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specialization : Biotechnology
Final report
Genetic engineering of plants for the
production of medicines
Group 5:
Iris Hensen
Emanuel Casagrande
Jan-Pieter Ploem
Thibaut Gabriel
Ilse Timmermans
Genetic engineering of plants for the production of
medicines
ince the beginning of the
earth,
humans
use
plants. Plants exist even
longer than humans and
we are still not aware of all their
opportunities. Scientists and
people who are interested by
these beautiful things present in
the wild life try to understand
how these plants operate. More
and more, they discover a large
variety of species and the
different possibilities of each
plant. Still, these days not all
species
of
plants
are
discovered. Estimated, there
are 380.000 different species of
plants.
S
The development in science is
also in progress and we are
able to modify some genetic
aspects. Geneticists are very
advanced in the field of
modifying DNA chain. They
develop new techniques and
methods every day to transfer
genes from an organism to
another.
How does the genetic proces work?
When were the techniques developed?
Which are the bacteria used to develop genetic modification?
Which medicines are the best: normal or genetic engineered medicines?
Genetic engneering of plantsfor the production of medicines
Table of contents
Table of contents ..................................................................................................................................... 2
Summary ................................................................................................................................................. 3
Genetic engineering ................................................................................................................................ 4
What is genetic engineering? .............................................................................................................. 4
History.................................................................................................................................................. 4
Techniques .......................................................................................................................................... 4
Recombinant DNA-molecules ......................................................................................................... 4
Eukaryotic cloning and expression systems .................................................................................... 4
Genetic engineering of plants .................................................................................................................. 5
Transformation..................................................................................................................................... 5
Dicotyledonous plants ..................................................................................................................... 5
Monocotyledonous plants ................................................................................................................ 6
Hepatitis B ............................................................................................................................................... 7
Contagion and patho-genesis.............................................................................................................. 7
History.................................................................................................................................................. 7
Vaccines .................................................................................................................................................. 8
History.................................................................................................................................................. 8
New vaccines....................................................................................................................................... 8
How do they work? .............................................................................................................................. 8
Current vaccine ................................................................................................................................... 9
Tobacco and hepatitis B ...................................................................................................................... 9
Potatoes and hepatitis B .................................................................................................................... 10
Comparison genetic engineering medicines and normal medicines ..................................................... 11
conclusion .............................................................................................................................................. 11
References ............................................................................................................................................ 12
Figure list ............................................................................................................................................... 13
Genetic engneering of plantsfor the production of medicines
Summary
Genetic engineering refers to all techniques that transfer genes from one organism to another, to
produce new or modified organisms. The most used general technique is the recombinant DNAtechnique. There also plant specific techniques like transformation by A. tumefaciens.
With these techniques, medicines can be made out of normal plants by modify them. An example from
this ‘genetic medicine’ is the hepatitis B vaccine made from genetic modified tobacco plants or
potatoes.
Hepatitis B is an infectious illness caused by a virus which infects the liver of humans and causes an
inflammation. The virus is spread through the blood through the body. Then , if the immune system
doesn’t response as it should be, chronic infection can arise.
Better is prevent hepatitis B by making vaccines to help the immune system. They contain living
weakened or dead micro-organisms. These micro-organisms will encourage the immune response
without making people sick.
Thanks to the recombinant DNA-technique, the tobacco plants or potatoes can used for making a
hepatitis B vaccine. By bringing a foreign gene in the tobacco or potato, the plant will start to make
antibodies against it. Then the plant can be eaten or making a pill from it, so it’s an oral vaccine.
These days, the vaccine against hepatitis B made from tobacco plants or potatoes is only tested on
mice.
So now is proved that making medicines from genetic modified plants is very useful, they will slowly
conquer the medicine world.
3
Genetic engneering of plantsfor the production of medicines
Genetic engineering
somes. A vector is cut with the
same restriction-endonucleases
as the frag-ment. This clutch
What
is
engineering?
can be made permanently by
another en-zyme: DNA-ligase.
genetic
Everyone knows Dolly the
sheep, the first cloned fullgrown animal in the world. For
a lot of people, it was the first
acquaintance with genetic engineering. This was in 1996, but
genetic engineering existed
even before then.
