Some
people don’t believe that gene therapy should be used in cases where the
disease can be helped by traditional methods. They think that gene therapy
should be a last resort, used by doctors when all else fails. Others believe
that gene therapy shouldn’t be used to manipulate the genetic make-up of an
individual for personal gain. Instead gene therapy should be used to help an
individual afflicted with a disease that is fatal. CF is just one example. The whole issue of cloning is
taking this technology too far or waiting for the technology to be well
established and verified by the relevant authorities.

The
main advantage of gene therapy is that it has the capability of producing a
normal life for the individual. The gene therapy is a fast-growing field of its
own and is being developed more and more every day. To oppose the argument of
the therapy being used excessively, when actively used it will probably be
regulated to prevent unnecessary treatment that may be harmful to the patient.

The
disadvantages of gene therapy are that no one knows the long-term effects of a
gene pool that exists after. Technology is not yet advanced enough to be used for
a range of diseases.

These
methods could be a breakthrough for cystic fibrosis and provides the best hope
for a life saving treatment. This is because rather than treating the symptoms,
the therapies treat the cause of cystic fibrosis. Also, cystic fibrosis is a
single-gene disease rather than a disease that is caused by multiple genes,
which means the procedure has a higher chance of success. One issue is that
there are many point of the complex treatments where the method could fail.
Also replacing the gene in one cell is neither effective nor sufficient.

Germ
line therapies that work have the possibility of eradicating a disease from a
family line and in the long term from the population.  Somatic therapy is looked at as less
controversial than germline therapy as it is not a permanent effect. However
repeated treatments are needed once the tissues die. One thing which may remain
unclear is the effect of the new gene that is inserted and whether it will have
any other effects. Depending on where the new gene inserts, since it is a
random insertion, it can be harmful or helpful. There are still a number of
hurdles to overcome. For one, the immune response to the foreign object
introduced into the tissues as it is recognised as an invader. Viral vectors
also carry risks of toxicity and an inflammatory response. A major issue is the
genome is very sensitive, hence introducing a piece of the DNA in the wrong
place e.g. in the middle of a tumour suppressor gene it could theoretically
induce a tumour.

With
somatic therapy as the tissue dies, so does the gene. This means that this
procedure does not have any permanent effects and only helps that one sufferer.

 Adenoviruses are currently used as vectors and
are responsible for a number of respiratory illnesses but since they are
weakened they are harmless to use for gene therapy The DNA incorporates itself
into the tissues cells. Ex vivo (meaning exterior) is done outside of the body
initially, but it later transferred into the patient. The gene is placed in
viral DNA and is combined with the target cells (commonly bone marrow or blood
cells) which are removed from the patient. This combination is then cultured
before being reintroduced into the body.

In vivo is done inside of the
body. The DNA is directly inserted into the patient’s tissue. The DNA is held
in a vector, but new research has now suggested that liposomes could be used in
the near future. The virus is pathogenically
disabled (it is no longer harmful to the cell it infects)
and incapable of reproducing itself. Liposomes are small, hollow spheres of
fatty molecules that are capable of carrying DNA inside of them. A liposome can fuse with the
cell membrane, releasing its contents into the cell interior. Plasmid DNA containing the
therapeutic gene is incubated with the empty liposomes under specific
conditions. The negatively charged DNA binds to the positively charged
liposomes and the plasmids are absorbed. Liposomes containing plasmid DNA are
called lipoplexes. The lipoplexes can subsequently
enter the cells of interest, and thus introduce the therapeutic DNA into the
cells. The use of lipoplexes for the treatment of cystic fibrosis is currently
being studied as well. In cystic fibrosis the lipoplexes that are administered
using an aerosol spray into the patient’s lungs, contain the gene for a
functional version of the CFTR. Lipoplexes are not as effective as viral
vectors in introducing genes into cells. To improve them, scientists are
attempting to integrate some viral proteins into the outer surfaces of
lipoplexes. More specifically, the viral proteins that recognize and bind to
specific molecules on the host cell’s surface, are being incorporated.

In
somatic therapy, body cells are targeted within one individual where the mutated
gene is substituted for a non-defective gene. Somatic refers to all cells in
the body except gametes (egg and sperm cells). This is further separated into
two approaches; in vivo and ex vivo. Cells targeted are gametes or
unspecialised cells- often from bone marrow.

 

 

6)   
The
cell makes the new protein using the new gene

5)   
The
vector then injects the new gene into the nucleus, where DNA synthesis occurs

4)   
The
vesicle is then broken down, leaving the DNA behind.

