Lentiviral vectors mediate stable and efficient gene delivery into primary murine natural killer cells

Natural killer (NK) cells are lymphocytes that provide an important line of defense against many types of microorganisms, viruses and tumors. The development of an efficient gene transfer system for genetically modifying primary murine NK cells will facilitate the studies of NK cell differentiation, acquisition of self-tolerance, and induction of anti-tumor responses. In this study we used an enhanced green fluorescent protein (EGFP)-expressing vector to carry out a systematic evaluation of the efficiency of lentiviral transduction of primary murine NK cells with or without prior interleukin-2 (IL-2) activation. In a single-step transduction protocol, we demonstrated that human immunodeficiency virus type 1-based lentiviral vectors support an average of 40% transduction efficiency on primary NK cells. These genetically modified NK cells are found to maintain stable EGFP transgene expression in vitro, and can be further expanded in IL-2 supplemented culture medium. Lentiviral transduction does not affect NK surface phenotypes or functions (apoptosis, cytokine production and cytotoxicity). We further demonstrated efficient gene transfer into differentiating NK cells derived from the lentiviral-transduced murine hematopoietic progenitor cells in vitro. This study therefore establishes a simple and efficient approach to the genetic engineering of primary murine NK cells, and will prove useful in studying basic NK cell biology and in exploring the therapeutic potential of NK cells in inbred and transgenic mouse models.