Genetic engineering refers to all
techniques that artificially move
or transfer genes from one
organism to another, to produce
new or modified organisms.
The target material is the
deoxyribonucleic acid (DNA)
molecule found in all living cells
of organisms, where genetic information
is
stored.
(J.Craig Venter Institute 2004)
History
Genetic
Engineering
first
appeared in 1972, nineteen
years after the discovery of the
DNA structure. It was Paul
Berg, an American scientist,
who produced the first DNA-recombinant molecule. Recombinant DNA is a type of DNA
that is artificially created by
inserting a strand or more of
DNA into a different set of DNA.
These DNA have different
origins, they come from other
organisms. Later, in 1976
Recombinant DNA is a type of
DNA that is artificially created
by inserting a strand or more of
DNA into a different set of DNA.
These DNA have different
origins, they come from other
organisms. bred the first
genetic modified mice. 10 years
after the mice, scientists modify
the first crop, a gene-altered
tobacco. These days, genetic
modification is one of the most
important subjects in the
biotechnology
(E.Wirix 2010;J.Craig Venter
Institute 2004)
Afterwards, the recombinant
DNA-molecule will be inserted
in a living host cell where it
replicates
(cloning).
Techniques
Recombinant DNA-molecules
When a DNA-molecule consists
of DNA coming from different
sources is called a recombinant
DNA-molecule. Genetic modification can be applied in
bacteria, plants and in animals.
The process in plants will be
described more in detail in
chapter 2.
Restriction-endonucleases
(cutting enzymes) cut the
genomic DNA in little fragments. This enzymes recognize
DNA-sequences from 4 to 8
nucleotides long present in the
target DNA molecule. So, a
certain
DNA-molecule
will
always be cut in the same way
by a certain restriction-enzym.
(E.Wirix 2010)
After the cutting, we end up
with restriction-fragments. The
most restriction-endonucleases
split the DNA in a certain way
that the fragments have a
single-stranded piece at the 3’
or 5’ end. These ends are
called
the
‘sticky
ends’.
Each fragment will be inserted
in a carrier molecule, which is
called a vector. A vector can
be: a plasmid, bacteriophages,
viruses or little artificial chromo-
Simple version of recombinant DNA
technique (national health museum 2010)
(E.Wirix 2010)
Eukaryotic
cloning
and
expression systems
These days, it’s possible to
develop recombinant DNAmolecules
which
will
be
inserted in the genome of
multicellular organisms. When a
zygote transforms with the
strange DNA, it will develop in
an organism which contains the
recombinant DNA in all cells. If
we breed with these organisms
we can get transgenic organisms, which contain the
recombinant DNA in all his
cells.
Plant specific techniques like
transformation will be explained
in
the
next
chapter.
(E.Wirix 2010)
Zygote
a term to refer to the cell in a
state between the fusion of
two haploid nuclei during
fertilization
until the first
cleavage.
4
Genetic engneering of plantsfor the production of medicines
Genetic engineering of plants
Genetic engineering is a
technique used to introduce
desired traits into a chosen
organism. To achieve this the
scientist has to insert a specific
gene which will encode for a
protein that is responsible for
the expression of a certain
defined trait. This insertion
followed by the expression of a
new feature is called ‘Transformation’.
It is possible to transform plants
due to their totipotent nature. A
new plant can grow from a
single cell. This means that if
an isolated cell is adjusted, all
the cells of the new plant will
have the new gene. Since all
the cells will be copies of the
adjusted cell. Some examples
of new traits are:
herbicide tolerance, drought
tolerance, resistance to pathogens and insects. But it is also
possible to insert a gene that is
responsible for higher nutrition
values or for the production of
certain products that can be of
interest.
The gene used to introduce the
traits can be of any origin.
There is only one condition, the
trait has to be compatible with
the host organism.
Totipotency
The ability to regenerate from
a single cell to become a full
grown plant.
To be certain that the plant is a
modified organism the desired
transgene will be accompanied
by a herbicide/antibiotic re-
sistance inducing gene. This is
a control mechanism which will
be used after the transformation. By adding the
herbicide or the antibiotic, to
which the modified plant should
be resistant, to the nutrition
medium the scientist can check
if the transformation worked
because only the plants with
the right gene will be able to
grow. The first generation of
transformed plants has to be
grown on a gel-like medium on
a petri dish, It is easier to
control the environment and the
growth factors in which the
transformation can take place
and
allows
the
cell
to
regenerate. Further generations
could be cultivated on the field.
