Summary auto-generated
This 1997 study demonstrates that baculovirus vectors can efficiently deliver foreign genes into various mammalian cell types, not just hepatocytes. Researchers engineered recombinant baculoviruses (Autographa californica nucleopolyhedrovirus) containing the CAG promoter—a strong, ubiquitous mammalian promoter—driving reporter genes like luciferase and lacZ. They tested these vectors in multiple mammalian cell lines including human hepatoma (HepG2, Huh7), cervical carcinoma (HeLa), and monkey kidney (COS7) cells. High-level gene expression was observed across diverse cell types. Importantly, the baculoviruses did not replicate in mammalian cells, with infectious titers decreasing significantly after infection, yet transgene expression persisted for at least 14 days. When compared directly to replication-defective adenovirus vectors using identical expression cassettes, baculoviruses achieved similar or superior gene expression levels in multiple cell lines with less cytotoxicity. As a functional demonstration, recombinant baculoviruses expressing hepatitis C virus structural proteins showed proper post-translational processing of viral proteins in mammalian cells. These results establish baculoviruses as viable, versatile gene delivery vectors for mammalian cells with advantages including large cargo capacity, non-replicating nature, and reduced toxicity compared to adenoviral alternatives.
Key findings
- Baculovirus vectors with CAG promoter efficiently delivered genes to both hepatic and non-hepatic mammalian cells including HeLa, CPK, and COS7 cells, achieving 90-100% transfection efficiency at high multiplicity of infection
- Baculoviruses do not replicate in mammalian cells; infectious titers decreased 100-fold by 48 hours and completely by day 9, yet transgene expression continued through day 14
- Gene expression by baculovirus vectors equaled or exceeded that of replication-defective adenovirus vectors in HepG2, HeLa, and COS7 cells with significantly lower cytotoxicity
- CAG promoter-driven baculoviruses achieved 10-fold higher expression than CMV promoter-driven vectors in HeLa cells, demonstrating promoter-dependent gene expression in mammalian cells
- Hepatitis C virus structural proteins expressed from baculovirus vectors underwent proper post-translational processing, confirming functional protein expression capability
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Abstract
A baculovirus (Autographa californica nucleopolyhedrovirus) vector containing a strong promoter, the CAG promoter, was developed to introduce foreign genes into mammalian cells. Recombinant baculoviruses carrying a reporter gene under the control of the CAG promoter were inoculated into various mammalian cell lines. High-level expression was observed not only in hepatocytes but also in other non-hepatic cell lines tested. Expression of the reporter gene was detected even 14 days after infection. The infectious titre of the recovered baculoviruses decreased significantly after infection, indicating that the baculoviruses did not replicate in mammalian cells. We then compared the efficiencies of gene expression by the baculovirus vector with that of a replication-defective adenovirus vector by using the same expression unit. The same level of expression was observed in HepG2, HeLa and COS7 cells by both vectors. Efficient expression and proper processing were observed in mammalian cells infected with baculoviruses carrying genes coding for structural regions of hepatitis C virus. These results suggest that the baculovirus vector is a good tool for gene delivery into various mammalian cells in order to study the function of foreign genes.