ADA Deficiency (ADA-SCID)
About 25% of the cases of severe combined immune deficiency (SCID) are due to abnormal ADA (adenosine deaminase) genes.
Because of the abnormal ADA genes, adenosine and deoxyadenosine are accumulated in the circulatory system, which are toxic to both the B cells and T cells
Gene Therapy for ADA-SCID
This was the first clinical trial gene therapy.
On 14th September, 1990, Culver, Blaese and Anderson initiated a clinical trial on ADA-deficient children.
Peripheral blood lymphocytes (T cells) from 2 girls were collected and expanded ex vivo. They were infected with LASN, a retroviral vector expressing the human ADA cDNA.
After 9 in vitro amplifications, 700 million autologous lymphocytes (corrected T cells) per kg of body weight were infused.
The same operation was repeated monthly, and the last infusion took place in October 1992.
Since then, both girls showed clinical improvements. The toxic level of adenosine and deoxyadenosine were lowered because of the presence of ADA+ circulating lymphocytes.
Familial Hypercholesterolemia
Familial Hypercholesterolemia is caused by a defect in the gene coding for the receptor of low density lipoproteins (LDL) in the patients' livers.
Consequently, fat bodies containing LDL cholesterol are not processed by the liver and continually circulate in the bloodstream, leading to arterial blockage.
Patients with this disease have early cardiovascular damage and severe heart disease.
Gene Therapy for Familial Hypercholesterolemia
A 29-year-old patient with no functional LDL-receptor gene underwent hepatic resection. Hepatocytes were isolated and transduced ex vivo with a retroviral vector expressing the cDNA for the LDL receptor.
Three days later, the hepatocytes were transfused into the patient's liver, where they became established, expressed the LDL receptor cDNA and produced functional LDL receptor.
Hypercholesterolemia of this patient was partially corrected, and maintained at a stable level for 18 months.
The patient's condition, based on lipid profiles, showed significant improvement. No immune response against the autograft was detected.
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