This however is not yet
commonly approved by law.
There are severe rules on the
cultivation of modified plants.
Within Europe the gmo has to
undergo a risk assessment
before the cultivation can be
approved.
(J.A.Thompson 2009)
Transformation
To insert this transgene in the
DNA of the plant the scientist
can chose between a few
techniques, one more favourable than the other.
There is a difference between
the insertion of a gene in
dicotyledonous
and
monocotyledonous plants.
Dicotyledonous plants
There are a few techniques
used to insert a gene in the
genome
of
the
plant.
(J.A.Thompson
2009)
Transformation
tumefaciens
by
A.
There is more and more
progress in the world of plant
genetic manipulation, but we
still use an older method with A.
tumefaciens.
Agrobacterium
tumefaciens(International
Microbial Ecology 2002)
Society
for
This still is a major method of
choice for trans-forming plant
cells. Despite these progresses,
we always work on this bacteria
to get a better understanding of
the mechanism of gene transfer
. A lot of important cereals have
now been transformed using A.
tumefaciens. These plants have
been transformed to gain a
higher tolerance against certain
herbicides or a higher nutrition
value.
(Newell, 2000)
A. tumefaciens seems to be the
best discovery to realize DNA
implantation
into
plant
genomes. Bacterial vectors
such as Eschericia coli have
already been used successfully
as vectors in microbiology
(Kikkert et al., 1999) ; that is
now extended to the world of
botany. These techniques have
been applied on several plants,
such as lettuce (Curtis, 1995),
rice (Hiei, 1997) and tomatoes
(Tzfira et al., 2002). This proves
5
Genetic engneering of plantsfor the production of medicines
that methods with direct gene
transfer, are not the only way
for transforming important crop
plants (Newell, 2000). The
transformation
by
A.
Tumefaciens permits insertion
of specific DNA-sequences into
the plant’s genome. This is a
good reason to choose this
method when compared with
other methods (see below)
although the success rate is not
100% (Gheysen et al., 1998).
There are however some valid
arguments against the validity
of A. tumefaciens mediated
transformation.
Dicotyledonous
plants
are
plants which develop from two
cotyledons in the seed. They
can be recognized by the
branching veins in their leaves.
Dicots of commercial value include many horticultural plants
such as petunias, and crops
such as tobacco, tomatoes,
cotton, soybean and potatoes.
Tobacco, due to its ease of
transformation, initially became
the workhorse of plant genetic
engineering, but more recently
the common wall or thale cress,
Arabidopsis
thaliana,
has
become very popular. It has the
advantage of not requiring
tissue
culture
during
its
transformation.
Tomatoes have been transformed to delay their ripening,
cotton to insect resistance and
herbicide tolerance, soybeans
to improved oil quality and herbicide tolerance, and potatoes
to resist viruses.
Other methods
For many years the only
alternative to A. tumefaciensmediated transformation was
the direct uptake of naked DNA
by plant protoplasts, achieved
by electroporation or mediated
by polyethylene glycol (PEG).
These methods depend on the
ability of plants to regenerate
from protoplasts, which varies
considerably between species.
For example, there are many
parameters to be successful
with PEG technique (such as
ion concentration, molecular
weight and concentration of
PEG, physical configuration of
nucleic acid,…). Linearized
double-stranded plasmid DNA
molecules are expressed and
integrated most efficiently.
Now the most widely used
alternative to transformation by
A. tumefaciens is biolistics.
Other
techniques
exists,
including pollen co-cultivation,
microinjection
of
somatic
embryos and liposome fusion
with
protoplasts.
(J.A.Thompson 2009)
Monocotyledonous plants
These plants require a different
approach to insert a gene.
Transformation
by
A.
tumefaciens
This method is used less
frequently but when it can be
used it is the preferred
technique. The problem here is
that some important monocots,
such as: maize, rice and wheat
are resistant to A. tumefaciens
and cannot be transformed.
