Title: Chapter 11 Medical Biotechnology and Gene Therapy
1Chapter 11 Medical Biotechnology and Gene Therapy
BTEC 3301
2How is biotechnology used in Medicine?
- Biotechnology is responsible for hundreds of
medical diagnostic tests that detect disease
earlier, enduring a more accurate, beneficial and
cost-effective outcome to disease.
3How is biotechnology used in Medicine?
- There are more than 350 biotechnology-based drug
products and vaccines currently in human trials
and more than 100 therapeutic drug products
already on the market, with many more in
development. - Some of these drugs are designed to treat cancer,
heart disease, diabetes, multiple sclerosis,
HIV-AIDS and obesity.
4Why Hunt for Human Gene Disorders?
- 6 dysfunctional genes per person
- 30 pediatric admissions to hospital due to
genetic problems - 12 adult admissions to hospital due to genetic
problems - 70-75 of products, prevention and gene therapy
goes for human species - There are 4000 known genetic disorders and of
these gt200 are enzymatic defects
5Few common examples of human diseases caused by
defective genes
6What is Gene Therapy?
- It encompasses repairing or replacing defective
genes and making tumors more susceptible to other
kinds of treatment. Thus, gene therapys
potential for preventing and curing disease is
vast
7What is Gene Therapy?
- Gene therapy is the insertion of genetic material
into cells to prevent, control, or cure disease,
especially genetic disorders. - Gene therapy is "a therapeutic technique in which
a functioning gene is inserted into the somatic
cells of a patient to correct an inborn genetic
error or to provide a new function to the cell"
8What is Gene Therapy?
- There have been many human gene therapy clinical
trials, involving over 700 patients world-wide
(by 1996), for several different diseases
including several cancers. - In the USA the trials must be approved by the
Recombinant DNA Advisory Committee (RAC) and the
FDA
9What is Gene Therapy?
- Gene therapy is a technique for correcting
defective genes responsible for disease
development. Researchers may use one of several
approaches for correcting faulty genes - Carriers of therapeutic genes include
10What is Gene Therapy?
- Carriers of therapeutic genes include
- harmless viruses that have undergone genetic
alteration and can carry selected genetic
material into human cells and - liposomesinjectable microscopic fatty globules
that can enclose and protect DNA segments (e.g.,
a "suicide gene" for insertion into cancer
cells.) - Genes, which are carried on chromosomes, are the
basic physical and functional units of heredity.
11What is Gene Therapy?
- Carriers of therapeutic genes include
- Genes are specific sequences of bases that encode
instructions on how to make proteins. - Although genes get a lot of attention, its the
proteins that perform most life functions and
even make up the majority of cellular structures. - When genes are altered so that the encoded
proteins are unable to carry out their normal
functions, genetic disorders can result.
12How it done?
- A normal gene may be inserted into a nonspecific
location within the genome to replace a
nonfunctional gene. This approach is most common. - An abnormal gene could be swapped for a normal
gene through homologous recombination. - The abnormal gene could be repaired through
selective reverse mutation, which returns the
gene to its normal function. - The regulation (the degree to which a gene is
turned on or off) of a particular gene could be
altered.
13Two types of Gene Therapy "platforms"
- 1. Ex vivo therapies
- Ex vivo therapies involve treating cells that
have been removed from a patient with a
functional gene to restore protein activity. The
cells are then returned to the patients to have a
therapeutic benefit. (ADA, sickle cell disease -
blood cell diseases or immune system diseases)
14Two types of Gene Therapy "platforms"
- 2. In vivo therapies
- The use of in vivo therapies generally involves
injection or inhalation of a product that
contains a therapeutic gene together with some
sort of gene delivery system. (CF, DMD - diseases
where the tissue generally cannot be removed and
replaced).
15How does gene therapy work?
- Gene Delivery System
- Therapeutic genes and
- an efficient gene delivery system
- a way to get the correct genes into the correct
cells .
16How does gene therapy work?
- Gene Delivery System
- Viruses attack their hosts to insert their
genetic material into the genetic material of the
host. - This genetic material contains instructions to
produce these viruses. The host cell will carry
out these instructions and produce the viruses.
This is how viruses spread, in general.
