Unit 2 - Antibody therapeutics Flashcards

1
Q

What is antithymocyte globulin?

A

Purified gamma globulin (serum of rabbits immunised with human thymocytes)

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2
Q

How does antithymocyte globulin work?

A

Contains antibodies that binds to

  • CD2
  • CD3
  • CD4
  • CD8
  • CD11a
  • CD18
  • CD25
  • CD28
  • CD44
  • CD45
  • HLA class I
  • HLA class II
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3
Q

What effect do the antibodies in antithymocyte globulin have?

A

Antibodies deplete circulating lymphocytes by direct cytotoxicity
- complement (CMC)
- cell-mediated (ADCC)
Binding to cell surface molecules block lymphocyte function, leading to induction of apoptosis

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4
Q

What are the side effects of antithymocyte globulin?

A

Fever and chills with or without hypotension (major side effect)
Possibly premedicate with corticosteroids, H-blocker
Serum sickness and glomerulonephritis
Anaphylaxis
Leukopenia and thrombocytopenia
Risk of infection
Antibody development
- 68% of patients developed anti-rabbit antibodies

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5
Q

How are therapeutic proteins produced?

A

Polypeptides produced in microorganisms and cells

  • humans
  • animals
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6
Q

Give some examples of therapeutic proteins?

A
  • hormones
  • cytokines
  • enzymes
  • fusion proteins
  • antibodies
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7
Q

What are the five classes of antibody?

A
IgG
IgA
IgM
IgD
IgE
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8
Q

What is the structure of IgG?

A

Monomer

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9
Q

What two essential functions do antibodies perform?

A
  • antibodies bind to an epitope on an antigen with the arms of the Y. Each arm or monovalent antibody fragment (Fab 1) domain contains a binding site, making each antibody molecule at least bivalent
  • the Fc domain of the Y imparts the antibody with biological effector functions such as natural killer cell activation, activation of the classical complement pathway and phagocytosis
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10
Q

What is a monoclonal antibody?

A

One type of antibody, complementary to one type of antigen, made by one type of plasma cell

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11
Q

What is a polyclonal antibody?

A

Antibodies from multiple B cells that bind to a single antigen with specificity for MULTIPLE epitopes on that antigen

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12
Q

What is a hybridoma?

A

A mouse B-lymphocyte cell and a tumour cells fused together so that as it divides many of the same antibodies are produced

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13
Q

What are the advantages of therapeutic antibodies?

A
  • ability to bind with high specificity and affinity to a wide variety of molecules
  • stable molecules, thus ideal molecules to be used as targeting reagents
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14
Q

What are the disadvantages of therapeutic antibodies?

A
  • the first monoclonal antibodies were murine molecules and were recognised as foreign when infected into patients, leading to their elimination by the patient’s immune system
  • in order to be effective, antibodies often need to interact with certain elements of the immune system such as receptors displayed on effector cells or the complement cascade. Murine antibodies could not do this
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15
Q

What is a chimeric antibody?

A

Fusion of murine variable domains, responsible for the binding activity, with human constant domains

  • 70% human
  • fully human Fc portion
  • less immunogenic in humans
  • interaction with human effector cells and the complement cascade
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16
Q

What is a humanised antibody?

A

Hypervariable loops of a fully human antibody were replaced with the hypervariable loop of the murine antibody of interest

  • humanised antibodies are 85-90% human
  • less immunogenic than chimeric antibodies
17
Q

What technique relies on the ability to establish a physical link between a protein and gene encoding this protein?

A

In vitro selection - phage display

18
Q

What is displayed at the surface of the phage in phage display?

A

A protein fused to a filamentous phage capsid protein

19
Q

What are transgenic ‘humanised’ mice?

A

Mice with fully human antibodies

- created by replacing the entire mouse IgG repertoire with a human repertoire

20
Q

What do humanised mice produce on immunisation?

A

Human IgGs

- conventional hybridoma techniques can be used to clone human antibodies

21
Q

What is the advantage of using transgenic ‘humanised’ mice?

A

Directly lead to full length IgG, which is often the preferred format for therapy

22
Q

What are the disadvantages of using transgenic ‘humanised’ mice?

A

Cannot be used effectively when

  • the immunogen is toxic
  • the targeted antigen shares a high degree of homology with its murine ortholog
23
Q

What are the mechanisms of action of therapeutic proteins?

A
  • blocking
  • signalling
  • targeting
  • CDC (complement-dependent cytotoxicity)
  • ADCC (antibody-dependent cell-mediated cytotoxicity)
24
Q

between Murine, chimeric, humanized and human which antibodies have the least potential for immunogenicity?

A

Human have the least potential to cause immunogenicity

25
Q

what are the limitations of antibody therapy?

A

The limitations of traditional antibody-based therapies include the high cost associated with production of complex biomolecules in mammalian cell culture systems. In addition, the size of the molecule, coupled with sensitivity to proteolytic degradation and the quantities of clinical grade material required to obtain a therapeutic effect, limits delivery routes to intravenous and subcutaneous delivery, and in so doing reduces the range of therapeutic indications that would warrant such approaches.