Gene Therapy for Choroideremia by Jennifer Chick Barbara

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

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

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

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

i. Clicker: 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

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

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

Structure & Function of Human Eye ● Cornea: ○ ○ Referred to as the “window of the eye” It is composed of 5 layers ■ ■ ● 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: ○ ○ ● Inner layers provide strength Pupil: ○ ○ ● Outermost layer is the epithelium which provides protection The colored part of the eye surrounding the pupil. Controls size of the pupil Sclera:

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

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.

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

Why Mainly Males Are Affected • Inherited via an X-linked recessive pattern. o It is much more common for males to be affected by X-linked recessive conditions, such as Choroideremia § CHM located on the X chromosome. o Since males only have one copy of the X chromosome, one altered copy of the gene is sufficient to cause condition o For females to have the condition, both of their X chromosomes need to have the same mutation o 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.

Symptoms of Choroideremia o 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. o First symptom is usually impairment of night vision (“night blindness”) § can occur in early childhood o The disease develops further to affect the field of vision § Field of vision progressively narrows (“tunnel vision”) o Loss of ability to see detail follows (“visual acuity”) o 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

• 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 o This network of blood vessels is known as the choroid o Eventually the light detecting cells in the retina die completely, resulting in blindness

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

Diagram of Choroideremia Gene Therapy

Significance of Choroideremia treatment for other similar retinal diseases • • Successful use of gene therapy for choroideremia offers hope for treatment of other retinal diseases o There are currently other successful trials using gene therapy to treat retinal diseases o 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 o Not sure if gene therapy will slow retinal degeneration in the long term

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.

Gene Therapy & Macular degeneration ● Just as with the process involved in treating Choroideremia, other eyesight 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 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.

Gene Therapy & Other Retinal diseases

i. Clicker: 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

i. Clicker: 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