1. ¹Laboratory of Experimental Virology, Department of Medical Microbiology, Center for Infection and Immunity Amsterdam (CINIMA), Academic Medical Center of the University of Amsterdam (AMC-UvA), Amsterdam, The Netherlands
2. ²Department of Cell Biology and Histology, Center for Immunology of Amsterdam (CIA), Academic Medical Center of the University of Amsterdam (AMC-UvA), Amsterdam, The Netherlands
3. ³Department of Experimental Hepatology, Liver Center, Academic Medical Center of the University of Amsterdam (AMC-UvA), Amsterdam, The Netherlands

Correspondence: Dr N Legrand, Department of Cell Biology and Histology, Academic Medical Center of the University of Amsterdam (AMC-UvA), Room L3-117, Meibergdreef 15, Amsterdam 1105 AZ, The Netherlands. E-mail: n.legrand@amc.uva.nl

⁴Part of the Human Vaccine Consortium, 'Grand Challenge in Global Health #4: devise reliable testing systems for new vaccines', http://www.hv-consortium.org

Received 22 April 2009; Revised 4 June 2009; Accepted 6 June 2009; Published online 3 September 2009.

Abstract

The efficient control of gene expression in vivo from lentiviral vectors remains technically challenging. To analyze inducible gene expression in a human setting, we generated 'human immune system' (HIS) mice by transplanting newborn BALB/c Rag2^-/-IL-2R_c^-/- immunodeficient mice with human hematopoietic stem cells transduced with a doxycycline-inducible lentiviral vector. We compared several methods of doxycycline delivery to mice, and could accurately measure doxycycline in vivo using a new sensitive detection assay. Two different lentiviral vector designs with constitutive (TRECMV-V14) or autoregulatory (TREAuto-V14) expression of an optimized reverse tetracycline transactivator were used to transduce human hematopoietic stem cells. After transplantation into immunodeficient mice, we analyzed the expression of the green fluorescent protein (GFP) reporter gene in the human hematopoiesis-derived cells that develop and accumulate in the generated HIS mice. We show efficient inducible GFP expression in adult HIS mice containing TREAuto-V14-transduced human cells, whereas GFP expression is poor with the TRECMV-V14 vector. Multiple cycles of doxycycline exposure in the TREAuto-V14 group result in repeated cycles of GFP expression with no loss of intensity. These findings are of major interest for gene therapy and basic research settings that require inducible gene expression.