3)   
A
vesicle is formed inside the cell which contains both the vector and DNA

2)   
The
vector the binds to the cell membrane so the DNA can enter the cell.

1)   
Modified
DNA is injected into a vector. A vector is a method of transport for the DNA
and is recognised as the body’s own so there is no immune response to the
‘alien’ DNA.

With germline therapy, the baby’s
genome is altered before it has been born. This can be done in two ways. The
genome can be treated pre-embryo directly or the gametes of the two parents are
altered. This therapy is often permanent as when the sufferer goes to reproduce
later on, the ‘normal’ gene is inherited and passed down through generations.

A new line of research is gene
therapy. This is where defective genes are either replaced or deleted.
Branching off from this are two procedures; somatic and germline. Both these
methods ultimately result in the altering of the CFTR gene.

Lung transplantation becomes
imperative as lung function declines. However, both lungs must be transplanted
as the other lung may still have bacteria and it is possible for the
transplanted lung to become infected.

Cystic fibrosis can be diagnosed
through many methods. It is possible to diagnose through new-born screening,
genetic testing and sweat testing. Abnormal concentrations of immunoreactive
trypsinogen in the blood would require a sweat test. Levels of this could be
higher in the presence of one mutated CFTR gene.

CFTR is attached to the outer
membrane of cells in the exocrine glands, lungs, pancreas and sweat glands. In
the sweat glands the protein is responsible for the movement of chloride ions,
this means when the CFTR isn’t functioning the ions cannot move into the cells.
These negatively charged ions which are accumulating bind to sodium forming a
salt. This salt is lost in excess via sweat of sufferers. Due to the thick and
sticky mucus, cilia movement is limited hence clearance is limited and is
inhabited by bacteria causing infections. Due to weakened immune systems, individuals
with cystic fibrosis are often isolated from each other to limit the spread of
bacterial strains.

Cystic fibrosis is caused by a
mutation in the CFTR protein. Over 1000 mutations can result in cystic
fibrosis. The most common mutation is the deletion of a codon (three
nucleotides) which removes the amino acid phenylalanine. Naturally different mutations
mean different levels of defects, severity and symptoms. For example, some
mutations create proteins that do not fold normally and another result in a
protein which is too short etc. The CFTR protein is a chloride ion channel
which is imperative in creating mucus, sweat and digestive fluids.

Both male and female sufferers often
have problems with fertility but can have children with assisted reproductive
techniques. Men are usually infertile due to abnormal sperm with poor motility.
Women have difficulties due to thickened cervical mucus which would be
difficult for sperm to travel through and reach the ovum.

Screenings can be done to check if
the child will be a sufferer. Symptoms often surface in infancy, one main
factor is poor growth as it is multi-factorial and are due to chronic lung
infections, poor absorption and increased metabolism due to frequency of
illnesses. Many of the symptoms are interlinked and are caused as a chain
result. The CFTR protein causes the build up of thick, sticky mucus which then
clogs up the lungs and results in inflammation and infection which can cause
permanent damage in terms of structure and function for example in the airways
(bronchiectasis) hence the difficulty in breathing. Other problems which would
arise from structural changes are coughing up blood, high blood pressure and hypoxia.
The volume of oxygen which is taken in is also affected as lack of oxygen also
leaves the sufferer fatigued as the cells aren’t receiving oxygen for
respiration. The lungs are not the only areas affected. Facial pain, nasal
drainage, headaches and fever are caused by mucus blocking the sinuses.

There are currently no known cures
for cystic fibrosis, instead symptoms are managed to improve quality f life.
Lung infections are treated by antibiotics which can be given in several ways
from inhalation to mouth. In extreme cases a lung transplant could be considered
an option. Non-invasive and therapeutic techniques such as chest therapy is
used to unclog and clear airways but isn’t effective in the long run. 

Cystic fibrosis is a genetic
disorder which is inherited in an autosomal recessive manner. It primarily affects
the lungs but also other organs including the pancreas, kidneys, liver and intestines.
Caused by the presence of mutations in both copies of the gene CFTR (cystic
fibrosis transmembrane conductance regulator) protein, which means a person
only suffers from this disorder if the genes are recessive. If only one of the
two genes are functioning and has not been mutated, this means the person is a
carrier. On the surface carriers have normal functioning of the production of
mucus, sweat and other fluids. When the CFTR protein is not functional,
secretions are usually thin. Common long-term problems for sufferers consist of;
breathing difficulties, lung and chest infections due to the build-up of thick
and sticky mucus, coughing of mucus. Less common signs are poor growth despite
seemingly normal food intake, infertility and fatty stool.