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Cloning and Large-Scale Production of High-Capacity Adenoviral Vectors Based on the Human Adenovirus Type 5
Published on: January 28, 2016
Generation and characterization of E1/E2a/E3/E4-deficient adenoviral vectors encoding human factor VIII
J L Andrews1, M J Kadan, M I Gorziglia
1Genetic Therapy, Inc. (A Novartis Company), 9 West Watkins Mill Road, Gaithersburg, Maryland 20878, USA.
Summary
Fourth-generation adenoviral vectors show reduced toxicity in gene therapy. While highly attenuated vectors decreased liver toxicity, they also shortened the duration of therapeutic gene expression in hemophilia models.
Area of Science:
- Gene Therapy
- Virology
- Immunology
Background:
- Adenoviral vectors are crucial for gene therapy but face limitations due to host immune responses and toxicity.
- Attenuating viral gene expression is a strategy to mitigate these challenges.
Purpose of the Study:
- To develop and evaluate highly attenuated, fourth-generation adenoviral vectors (Av4) for gene therapy.
- To compare the immunogenicity, toxicity, and efficacy of Av4 vectors against a third-generation vector in a hemophilia mouse model.
Main Methods:
- Generated two fourth-generation (Av4) E1/E2a/E3/E4-deficient adenoviral vectors encoding human factor VIII (FVIII).
- One Av4 vector (Av4DeltaE4FVIII) lacked the entire E4 region; the other (Av4orf3FVIII) retained E4 open reading frame 3.
- Compared these vectors with a third-generation vector (Av3H8101) in vitro and in vivo in hemophiliac mice.
Main Results:
- All vectors expressed functional FVIII in vitro.
- Av4DeltaE4FVIII could not be scaled for in vivo studies.
- Av4orf3FVIII showed significantly reduced hepatotoxicity compared to Av3H8101.
- While initially similar, FVIII expression persisted longer with Av3H8101 than with Av4orf3FVIII at 3 months.
Conclusions:
- Further attenuation of adenoviral vectors by removing most of the E4 region significantly reduces toxicity.
- This enhanced attenuation comes at the cost of reduced duration of transgene expression.
- Balancing vector safety and therapeutic efficacy remains critical in adenoviral gene therapy development.