There have been some efforts
to alter the A. tumefaciens to
make it able to infect these
monocots. Until now the greatest success has been with rice.
(J.A.Thompson)
Biolistic transformation
“This technique of particle
bombardment, or biolistics, is
the most versatile and effective
way of creating many transgenic plant species, including
elite lines.”
When this technique is used, an
isolated DNA-fragment has to
be coated on a metal particle.
Currently gold and tungsten are
often used metals because of
their inert nature.
The coated particles are shot
into the cell with a gene gun, a
biolistic device driven by a gas,
Helium for example.
When the particles pass
through the cell there is a
chance that the new gene will
be introduced in the genome of
the plant. Previous tests had a
success rate of 54%. This
chance is dependent on several
factors like humidity, duration
temperature, composition of the
chosen particle and the form of
the used DNA-fragment.
Modifying plants
The actual genetic modification, the transfer of foreign genes in the plants own genome is
done by following the next few steps.
-
Mapping = Finding + isolating the gene responsible for the desired characteristics
PCR = copying the isolated gene
Transformation = transfer and insertion of the gene
Creation of a new plant for the modified tissue
Verification:
o Does the gene work?
o Is the gene inherited by the progeny of the plant?
6
Genetic engneering of plantsfor the production of medicines
Hepatitis B
Hepatitis B is an infectious
illness caused by hepatitis B
virus which infects the liver of
primates, including humans,
and causes an inflammation
called hepatitis.
The hepatitis B virus infects the liver of the
human's
body
and
causes
an
inflammation.(Soucaze M. 2009)
Originally known as "serum
hepatitis", the disease has
caused epidemics in parts of
Asia and Africa, and it is
endemic in China. About a third
of the world's population, more
than 2 billion people, have been
infected with the hepatitis B
virus. This includes 350 million
chronic carriers of the virus.
There’s no relationship between Hepatitis A and C with B.
(LCI 2008)
Contagion
genesis
and
patho-
Hepatitis B is spread mainly by
exposure to infected blood or
body secretions. In infected
individuals, the virus can be
found in the blood, semen,
vaginal fluid, breast milk, and
saliva. Hepatitis B is not spread
through food, water, or by
casual contact. Hepatitis B also
may be spread from infected
mothers to their babies at birth
(so-called 'vertical'transmission)
After entering, the Hepatitis B
virus is spread through the
blood through the body. By
adherence to specific sensors
the virus is incorporated in liver
cell but doesn’t damage these.
The immunological response of
the immunocompetent host to
presence of the Hepatitis B
virus, determines the clinical
picture. Cells that fulfill humoral
and cellular processes of the
immune system and also
contain the virus antigen, are
removed.. As a result of a
strong immune response at the
acute stage, an acute hepatitis
can show up. If the immune
response reacts as needed, the
virus is managed. When the immune system doesn’t response
as needed, a chronic infection
cangarise. The incubation period lasts 4 weeks to 6 months
(usually 2 to 3 months). The
variation depends on the
amount of virus in the inoculum,
the route of infection and host
factors such as host immunity.
(LCI 2008;Nettleman M. et al.
2010;Renaldo E. and ph D.
2000)
History
In 1885, a number of cases of '
Serumhepatitis’ were located in
Bremen (Germany) after being
administered the variola vaccine (that contained human
lymph) to workers. Just in the
years forty and fifty of the
previous century a clear distinction was made between
'serumhepatitis' and 'contagious
Jaundice' on the basis of
transmission experiments. In
search of genetic differences,
scientists in 1965 found a
particular protein in blood of
Aboriginals that they called '
Australian-antigen'. This proved
to be the later hepatitis B surface antigen (HBsAg).
The
introduction
of
safe
effective vaccines (plasma-prepared in 1983, and DNA
Transmission experiments
Experiment that examines
the transfer of an infectious
disease from one infected
individual to a susceptible
individual.
vaccines
in
1986)
have
increased the possibilities for
worldwide
suppression
of
hepatitis b virus (HBV) to
introduce vaccination programs
on child age.
7
illustration of hepatitis B virus (university of washington 2008)
Genetic engneering of plantsfor the production of medicines
Vaccines
Our immune system has the
important task to defend the
body. It attacks the pathogens
and eliminates them. Where the
defense fails, a vaccine is the
solution. A vaccine is a
treatment that encourage a
immune
response
without
making the human sick. Most
vaccines are administered in
the form of a shot or a liquid
that is consumed by mouth.
