Retroviral interleukin 1a gene transfer in bone marrow stromal cells in a primate model: induction of myelopoiesis stimulation Thierry de Revel, 1,2 Nicolas Becard, 1 Tania Sorg, 3 Sandrine Rousseau, 1 Jean Philippe Spano, 1 Hugues Thiebot, 1 Magid Methali, 3 Gabriel Gras, 1 Roger Le Grand 1 and Dominique Dormont 1 1 CEA, Service de Neurovirologie, CRSSA, EPHE, Fontenay-aux-Roses, 2 Service d’He ´matologie, Ho ˆpital d’Instruction des Arme ´es Percy, Clamart, and 3 Transgene SA, Strasbourg, France Received 28 November 2001; accepted for publication 18 February 2002 Summary. Effects of interleukin 1-a (IL-1a), a proinfla- mmatory cytokine with pleiotropic activity, in the myelo- poietic setting, is mainly linked to its ability to increase haematopoietic growth factor production by bone marrow stromal cells. In order to minimize systemic effects of IL-1a therapy, we proposed a model of retroviral IL-1a gene transfer within bone marrow stromal cells in the macaque cynomolgus. In vitro, 10–15% of bone marrow stromal cells was effectively transduced by retroviral vector (murine Moloney leukaemia virus-derived) expressing IL-1a/LacZ, or LacZ alone as control marker, as assessed by bGal staining. IL-1a gene expression was upregulated [semiquantitative reverse transcription polymerase chain reaction (RT-PCR)] within the transduced cells and the cell supernatant showed an increased production of granulocyte colony-stimulating factor (G-CSF) and granulocyte–macrophage (GM)-CSF (enzyme-linked immunosorbent assay) and an increased clonogenic activity (colony-forming cell assay). Ex vivo autologous expanded IL-1a/LacZ transduced bone marrow stromal cells were reinfused in two macaques (and two control animals for LacZ alone as controls), without clinical systemic toxicity; LacZ expression by RT-PCR was detected in one animal of each group between d 4 and 9. A slight increase of the peripheral blood leucocyte counts (both polymorphonuclear cells and monocytes) of the two animals transduced with IL-1a/LacZ was observed within 10 d, indicating stimulation of myelopoiesis. Keywords: IL-1a, gene transfer, stromal cells, haemo- poiesis, primate model. Haematopoietic growth factors (HGF) are a major thera- peutic tool to overcome infection risk related to prolonged leucopenia after chemotherapy or bone marrow trans- plantation. However, the efficacy of HGF in clinical practice may be hampered due to their systemic effects and/or their limited impact upon severely stressed hae- mopoiesis. The regulation of steady state haemopoiesis results from multiple interactions between stem/progenitor cells, stromal cells and cytokines locally produced within the bone marrow (Shadduck et al, 1983; Allen & Dexter, 1984; Quesenberry et al, 1987; Torok-Storb, 1988; Gordon & Greaves, 1989; Kittler et al, 1992). Thus, we can assume that altered myelopoiesis might be improved through direct delivery of HGF within the bone marrow. It has been previously demonstrated that cultured bone marrow stromal cells (BMSC) can be used as a vehicle for gene therapy and can engraft into animal recipients following intravenous infusion (Nolta et al, 1994; Allay et al, 1997; Hurwitz et al, 1997; Chuah et al, 1998; Ding et al, 1999; Chuah et al, 2000; Devine et al, 2001). In other respects, interleukin 1-a (IL-1a), a cytokine with pleiotropic effects, has a role in the regulation of haemo- poiesis which is mainly related to its ability to increase the production of HGF by the stromal cells of the bone marrow microenvironment (Babgy et al, 1986; Mochizuki et al, 1987; Neta et al, 1987; Yang et al, 1988; Haynes- worth et al, 1996). However, IL-1a is a highly pro- inflammatory cytokine and its clinical use is limited by its systemic side-effects (Smith et al, 1992; Dinarello, 1996). In the present study we have investigated in a non- human primate model whether IL-1a genetically modified BMSC could stimulate haemopoiesis by inducing locally high levels of HGF expression while reducing toxicity of systemic administration. To address this question we aimed to determine in vitro the consequences of IL-1a transgene expression within a cultured stromal cell population before testing transplantation of IL-1a genetic- ally modified BMSC in the animals. Correspondence: Thierry de Revel, MD, Service d’He ´matologie, Ho ˆpital Percy, 101 avenue H. Barbusse, 92141 Clamart, France. E-mail: thderevel@aol.com British Journal of Haematology, 2002, 118, 875–884 Ó 2002 Blackwell Science Ltd 875