IN THE NAME OF GODIN THE NAME OF GOD

Islamic Azad University of FalavarjanIslamic Azad University of Falavarjan

Department of BiologyDepartment of Biology

BiotechnologyBiotechnology

Dr. Keivan Beheshti MaalDr. Keivan Beheshti Maal

Gene TherapyGene Therapy

Mahzad TabeshMahzad TabeshNovember 2010November 2010

List of contentsList of contents

Genetic disorderGenetic disorder Gene therapyGene therapy Types of GTTypes of GT Gene delivery systemsGene delivery systems Gene transfer vectorsGene transfer vectors Genetic disorders treated with GTGenetic disorders treated with GT Wound healing with GTWound healing with GT Immunology of GTImmunology of GT

What is genetic disorderWhat is genetic disorder??

Genes are made of DNA-the code of life.Genes are made of DNA-the code of life.

Changes in sequence determine the inherited Changes in sequence determine the inherited differences between each of us.differences between each of us.

Some changes may cause serious disease like Cystic Some changes may cause serious disease like Cystic Fibrosis, Muscular Dystrophy and…Fibrosis, Muscular Dystrophy and…

So genetic disorders are medical conditions caused by So genetic disorders are medical conditions caused by an error in a person’s genetic material.an error in a person’s genetic material.

What is gene therapyWhat is gene therapy??

GT is the use of genes as GT is the use of genes as medicine.medicine.

Thus GT can be defined as the Thus GT can be defined as the use of genetic manipulation use of genetic manipulation for treatment of diseases, for treatment of diseases, instead of treating the instead of treating the symptoms of them. symptoms of them.

How does GT workHow does GT work??

There are 3 main steps in each GT trial:There are 3 main steps in each GT trial:

1. Isolate and clone the gene of interest.1. Isolate and clone the gene of interest. 2. Insert the gene into a vector to produce a 2. Insert the gene into a vector to produce a

“Chimera”.“Chimera”. 3. Insert the Chimera into the patient’s body cells.3. Insert the Chimera into the patient’s body cells.

So functional proteins are created from therapeutic So functional proteins are created from therapeutic gene, causing the cell to return to a normal state.gene, causing the cell to return to a normal state.

Approaches for correcting faulty genes Approaches for correcting faulty genes in GTin GT

An abnormal gene could be swapped for a normal An abnormal gene could be swapped for a normal gene.gene.

The abnormal gene could be repaired, returning the The abnormal gene could be repaired, returning the gene to it’s normal function.gene to it’s normal function.

The regulation (the degree to which a gene is The regulation (the degree to which a gene is expressed) of a particular gene could be altered.expressed) of a particular gene could be altered.

Types of gene therapyTypes of gene therapy

Somatic GT:Somatic GT: It will only change somatic It will only change somatic

cells in the body of the person cells in the body of the person being treated.being treated.

Germ line GT:Germ line GT: The therapeutic genes are The therapeutic genes are

transferred into the germ line transferred into the germ line cells (such as egg and sperms).cells (such as egg and sperms).

Types of gene delivery systemsTypes of gene delivery systems In-vivo:In-vivo: Genes will be delivered through a vector directly into Genes will be delivered through a vector directly into

the cells, while they are in the bodythe cells, while they are in the body..

Ex-vivo:Ex-vivo: Delivery of genes to the cells will be out of the body.Delivery of genes to the cells will be out of the body.

Vectors of gene therapyVectors of gene therapy Viral vectors:Viral vectors:• RetrovirusesRetroviruses• AdenovirusesAdenoviruses• Adeno-associated virusesAdeno-associated viruses• Herpes viruses…Herpes viruses…

Non-viral vectors:Non-viral vectors:• Naked DNANaked DNA• Liposomes Liposomes • DNA-Gold particle bombardment (gene gun)… DNA-Gold particle bombardment (gene gun)…

Examples of treated diseases with GTExamples of treated diseases with GT Severe Combined Severe Combined

Immunodeficiency Disease Immunodeficiency Disease (SCID)(SCID)

• Failure to develop functional T and B Failure to develop functional T and B lymphocytes due to the absence of lymphocytes due to the absence of Adenosine Deaminase (ADA).Adenosine Deaminase (ADA).

