gene therapy- a modern weapon to rely upon to fight diseases

1. Presented by:
DR. SUDESHNA RAY
2ND YEAR PGT
DEPARTMENT OF BIOCHEMISTRY
IMS & SUM HOSPITAL
GENE THERAPY
THE HOPE BEYOND MYTH

2. GENE THERAPY
• Definition: An experimental technique for
correcting defective genes that are responsible
for disease development
• The most common form of gene therapy
involves inserting a normal gene to replace an
abnormal gene
• Other approaches used:
 Replacing a mutated gene that causes
disease with a healthy copy of the gene.
 Inactivating, or “knocking out,” a mutated gene
that is functioning improperly.
 Introducing a new gene into the body to help
fight a disease

3. • Researchers are studying gene therapy for a
number of diseases, such as
 Severe combined immuno-deficiencies
(SCID)
 Hemophilia
 Blindness
 Parkinson's disease
 Cancer
 HIV

4. HISTORY AND DEVELOPMENT
• 1960: The concepts of Gene Therapy was introduced
• 1970: Friedmann and Roblin author of a paper in Science titled "Gene
therapy for human genetic disease” made the first attempt to perform gene
therapy
• 1990:
 The first approved gene therapy case at the National Institute of Health,
U.K. It was performed on a four year old girl named Ashanti DeSilva. It
was a treatment for a genetic defect that left her with an immune system
deficiency
 New gene therapy approach repairs errors in messenger RNA derived
from defective genes. This technique has the potential to treat the blood
disorder Thalassaemia, Cystic fibrosis, and some cancers
 Sickle cell disease is successfully treated in mice

5. • 1960: The concepts of Gene Therapy was introduced
• 1970: Friedmann and Roblin author of a paper in Science titled "Gene
therapy for human genetic disease” made the first attempt to perform
gene therapy
• 1990:
 The first approved gene therapy case at the National Institute of
Health, U.K. It was performed on a four year old girl named
Ashanti DeSilva. It was a treatment for a genetic defect that left
her with an immune system deficiency
 New gene therapy approach repairs errors in messenger RNA
derived from defective genes. This technique has the potential to
treat the blood disorder Thalassaemia, Cystic fibrosis, and some
cancers
 Sickle cell disease is successfully treated in mice

9. GERM LINE GENE THERAPY
• Results in permanent changes.
• Potential for offering a permanent therapeutic effect for all who inherit
the target gene.
• The therapy is passed to the offsprings and there is possibility of
eliminating some diseases from a particular family.
• Also raises controversy:
 Some people view this type of therapy as unnatural.
 Others have concerns about the technical aspects.

11. SOMATIC GENE THERAPY
• Affects only the targeted cells in the patient, and is not
passed to future generations.
• Short-lived because the cells of most tissues ultimately die
and are replaced by new cells.
• Transporting the gene to the target cells or tissue is also
problematic.
• Appropriate and acceptable for many disorders, including
cystic fibrosis, muscular dystrophy, cancer, and certain
infectious diseases.

12. TYPES OF SOMATIC GENE THERAPY

15. 1. VIRAL VECTOR
2. NON VIRAL VECTOR
BASIC METHODS OF GENE THERAPY

16. • GT utilizes the delivery of DNA into cells,
which can be accomplished by a number of
methods.
• The two major classes of methods :
Recombinant Viruses – VIRAL VECTOR
Naked DNA or DNA Complexes – NONVIRAL
VECTOR

17. VIRAL VECTOR
Viruses have evolved a way of encapsulating
and delivering their genes to human cells in a
pathogenic manner. Scientists have tried to
harness this ability by manipulating the viral
genome to remove disease-causing genes and
insert therapeutic ones .

18. VIRUS
• Viruses bind to their hosts and introduce their
genetic material into the host cell.
• Plausible strategy for gene therapy is by removing
the viral DNA and using the virus as a vehicle to
deliver the therapeutic DNA.
• The viruses used are altered to make them safe,
although some risks still exist with gene therapy.

19. TYPES OF VIRUS
• Many GT clinical trials rely on retroviruses or adenoviruses
to deliver the desired gene.
• Other viruses used as vectors include adeno-associated
viruses, retroviruses, pox viruses, alphaviruses, and herpes
viruses.
• Differ in how well they transfer genes to the cells they
recognize and are able to infect, and whether they alter the
cell’s DNA permanently or temporarily.

21. VIRAL VECTOR
• Are a tool commonly used by molecular biologists to deliver genetic material into
cells.
• Can be performed in vivo or in vitro.
• Viruses have evolved specialized molecular mechanisms to efficiently transport
their genomes inside the cells they infect.
• Delivery of genes by a virus is termed transduction and the infected cells are
described as transduced.

23. NON VIRAL VECTOR
• Methods of non-viral gene delivery
have also been explored using physical
(carrier-free gene delivery) and
chemical approaches (synthetic vector-
based gene delivery).

24. PHYSICAL METHOD
• Physical approaches, including
Needle injection
Electroporation
Gene gun
Hydrodynamic delivery
employ a physical force that permeates the cell
membrane and facilitates intracellular gene
transfer

25. I. NAKED DNA
• The simplest method of non-viral transfection.
• Clinical trials carried out on intramuscular injection of a
naked DNA plasmid have occurred with some success;
however, the expression has been very low in comparison
to other methods of transfection.
• This success, however, is very much low in comparison to
more efficient methods for delivery of the naked DNA such
as electroporation and the use of a "gene gun", which
shoots DNA coated gold particles into the cell using high
pressure gas.

