1. Gene Therapy for Choroideremia
by: Jennifer Chick, Barbara Gonzalez, Kenneth Karaivanov, Christine Murphy, Sean Roche, Michele Rozier, and Gabriel Stapleton

2. What is Gene Therapy? •Uses DNA as a drug to treat disease
•Uses functional DNA to replace mutated gene
•Three approaches to gene therapy
•1,700 clinical trials
•Major successes started in 2006
•2012 was first approved clinical trial

3. Timeline of Gene Therapy
A paper was proposed that claimed “good DNA” could replace defective DNA
6 patients suffering from Choroideremia, all vision was improved after treatment.
First major setback in gene therapy when Jesse Gelsinger died in a clinical trial
Successfully treated aspects Melanoma, granulomatous disease, and HIV
1990
1992
2007
2003
Now
2006
First Gene Therapy case by William Anderson on a girl with an immune deficiency
First stem cell procedure using hematopoietic cells to correct a hereditary disease
Gene therapy is used to access the brain with liposomes
Most recently there have been promising results with treatment of HIV patients
1972
1999
First gene therapy for inherited retinal disease
2014

4. iClicker: Would you feel comfortable receiving gene therapy as treatment for an inherited disease or disorder?
A. Yes
B. No
C. Unsure

5. iClicker: Which of these diseases does not have the potential to be treated with gene therapy?
A. Common Cold
B. Parkinson’s Disease
C. Cancer
D. HIV/AIDS
E. Hemophilia

6. Vectors and Gene Therapy
Parts of the vector
Promoter
Enhancer
Functional copy of the gene

7. Possible Issues with Gene Therapy
Immune rejection of foreign vectors could be dangerous.
Researching and synthesizing vectors that work is very expensive.
Vectors integrate into the DNA. Possible gene disruption?
Very individualized response to complex diseases

8. Structure & Function of Human Eye
Cornea:
Referred to as the “window of the eye”
It is composed of 5 layers
Outermost layer is the epithelium which provides protection
Inner layers provide strength
Pupil:
Black circle in the middle of the eye
Controls the amount of light entering the eye
The pupil becomes smaller to allow less light through in a bright environment
The pupil expands to allow more light to reach the back of the eye in a dark environment.
Iris:
The colored part of the eye surrounding the pupil.
Controls size of the pupil
Sclera:
White part of the eye surrounding the iris.
Provides structure, strength, and protection to the eye

9. Structure & Function of Human Eye
Aqueous Humor:
Thin, watery fluid that fills the space between the cornea and the iris.
Nourishes the cornea and the lens.
Gives the eye its shape.
Lens:
The clear structure located behind the pupil.
Provides fine-tuning for focusing and reading.
Performs this function by altering its shape
Vitreous Humor:
The clear, gel-like substance located inside the eye’s cavity.
Provides a spherical shape to the eye.
Retina:
Consists of fine nerve tissue which lines the inside wall of the eye and acts like a film in a camera
It transmits images to the brain.
Optic Nerve:
carries images from the retina to the brain.

10. Structure & Function of Human Eye
The eye is systematically separate from the rest of the body.
Light enters the eye through the cornea via the pupil at the center of the iris.
The pupil controls the amount of light admitted while the cornea does most of the focusing.
Light then passes through the lens, where it is finely focused, and then travels back through the eye to the retina.
The retina interprets images and then sends the information to the brain via the optic nerve.

11. What is Choroideremia?
Choroideremia is a disease of the eye associated with progressive vision loss
It accounts for roughly 4% of blindness related disorders.
It mainly affects males, but women who hold one copy of the gene (carriers), may develop eye impairment later on in life, as well.
Inherited via an X-linked recessive pattern.
Gene responsible for Choroideremia, CHM, found on the X chromosome.

12. Why Mainly Males Are Affected
Inherited via an X-linked recessive pattern.
It is much more common for males to be affected by X-linked recessive conditions, such as Choroideremia
CHM located on the X chromosome.
Since males only have one copy of the X chromosome, one altered copy of the gene is sufficient to cause condition
For females to have the condition, both of their X chromosomes need to have the same mutation
Affected males can pass the link on to their female offspring, but not to their male. A carrier female has 50% chance of passing on to offspring.

13. Symptoms of Choroideremia
It is estimated that 1/50,000 people are affected by Choroideremia, although, scientists believe that its prevalence may actually be more substantial.
This is because Choroideremia shares many similarities to other eye disorders and therefore may be misdiagnosed.
First symptom is usually impairment of night vision (“night blindness”)
can occur in early childhood
The disease develops further to affect the field of vision
Field of vision progressively narrows (“tunnel vision”)
Loss of ability to see detail follows (“visual acuity”)
For all individuals, the disease gets worse over time, but the rate of progression varies among individuals
All affected individuals eventually go completely blind by late adulthood

14. How is the Eye Affected by Choroideremia?
The eye experiences an ongoing loss of cells (atrophy) in the retina and its network of blood vessels
This network of blood vessels is known as the choroid
Eventually the light detecting cells in the retina die completely, resulting in blindness

15. How Gene Therapy is Used in Treating Choroideremia
This specific gene therapy involves inserting a gene into the eye to repair light detecting cells
This treatment not only prevents further degeneration but also improves eyesight
This is the first gene therapy procedure to target photoreceptors in the eye

16. Diagram of Choroideremia Gene Therapy

17. Significance of Choroideremia treatment for other similar retinal diseases
Successful use of gene therapy for choroideremia offers hope for treatment of other retinal diseases
There are currently other successful trials using gene therapy to treat retinal diseases
Knowledge gained from choroideremia trials is very useful
Offers hope for the human trials being conducted for other diseases such as age related macular degeneration, glaucoma and Usher Syndrome
Still some uncertainty about long term cure
Not sure if gene therapy will slow retinal degeneration in the long term

18. From Choroideremia: Applying Gene Therapy to treat other retinal diseases
1) MACULAR DEGENERATION
Macular degeneration, or age-related macular degeneration (AMD), is a leading cause of vision loss in Americans 60 and older. It is a disease that destroys your sharp, central vision. You need central vision to see objects clearly and to do tasks such as reading and driving.

19. Gene Therapy & Macular degeneration
Just as with the process involved in treating Choroideremia, other eye-sight conditions such as wet-related macular degeneration can also be treated using genes therapy.
This is done through a virus vector (a sort of transport vehicle) carries the therapy to the retina. A piece of DNA is spliced into an engineered virus.This will code for a vascular endothelial growth factor (VEGF)- binding protein that is inserted in the eye through subretinal injections.The epithelial architecture of the retina allows the vector to come into contact with the populations of cells and the contact with the systemic immune system promotes tolerance of foreign antigens.

20. Gene Therapy & Other Retinal diseases
Leber congenital amaurosis type 2: a retinal disease that affects children
Retinitis Pigmentosa: a chronic hereditary eye disease characterized by black pigmentation and gradual degeneration of the retina.

21. iClicker: After learning the information from this presentation, would you feel comfortable receiving gene therapy as treatment for an inherited disease or disorder?
A. Yes
B. No
C. Unsure

22. iClicker: Should people be allowed to use gene therapy to enhance basic human traits, like height, skin color, or behavioral characteristics?
A. Yes
B. No
C. Unsure