Gutted adenoviral vector growth using E1/E2b/E3-deleted helper viruses

Area of Science:

• Biotechnology
• Gene Therapy
• Virology

Background:

• Helper-dependent adenoviruses (Ad) offer reduced immunotoxicity due to lacking viral coding sequences.
• Their production requires a conventional Ad for replication and packaging functions.
• Efficient high-titer production of gutted Ad vectors with low helper contamination is crucial for in vivo applications.

Purpose of the Study:

• To develop improved methods for high-titer production of helper-dependent (gutted) adenoviruses.
• To reduce helper virus contamination in gutted Ad vector preparations.
• To facilitate the use of gutted Ad vectors in vivo.

Main Methods:

• Generation of replication-defective helper viruses lacking Ad E1, E2b, and E3 genes, with loxP sites flanking the packaging signal.
• Development of complementing Ad packaging cell lines (C7-cre cells) by transfecting 293 cells with Ad E2b genes and cre-recombinase.
• Utilizing cre-loxP-mediated excision to control helper virus replication.

Main Results:

• C7-cre cells enable efficient production of gutted Ad using deltaE1 + deltaE2b + deltaE3 helper viruses.
• High titers of gutted Ad vectors with approximately 28 kb expression cassettes were achieved, comparable to E2b+ helper systems.
• Helper contamination was reduced to less than 1%.

Conclusions:

• Novel packaging cell lines and helper viruses significantly enhance gutted Ad vector production.
• Reduced passage numbers decrease the likelihood of rearranged products during amplification.
• E2b-deleted helper viruses lead to profound reduction in viral gene expression, minimizing immunogenicity in vivo.