Research

A method to estimate the efficiency of gene expression from an integrated retroviral vector

Hoi Ping Mok and Andrew Lever

Department of Medicine, University of Cambridge, Level 5, Addenbrooke's Hospital, Hill's Road, Cambridge, CB2 2QQ, UK

author email corresponding author email

Retrovirology 2006, 3:51doi:10.1186/1742-4690-3-51

Published:	17 August 2006

Abstract

Background

Proviral gene expression is a critical step in the retroviral life cycle and an important determinant in the efficiency of retrovirus based gene therapy vectors. There is as yet no method described that can assess the efficiency of proviral gene expression while vigorously excluding the contribution from unstable species such as passively transferred plasmid and LTR circles. Here, we present a method that can achieve this.

Results

Proviral gene expression was detected by the activity of the puromycin resistance gene encoded in the viral vector, and quantified by comparing the growth curve of the sample under puromycin selection to that of a series of calibration cultures. Reproducible estimates of the efficiency of proviral gene expression could be derived. We confirm that contamination from unstable species such as passively transferred plasmid used in viral vector production and unintegrated viral DNA can seriously confound estimates of the efficiency of transduction. This can be overcome using a PCR based on limiting dilution analysis.

Conclusion

A simple, low cost method was developed that should be useful in studying the biology of retroviruses and for the development of expression systems for retrovirus based gene therapy.