Plasmoviruses: nonviral/viral vectors for gene therapy

Area of Science:

• Gene Therapy
• Molecular Biology
• Virology

Background:

• Gene therapy vectors face challenges in balancing infectivity, expression, and safety.
• Current viral vectors can pose risks of generating replication-competent retroviruses.
• Non-viral vectors often lack efficient in vivo delivery and long-term expression.

Purpose of the Study:

• To engineer a novel chimeric gene transfer vector, termed "plasmovirus."
• To combine the manufacturing simplicity of plasmids with the infectivity of retroviruses.
• To ensure safety by minimizing the risk of generating replication-competent retroviruses.

Main Methods:

• Generated a chimeric vector by replacing the env gene of a Moloney murine leukemia virus-derived provirus with a foreign gene.
• Incorporated an independent expression cassette with a cytomegalovirus promoter and an amphotropic retroviral envelope.
• Designed constructs with minimal homology (157-bp sequence, 53% identity) to reduce recombination risk.

Main Results:

• Transfection of the plasmid generated infectious but defective retroviral particles capable of efficient transgene expression.
• In vitro, transgene expression increased 10-60 fold within 8 days post-transfection.
• Intratumoral injection led to foci of transgene-expressing cells, indicating in situ propagation without evidence of replication-competent retrovirus generation.

Conclusions:

• Plasmoviruses effectively combine advantages of viral and non-viral gene delivery systems.
• These vectors facilitate efficient and safe in situ targeting of tumor cells.
• The technology holds potential for large-scale production of clinical-grade gene therapy materials.