However, some vaccines are
inhaled as aerosols or powders.
(Rijkers G. et al. 2009)
New vaccines
History
Recently we see more and
more the appearance of new
vaccines in the pharmaceutical
market. The improvement of
classical
biochemistry,
recombinant DNA technology,
peptide synthesis, molecular
genetics and protein purification
has laid the foundations for the
development of new, genetically modified vaccines. New
vaccines have a lot of
advantages, but they have also
disadvantages.
The vaccine exists longer than
the most people think. In 1800,
Edward Jenner was the first
one who experimented with
terms like immunology and
vaccination. He saw that
milkmaids, which had smallpox
infection from cows by milking
cows, received no human
smallpox. Jenner thought that
people could made immune to
the human smallpox by infect
them first with cow smallpox.
His way of thinking was right.
But the people were suspicious.
However, after Jenner his results, a big vaccination campaign was set. In the fifties,
doctors started to vaccinate
children against diphtheria,
whooping-cough, tetanus and
polio. These days, 95% of the
Belgian children is vaccinated.
A vaccine helps the immune system to
defend the body(Fitandwell's weblog
2008;Kroosduiker
2009)
First, the new generation
vaccines, would be cheaper,
safer, fewer side effects and
more
effective.
But
a
disadvantage of live vaccines is
to ensure that the virus is
sufficiently attenuated to not
cause disease but still respond
to the immune system to
produce
these
antigens.
Another disadvantage is the
possibility that the vaccine virus
can recombine with other viral
strain.
(Rijkers G., Kroese M., &
Kallenberg M. 2009)
How do they work?
The vaccines can be made of
living weakened or dead microorganisms. With dead microorganisms it’s important that the
antigen, against which the
protective immune response
must be formed, stays intact.
Examples of working vaccines
that exists of dead microorganisms are the bacteria
Bordetella
pertussis,
Salmonella typhi and Vibrio
cholera.
The living weakened microorganisms form more powerful
vaccines than the vaccines
made of dead micro-organisms.
Weakening
or
attenuating
means
that
by
different
techniques a variant has been
made with strong reduced
malignance. Attenuating can be
reached by high temperatures,
bred
micro-organisms
in
another animal species or by
recombinant techniques. With
recombinant techniques it’s
possible
to
use
microorganisms from other animal
species and put relevant
antigens into it for the vaccine.
After this they put the microorganism in other animal
species. There’re a two reasons
that a living weakened microorganisms vaccine is more
effective than vaccines made of
dead micro-organisms. First of
all, the micro-organism can
multiply itself and confront the
immune system with a higher
dose that’s longer present. A
second reason is that in case of
viral
living
vaccines
the
naturally target cells can be
infected. Of course, dead
viruses can’t infect the host cell
8
Genetic engneering of plantsfor the production of medicines
and multiply themselves. So the
immune response that’s been
caused by vaccines made of
living micro-organisms is better
to compare with the natural
immune response. However,
living weakening vaccines are
discouraged by patients with a
less strong defense because a
potential danger provides that
attenuated micro-organisms go
back to their not-attenuated
situation. It gets back to the
originally
malignance.
Examples of living weakened
vaccines are parotitis viruses,
measles viruses and rubella
virus.
If it’s known to which part from
a micro-organisms the protective
immune
responds,
there’s a possibility to use only
this antigen in the vaccine.
These vaccines are called
subunitvaccines. Examples of
this vaccine is the hepatitis B
and tetanustoxoïd vaccine.
category of “subunit vaccines.”
The
gene
encoding
the
hepatitis B surface antigen
(HBsAg) is expressed in yeast
cells grown by fermentation; the
cells are broken, the protein is
collected, and the HBsAg is
caused to refold by chemical
treatment to yield virus-like
particles that can be formulated
for injection. However, it is
technology-intensive so it’s very
expensive.
Tobacco and hepatitis B
The Tobacco plant, is a
perennial herbaceous plant
that’s only found in cultivation. It
commercially grows in a lot of
countries to be processed into
tobacco. The tobacco plant is
easy to recognize at his pink
flowers
and
big
leaves.
