Construction of human factor IX expression vectors in retroviral vector frames optimized for muscle cells

Area of Science:

• Gene Therapy
• Molecular Biology
• Biotechnology

Background:

• Hemophilia B requires effective gene therapy for durable treatment.
• Current gene therapy approaches need refined expression vector systems for enhanced efficacy.

Purpose of the Study:

• To construct and optimize retroviral vectors for high-level human factor IX (hFIX) expression in skeletal muscle cells.
• To identify optimal vector components including promoters, enhancers, and expression units for hemophilia B gene therapy.

Main Methods:

• Construction of Moloney murine leukemia virus (MoMLV)-derived retroviral vectors with modified LTRs.
• Insertion of hFIX expression units, including cDNA and minigenes (hIXm1, hIXm2), in various configurations (pdL, pdLIn, pdLi).
• Systematic evaluation of different promoters (e.g., beta-actin, myogenin) and muscle creatine kinase enhancer (Me) elements on hFIX expression levels in myoblasts and myotubes.

Main Results:

• hFIX minigenes (hIXm1, hIXm2) yielded 10-14 fold higher expression than hFIX cDNA.
• The muscle creatine kinase enhancer (Me) significantly increased expression (4.5-19 fold) in myotubes, but not myoblasts.
• An optimal vector structure was identified: pdLi frame with beta A200 promoter, 2-4 copies of Me, and hIXm2 minigene.

Conclusions:

• A highly refined retroviral vector system has been developed for skeletal muscle-targeted hFIX expression.
• The optimized vector components provide a critical foundation for advanced hemophilia B gene therapy.
• This research represents a significant step towards durable and effective gene therapy for hemophilia B.