Gene therapy, Gene therapy methods, ADA deficiency, SCID, Cloning. Gene therapy successful?

1. DR. ISHAN Y. PANDYA
PHD. BIOTECHNOLOGY
G.E.E.R. FOUNDATION,
GANDHINAGAR, GUJARAT, INDIA
E-MAIL:
GENOMES.WORLD37@GMAIL.CO
M
GENE THERAPY

2. Topics for Discussion
1. What is gene therapy.
2. History
3. How it works
4. Problems
5. Success
6. Cancer and gene therapy
7. Current status
8. Research
9. Ethical consideration
10. References

3. What is Gene Therapy
- It is a technique for correcting defective
genes that are responsible for disease
development
 There are four approaches:-
1. normal gene inserted to compensate for a
nonfunctional gene.
2. An abnormal gene traded for a normal gene
3. An abnormal gene repaired through selective reverse
mutation
4. Change the regulation of gene pairs

4. Target tissue for gene delivery
 Bone marrow
 Muscle
 Liver
 Other tissue (Brain, trachea)

5. Gene Therapy

7. The Beginning…
 In the 1980s, Scientists began to look into gene
therapy.
 They would insert human genes into a bacteria cell.
 Then the bacteria cell would transcribe and translate the
information into a protein
 Then they would introduce the protein into human cells

8.  September 14, 1990 @ NIH, French Anderson
and R. Michael Blaese perform the first GT Trial-
Ashanti (4 year old girl)
Her lymphocytes were gene-altered
(~109) ex vivo  used as a vehicle for
gene introduction using a retrovirus
vector to carry ADA gene (billions of
retroviruses used)
Cynthia (9 year old girl) treated in same
year
 Problem: WBC are short-lived, therefore
treatment must be repeated regularly.

9. The First Case
 The first gene therapy was performed on
September 14th, 1990
 Ashanti DeSilva was treated for SCID
 Sever combined immunodeficiency
 Doctors removed her white blood cells, inserted the
missing gene into the WBC, and then put them back into
her blood stream.
 This strengthened her immune system
 Only worked for a few months 

10. September 17, 1999
Ornithine transcarbamylase (OTC) deficiency
-Urea cycle disorder (1/10,000 births).
-Encoded on X chromosome
-Females usually carriers, sons have
disease
Urea cycle = series of 5 liver enzymes that rid
the body of ammonia (toxic breakdown
product of protein).
-If enzymes are missing or deficient,
ammonia accumulates in the blood and
travels to the brain (coma, brain damage or
death).

11. How It Works
 A vector delivers the therapeutic gene into a
patient’s target cell
 The target cells become infected with the viral
vector
 The vector’s genetic material is inserted into the
target cell
 Functional proteins are created from the
therapeutic gene causing the cell to return to a
normal state

12. Picture 

13. - Mutagensis
Inactivation of tumor suppressor genes
Activation of proto-oncogene
Greater risk one allele needed
Retrovirus life cycle makes insertion at
active gene more likely.
Risks of gene therapy

14. Unsuccessful Gene therapies
 Jesse Gelsinger, a gene therapy patient who lacked
ornithine transcarbamylase activity, died in 1999.
 Within hours after doctors shot the normal OTC gene
attached to a therapeutic virus into his liver, Jesse
developed a high fever. His immune system began
raging out of control, his blood began clotting,
ammonia levels climbed, his liver hemorrhaged and a
flood of white blood cells shut down his lungs.
 One problem with gene therapy is that one does not
have control over where the gene will be inserted into
the genome. The location of a gene in the genome is of
importance for the degree of expression of the gene and
for the regulation of the gene (the so-called "position
effect"), and thus the gene regulatory aspects are
always uncertain after gene therapy

15. Successful Gene Therapy for Severe
Combine Immunodeficiency
 Infants with severe combined
immunodeficiency are unable to mount an
adaptive immune response, because they have a
profound deficiency of lymphocytes.
 severe combined immunodeficiency is inherited
as an X-linked recessive disease, which for all
practical purposes affects only boys. In the other
half of the patients with severe combined
immunodeficiency, the inheritance is autosomal
recessive — and there are several abnormalities
in the immune system when the defective gene
is encoded on an autosome.

16. Continued…..
 A previous attempt at gene therapy for
immunodeficiency was successful in children
with severe combined immunodeficiency due to
a deficiency of adenosine deaminase.
 In these patients, peripheral T cells were
transduced with a vector bearing the gene for
adenosine deaminase.
 The experiment was extremely labor intensive,
because mature peripheral-blood T cells were
modified rather than stem cells, and the
procedure therefore had to be repeated many
times to achieve success.

17. Therapy Trial For Parkinson's
Disease
 Neurologix a biotech company announced that
they have successfully completed its landmark
Phase I trial of gene therapy for Parkinson's
Disease.
 This was a 12 patient study with four patients in
each of three dose escalating cohorts. All
procedures were performed under local
anesthesia and all 12 patients were discharged
from the hospital within 48 hours of the
procedure, and followed for 12 months.
 Primary outcomes of the study design, safety
and tolerability, were successfully met. There
were no adverse events reported relating to the
treatment.

