Long-term episomal transgene expression from mitotically stable integration-deficient lentiviral vectors

Area of Science:

• Gene Therapy
• Molecular Biology
• Cell Biology

Background:

• Nonintegrating gene delivery vectors offer improved safety over integrating vectors.
• However, episomal transgene retention is limited due to dilution during cell division.

Purpose of the Study:

• To develop an integration-deficient lentiviral vector (IDLV) system for stable, long-term transgene expression.
• To investigate methods for enhancing episomal retention and mitigating vector dilution.

Main Methods:

• Utilized an integration-deficient lentiviral vector (IDLV) system.
• Induced transient cell cycle arrest during transduction.
• Employed techniques including linear amplification-mediated PCR, Southern blotting, and FISH to assess vector episomal status.

Main Results:

• Achieved mitotically stable episomes with long-term transgene expression (over 100 cell generations) in 13-45% of CHO cells without selection.
• Scaffold/matrix attachment regions did not improve episomal retention.
• Confirmed non-integration of the vector genome in the majority of cells.

Conclusions:

• Developed an IDLV procedure yielding mitotically stable episomes for sustained transgene expression.
• This approach holds potential for improving the safety of stem and progenitor cell gene therapies.