Scientists at University of Pittsburgh, Medical Department detail research in gene therapy

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March 9th, 2009

   2009 MAR 9 -- "Herpes simplex virus type 1 (HSV-1) represents an attractive vehicle for a variety of gene therapy applications. To render this virus safe for clinical use, its cytotoxic genes must be removed without losing its ability to express transgenes efficiently," scientists writing in the journal Biotechnology and Bioengineering report.

   "Our vectors are deleted for the essential immediate early genes ICP4 and ICP27. These genes are controlled by unique promoters having enhancer elements responsive to a viral structural protein VP16. The expression of these genes occurs prior to the activation of all other lytic functions and is thus required to initiate and complete the virus replication cycle. For large scale manufacture of clinical grade vectors, efficient cell lines must be generated that express the essential viral gene products in trans during vector propagation. Here we describe methods for engineering HSV-1 production cell lines that improve vector growth by altering the kinetics of complementing gene expression. We examined the ability of Vero cells independently transduced with ICP4 and ICP27 under transcriptional control of their respective promoters to Support the growth of a replication defective vector (JDTOZHE), deleted for ICP4, ICP27 and approximately 20 kb of internal elements that are not required for virus growth in Vero cells. Vector yield on this cell line was 3 logs lower than wild-type virus grown on Vero cells. To understand the mechanism underlying poor vector yield, we examined the expression of ICP4 and ICP27 during Virus complementation. While ICP27 was expressed immediately on vector infection, the expression of ICP4 was considerably delayed by 8-10 h, suggesting that the ICP4 promoter was not adequately activated by VP16 delivered by the infectious vector particle. Use of the ICP0 promoter to express ICP4 from the cellular genome resulted in higher induction levels and faster kinetics of ICP4 expression and a 10-fold improvement in vector yield," wrote K.G. Grant and colleagues, University of Pittsburgh, Medical Department.

   The researchers concluded: "This study suggests that vector complementation is highly dependent on the kinetics of complementing gene expression and can lead to large differences in vector yield."

   Grant and colleagues published their study in Biotechnology and Bioengineering (Engineering Cell Lines for Production of Replication Defective HSV-1 Gene Therapy Vectors. Biotechnology and Bioengineering, 2009;102(4):1087-1097).

   Additional information can be obtained by contacting J.C. Glorioso, University of Pittsburgh, School Medical, Dept. of Microbiology & Molecular Genetics, Pittsburgh, PA 15261, USA.

   The publisher of the journal Biotechnology and Bioengineering can be contacted at: John Wiley & Sons Inc., 111 River St., Hoboken, NJ 07030, USA.

   Keywords: United States, Pittsburgh, Bioengineering, Biotechnology, Gene Therapy, Genetics, Genomics, HSV-1, Herpes Simplex Virus, Herpesvirus, Treatment, Virology, University of Pittsburgh, Medical Department.

   This article was prepared by Biotech Business Week editors from staff and other reports. Copyright 2009, Biotech Business Week via NewsRx.com.

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