SAMENVATTING TOEGEPASTE IMMUNOLOGIE
Inhoud
SAMENVATTING TOEGEPASTE IMMUNOLOGIE .......................................................................... 1
Chapter 1: Generation of Antibodies ....................................................................................................... 3
Introduction ......................................................................................................................................... 3
A. B-cell Development and Antibody Production........................................................................... 3
B. Antibodies Come In Many Shapes ........................................................................................... 10
C. Structur of an IgG ..................................................................................................................... 20
D. Antigen-binding antibody fragments........................................................................................ 32
E. Recombinant antibodies ........................................................................................................... 37
F. Alternative affinity reagents ..................................................................................................... 42
Chapter 2: Selection of antigen-specific antibodies .............................................................................. 44
A. Producing Ag-specific polyclonal antibodies ........................................................................... 44
B. Selecting Ag-specific monoclonal antibodies: hybridoma’s .................................................... 48
C. Selecting Ag-specific recombinant Abs.................................................................................... 53
Chapter 3: Chimeric, humanized and human antibodies ....................................................................... 87
Introduction ....................................................................................................................................... 87
A. First attempt: Chirmeric Ab’s ................................................................................................... 89
B. Humanization of Ab’s: Rational vs empirical approaches........................................................ 91
C. Production of fully human antibodies ...................................................................................... 96
Chapter 4: Additional Antibody Improvements .................................................................................... 97
1) Affinity maturation ................................................................................................................... 97
2) Stability improvements........................................................................................................... 100
3) Engineering effector functions ............................................................................................... 102
Chapter 5: Applications with Recombinant Antibodies: Nanobodies as an Example ......................... 103
A. Heavy chain antibodies and Nanobodies: structural and functional properties ...................... 103
B. Key advantages of nanobodies as antigen-binding fragments................................................ 106
C. Nanobodies in research, diagnosis and therapy ...................................................................... 107
D. Selected applications of nanobodies in research, diagnosis and therapy ............................... 109
Chapter 6: Vaccine Technology ............................................................................................................114
Introduction ......................................................................................................................................114
1. Vaccines and vaccination in historical perspective ................................................................ 120
2. Vaccine requirements and classification ................................................................................. 123
Take home messages up to now ...................................................................................................... 128
3. Traditional vaccines: an overview .......................................................................................... 128
4. New generation vaccines: an overview .................................................................................. 129
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, 5. Adjuvants ............................................................................................................................... 130
6. Immunological background on how adjuvants work ............................................................. 131
7. Working mechanism of a live attenuated vaccine .................................................................. 138
8. Working mechanism of adjuvants .......................................................................................... 138
9. Vaccine production ................................................................................................................. 143
10. Predictability of vaccine efficiency .................................................................................... 148
11. Cancer progression: growth, invasion, metastasis ............................................................. 149
12. Adoptive (passive) immunotherapy OR Adoptive Cell Therapy (ACT) ........................... 154
13. Active immunotherapy....................................................................................................... 160
Hoofdstuk 7: SARS-Cov2 vaccins ...................................................................................................... 165
1. Vaccine development in pandemic times: < 1 year thanks to overlapping phases ................ 165
2. Some of the most widely used vaccines ................................................................................. 165
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,Chapter 1: Generation of Antibodies
Introduction
Antibodies are part of the immune system. The immune system can be subdivided into 'humoral' or
'cellular'. The humoral immune response includes proteins found in the body's fluids such as antibodies
produced by B cells, as well as cytokines, complement proteins, ... The cellular response consists of NK
cells, macrophages, dendritic cells, and others, in addition to T lymphocytes.
The immune system can be divided according to specificity: nonspecific or innate immunity and antigen-
specific immunity or adaptive immunity.
Nonspecific immunity includes the skin barrier, gastric acid, mucus, NK cells, macrophages (phagocytic
cells), polymorphonuclear cells, and soluble factors such as cytokines. None of these rely on specific
antigen recognition. The advantage is that they are always present and ready to act.
In antigen-specific immunity, we see a specific reaction against certain molecules originating from
potential pathogens. After infection, we have the production of antibodies against a particular pathogen.