(Anon 2008)
Now the different ways of
making vaccines are known,
The next question is how to
make them from modified
plants like the tobacco and
potato. This will be discussed in
the
next
chapter.
(Rijkers G., Kroese M., &
Kallenberg M. 2009)
Vaccines
There are 2 types of vaccines:
-
Injection vaccines
Oral vaccines
Oral vaccines are taken by the
mouth and it is this type of
vaccine that can be produced
by plants.
Current vaccine
The existing vaccine to prevent
HBV infection is a biotechnology product that falls in the
The tobacco plant can be recognized at
his pink flowers and big leaves
(Kroosduiker 2009)
The first ever experimental
immunogenic protein that was
produced in plants, was the
hepatitis B vaccine in tobacco.
Since 1989, antibodies (also
called plantibodies) can be
produced by plants. This give a
lot of possibilities in the passive
immunotherapy.
Passive
immunotherapy means that the
human body doesn’t make the
antibodies by itself, but they are
administered from outside.
For the production of antibodies
against Hepatitis B in tobacco,
first the plant must have the
Hepatitis B surface antigen.
This is a protein that is present
on the surface of the virus.
Therefore,
recombinant
hepatitis B surface antigen
must be inserted in the plant.
This can happen with the help
of a bacteria, in this case
‘Agrobacterium
tumefaciens’
which is a natural carrier of the
Ti-plasmid. This means that Tiplasmid is a vector. The
Hepatitis B surface antigen will
be inserted in the Ti-plasmid
and forms a recombinant
hepatitis B surface antigen.
Now, they put the antigen in the
tobacco plant. The plant brings
the recombinant antigen at
expression so the plant will start
making a lot of antibodies,
which are abbreviated antiHBsAg, to defend himself
against
this
recombinant
hepatitis B surface antigen.
After this process, the leaves of
the plant will be harvested and
the antibodies will be extracted
from the leaves. Then the antiHBsAg will be cleaned and are
now ready to made in to
vaccine.
These days, the vaccine is only
tested in mice by exposed them
to smoke from the recombinant
tobacco plant. T-cells, or also
called the T lymphocytes,
belong to a group of white
blood cells which play an
important role in the immune
response. They were obtained
from mice primed with the
Perennial herbaceous plant
A perennial plant is a plant that lives for more than two years A
herbaceous plant is a plant that has leaves and stems that die
down at the end of the growing season to the soil level
9
Genetic engneering of plantsfor the production of medicines
tobacco-derived
recombinant
hepatitis B surface antigenic
peptide that represents part of
the determinant of hepatitis B
surface antigen.
The mice were administer
tobacco smoke for 3 days, 18
weeks or 28 weeks. Mice
exposed to smoke for 3 days or
18 weeks produced a reduction
in the magnitude and the
duration of the primary immune
response. Mice exposed to
smoke for 28 weeks have a
better immune response. The
results prove that tobacco
smoke
extracts
stimulated
immune responses to tobacco
leaf antigens in mice. Because,
the test on mice was very
successful (the mice become
immune for hepatitis B), the
next big step is testing the
vaccine
on
humans.
(Diederick
2010;G.B.Sunil
KumarT. et al. 2007;I.Smets
2010;M.Keulenmans
2008;Ross I. 2008)
Potatoes and hepatitis B
The
potato
or
Solanum
tuberosum is a starchy tuber
originally from South America.
It’s cultivated all over the world,
and more than thousand
varieties are known but only a
fraction of this number are
cultivated commercially. Most of
all, the potato is used as food,
but in these days full of
techniques, the potato has a
new goal. They are used to
produce
medicines.
(S.E.Smith 2010)
If you have the choice between
a needle in your arm and a few
lunches of (raw) potato chips
containing a vaccine, which
would
you
prefer?
The oral immunogenicity (how
strong it provokes an immune
response)
of
hepatitis
B
recombinant surface antigen
(HBsAg) produced in yeast,
which is a traditional way to
produce the medicine , is
compared to the hepatitis B
recombinant surface antigen in
transgenic
potatoes
(not
cooked or processed). Just like
the tobacco, Ti-plasmids from
the bacteria Agrobacterium
tumefaciens are used to bring
the HBsAg in the potato plant
so that the potato create
antibodies. But in this case,
they
don’t
extract
the
antibodies, they leave them in
the raw potato. Scientists hope
that by eating raw potatoes,
you’re
vaccinated
against
hepatitis B.
