ANTIBODIES AND VACCINES

Question 1

describe polyclonal and monoclonal antibodies.

Answer 1

Polyclonal antibodies are involved in passive immunity.
Monoclonal antibodies are involved in passive immunity, diagnostic imaging, treatment of cancer, transplantation and CVD.

Question 2

Describe the structure of antibodies.

Answer 2

Immunoglobulin monomers with 2 identical light (L) chains (1 constant and 1 variable domain), and 2 identical heavy (H) chains (3 constant and 1 variable domain).

Question 3

What are the variable domains of antibodies for?

Answer 3

Antigen binding, CDR loops (for diversity and specificity of antibody)

Question 4

What are some biological effects of antibodies?

Answer 4

Reduced damage to host cells from inflammatory response, generation of oxidants (neutrophils), direct antimicrobial activity, antibody-dependent cell cytotoxicity ( T, NK and macrophage cells), virus and toxin neutralisation, activation of complement and opsonisation.

Question 5

Describe the therapeutic use of polyclonal antibodies.

Answer 5

use for more than 1– years to induce passive immunisation to infectious agents and toxins. Takes 2-3 weeks to have either prophylactic or therapeutic effect.

Question 6

How are polyclonal antibodies produced?

Answer 6

1. large animal, such as a horse, is immunised.
2. serum is collected from the animal (contains antibody-containing antiserum)
3. Innitial purification (precipitation)
4. High res chromatographic purification (eg ion exchange)
5. addition of stabilisers, preservatives and potency adjustment
6. sterile filtration and aseptic filling –> liquid product
7. Freeze drying –> powdered product

Question 7

Describe the production of monoclonal antibodies.

Answer 7

1. mouse is immunised with antigen.
2. immune cells are isolated, and antibody-forming cells are isolated.
3. antibody-forming cells are fused with tumour cells to form hybridomas.
4. hybridomas are screened for production of desired antibody
5. antibody-producing hybridomas are cloned
6. clonal expansion –> monoclonal antibodies

Question 8

Describe applications of monoclonal antibodies.

Answer 8

Single largest category of therapeutic biopharmaceutical substances under investigation.
Used for passive immunity, diagnostic imaging and therapy.
Eg drug-based tumour immunotherapy.

Question 9

What are the limitations of mouse monoclonal antibodies?

Answer 9

Short serum half life
Inability to trigger human effector functions
Production of human anti mouse-antibodies

Question 10

What are the 3 types of antibody engineering?

Answer 10

Chimeric, humanised and human

Question 11

Describe chimeric antibody engineering.

Answer 11

Cloning of mouse variable genes into human constant region genes.

Question 12

Describe humanised antibody engineering.

Answer 12

Insertion of mouse complementary determining regions onto human constant and variable domain frameworks.

Question 13

Describe human antibody engineering.

Answer 13

Selection of human antibody fragments from in vitro libraries or by production of transgenic mice.

Question 14

What are the mechanisms of action of therapeutic antibodies?

Answer 14

Bind ligands and receptors to prevent binding and receptor activation.
Bind receptors to initiate internalisation and down-regulation of receptors.
Bind receptors to deplete antigen bearing cells through complement-mediated lysis and opsonisation.
Anso induce active signals that alter cell fate.

Question 15

Describe live attenuated vaccines.

Answer 15

weakened version of living virus.
Elicits strong immune response
Eg MMR vaccine

Question 16

Describe inactivated vaccines.

Answer 16

Microbe is killed either by heat, chemicals or radiation.

Stimulates a weaker immune response than live vaccines.

Question 17

Describe toxoid vaccines.

Answer 17

For bacteria that secrete toxins.
“detoxified” toxins prepare immune system to attack natural toxin.
Eg diptheria and tetanus vaccinations

Question 18

Describe recombinant subunit vaccines.

Answer 18

Part(s) of a microbe are used in the vaccine. It provides the most immunogenic of vaccines.
Advantages:
-clinically safe product (expressed in non pathogenic recombinant host) and no undetected pathogen used.
-unlimited supply
-consistent production of defined product (no unexpected side effects)

Question 19

Describe conjugate vaccines and give an example.

Answer 19

Hib vaccine uses a protein-polysaccharide conjugate (protein acts as a carrier molecule). Protein may be diphtheria toxoid.
Meningococcal vaccine and pneumococcal vaccines are also conjugates.

Question 20

Describe the immune response to conjugate vaccines.

Answer 20

1. polysaccharides from the disease-causing bacteria stimulate B cells by cross-linking the B-cell receptor and drive the production of Ig. This causes a lack of production of new memory B cells and depletion of the memory B cell pool, such that subsequent immune responses are decreased.
2. The carrier protein from the conjugate vaccine is processed by the polysaccharide-specific B cell, and peptides are presented to carrier-peptide-specific T cells, resulting in T cell help for the production of both plasma cells and memory B cells

Question 21

Describe vaccine vectors

Answer 21

Incorporation of a pathogen-derived antigen sequence into a non-pathogenic species
Mostly viral-based Eg poxviruses and adenoviruses.
Strong hum oral and cell-mediated immunity.

Question 22

What are the possible routes of immunisation for human vaccines?

Answer 22

Intranasal
Oral
Intramuscular
Intraperitoneal
Aerosolised
Intradermal
Intravenous