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.

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.

How is biotechnology used in Medicine?

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

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

Why Hunt for Human Gene Disorders?

Few common examples of human diseases caused by

defective genes:

Disease Genetic defect

hemophilia A absence of clotting factor VIII

cystic fibrosis defective protein

muscular dystrophy defective muscle protein

sickle-cell disease defective beta globin

hemophilia B absence of clotting factor IX

severe combined immunodeficiency (SCID)

cell-mediated immune responses nor is able to make antibodies.

Genetic Engineering of a Milk Protein

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.

What is Gene Therapy?

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.

How it done?

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.

Two types of Gene Therapy "platforms":

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 patient5.Able to handle a wide range of therapeutic genes6.Able to demonstrate a dose-response relationship7.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

How does gene therapy work?

Types of viruses are currently used as vectors in gene therapy:

retroviruses, adenovirusesadeno-associated viruses andHerpes 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

Types of vectors

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).

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.

What is the current status of gene therapy

research?

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/techresources/Human_Genome/medicine/genetherapy.shtml

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

“http://www.medicalnewstoday.com/articles/42339.php

What is the current status of gene therapy

research?

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 long-term 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 factors have kept gene therapy from becoming an effective treatment for genetic

disease?

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 ?

What are some of the ethical considerations for using gene

therapy?

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:

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?

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

What are some recent developments in gene therapy

research?

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

Additional Notes:

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

Gene Therapy Links and Research Institutes:

• Therapeutic protein• www.icr.org/article/428/• www.marketresearch.com/

product/display.asp?productid=1118842&g=1

• 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)

Gene Therapy Links and Research Institutes: