Approach to Establish Long Term Anti-Acute Myeloid Leukemia (AML) Immune Responses by Inducing Central Memory AML Specific CD4 T Cells

The efficacy of adoptive cell therapy of cancer and leukemia is often limited by the failure of cultured T cells, particularly cloned CD8+ T cells, to persist in vivo, and insight into the basis for the poor survival of the transferred cells is lacking. We previously reported a novel culture method that induces AML dendritic cell differentiation and primes in situ AML-reactive T cells (AMLDC culture) (Zhong et al. Exp Hematol2008, 36:486). Highly reactive anti-AML T-cell lines were generated. These T-cell lines caused specific lysis of autologous AML cells, but not autologous LCL or allogeneic AML cells, and they depleted autologous AML colony-forming cells (CFC), but not normal CFC. The culture procedure has been further optimized in this study. We found that by the addition of the TLR-4 agonist LPS,(1–100 ng/ml) in the last 24 hours of AMLDC culture (day 6), CD80, CD86, CD53, CD83 or HLA-Dr expression of AML cells pre-induced by cytokine combination GM-CSF/IL-4 or GM-CSF/IL4/IL2/IL7/IL12 could be significantly enhanced (n=6, P Conclusions: Timely exposure of AMLDC culture to TLR-4 agonists, followed by T cell expansion, may promote the generation of AML-reactive T cells and differentiation toward the central memory phenotype. Theoretically, this should promote long-term maintenance and potential of regulation of both humoral and cellular immune responses against AML upon infusion of AML reactive autologous T cells derived from such cultures and may therefore enhance the therapeutic efficacy of these cells.