18. Parkinson's Disease Cont.
 The gene transfer procedure utilized the AAV
(adeno-associated virus) vector, a virus that has
been used safely in a variety of clinical gene
therapy trials, and the vehicle that will be used
in all of the company's first generation products,
including epilepsy and Huntington's disease.
 In its Parkinson's disease trial, Neurologix used
its gene transfer technology.

20. Gene Therapy for Cancer
 It cause either loss of tumour suppressor gene
(p53) due to mutation in this gene,insertion of
copy of wild type p53 result in death of tumour
cells.
 If it cause by overexpression of an oncogene (K-
RAS), an antisence gene has disable
overexpression of this gene.
 Therapy using immunostimulatory genes (IL-2)
may lead to distruction of tumour cells.

21.  In all approaches need to efficient
delivery system.
 No gene deliver is 100% efficient.
 Adenovirus vectors are efficient.
 Clinical trials appropriate ethically
for incurable cancers, it few
weeks/months, rather than years in
genetic diseases.
 Approval of trials is also easy.

22. Methods for gene therapy of
cancer
 Viruses
 Naked DNA (vector-free)
 Liposomes
 Protein-DNA complexes
 Gene gun
 Calcium phosphate precipitation
 Electroporation
 Intracellular microinjection

24.  University of California, Los Angeles, research team gets genes
 into the brain using liposomes coated in a polymer called (PEG).
 Potential for treating parkisons disease.
 RNA interference or gene silencing may be a new way to treat
Huntington's
 New gene therapy approach repairs errors in messenger RNA
 derived from defective genes. Technique has potential to treat
the
 blood disorder thalassaemia, cystic fibrosis, and some cancers
Current progress

25. • Gene therapy for treating
children with X-SCID (severe
combined
immunodeficiency) or the "bubble
boy" disease is stopped in
France when the treatment causes
leukemia in one of the patients.
Current progress

26. Recent Developments
- RNA interference or gene silencing to treat
Huntington’s
 siRNAs used to degrade RNA of particular sequence
 abnormal protein wont be produced
 blood disorder thalassaemia, cystic fibrosis, and
some cancers.
Create tiny liposomes that can carry therapeutic
DNA through pores of nuclear membrane
 Sickle cell successfully treated in mice

27. Current Status
 FDA hasn’t approved any human gene therapy
product for sale
Reasons:
 In 1999, 18-year-old Jesse Gelsinger died from
multiple organ failure 4 days after treatment
for omithine transcarboxylase deficiency.
 Death was triggered by severe immune response to
adenovirus carrier
 January 2003, halt to using retrovirus vectors
in blood stem cells because children developed
leukemia-like condition after successful
treatment for X-linked severe combined
immunodeficiency disease

28. More than 5000 patients have
been treated in last ~12 years
worldwide.

29. Nanotechnology for Drug Targeting and Gene
therapy
 Selective delivery of drug to specific area in body
is necessary.
 It involve use of nanoparticles (< 1 µm, usually
<500 nm in diameter).
 These particulates include not only solid
structure ( form of nanocapsules),but also
liposomes and emulsion, that can reach specific
tissue.
 Used for vaccine administration and for
Diagnostic imaging.

30. Gene Therapy using Nanotechnology
 Gene delivery using 3 systems:-
 1.viral vectors
 2. non-viral vectors (particles & polymers)
 3. Gene guns.( Direct injection)
 Using nanoparticles targets for liver
hepatocytes, endothelial cells, spleen and lymph
nodes..

31. Non viral vectors for Gene therapy based
on nanoparticles
System Animal Reute Fate
Naked DNA Mouse Intravenous Liver
Liposome Rat Intravenous Liver
Cationic lipid Mouse, men Nasal spray Lung deposition

32. What are some recent developments in
gene therapy research?
Results of world's first gene therapy for inherited
blindness show sight improvement. 28 April 2008. UK
researchers from the UCL Institute of Ophthalmology and
Moorfields Eye Hospital NIHR Biomedical Research Centre have
announced results from the world’s first clinical trial to test a
revolutionary gene therapy treatment for a type of inherited
blindness. The results, published today in the New England Journal
of Medicine, show that the experimental treatment is safe and can
improve sight. The findings are a landmark for gene therapy
technology and could have a significant impact on future treatments
for eye disease.
(May 1, 2007): A team of British doctors from Moorfields Eye
Hospital and University College in London conduct first human gene
therapy trials to treat Leber's congenital amaurosis, a type of
inherited childhood blindness caused by a single abnormal gene. The
procedure has already been successful at restoring vision for dogs.

34. Ethical considerations for using gene
therapy
Some Questions to Consider
What is normal and what is a disability or disorder, and
who decides?
Are disabilities diseases? Do they need to be cured or
prevented?
Does searching for a cure demean the lives of
individuals presently affected by disabilities?

35. Is somatic gene therapy (which is done in the adult
cells of persons known to have the disease) more or
less ethical than germ line gene therapy (which is done
in egg and sperm cells and prevents the trait from
being passed on to further generations)? In cases of
somatic gene therapy, the procedure may have to be
repeated in future generations.
Preliminary attempts at gene therapy are exorbitantly
expensive. Who will have access to these therapies?
Who will pay for their use?

37. Conclusion:-

38. REFERENCES
 1. Gene cloning by T.A.BROWN.
 2. Biotechnology and genomics by P.K.Gupta
 3.Molecular biotechnology by B.R. Glick
 3. www.google.com
 4. www.wikipedia.com