26. CHEMICAL METHODS
THAT ENHANCE THE
DELIVERY OF GENE THERAPY
-LIPOPLEXES & POLYPLEXES-

27. LIPOPLEXES
• DNA must be protected from damage before its entry
into the cell.
• Plasmid DNA can be covered with lipids in an
organized structure like a micelle or a liposome
complexed with DNA it is called a lipoplex.
• 3 types of lipids:
• anionic (negatively charged)
• neutral
• cationic (positively charged)

28. Initially, anionic and neutral lipids :
• -were used for the construction of lipoplexes for synthetic vectors.
• -but, there is little toxicity associated with them
• -they are compatible with body fluids
• -there was a possibility of adapting them to be tissue specific
Cationic lipids, due to their positive charge,
• -naturally complex with the negatively charged DNA.
• -they easily interact with the cell membrane
• -endocytosis of the lipoplex occurs
• -DNA is released into the cytoplasm.
• -The cationic lipids also protect against degradation of the DNA by the cell.

29. COMMON USES OF LIPOPLEXES
• In gene transfer into cancer cells, where the
supplied genes have activated tumor
suppressor control genes in the cell.
• decrease the activity of oncogenes.
• useful in transfecting respiratory epithelial
cells, so they may be used for treatment of
genetic respiratory diseases such as cystic
fibrosis.

30. POLYPLEXES
• Complexes of polymers with DNA are called
polyplexes
• consist of cationic polymers and their production is
regulated by ionic interactions.
• large difference compared to lipoplexes is that
polyplexes cannot release their DNA load into
the cytoplasm,
• co-transfection with endosome-lytic agents such as
inactivated adenovirus must occur (to lyse the
endosome that is made during endocytosis, the
process by which the polyplex enters the cell)

31. SUCCESS CASES OF GENE THERAPHY
PARKINSON’S
DISEASE
BLINDNESS

32. GENE THERAPY CURES BLINDNESS
• Cure blindness of inherited condition
• Leber’s congenital amaurosis
- inherited disease caused by an abnormality in a gene
called RPE65.
- The condition appears at birth or in the first few months
of life and causes progressive loss of vision.

33. HOW IT WORKS??
• Uses a harmless virus
• enable access to the cells beneath the retinas of patients
• By using a very fine needle
-safe in an extremely fragile tissue and can improve vision in a
condition previously considered wholly untreatable.
• http://www.youtube.com/watch?v=d_YJZn-ft_Q

34. GENE THERAPY REDUCES PARKINSON’S DISEASE SYMPTOMS
• it significantly improved the intensity of the symptoms
such as tremors, motor skill problems, and rigidity.
• Main overactive brain region: the subthalamic nucleus
should be introduced with gene
• that would produce GABA—an inhibitory chemical—then
they could potentially suppress that brain region and
alleviate tremors.

35. HOW IT WORKS??
• Done with local anaesthesia, used a harmless,
inactive virus [adeno associated virus]
• Deliver the GAD gene into patient’s subthalamic
nucleus
• The gene instructs cells to begin making GABA
neurotransmitters to re-establish the normal chemical
balance that becomes dysfunctional as the disease
progresses.

36. • The genetic testing, screening and research in finding the
availability of certain gene is very controversial.
• May increase the rate of abortion if prenatal test regarding baby
with genetic disease is done.
• The cost is very high and the patient might need an insurance to
cover the treatment.
• Cosmetic industry may monopolize this gene therapy if it is used
in enhancing beauty and in vanishing the ageing effect, rather
than used for treatment of a disease.
DISADVANTAGES OF
GENE THERAPY

37. • Give a chance of a normal life to baby born with
genetic disease.
• Give hope of healthy life to cancer patient.
• For certain disease that do not have any cure
except gene therapy, it could save many lives.
ADVANTAGES OF GENE THERAPY

38. • In 1990, gene therapy suffered a major setback woth the death
of 18 year old Jesse Gelsinger. Jesse was participating in a
gene therapy trial for ornithine transcarboxymylase deficiency.
He died from multiple organ failure 4 days after starting the
treatment. His death was believed to have been triggered by a
severe immune response to the adeno virus carrier.
• In 2003, FDA placed a temporary halt on all gene therapy trials
after a child treated in a French gene therapy trial developed a
Leukemia-like condition. But later this child and another who
had developed a similar condition in August 2002 had been
successfully treated by gene therapy for X-linked SCID.

39. ETHICAL QUESTIONS
Because gene therapy involves making changes to the body’s set of basic instructions, it
raises many unique ethical concerns. The ethical questions surrounding gene therapy
include:
• How can “good” and “bad” uses of gene therapy be distinguished?
• Who decides which traits are normal and which constitute a disability or disorder?
• Will the high costs of gene therapy make it available only to the wealthy?
• Could the widespread use of gene therapy make society less accepting of people who
are different?
• Should people be allowed to use gene therapy to enhance basic human traits such as
height, intelligence, or athletic ability?
• The idea of germ-line gene therapy is controversial. While it could spare future
generations in a family from having a particular genetic disorder, it might affect the
development of a fetus in unexpected ways or have long-term side effects that are not
yet known. Because people who would be affected by germ-line gene therapy are not yet
born, they can’t choose whether to have the treatment. Because of these ethical
concerns, the U.S. Government does not allow federal funds to be used for research on
germ-line gene therapy in people.

40. • Some of the institutes in India where researches in Gene
Therapy are done –
• CMC, Vellore
• Vivekananda Institute of Medical Sciences, Kolkata
• Madras Diabetes Research Foundation, Chennai