Chapter 11 Medical Biotechnology and Gene Therapy

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Chapter 11 Medical Biotechnology and Gene Therapy
BTEC 3301
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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.

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How 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.

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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 gt200 are enzymatic defects

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Few common examples of human diseases caused by
defective genes
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What 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

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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"

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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

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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

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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
• 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.

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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, 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.

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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.

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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)

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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. (CF, DMD - diseases
  where the tissue generally cannot be removed and
  replaced).

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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 .

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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.

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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

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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
• 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

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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
• 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

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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

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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

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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.

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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.

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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.

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• 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.

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• 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.

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• 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).

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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

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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).
  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.

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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.

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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 (X-SCID), also known as
  "bubble baby syndrome."

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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.

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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 long-term benefits. Patients will have to
  undergo multiple rounds of gene therapy.

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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 it has seen before makes it
  difficult for gene therapy to be repeated in
  patients.

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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.

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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.

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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?

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What 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?

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Reading Materials it is a MUST that you read the
followings

• What are some recent developments in gene therapy
  research?

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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).

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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).

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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).

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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).

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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).

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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

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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, 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.

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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

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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

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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

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Gene 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

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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, lets not neglect IUPUI -
• Riley Hospital Wells Center (Children's cancer
  research)