Work

Generation Of CLL-Specific CTL Effectors From Partially HLA-Matched Umbilical Cord Blood Grafts Using CD154-Transduced CLL Cell S As APCs

Year: 2009

Type: article

Abstract: Introduction: Long-term remissions have been observed following allogeneic hematopoietic stem cell transplantation (allo-HSCT) for the treatment of chronic lymphocytic leukemia (CLL). Unfortunately, many CLL patients are ineligible for transplant due to the lack of an HLA-compatible donor. Umbilical cord blood (UCB) HSCT permits transplantation of many individuals who are ineligible for allo-HSCT due to its reduced requirement for stringent HLA matching; however, disease relapse remains a significant complication. Further, unlike allo-HSCT, donor lymphocyte infusion (DLI) cannot be employed as a post-transplant therapy. To address this issue we are developing a strategy to generate CLL-specific T-lymphocytes to be employed as a post-UCB-HSCT therapeutic treatment. Methods: CLL-specific antigen presenting cells (APC) were generated by the transduction of CLL cells with an adenoviral vector encoding CD154 (CD40L). Successful transduction and subsequent CD40 ligation in CLL cells were verified by monitoring CD95 expression. CLL APC were then used to prime partially HLA matched (typically 4/6) UCB lymphocytes in the presence of IL-12, IL-2, IL-7, and IL-15. Expanded UCB lymphocytes were phenotyped by flow cytometry, and CLL specificity was determined by ELISpot and 51Cr lysis using non-CLL (CD19-/CD3+) patient lymphocytes as allo-antigen controls. Results: Effector cell phenotype was predominantly (>80%) CD4+; however, skewing toward CD8+ expansion could be achieved by incubation in IL-12 during priming. Significant populations of effector memory (CD62L+CD127+) and central memory (CD62L-CD127+) cells were observed following repeated stimulations with CLL-APC. Significant expansion (>4 fold) of UCB lymphocyte populations was typically observed. In ELISpot assays, CLL-APC primed UCB lymphocyte responders exhibited a significant increase (p > 0.05) in IFN-γ ELISpots when incubated with CLL stimulators in comparison to non-CLL control stimulators. Cytolytic activity was demonstrated against unmodified CLL cells by 51Cr release assays in which percent lysis of CLL targets was 30–50% at E:T ratios of 10:1 and 20:1. Lysis of autologous non-CLL control targets was negligible. Conclusions: Our results demonstrate that in vitro generation of CLL-specific effectors from partially HLA-matched UCB lymphocytes is both feasible and practical. These preclinical results support further exploration of this technique as a promising treatment modality in conjunction with UCB-HSCT.

Source: Transplantation and Cellular Therapy

DOI: 10.1016/j.bbmt.2008.12.378