17How does gene therapy work?
- Gene Delivery System
- In addition to the instructions producing the
components of the virus itself, viruses can carry
additional genes containing instructions for
creating other kinds of proteins. - In theory, if we insert a gene that is missing
from a patient in a virus, and infect that
patient with the virus, the virus will spread the
missing gene in all the cells of the patient. - The missing gene is now replaced and the disease
is cured
18How does gene therapy work?
- The 7 requirements of a successful gene delivery
system - A practical gene delivery system (the vector)
must meet seven characteristics - Efficient in introducing the genes to recipient
cells - Capable of achieving long term expression or
short term expression (depending on use) - Flexible with respect to the target tissues it
can deliver to
19How does gene therapy work?
- The 7 requirements of a successful gene delivery
system - A practical gene delivery system (the vector)
must meet seven characteristics - Harmless to the patient
- Able to handle a wide range of therapeutic genes
- Able to demonstrate a dose-response relationship
- Supplied in a form familiar and comfortable to
the medical community. - The biggest hurdle to overcome (still) of gene
therapy is finding effective, safe vectors
20Types of vectors
- Types of viruses are currently used as vectors in
gene therapy - retroviruses,
- adenoviruses
- adeno-associated viruses and
- Herpes simplex viruses
- They differ in their mechanisms of action and
results
21Types of vectors
- viruses are currently used as vectors in gene
therapy - Retroviruses
- A class of viruses that can create
double-stranded DNA copies of their RNA genomes.
These copies of its genome can be integrated into
the chromosomes of host cells. Human
immunodeficiency virus (HIV) is a retrovirus
22Types of vectors
- Three types of viruses are currently used as
vectors in gene therapy - Adenoviruses
- A class of viruses with double-stranded DNA
genomes that cause respiratory, intestinal, and
eye infections in humans. The virus that causes
the common cold is an adenovirus.
23Types of vectors
- Three types of viruses are currently used as
vectors in gene therapy - Adeno-associated viruses
- A class of small, single-stranded DNA viruses
that can insert their genetic material at a
specific site on chromosome 19.
24Types of vectors
- Three types of viruses are currently used as
vectors in gene therapy - Herpes simplex viruses
- A class of double-stranded DNA viruses that
infect a particular cell type, neurons. Herpes
simplex virus type 1 is a common human pathogen
that causes cold sores.
25- Non-virus-mediated delivery system
- Direct introduction
- There are several nonviral options for gene
delivery. - The simplest method is the direct introduction of
therapeutic DNA into target cells. - This approach is limited in its application
because it can be used only with certain tissues
and requires large amounts of DNA.
26- Non-virus-mediated delivery system
- Artificial lipid
- Another nonviral approach involves the creation
of an artificial lipid ,a liposome, which carries
the therapeutic DNA which delivers the DNA
through the target cell's membrane.
27- Non-virus-mediated delivery system
- Special cell receptors as chemical links
- Therapeutic DNA also can get inside target cells
by chemically linking the DNA to a molecule that
will bind to special cell receptors. - Once bound to these receptors, the therapeutic
DNA constructs are engulfed by the cell membrane
and passed into the interior of the target cell
(Less effective).
28What is the current status of gene therapy
research?
- The Food and Drug Administration (FDA) has not
yet approved any human gene therapy product for
sale. - Current gene therapy is experimental and has not
proven very successful in clinical trials. - Little progress has been made since the first
gene therapy clinical trial began in 1990
29What is the current status of gene therapy
research?
- In 1999, gene therapy suffered a major setback
with the death of 18-year-old Jesse Gelsinger.
Jesse was participating in a gene therapy trial
for ornithine transcarboxylase deficiency (OTCD).
He died from multiple organ failures 4 days after
starting the treatment. His death is believed to
have been triggered by a severe immune response
to the adenovirus carrier.
30What is the current status of gene therapy
research?
- Another major blow came in January 2003, when the
FDA placed a temporary halt on all gene therapy
trials using retroviral vectors in blood stem
cells.
31What is the current status of gene therapy
research?
- FDA took this action after it learned that a
second child treated in a French gene therapy
trial had developed a leukemia-like condition. - Another child developed leukemia-like conditions
(August 2002 ) when tested for combined
immunodeficiency disease (X-SCID), also known as
"bubble baby syndrome."
