| BACKGROUND: B cell chronic lymphocytic leukaemia (CLL) is the most common leukaemia in adults in the Western world. Although chemotherapy may induce clinical remissions, it does not cure CLL. Thus, it is necessary to develop new treatment strategies. Because of its in general slowly progressive behaviour CLL is an attractive target for immunotherapy. Apart from the sIg idiotype, the frequent complex cytogenetic abnormalities accumulating over time might result in CLL specific tumour antigens. However, because of a lack of important costimulatory molecules, CLL B cells are poor antigen-presenting cells. Kipps et al. have shown that after transduction with the TNF family member CD40-ligand (CD154), B CLL cells (constitutively expressing the TNFR family member CD40) become highly effective APC that can induce CLL-specific cytotoxic T cells. Infusion of these transduced CLL cells resulted in significant reductions in leukaemia cell counts and lymph node size. Previously our group has shown that not only CD40 but also the TNFR family member CD27 is abundantly present on all B CLL cells. Its ligand (the TNF family member CD70) was found to be weakly expressed, and only in a minority of B CLL patients. During the last years we have shown, both in vitro and in vivo, that the interaction between CD70 and CD27 provides a potent costimulatory signal for T cell activation, and contributes to the expansion of effector T cells. To study functional consequences of prolonged CD27 ligation in vivo, CD70 was expressed in transgenic mice under control of the CD19 promoter. The B cell specific CD70TG mice not only had a considerable expansion of activated memory/effector T cells but, rather surprisingly, also showed a progressive B cell depletion resulting in a total disappearance of B cells by the age of 12 weeks. We could show that this B cell depletion absolutely requires CD27-CD70 interaction, is mediated by T cells and is strictly dependent on interferon-gamma (IFg). These data indicate that CD70-CD27 interaction provides one of the most powerful T cell co-stimulatory signals in vivo. AIM: To develop a CD70- based immuno-gene therapy for CLL. PLAN OF INVESTIGATION: We will generate a high titer replication defective Adenovirus vector (Av) expressing human CD70 and use it for CD70 transduction of B-CLL cells (avCD70-CLL). These transductions will be performed under GMP conditions at the AMT facilities. In the preclinical in vitro part (first 2 years) of the project, the avCD70-CLL cells will be analysed as to sterility and free virus production, viability and survival, expression of co-stimulatory / TNF(R) family member molecules, adhesion and HLA class I/II molecules, and cytokine production. Next, we will study their capacity to induce phenotypic and/or functional changes in non-tranduced bystander B-CLL cells. Importantly, we will examine their ability to induce autologous T cell proliferation and differentiation of cytotoxic effector cells. If so, we will investigate mechanism (involvement of the CD70-CD27 path, other (costimulatory) pathways and cytokines) and specificity (HLA restriction and idiotype specificity) of the T cell response. Finally, in collaboration with Prof T. Kipps (sAN Diego) results will be compared with CD40-ligand (CD154) transduced CLL cells, as well as with combined CD70 and CD154 transduction. In the clinical part of this project we will initiate a phase I clinical trial, infusing escalating doses of autologous avCD70-CLL cells (or adCD40L/avCD70-CLL) in therapy resistant CLL patients. These patients will be studied as to clinical efficacy and toxicity and immunological responses: analysis of immunophenotype of non-transduced CLL cells, plasma cytokine levels (notably IFg, IL12, IL6, TNFa), number and immunophenotype of T cells, generation of CLL specific T cells (Elispot). RELEVANCE FOR CANCER RESEARCH: This project will provide an important contribution to the further development of new immuno-gene therapeutic strategies, applicable not only for the treatment of lymphoid malignancies but also in solid tumours. |
