 22 are non-synonymous, scattered throughout genome
• Induces neutralising antibodies and T cell responses

Question 21

Polio sabin attenuated vaccine

Answer 21

• Grows in epithelial cells
• Does not grow in nerves (no paralysis)
• Local gut immunity (IgA), important as virus replicates in gut
• 1 in 4,000,000 vaccine infections

Question 22

Polio salk killed vaccine

Answer 22

• Formaldehyde fixed
• No reversion
• No gut immunity
• Cannot wipe out wild type virus

Question 23

Subunit vaccine advantages

Answer 23

• Prepared from components of virus (proteins). May self aggregate to produce virus like particles
• Recombinant DNA technology
• No viral genomes or infectious virus

Question 24

Subunit vaccine disadvantages

Answer 24

• Expensive
• Injected
• Poor antigenicity

Question 25

HPV vaccine

Answer 25

- HPV vaccine is a non infectious virus like particle - One of most successful vaccine - Quadrivalent vaccine includes HPV types 6, 11, 16 and 18

Question 26

Polysaccharide vaccines

Answer 26

- Induce short lived antibody producing plasma cells by cross linking the BCR - Affinity maturation of the antibody response and the induction of memory B cells do not occur

Question 27

Protein polysaccharide conjugate vaccines

Answer 27

- Can engage T cells that recognize the carrier protein, as well as B cells that recognize the polysaccharide. - T cells provide help to B cells, leading to affinity maturation and the production of both plasma cells and memory B cells.

Question 28

Adjuvant

Answer 28

Substance added to vaccine to increase body's immune response to vaccine

Question 29

How do adjuvants work

Answer 29

- Act as antigen depot, releasing it slowly - Inducing an inflammatory response that enhances the host immune response to the vaccine antigen

Question 30

Is T cell vaccination predicted to prevent infection

Answer 30

No, but is predicted to control the viral load until escape mutants arise

Question 31

Features of effective vaccines

Answer 31

- Safe - Protective - Gives sustained protection - Induces neutralising antibody - Induces protective T cells - Practical considerations