• Accumulation of nucleotide metabolites= Accumulation of nucleotide metabolites= Toxic to developing T lymphocytes.Toxic to developing T lymphocytes.

• Death due to untreated severe infections.Death due to untreated severe infections.

• GT aims at delivering ADA gene into the GT aims at delivering ADA gene into the lymphocytes in the peripheral blood.lymphocytes in the peripheral blood.

Cystic FibrosisCystic Fibrosis• The most common congenital The most common congenital

disease;the child’s lungs and disease;the child’s lungs and pancreas and intestines become pancreas and intestines become clogged with thick mucusclogged with thick mucus. .

• Defective gene: Cystic Fibrosis Defective gene: Cystic Fibrosis Transmembrane Conductance Transmembrane Conductance Regulator gene.Regulator gene.

• CFTR makes a protein that CFTR makes a protein that controls the movement of salt controls the movement of salt and water in and out of the cells and water in and out of the cells in the body.in the body.

• GT aims at delivering CFTR GT aims at delivering CFTR gene directly into the epithelial gene directly into the epithelial cells lining airways in lungs.cells lining airways in lungs.

Familial Familial Hypercholesterolemia (FH)Hypercholesterolemia (FH)

• Patients have greatly elevated levels Patients have greatly elevated levels of serum cholesterol and suffer of serum cholesterol and suffer from heart attacks early in life. from heart attacks early in life.

• FH is caused by absence or grossly FH is caused by absence or grossly malfunctioning low-density malfunctioning low-density lipoprotein (LDL) receptors.lipoprotein (LDL) receptors.

• GT aims at delivering LDL GT aims at delivering LDL receptor gene into the hepatocytes receptor gene into the hepatocytes in the liver.in the liver.

Color BlindnessColor Blindness• A condition in which certain colors A condition in which certain colors

cannot be distinguished.cannot be distinguished.

• Red-Green CB is the most Red-Green CB is the most common form(99%).common form(99%).

• CB is the result of one or more of CB is the result of one or more of the cone cell color coding the cone cell color coding structures being absent or not structures being absent or not functioning properly.functioning properly.

• Usually CB is caused by absence of Usually CB is caused by absence of certain pigments (Opsin) in certain pigments (Opsin) in photoreceptor cells of Retina.photoreceptor cells of Retina.

• GT aims at delivering specific GT aims at delivering specific Opsin gene into the cone cells of Opsin gene into the cone cells of the Retina in the eye.the Retina in the eye.

Ishihara TestIshihara Test

Better wound healing process with GTBetter wound healing process with GT

GT offers significant possibilities GT offers significant possibilities

for the modification of adult for the modification of adult

wound healing processes by wound healing processes by

mimicking the cytokine profile mimicking the cytokine profile

of fetal wounds and by reducing of fetal wounds and by reducing

the inflammatory responses to the inflammatory responses to

cutaneous injuries by shooting cutaneous injuries by shooting

EGF and IGF genes into the EGF and IGF genes into the

wounds.wounds.

Immunology of gene therapyImmunology of gene therapy

Immunological Responses to GT Immunological Responses to GT includes both Humoral and Cell-includes both Humoral and Cell-mediated immunity.mediated immunity.

These responses lead to many These responses lead to many problemsproblems::

• Transient expression of therapeutic geneTransient expression of therapeutic gene• Non-efficient re-administration of the same Non-efficient re-administration of the same

vectorsvectors• Severe side-effects in clinical trialsSevere side-effects in clinical trials

Immunology of gene therapyImmunology of gene therapy

Factors affecting the immune responses to Factors affecting the immune responses to gene transfer:gene transfer:

1.Host factors such as recipient immunogenotype, prior 1.Host factors such as recipient immunogenotype, prior exposure to viruses, maturity of immune system and…exposure to viruses, maturity of immune system and…

2.Gene transfer protocol factors such as route of transgenic 2.Gene transfer protocol factors such as route of transgenic delivery and type of delivery system.delivery and type of delivery system.

3.Transgene delivery vehicle factors such as type of viral 3.Transgene delivery vehicle factors such as type of viral vector, presence of vector preparation contaminants, pseudo vector, presence of vector preparation contaminants, pseudo type of vector particle. type of vector particle.

Thank You For Your Thank You For Your AttentionAttention..