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Hadassah's Gene Therapy Institute:
New Approaches to Genetic Disorders

Dr. Miryam Z. Wahrman

"There is no medical discipline whatsoever that does not have a strong genetic involvement," declared Dr. Gideon Bach, head of the Department of Human Genetics in Jerusalem's Hadassah Hospital.

Bach's talk, in Bergen County, NJ, was part of Hadassah's Mediscope Project - in which Israeli doctors address American groups to provide updates and information on research at Hadassah Hospital. Bach spoke on the topic "Prevention vs. Possible Cures In Human Genetics Disorders".

"We are at the final stages of the biggest scientific project ever conducted, the Human Genome Project," reported Bach. He explained that this landmark project, which aims to sequence all genetic information of the human cell, involves scientists from all over the world, including the U.S., Europe, Japan and Israel.

The goal of the project is "not just to get an aloof structure, but the tools to identify the 80 to 100,000 different genes that constitute ourselves - our being," Bach continued.

Bach went on to describe how mistakes in our genetic material, known as genetic mutations, can lead to devastating diseases, including those diseases and conditions most frequently associated with Jewish populations. For instance Tay Sachs disease, Canavan disease and a specific form of cystic fibrosis are examples of diseases which appear at higher frequency in the Ashkenazi Jewish population. All three are lethal diseases for which genetic screening tests are now available. Screening tests allow prospective parents to determine whether they are carriers for genes. When both parents are carriers for a particular genetic disease, that couple has a one-in-four chance of conceiving a child with that disease.

Mutations can occur in any cell of the body, including the sperm and eggs. "A mutation in a single cell doesn't really mean much, except for genes which control cell division," Bach explained. "If [cell division ] genes get mutated in a single cell, the cell goes on and divides more and more - this is the basis for cancers. When there's a mutation in sperm cells or eggs, then the mutation is transmitted from generation to generation."

"And although a carrier usually doesn't know he's a carrier, every one of us are carriers for many recessive disorders," continued Bach. "Today you don't have to give birth to an affected child ... a blood test can determine if you are a carrier. And since many of these disorders are incurable, prevention is the most important tool."

Prenatal diagnosis can detect fetuses with lethal genetic disorders very early in a pregnancy. Screening programs such as the one at Hadassah Hospital have reduced the number of Israeli babies born with cystic fibrosis and Tay Sachs to almost negligible numbers. "Today you see [patients with those diseases only] in textbooks... today you hardly see them at all. At least 90 percent have been eradicated or avoided," reported Bach.

Even Ultra-Orthodox, or Haredi, Jews in Israel participate in screening for genetic diseases. However, since Haredi rabbis usually do not permit abortions, in that community they do not wait for screening until a couple conceives. They do not even wait for a couple to meet. In the Haredi, community there is a program called Dor Yesharim, where couples are pre-screened before meeting.

"It is a screening project for various Ashkenazi disorders, but it is pre-engagement screening," Bach explained. "Almost all engagements are prearranged today [in that community]. The couple will not meet until they have a genetic I.D. It is done anonymously, and they don't get the results unless both partners are carriers of the same disease." In those cases, the "match" is simply never made.

"They participate in this program very enthusiastically," said Bach. "At least 99 percent of their youth is tested."

"Our department is involved in research on genetic disorders in high frequency in Israel in the general population," informed Bach. And in addition to Ashkenazic Jews, this population also includes Sephardic Jews and Arabs. "We are the referral center from all over Israel and neighboring Arab countries."

"A large fraction of our patients are Arabs," revealed Bach. "More than 60 percent of marriages in Arabs are îin the family' - consanguineous. This inbreeding leads to an higher incident of genetic disorders."

According to Bach, there are numerous other conditions and afflictions which can be transmitted genetically, including heart problems, high cholesterol, cancers, diabetes, arthritis and mental disturbances. "They can all be transmitted from generation to generation," said Bach. "Knowing the gene and knowing the mutations gives us the most important mechanism to diagnose the disease."

But for people already affected by genetic disease, is there any hope for a cure? One approach to treat genetic disorders is to supply the body with the protein it is missing. Genes direct the production of proteins and a faulty gene can produce a dysfunctional protein. If that protein is replaced it can allay the symptoms of the disease.

"We treat Gaucher's disease. Type I [Gaucher's] affects primarily the liver, spleen and bones." reported Bach. "It is treated with the enzyme, [a protein] which is produced and injected periodically into patients. Enzymes enter the cells which are affected by the disease. It is a very effective [treatment]."

These approaches are extremely expensive, in part because some of these enzymes are patented. "One company, Genzyme, developed the treatment [for Gaucher's disease], and by U.S. law they have the right to be the only producer of this enzyme for ten years," revealed Bach. "This company makes billions of dollars from sale of this product."

"For Tay Sachs we also know the enzyme which is affected, but the brain is the target," Bach said. Because there is a barrier which does not allow large molecules to pass from the blood to the brain, "the enzyme can be injected into the blood, but won't reach the brain," he explained. Thus, Tay Sachs still has no known treatment and all babies born with that disease are doomed to die within a few short years.

Gene therapy, where the genetic material itself - the DNA molecule - is actually corrected, is very difficult and expensive, but it holds out the best hope for curing patients with genetic diseases.

"We can attempt to change the property of the mutated gene... to overcome the mutation," informed Bach. "Alternatively we can introduce the normal gene which will function and overcome the mutated gene. This is the basis for gene therapy."

"There are only ten genetic [therapy] research centers in the world and Hadassah has been designated as one of them," boasted Yvette Tekel of Haworth, chair of the evening's event. The Goldyne Savad Institute of Gene Therapy of the Hadassah Medical Organization, which opened in November 1998, consists of: A research laboratory which focuses on diagnosing genetic disorders and developing approaches to cure disease using gene therapy; the Norman and Selma Kron Gene Therapy Center, which is the clinical arm of the Institute; and a GMP, or Good Manufacturing Practice Laboratory, which has been established to develop products under the strictest quality control and testing, to eventually be used in treating patients.

Unfortunately, gene therapy is a science which is still in its infancy, and scientists working in this field report only limited success with the approach. There have been hundreds of gene therapy trials at a medical research centers worldwide. However, none has yielded an effective cure for genetic disease.

The major problem with the approach appears to be the delivery of the gene to the right cells and getting those genes to work appropriately. Although Hadassah clinics are not yet working on gene therapy with human subjects, Hadassah scientists Hilla Giladi, Ariella Oppenheim, Israel Steiner, Amos Panel and Dan Gazit are developing improved methods to transfer genes into specific cells of the body. They are developing new viruses which are modified, so that instead of causing disease, they can enter cells, lock onto specific sites on a chromosome and become part of the chromosome, repairing or replacing the faulty gene.

Scientists at the Savad Institute of Gene Therapy are hopeful that their research into genetic mechanisms of disease will ultimately lead to cures, and they are planning on treating patients in the not too distant future.

"Of course we'll find treatments and cures for a lot of disorders," Bach predicted confidently.

Hadassah can be reached at (212) 303-4543 or on the web at www.hadassah.org



    •Copyright, 2000 Miryam Z. Wahrman

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