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Chapter 11
Medical Biotechnology and
Gene Therapy
BTEC 3301
How 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.
How is biotechnology used
in Medicine?
 There are more than 350 biotechnologybased 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.
Therapeutic proteins
• Proteins made by genetic engineering
processes that patients cannot make
themselves due to defective genes
• Therapeutic proteins can be produced
by
– Bacteria
– Animals
– Plants
• With genetic manipulation, pigs, cows,
goats, and other animals can produce
human proteins in its milk
• Proteins can also be engineered in
eggs
• Drug delivery is simple and
inexpensive
Why 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 >200 are enzymatic defects
Few common examples of human
diseases caused by defective genes:
Disease
hemophilia A
cystic fibrosis
muscular dystrophy
sickle-cell disease
hemophilia B
severe combined
immunodeficiency (SCID)
Genetic defect
absence of clotting factor VIII
defective protein
defective muscle protein
defective beta globin
absence of clotting factor IX
cell-mediated immune
responses nor is able to make
antibodies.
Genetic Engineering of a
Milk Protein
What is Gene Therapy?
It encompasses repairing or replacing
defective genes and making tumors
more susceptible to other kinds of
treatment. Thus, gene therapy’s
potential for preventing and curing
disease is vast
What 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"
What 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
What 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:
What 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
 liposomes—injectable 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.
What 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, it’s
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.
How 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.
Two 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)
Two 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.
How 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 .
How 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.
How 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
How does gene therapy work?
The 7 requirements of a successful gene
delivery system:
 A practical gene delivery system (the
vector) must meet seven characteristics:
1. Efficient in introducing the genes to
recipient cells
2. Capable of achieving long term
expression or short term expression
(depending on use)
3. Flexible with respect to the target
tissues it can deliver to
How does gene therapy work?
The 7 requirements of a successful gene delivery system:
A practical gene delivery system (the vector) must meet
seven characteristics:
4.Harmless to the patient
5.Able to handle a wide range of
therapeutic genes
6.Able to demonstrate a dose-response
relationship
7.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
Types 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:
Types 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
Types 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.
Types 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.
Types 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 & eye infection
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.
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.
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).
What 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
What 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) also
known as Urea cycle.
 Jesse 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.
The urea cycle is the sole source of
endogenous production of arginine
and it is the principal mechanism
for the clearance of waste
nitrogen resulting from protein
turnover.
http://www.ornl.gov/sci/techresource
s/Human_Genome/medicine/geneth
erapy.shtml
What 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.

Gene Therapy X-SCID Poses Substantial
Cancer Risk
What 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 (XSCID), also known as "bubble baby
syndrome:
 “http://www.medicalnewstoday.com/articles/
42339.php
What 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.
What 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 longterm benefits. Patients will have to
undergo multiple rounds of gene therapy.
What 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 makes it difficult for
gene therapy to be repeated in patients.
What 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 and become virulent
What 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.
What 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?
What are some of the ethical
considerations for using gene therapy?
Some Questions to Consider...............
 Is somatic gene therapy more or less ethical
than germline gene therapy?


Preliminary attempts of gene therapy are
exorbitantly expensive.
Who will have access to these therapies? Who
will pay for the cost ?
Gene 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:
Reading Materials
• It is a MUST that you read the rest of the
slides which gives more examples of
gene therapies and disasters
• What are some recent developments in
gene therapy research?
What 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).
What 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).
What 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).
What 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).
What 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).
What 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
Additional 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, 266:66-71 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.
Additional 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
Gene 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:
Gene Therapy Links and Research
Institutes:
• Genetic Disease Information
•http://www.fortunecity.com/victorian/orwell/1133/linklife.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
–
Animations of Induction of Genes (Gene Therapy)
–
Animations of Problems in Gene Therapy
• Therapeutic protein
• www.icr.org/article/428/
• www.marketresearch.com/product/di
splay.asp?productid=1118842&g=1
Gene 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, let’s not neglect IUPUI •Riley Hospital Wells Center (Children's cancer research)