GENE THERAPY S.RAM PRAKASH IIIrdBSC BIOTECHNOLOGY, AYYA NADAR JANAKI AMMA COLLEGE, SIVAKASI, TAMIL NADU.

1. S.RAM PRAKASH
18UT38
IIIrd BSC BIOTECHNOLOGY
GENE THERAPY
(ANIMAL BIOTECHNOLOGY AND STEM
CELLS)

2. What is Gene Therapy?
 Human gene therapy seeks to modify or manipulate the expression
of a gene or to alter the biological properties of living cells for
therapeutic use .
 Gene therapy is a technique that modifies a person’s genes to treat
or cure disease. Gene therapies can work by several mechanisms:
 Replacing a disease-causing gene with a healthy copy of the gene
 Inactivating a disease-causing gene that is not functioning properly
 Introducing a new or modified gene into the body to help treat a
disease
 Gene therapy products are being studied to treat diseases including
cancer, genetic diseases, and infectious diseases.

3. How Gene Therapy Works
 Gene therapy can be performed both inside and
outside the body. This infographic illustrates in simple
terms how gene therapy works inside the body.
 Sometimes the whole or part of a gene is defective or
missing from birth, or a gene can change or mutate
during adult life. Any of these variations can disrupt
how proteins are made, which can contribute to health
problems or diseases.
 In gene therapy, scientists can do one of several
things depending on the problem that is present. They
can replace a gene that causes a medical problem
with one that doesn’t, add genes to help the body to
fight or treat disease, or turn off genes that are
causing problems.

5.  There are two different types of gene therapy
depending on which types of cells are treated:
 Somatic gene therapy: transfer of a section of
DNA to any cell of the body that doesn’t produce
sperm or eggs. Effects of gene therapy will not be
passed onto the patient’s children.
 Germline gene therapy: transfer of a section of
DNA to cells that produce eggs or sperm. Effects of
gene therapy will be passed onto the patient’s
children and subsequent generations.

6. There are two types of gene therapies:
 I. Ex vivo gene therapy:
 This involves the transfer of genes in cultured
cells (e.g., bone marrow cells) which are then
reintroduced into the patient.
 II. In vivo gene therapy:
 The direct delivery of genes into the cells of a
particular tissue is referred to as in vivo gene
therapy.

7. Ex Vivo Gene Therapy:
The ex vivo gene therapy can be applied to only selected tissues
(e.g., bone marrow) whose cells can be cultured in the
laboratory. The technique of ex vivo gene therapy involves the
following steps (Fig. 13.2).
1. Isolate cells with genetic defect from a patient.
2. Grow the cells in culture.
3. Introduce the therapeutic gene to correct gene defect.
4. Select the genetically corrected cells (stable trans-formants)
and grow.
5. Transplant the modified cells to the patient.
The procedure basically involves the use of the patient’s own
cells for culture and genetic correction, and then their return back
to the patient. This technique is therefore, not associated with
adverse immunological responses after transplanting the cells.
Ex vivo gene therapy is efficient only, if the therapeutic gene
(remedial gene) is stably incorporated and continuously

9. In Vivo Gene Therapy:
 The direct delivery of the therapeutic gene (DNA) into the target cells
of a particular tissue of a patient constitutes in vivo gene therapy
(Fig. 13.6). Many tissues are the potential candidates for this
approach. These include liver, muscle, skin, spleen, lung, brain and
blood cells. Gene delivery can be carried out by viral or non- viral
vector systems. The success of in vivo gene therapy mostly depends
on the following parameters
 i. The efficiency of the uptake of the remedial (therapeutic) gene by
the target cells.
 ii. Intracellular degradation of the gene and its uptake by nucleus.
 iii. The expression capability of the gene.
 In vivo gene therapy with special reference to gene delivery systems
(viral, non-viral) with suitable examples is described.

11. Risks
 Gene therapy has some potential risks. A gene can't easily be
inserted directly into your cells. Rather, it usually has to be
delivered using a carrier, called a vector.
 The most common gene therapy vectors are viruses because
they can recognize certain cells and carry genetic material into
the cells' genes. Researchers remove the original disease-
causing genes from the viruses, replacing them with the genes
needed to stop disease.
 This technique presents the following risks:
 Unwanted immune system reaction. Your body's immune
system may see the newly introduced viruses as intruders and
attack them. This may cause inflammation and, in severe
cases, organ failure.
 Targeting the wrong cells. Because viruses can affect more
than one type of cells, it's possible that the altered viruses may
infect additional cells — not just the targeted cells containing
mutated genes. If this happens, healthy cells may be
damaged, causing other illness or diseases, such as cancer.

12.  Infection caused by the virus. It's possible that once
introduced into the body, the viruses may recover their original
ability to cause disease.
 Possibility of causing a tumor. If the new genes get inserted in
the wrong spot in your DNA, there is a chance that the insertion
might lead to tumor formation.
 The gene therapy clinical trials underway in the U.S. are
closely monitored by the Food and Drug Administration and
the National Institutes of Health to ensure that patient safety
issues are a top priority during research.