L17- Vaccines

Question 1

What is immunisation?

Answer 1

A procedure designed to increase concentrations of antibodies and/or effector T cells which are protective against infectious agents and cancer

Question 2

What is immunoprophylaxis?

Answer 2

Immunisation performed before exposure to infectious organisms (to prevent disease developing in healthy individuals)

Question 3

What is immunotherapy?

Answer 3

Immunisation performed during an infection (or cancer) intended to treat existing disease by strengthening the body’s natural antimicrobial/viral or anti-tumour response

Question 4

What is a vaccine?

Answer 4

A preparation of a pathogen that is used to establish immunity ,by stimulating the body’s own immune system to protect against infections, without causing disease or adverse toxicity

Question 5

What is the vaccine used for smallpox?

Answer 5

Bovine analalog of smallpox that causes cowpox but can provide protective immunity against smallpox in humans without risk of significant disease

Question 6

What are the requirements for an effective vaccine?

Answer 6

• Provides host defence at the point of entry of the infectious agent
• Safe (low level toxicity is unacceptable)
• Must produce protective immunity in a high proportion of people it is given to
• Cost-effective
• Long-lasting and appropriate immunological memory

Question 7

What is the mechanism of action of a vaccine?

Answer 7

• Phagocytosed by an APC
• APC activates T cells to become CD4+ cells
• CD4+ cells activate B cells
• B cells divide into memory and plasma cells (Abs)- secondary immune response

Question 8

What is herd immunity?

Answer 8

Vaccination of a significant portion of a population (herd) provides a measure of protection for individuals who have not developed immunity.
• Lowering the number of susceptible members of a population reduces the probability of infection transmission

Question 9

What are the mechanisms of immunisation?

Answer 9

1. Passive- individual gains protective antibodies from another who has produced them
2. Active immunisation- can be achieved through natural infection by a pathogen or artificially via vaccines

Question 10

How does passive immunity occur at birth?

Answer 10

Occurs naturally by transfer of maternal antibodies (IgG) across the placenta or in breast milk.
Allows protection against= diptheria, mumps, measles for first 6 months of life

Question 11

What does injection with preformed antibodies protect against?

Answer 11

HepA
Rabies
Tetanus

Question 12

What does injection with humanised monoclonal antibodies protect against?

Answer 12

Respiratory syncytial virus

Question 13

What does injection with antitoxins protect against with?

Answer 13

Botulism

Snake/spider bite

Question 14

What is an adjuvant?

Answer 14

A chemical substance that can be added to a vaccine in order to enhance the immune response to the vaccine.

Purified antigens are not normally immunogenic on their own and most acellular vaccine require the addition of an adjuvant

Question 15

What is immunogenicity?

Answer 15

Immunogenicity is the ability of a foreign substance, such as an antigen, to provoke an immune response in the body of a human or other animal.

Question 16

What is an example of an adjuvant?

Answer 16

Tetanus toxoid vaccines contain aluminium salts which selectively stimulate antibody responses

Effects of many adjuvants is on APC’s by activation via TLR’s to secrete cytokines and stimulate T cells

Monophosphoryl lipid A is a ligand used for TLR-4

Question 17

What are ISCOMs?

Answer 17

Immune stimulatory complexes- lipid carriers acting as adjuvants with antigens incorporated into them

Delivery vehicles, minimal toxicity

Question 18

What are the different routes of vaccination?

Answer 18

• Injection (expensive, painful, may not be most effective as do not mimic usual route of entry)
• Intradermal administration
• Oral administration
• Intranasal (can induce mucosal antibodies)

Question 19

How can the effectiveness of a vaccine be increased?

Answer 19

By targeting it to the site of antigen presentation

Question 20

What are the ways of targeting a vaccine to the site of APC?

Answer 20

• Vaccine adjuvants (preserve Ag structure via injection)
• Coat antigen to mannose to enhance uptake by mannose receptors
• Present antigen as immune complex to exploit complement binding by Fc
• Target vaccine antigens selectively into APC pathways within cell