A new avian leukosis virus-based packaging cell line that uses two separate transcomplementing helper genomes

Area of Science:

• Molecular Biology
• Virology
• Cell Biology

Background:

• Avian leukosis virus (ALV) is a retrovirus with applications in gene delivery.
• Developing stable, high-titer packaging cell lines is crucial for efficient retroviral vector production.
• Previous methods for ALV packaging cell line construction had limitations in efficiency and safety.

Purpose of the Study:

• To construct and characterize a novel avian leukosis virus-based packaging cell line.
• To assess the efficiency of gene transfer using replication-defective vectors produced by the new cell line.
• To ensure the safety of the packaging cell line by testing for replication-competent virus generation.

Main Methods:

• Constructed a packaging cell line using Rous-associated virus type 1 (RAV-1) genome components.
• Separated viral genes (gag, pol, env) onto distinct plasmids with selectable markers (hygromycin, phleomycin resistance).
• Transfected QT6 cells and selected high-producing clones for gag and env proteins, then tested vector packaging efficiency.

Main Results:

• Generated a stable avian leukosis virus packaging cell line (Isolde).
• Achieved high titers (10^5 RFFU/ml) for NeoR-expressing replication-defective vectors, comparable to RAV-1 infected cells.
• Demonstrated no evidence of replication-competent virus generation, indicating safety.

Conclusions:

• The developed packaging cell line is efficient and safe for producing replication-defective ALV vectors.
• The strategy of using selectable genes adjacent to viral genes facilitates the generation of high-producer packaging cell lines.
• This system offers a valuable tool for gene therapy and retroviral vector research.