Long-term expression of human factor IX cDNA in rabbits

Area of Science:

• Biotechnology
• Hematology
• Gene Therapy

Background:

• Hemophilia B is a genetic bleeding disorder caused by deficiency in coagulation factor IX.
• Current treatments for hemophilia B involve factor replacement therapy, which has limitations.
• Gene therapy offers a potential alternative for long-term correction of factor IX deficiency.

Purpose of the Study:

• To evaluate the efficacy of gene therapy for hemophilia B in a rabbit model.
• To assess the long-term expression of human factor IX following gene transfer.
• To develop and optimize a practical method for somatic cell gene therapy delivery.

Main Methods:

• Cultured normal rabbit skin fibroblasts (RSF) were genetically modified using recombinant plasmid (pCMVIX) or retrovirus (XL-IX, N2CMVIX) to express human factor IX cDNA.
• Infected fibroblasts were embedded in a collagen matrix and surgically implanted (autografts/allografts) or injected subcutaneously.
• Human factor IX levels in rabbit plasma were monitored over time.

Main Results:

• Surgically implanted grafts resulted in detectable human factor IX in plasma, maintained for over 10 months.
• A simplified subcutaneous injection method using the infected cell-collagen mixture led to peak plasma levels of 480 ng/ml.
• Factor IX expression persisted for over 3 months with the subcutaneous injection method.

Conclusions:

• Gene-modified rabbit skin fibroblasts can achieve sustained expression of functional human factor IX in vivo.
• Subcutaneous injection of infected fibroblasts represents a simplified and effective delivery method for somatic cell gene therapy.
• This approach holds promise for practical application in human clinical trials for hemophilia B.