Lecture 5 - Monoclonal Antibodies

Question 1

Why do monoclonal antibodies have great therapeutic potential?
1)
2)
3)

Answer 1

1) Very well tolerated
2) Long half-life
3) Very specific and selective

Question 2

Original strategy for making monoclonal antibodies:
1)
2)
3)
4)

Answer 2

1) Take B cells from an animal that has been injected with antigen of interest
2) Fuse B cells with myeloma cells
3) This makes hybridomas, with fused nuclei of myeloma cells and plasma cells
4) Select hybridoma expressing antibody of interest

Question 3

Issues with first generation of monoclonal antibodies

Answer 3

1) Made in mice, so rejected as foreign by human immune system
2) Short serum half-life, from being rejected
3) Lack some effector functions, as Fc region couldn’t bind to human Fc receptors

Question 4

Partial solution to monoclonal antibodies being rejected in humans

Answer 4

Graft human heavy chain onto mouse light chains

Question 5

Issues with chimeric human-mouse antibodies

Answer 5

Antigen-binding site still recognised as foreign

Question 6

More sophisticated way of making human/murine chimeric antibodies

Answer 6

Graft mouse CDR1, CDR2 and CDR3 regions into human antibody

Question 7

Way to create mouse producing human antibodies

Answer 7

Create transgenic mouse with human Ig genes.

Question 8

Generic way to make human B cells make monoclonal antibodies
1)
2)

Answer 8

1) Take human B cell that have survived infection, are high affinity and are expressing IgG.
2) Infect B cells with EBV (EBV can make B cells immortal)

Question 9

Drawbacks to immortalising human B cells

Answer 9

B cells will only produce antibodies against an antigen that the person has encountered (must have naturally encountered antigen. Infecting humans with antigens of interest is unethical

Question 10

Advantages of immortalising human B cells

Answer 10

1) Very well-tolerated

2) Will proliferate monoclonal antibodies that were effective in protecting the donor against past infection

Question 11

How can mAbs be used to deliver drugs?

Answer 11

Bind drug to antibody

Antibody has specificity to bind to an area where the drug is to be delivered

Question 12

How can antibodies be used to bring together cells?

Answer 12

Create an antibody that has two specificities, one for each cell of interest (EG: target call and NK cell)

Question 13

Possible actions of mAbs
1)
2)
3)
4)

Answer 13

1) Ligand blockade
2) Receptor blockage or downregulation
3) Target cell depletion
4) Target cell activation

Question 14

Example of mAb ligand blockade

Answer 14

Infliximab
Anti-TNFa antibody
Used to treat rheumatoid arthritis, Crohn’s disease, psoriasis
If inflammatory cells don’t receive stimulation from TNFa, they become inert or die

Question 15

Other examples of mAb ligand blocking

Answer 15

Anti-VEGFA agent
Blocks angiogenesis in cancers
Anti-RANKL antibody to prevent bone reabsorption in B cell lymphomas

Question 16

Example of mAb receptor blocking

Answer 16

Anti-HER2
Trastuzumab
HER2 is a member of epidermal growth factor ligands. Is involved in some breast cancers

Question 17

Ways that mAbs can lead to target cell depletion
1)
2)
3)

Answer 17

1) Complement activation
2) NK cell activation
3) Macrophage activation
All against target cell opsonised with mAb

Question 18

Example of mAb target cell depletion

Answer 18

Anti-CD20
Rituximab
B cells (not plasma cells) express CD20 on cell surface
Used to treat B cell lymphomas

Question 19

Type of immunosuppression caused by rituximab

Answer 19

Depletes B cells, but not plasma cells
Therefore patient will be able to produce antibodies against previously encountered antigens, but won’t be able to mount a humoral response against novel antigens

Question 20

mAb target cell activation

Answer 20

Can crosslink TCR-CD3 complexes on T cells, resulting in activation without antigen

Question 21

Example of mAb target cell activation

Answer 21

Ipilimumab
Anti-CTLA4 antibody
CTLA4 is a T cell negative receptor, expressed on a T cell when the T cell binds to an antigen
Ipilimumab prevents binding to CTLA4, and therefore suppression of T cell response

Question 22

What is Ipilimumab used for?

Answer 22

Treating severe metastatic melanoma

Question 23

Limitations of mAbs
1)
2)
3)
4)
5)

Answer 23

1) Unpredictable effects
2) Cardiotoxicity
3) Infections, when target is immune cells
4) Acute anaphylaxis
5) Production of anti-mAb antibodies

These effects aren’t necesarily the case with all mAbs. Most are specific to certain mAbs

Question 24

Chimeric antigen receptor treatment

Answer 24

Grafting antibody specificity onto T cell activation molecules, and then inserting molecules into a T cell using a viral vector

Question 25

Structure of a chimeric antigen receptor

Answer 25

Membrane-bound protein

1) Antibody binding site, specific to desired antigen. Expressed on cell surface
2) T cell activating molecules, expressed on cytosolic side of cell membrane

Question 26

Aim of producing chimeric antigen receptors

Answer 26

Fuse the specificity and binding affinity of antibody receptors with CD8+ T cell cytotoxicity

Question 27

Experimental use of chimeric antigen receptors

Answer 27

Expressing anti-CD19 receptors, fused to CD8 T cell surface

Killed B cells expressing CD19 (CD19 like CD20 - expressed on all B cells except plasma cells)

Question 28

How did anti-CD19 chimeric antigen receptor therapy work?
1)
2)
3)

Answer 28

1) Take blood sample from patient, isolate T lymphocytes. Introduce chimeric antigen receptor gene into T cells.
2) Deplete patient’s lymphocytes with chemotherapy
3) Reinfuse lymphocytes expressing chimeric antigen receptor

Question 29

Example of an ‘orphan drug’

Answer 29

Anti-IL-1b mAb

Question 30

What is anti-IL-1b mAb used to treat?

Answer 30

Cryopyrin-associated periodic syndromes

Systemic, uncontrolled inflammation