namic gene delivery technique; this permitted hepatocytes to produce and secrete the soluble protein. This technique uses hydrodynamic force, generated by an injection of a large volume (10% of body weight) of DNA solution (30 ig/mL) over 5–7 seconds through the tail vein, to permeabilize the capillary endothelium of the liver and generate ‘pores’ in the plasma membrane of the surrounding parenchymal cells, thereby allowing DNA to reach the cell interior. With time, the membrane pores close, trapping these molecules inside. At that point, transfected cells transiently produce the molecule encoded by the vector. We generated a CD40L construct consisting of the soluble part of human CD40L and the trimerization domain of adiponectin (ADPN-CD40L). We also created a similar construct for human interleukin (IL)-4. The adiponectin domain creates a trimer that can also dimerize to a hexamer, creating multimeric forms with greater biological activity. Furthermore, glycosylation of adiponectin increases the stability of these molecules. After hydrodynamic gene delivery of the ADPN-CD40L or the ADPN-IL-4 expression vector, high levels of ADPN-CD40L ( 5 ng/mL) and ADPN-IL-4 ( 3 ng/mL) were found in the sera of treated mice for more than 6 months. Similar data were obtained when both constructs were injected simultaneously. Next, CFSE-labeled CLL peripheral blood mononuclear cells, followed by anti-CD3 monoclonal antibodies, were injected in these mice. Untreated mice and mice that were co-injected with allogeneic monocytes served as negative and positive controls. Ten days after CLL cell injection into mice with circulating ADPN-CD40L, we documented leukemia cell proliferation in the blood and spleen by CFSE dilution for every CLL sample studied, although the degree of proliferation varied among samples. Nevertheless, proliferation could be extensive; in some cases, leukemic cells underwent more than 6 rounds of division. Mice that received only ADPN-IL-4 did not show enhanced CLL cell proliferation but had increased viability over control animals. Finally, mice that received ADPN-CD40L plus ADPN-IL-4 had the greatest degree of CLL cell proliferation and viability, exceeding that in mice receiving ADPN-CD40L or ADPN-IL-4 alone. At the same time point, no proliferation in untreated mice and negligible or minimal CLL cell proliferation was found in mice receiving monocytes. Thus, this approach reduces or may eliminate a downside of our initial model, in which necessary but uncontrolled T-cell expansion to allo-antigens generated graft-versus-host disease and a graftversus-leukemia effect, making the model short term. This new approach may lead to a long-term model that would allow more complex preclinical studies or would be a better tool to study the basic biology of CLL cells in vivo. Experiments testing this are currently in progress.