Conventional plasmid DNAs with a CpG-containing backbone achieve durable transgene expression in mouse liver

Area of Science:

• Biotechnology
• Gene Therapy
• Molecular Biology

Background:

• Durable transgene expression is crucial for effective gene therapy using non-viral vectors.
• Comparing CpG-containing and CpG-free plasmid DNA backbones is important for understanding expression durability.

Purpose of the Study:

• To evaluate the durability of transgene expression from plasmid DNAs with different backbones and regulatory elements.
• To determine if CpG-free designs are necessary for long-term gene expression in non-viral gene therapy.

Main Methods:

• Constructed plasmid DNAs with CpG-containing backbones, various regulatory sequences, and Gaussia princeps luciferase gene.
• Utilized tail vein hydrodynamic injection in mice for plasmid delivery.
• Monitored luciferase activity in serum for 28 days post-injection.

Main Results:

• Plasmid DNAs with albumin promoter (with/without CMV enhancer) and EF1α promoter (plus CMV enhancer) showed long-term luciferase expression.
• Expression from albumin promoter without CMV enhancer was sustained for at least 24 weeks, comparable to CpG-free plasmids.
• The presence or absence of CpG motifs in the backbone did not impede long-term expression when appropriate regulatory elements were used.

Conclusions:

• Special sequences or systems are not required for durable transgene expression.
• Properly selected transcription regulatory sequences are sufficient for achieving long-term gene expression from plasmid DNAs.
• This finding simplifies the design of non-viral vectors for gene therapy applications.