Autologous antileukemic immune response induced by chronic lymphocytic leukemia B cells expressing the CD40 ligand and interleukin 2 transgenes

Although the B cells of chronic lymphocytic leukemia (B-CLL cells) express both tumor-specific peptides and major histocompatibility complex (MHC) cla ss I antigens, they lack the capacity for costimulatory signaling, contribu ting to their protection against host antitumor immunity. To stimulate CLL- specific immune responses, we sought to transfer the human CD40 ligand (hCD 40L) gene to B-CLL cells, using an adenoviral vector, in order to upregulat e costimulating factors on these cells. Because efficient gene transduction with adenoviral vectors requires the expression of virus receptors on targ et cells, including the coxsackievirus B-adenovirus receptors (CAR) and alp ha (v) integrins, we cocultured B-CLL cells with human embryonic lung fibro blasts (MRC-5 line). This exposure led to increased expression of integrin alpha (v)beta (3) on B-CLL cells, which correlated with higher transduction rates. Using this novel prestimulation system, we transduced B-CLL cells w ith the hCD40L gene. The Ad-hCD40L-infected cells had higher expression of B7 molecules and induced activation of autologous T cells in vitro, but the se T cells could not recognize parental leukemic cells. By contrast, an adm ixture of Ad-hCD40L-positive cells and leukemic cells transduced with the h uman interleukin 2 (IL-2) gene produced greater T cell activation than did either immunostimulator population alone. Importantly, this combination gen erated autologous T cells capable of specifically recognizing parental B-CL L cells. These findings suggest that the combined use of genetically modifi ed CD40L-expressing B-CLL cells in combination with IL-2-expressing B-CLL c ells may induce therapeutically significant leukemia-specific immune respon ses.