Antigen-specific immunity is also called adaptive immunity because it develops during an individual's
lifetime as an adaptation to infection with that pathogen. Adaptive immunity takes time to develop but
is very specific. This specific immune response offers numerous possibilities in terms of molecule
recognition and can be used in various applications that we will explore later.
A. B-cell Development and Antibody Production
A.1 Immunogenicity vs. antigenicity
How is an antigen-specific response initiated? Antibodies are elicited by molecules considered as foreign
by the body.
A distinction can be made between 'immunogen' and 'antigen'. Immunogenicity is the ability to induce
a humoral and/or cellular immune response (antibodies) in, for example, humans or other vertebrate
animals. Antigenicity is the ability to specifically bind to the final products of the immune response
(i.e., to be recognized by (secreted) antibodies and/or surface receptors on T-cells) Although all
molecules that are immunogenic are also antigenic, the reverse is not always true.
If antibodies cannot be produced against a certain antigen in a particular animal species (e.g., self-
antigen), it is likely that antibodies can still be elicited in another animal species, such as rabbits or mice.
Recap: An antigenic molecule is a molecule that has the capacity to bind antibodies. Immunogenic
molecules have the capacity to raise an immune response.
A.2 Recap on antibodies
Antibodies are also called immunoglobulins. When talking about the structure of an antibody, one talks
abouts an immunoglobulin fold
Which species/animals have antibodies? All vertebrates have antibodies. Antibodies are elicited very
rapidly in vertebrates and are available in nearly unlimited amounts. How many different antibodies can
be produced in a lifetime? 1012 antibodies.
Antibodies are produced by B-lymphocytes, or B cells, first in membrane-form (B-cell receptor) and
then secreted by plasma cells.. The "B" in B-cells comes from the Bursa of Fabricius, an organ found in
birds where these cells were first discovered. Though initially identified in birds, B-cells have since been
found in mammals as well.
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, Where do B cells originate? B-cells originate from hematopoietic stem cells (HSCs) in the bone
marrow. These stem cells have the ability to differentiate into various types of blood cells, including B-
cells.
What is a BCR? A B-cell receptor is an antibody complex found on the surface of B cells, The BCR
plays a crucial role in recognizing and binding to specific antigens (foreign substances such as bacteria,
viruses, etc) present in the body. When there is an infection, B-cells are secreted as plasma cells.
The adaptive immune response creates a memory. The "memory cells" of the adaptive immune system
are specialized immune cells formed after initial exposure to a specific antigen. These memory B-cells
are part of the body's immune response mechanism.
Is there a difference between a 1st infection/antibody response and a later infection/antibody response?
Indeed, memory B-cells arise from activated B-cells and remain in the body after an infection or
vaccination. They "remember" the specific antigens they have encountered, leading to a rapid and robust
response upon subsequent exposure to the same antigen. This results in faster antibody production,
providing quicker and more effective protection against reinfection.
This system is exploited in vaccination.
An Ab possesses a high specificity for its cognate antigen (if not, possible auto-immunity). Through
affinity-maturation, an Ab will bind its cognate antigen with high affinity.
Abs are large & complex, but their generation, in vivo selection and the antibody architecture are well-
established.
A.3 Development of B-cells
In the bone marrow:
Every lymphoid precursor gives rise to a large number of
lymphocytes, each bearing a distinct antigen receptor (BCR).
Individual lymphocytes carry numerous copies of a single antigen
receptor with a unique antigen-binding site, determining which
antigens the lymphocyte can bind.
Each person possesses billions of lymphocytes. As a result (of all cells
together), it is possible to generate a response against the wide variety
of antigens.
Lymphocytes with receptors that bind ubiquitous self-antigens are
eliminated before they become fully mature, ensuring tolerance to
such self-antigens. B-cells that don’t develop a receptor are also
eliminated. The other cells mature and migrate to the lymphoid
organs (naïve B-cells). There they will amplify and differentiate and
get a different effector function.
The diversity of these BCRs is nearly unlimited, known as the
antibody repertoire or immunoglobulin repertoire, and in humans it
comprises at least 1011 different BCRs and likely orders of magnitude larger. However, the number of
different antibodies present at any given time is limited by the total number of B-cells in an individual
(as well as by each individual's previous encounters with antigens).
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