1. ¹Department of Biotechnology and Molecular Medicine, AI Virtanen Institute for Molecular Sciences, University of Kuopio, Kuopio, Finland
2. ²Ark Therapeutics Oyj, Kuopio, Finland
3. ³Department of Biological and Environmental Science, NanoScience Center, University of Jyväskylä, Finland
4. ⁴Department of Medicine and Gene Therapy Unit, University of Kuopio, Kuopio, Finland
5. ⁵Kuopio University Hospital, Kuopio, Finland

Correspondence: Professor S Ylä-Herttuala, Department of Biotechnology and Molecular Medicine, AI Virtanen institute for Molecular Sciences, University of Kuopio, PO Box 1627, Kuopio, FIN-70211, Finland. E-mail: seppo.ylaherttuala@uku.fi

Received 19 December 2007; Revised 29 February 2008; Accepted 14 March 2008; Published online 8 May 2008.

Abstract

In spite of advances in conventional four-plasmid transient transfection methods and development of inducible stable production cell lines, production of replication-defective lentiviral vectors in clinical scale has been challenging. Baculovirus technology offers an alternative to scalable virus production as a result of fast and easy production of baculoviruses, efficient transduction of mammalian cells and safety of the baculoviruses. As a first step toward scalable lentiviral production system, we have constructed four recombinant baculoviruses: the BAC-transfer virus expresses green fluorescent protein (GFP) as a transgene and BAC-gag-pol, BAC-vesicular stomatitis virus glycoprotein G and BAC-rev express all elements required for a safe lentivirus vector generation. Following 293T cell transduction with recombinant baculoviruses functional lentiviruses were produced. Different baculovirus concentrations, mediums and transduction times were used to find optimal conditions for lentivirus production. The unconcentrated lentiviral titers in cell culture mediums were on average 2.5 10⁶ TU ml^{- 1}, which are comparable to titers of the lentiviruses produced by conventional four-plasmid methods. Lentiviruses produced by baculovirus method transduced HeLa cells and showed sustained GFP expression. No evidence of the formation of replication competent lentiviruses was detected by p24 enzyme-linked immunosorbent assay. Our results show that baculoviruses are an attractive alternative for the production of lentiviruses in mammalian cells.