32What factors have kept gene therapy from becoming
an effective treatment for genetic disease?
- Short-lived nature of gene therapy
- Before gene therapy can become a permanent cure
for any condition, the therapeutic DNA introduced
into target cells must remain functional and the
cells containing the therapeutic DNA must be
long-lived and stable.
33What factors have kept gene therapy from becoming
an effective treatment for genetic disease?
- Short-lived nature of gene therapy
- Problems with integrating therapeutic DNA into
the genome and the rapidly dividing nature of
many cells prevent gene therapy from achieving
any long-term benefits. Patients will have to
undergo multiple rounds of gene therapy.
34What factors have kept gene therapy from becoming
an effective treatment for genetic disease?
- Immune response
- Anytime a foreign object is introduced into human
tissues, the immune system is designed to attack
the invader. - The risk of stimulating the immune system in a
way that reduces gene therapy effectiveness is
always a potential risk. - Furthermore, the immune system's enhanced
response to invaders it has seen before makes it
difficult for gene therapy to be repeated in
patients.
35What factors have kept gene therapy from becoming
an effective treatment for genetic disease?
- Problems with viral vectors
- Viruses, while the carrier of choice in most gene
therapy studies, present a variety of potential
problems to the patient -toxicity, immune and
inflammatory responses, and gene control and
targeting issues. - In addition, there is always the fear that the
viral vector, once inside the patient, may
recover its ability to cause disease.
36What factors have kept gene therapy from becoming
an effective treatment for genetic disease?
- Multigene disorders
- Conditions or disorders that arise from mutations
in a single gene are the best candidates for gene
therapy. - Unfortunately, some the most commonly occurring
disorders, such as heart disease, high blood
pressure, Alzheimer's disease, arthritis, and
diabetes, are caused by the combined effects of
variations in many genes. - Multigene or multifactorial disorders such as
these would be especially difficult to treat
effectively using gene therapy.
37What are some of the 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?
38What are some of the ethical considerations for
using gene therapy?
- Some Questions to Consider...............
- Is somatic gene therapy (which is done in the
adult cells of persons known to have the disease)
more or less ethical than germline 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?
39Reading Materials it is a MUST that you read the
followings
- What are some recent developments in gene therapy
research?
40What are some recent developments in gene therapy
research?
- Some Questions to Consider...............
- University of California, Los Angeles, research
team gets genes into the brain using liposomes
coated in a polymer call polyethylene glycol
(PEG). The transfer of genes into the brain is a
significant achievement because viral vectors are
too big to get across the "blood-brain barrier."
This method has potential for treating
Parkinson's disease. See Undercover genes slip
into the brain at NewScientist.com (March 20,
2003).
41What are some recent developments in gene therapy
research?
- Some Questions to Consider...............
- RNA interference or gene silencing may be a new
way to treat Huntington's. Short pieces of
double-stranded RNA (short, interfering RNAs or
siRNAs) are used by cells to degrade RNA of a
particular sequence. If a siRNA is designed to
match the RNA copied from a faulty gene, then the
abnormal protein product of that gene will not be
produced. See Gene therapy may switch off
Huntington's at NewScientist.com (March 13, 2003).
42What are some recent developments in gene therapy
research?
- Some Questions to Consider...............
- 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. See Subtle gene therapy tackles blood
disorder at NewScientist.com (October 11, 2002).
43What are some recent developments in gene therapy
research?
- Some Questions to Consider...............
- Gene therapy for treating children with X-SCID
(sever combined immunodeficiency) or the "bubble
boy" disease is stopped in France when the
treatment causes leukemia in one of the patients.
See 'Miracle' gene therapy trial halted at
NewScientist.com (October 3, 2002).
44What are some recent developments in gene therapy
research?
- Some Questions to Consider...............
- Researchers at Case Western Reserve University
and Copernicus Therapeutics are able to create
tiny liposomes 25 nanometers across that can
carry therapeutic DNA through pores in the
nuclear membrane. See DNA nanoballs boost gene
therapy at NewScientist.com (May 12, 2002).
45What are some recent developments in gene therapy
research?
