1. ¹Department of Microbiology, Immunology and Pathology, Colorado State University, 1619 Campus Drive, Fort Collins, Colorado 80523, USA
2. ²Division of Molecular Biology, Beckman Research Institute of the City of Hope, 1450 East Duarte Road, Duarte, California 91010, USA

Correspondence: Ramesh Akkina, Fax: (970) 491-1009. E-mail: akkina@colostate.edu

Received 24 March 2003; Accepted 1 April 2003.

Abstract

The phenomenon of RNA interference mediated by small interfering RNAs (siRNAs) is a potent gene-silencing mechanism. A number of recent studies demonstrated inhibition of HIV-1 replication in cultured cells using this approach. To make further progress and harness this technology for HIV-1 gene therapy in a stem cell setting, in vivo studies using primary hematopoietic cells are needed. Using an HIV-based lentiviral vector we introduced an anti-Rev siRNA construct into CD34⁺ hematopoietic progenitor cells. The siRNA-transduced progenitor cells were allowed to mature into macrophages in vitro and T cells in vivo in SCID-hu mouse thy/liv grafts. Phenotypically normal T cells and macrophages displaying characteristic surface markers were obtained. In vitro HIV-1 challenge of the siRNA-expressing macrophages and T cells with macrophage-tropic and T-cell-tropic HIV-1, respectively, showed marked viral resistance. These experiments demonstrate the utility of siRNAs delivered into hematopoietic stem cells via lentiviral vectors for future in vivo applications.