So the scientists fed mice three
doses
of
raw
potatoes
containing the hepatitis B
surface antigen (HBsAg) and
also gave them cholera toxin.
Cholera toxin is an oral
adjuvant, which is used to
increase immune responses.
After three weeks, the mice
developed antibodies against
hepatitis B; this response
declined within weeks. But
when the mice were injected
with a low dose of a commercial
vaccine at this point ("low"
meaning not enough to make
them immune), the antibodies
came back to very high levels.
Thus, the potato vaccine had
probably created memory cells
that the injection activated.
Transgenic
plant
material
containing HBsAg gave the
best response in mice (Best
induction of a primary immune
response in mice and preparation of an additional
booster injection of HBsAg).
Protective
levels
of
10
milliunits/ml antibody is ach-
ieved when the transgenic
HBsAg mice were fed with the
HBsAg-transgenic
potatoes
produced HBsAg and you also
get a strong long lasting
secondary antibody response.
The advantage of oral vaccines
are that it’s easy to use and
there’s a better control of
intake. There’s also a better
immune response at the level of
mucosa, which is important for
pathogens that enter enteric,
respiration, or sexual systems.
They stimulate the humoral
immunity that is based on
antibodies. And because the
tradition
vaccine
is
very
expensive : edible crops can be
produced at low cost and can
spot out in areas where the
vaccine is needed. The next
step will be to test the effects of
the potato hepatitis vaccine in
humans. This testing has
already been done with edible
vaccines against the Norwalk
virus and against pathogenic
forms of E.coli, which both
cause diarrhea. Ultimately, a
cheap
plant
vaccine
for
hepatitis B could help the two
billion people who are infected,
many of them in developing
countries.
(C.J.Arntzen
2001;G.B.Sunil
KumarT.,
R.Ganapathi,
&
V.A.Bapat
2007)
A simple potato can prevent a
infectious illness like Hepatitis B. (Drent
E.
2010)
10
Genetic engneering of plantsfor the production of medicines
Comparison
medicines
genetic
engineering
Genetic engineering medicines
Controversial
Cheaper
Intake by food possible
The table shows us some comparisons of genetic engineering
medicines and normal medicines. But the subject genetic
engineering is nowadays very
controversial. Genetics, used in
medicine can also be dangerous. Scientists have to be
careful because by trying to
cure a disease, they can also
increase the risk of upgrading a
more dangerous one. For
example, if they introduce a
gene which will eliminate a
medicines
and
normal
Normal medicines
People think it’s more safe
Expensive
Only intake by pills, injections
disease, this gene could also
make another disease stronger.
But the genetic engineering
medicines that are officially on
the market are well tested and
safe. The normal medicines are
more expensive because of the
highly priced chemicals used
for processing the medicines.
For genetic engineering medicines you also need to process
but the materials that are used
are very cheap. Plants and
bacteria can be easy cultivated.
Than the intake of medicines.
The normal medicines, that we
mostly now, are oral in taken by
pills or injections. The genetic
engineering medicines allows
the intake by food. Because of
the two last advantages for
genetic engineering medicines
it’s a great opportunity for
solving vaccine shortage and
the scarcity of medicines in the
whole world.
conclusion
As shown above the genetic
engineering medicines have
more advantages than normal
medicines. But it’s still a
controversial
subject.
The
techniques are not yet 100%
developed, but are already
used in different continents. It’s
mostly practiced in America and
less in Europe. Though, a lot of
scientists are working on it.
Genetic engineering medicines are mostly used in
America, but Europe is following (Spök A. 2008)
Genetic engineering medicines
are also cheap. So it will help
moving forward the third world
countries.
Especially
the
hepatitis B vaccine will reduce
the number of liver infections.
In this article are two plants
discussed but there are a lot of
different plants that can be
used.
A lot of different plants can be used for making the
medicines.(Spök A. 2008)
11
Genetic engneering of plantsfor the production of medicines
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