- Some Questions to Consider...............
- Sickle cell is successfully treated in mice. See
Murine Gene Therapy Corrects Symptoms of Sickle
Cell Disease from March 18, 2002, issue of The
Scientist. - Do not ignore
- Know how it happens
46Additional Notes
- Breast cancer
- The discovery of the gene BRCA1 was reported in
September 1994 after an intense and competetive
search, by a team of researchers led by Mark
Skolnick of the University of Utah and Myriad
Genetics Inc. (Science, 26666-71 and 120-2,
1994). - BRCA1 (and the related BRCA2) are tumor
suppressor genes that, when working normally,
keep cell growth in check. - When one copy of the tumor suppressor gene is
damaged or lost, uncontrolled cell growth occurs. - Women who inherit the faulty gene may have up to
an 85 percent risk of developing breast cancer.
47Additional Notes
- Xenotransplantation
- There is a worldwide shortage of organs for
clinical transplantation and, sadly, many
patients due to receive new organs die on the
waiting list. - Recent advances in understanding the mechanisms
of transplant organ rejection have brought us to
a stage where it is reasonable to consider that
organs from other species, probably pigs, may
soon be engineered to minimize the risk of
serious rejection and used as an alternative to
human tissues, possibly ending organ shortages. - Other procedures, some of which are being
investigated in early clinical trials, aim to use
cells or tissues from other species to treat
life-threatening illnesses such as cancer, AIDS,
diabetes, liver failure and Parkinson's disease
48Gene Therapy Links and Research Institutes
- For more information on different types of
genetic disease and gene therapy - Must visit these sites to enrich your knowledge
about what are being done around you, if not for
the present but for our children
49Gene Therapy Links and Research Institutes
- For more information on different types of
genetic disease and gene therapy - Must visit these sites to enrich your knowledge
about what are being done around you, if not for
the present but for our children
50Gene Therapy Links and Research Institutes
- Genetic Disease Information
- http//www.fortunecity.com/victorian/orwell/1133/l
inklife.html - http//www.ornl.gov/sci/techresources/Human_Genome
/medicine/genetherapy.shtml - www.geneclinics.org
- MEDLINEplus Genes and Gene Therapy - Access
news, information from the National Institutes of
Health, clinical trials information, research,
and more. - Recombinant DNA and Gene Transfer - National
Institutes of Health Guidelines - Questions and Answers about Gene Therapy - A fact
sheet from the National Cancer Institute. - Introduction to Gene Therapy - An overview by
Access Excellence. - A Gene Therapy Primer - Introduction to gene
therapy from the bio.com. - Gene Therapy and Your Child - From KidsHealth for
Parents. - Pioneering gene treatment gives frail toddler a
new lease of life - Gene Transfer - An overview of gene therapy
science issues, ethical concerns, and regulation
and policy from the Genetics Public Policy
Center. - Cures - An introduction to gene therapy provided
by discoveryhealth.com. - Delivering the Goods - An article describing the
different types of gene therapy approaches. From
October 2, 2000, issue of The Scientist. - How to Turn on a Gene - An article from Wired
Magazine. - How Viruses Are Used in Gene Therapy - From The
DNA Files, a series of radio programs from Sound
Vision Productions. - Human Gene Therapy Present and Future - A Human
Genome News article. - Gene Therapy - A News Hour with Jim Lehrer
transcript covering the death of gene therapy
patient, Jesse Gelsinger (February 2, 2000). - Animations from the Tokyo Medical University
Department of Pediatrics Genetics Study Group
51Gene Therapy Links and Research Institutes
- Gene Therapy Research Institute
- The Institute for Human Gene Therapy (IHGT) -
University of Pennsylvania Philidelphia - Virtual Lecture on gene therapy with James M.
Wilson - Gene Therapy Courses at U Penn
- (Some very sad news September 17, 1999 - patient
Jesse Gelsinger dies while receiving gene
therapy) - The Pittsburgh Human Gene Therapy Center (PHGTC)
- UCSD Program in Human Gene Therapy
- University of North Carolina Chapel Hill (UNC-CH)
Gene Therapy Center - And of course, lets not neglect IUPUI -
- Riley Hospital Wells Center (Children's cancer
research)