Gene therapy

1. GENE
THERAPY

2. What is Gene Therapy?
• It is intracellular delivery of genes to
generate a therapeutic effect by correcting
an existing abnormality.
• The Human Genome Project provides
information that can be used to help replace
genes that are defective or missing in people
with genetic diseases.

3. What is the outcome of gene
therapy?
1. GENE AUGMENTATION THERAPY
2. TARGETED MUTATION CORRECTION
3. INHIBITION OF GENE EXPRESSION
4. GENE THERAPY TO ACHIEVE
PHARMACOLOGICAL EFFECTS

4. STEPS IN GENE THERAPY
1. Identification of the defective gene.
2. Cloning of normal healthy gene.
3. Identification of target cell / tissue / organ.
4. Insertion of the normal functional gene into the
host DNA.

5. METHODS OF GENE DELIVERY
1. PHYSICAL METHODS:
-Parenteral injection
-Microinjection
-Aerosol
-Gene gun
2. CHEMICAL METHODS:
-Calcium phosphate
-Liposomes
3. BIOLOGICAL METHODS:
Viral Vectors like
-Retrovirus -Adenovirus -HSV

6. • METHODS OF GENE DELIVERY
contd…
4. NEO-ORGAN IMPLANTS
5. TISSUE TRANSPLANTATION
6. HUMAN ARTIFICIAL CHROMOSOMES

7. How to introduce the genes ?
Two Approaches to deliver genes:
1. Ex vivo approach
2. In vivo approach

9. 1. Ex vivo approach:
-Target cells are removed from the body and grown in
vitro.
-The gene is then introduced into the cultured cells.
-These cells are then re-introduced into the same
individual
-Examples: Fibroblast cells, Hematopoietic cells.

10. IN -VIVO

11. 2. In vivo approach:(Direct GeneTransfer)
-Cloned therapeutic gene is introduced directly
into the affected tissue, without removing cells
from the body.
-Specially designed vehicles are needed.
-Examples are: Lungs, Brain

12. Where to introduce the genes ?
Somatic cells or the Germ line cells are the
cells to accept the introduced genes.
TYPES OF GENE THERAPY:
1. SOMATIC CELL THERAPY
2. GERM LINE THERAPY

13. 1.SOMATIC CELL THERAPY:
• Insertion of therapeutic gene into somatic cells like
fibroblasts,myoblasts,epithelial cells, nervous cells,glial
cells etc.
• This can correct the genetic defect in the patient
• However,in somatic cell therapy, Transgene cannot be
passed on to the siblings etc.

14. 2. GERMLINE THERAPY:
• Introduction of the foreign gene into germ cells like
sperm / ovum / fertilized egg.
• Results in expression of modified features in both
somatic as well as germ cells of the offspring.
• Considered unethical, and is not advocated in humans.

15. COMMON VECTORS USED FOR GENE
THERAPY:
• 1.Retro viruses
• 2. Adeno viruses
• 3. Liposomes

16. 3.LIPOSOMES:
• These are lipid bilayers surrounding an aqueous vesicle.
• Can be used to introduce foreign DNA into a target cell.
Advantages:
• Safer when compared to Viral vectors.
• Can carry large DNA molecules.
Disadvantages:
• Inefficient transfer.
• Transient expression.

19. Accomplishments of Gene
Therapy
• Severe combined
Immuno deficiency
(SCID)- It is caused by
the deficiency of
adenosine Deaminase
enzyme. The first trial
of gene therapy was
done on this disease.
Follow up studies show
the presence of normal
immune functions in
recipients compatible
with life.

20. Some results of gene therapy:
1. Severe Combined Immuno Deficiency:
Adenosine Deaminase deficiency: First attempt at gene therapy.
2. Hemophilia A & Hemophilia B:
-Ex vivo method using fibroblasts
-Clinical improvement was present.
3. Cystic Fibrosis:
-In vivo trials with Transmembrane Conductance
Regulator CFTR.

21. Targets for gene therapy
Genetic disorders –
1) Duchenne Muscular dystrophy
2) Cystic fibrosis
3) Familial hypercholesterolemia
4) Hemophilia
5) Haemoglobinopathies
6) Gaucher’s disease
7)Albinism
8) Phenyl ketonuria.

22. Acquired diseases
• Cancers
• Infectious disease- HIV
• Neurological disorders
• Cardiovascular diseases
• Rheumatoid arthritis
• Diabetes mellitus

23. RISKS OF GENE THERAPY
• 1.Adverse reactions due to the virus or
new genes.
• 2.Activation of proto-oncogene leading to
formation of oncogene.
• 3.Introduction of a mutation to the next
generation.

24. GENE THERAPY (Summary)
• Steps in Gene therapy
• Approaches:
- Ex-vivo -In-vivo
• Types:
-Somatic cell therapy -Germ line
therapy
• Methods of delivery:
-Physical -Chemical -Biological etc
etc
• Strategies.