Serum alters the uptake and biologic activity of CpG oligodeoxynucleotides in B cell chronic lymphocytic leukemia

Acute lymphoblastic leukemia cells treated with CpG oligodeoxynucleotides, IL-4 and CD40 ligand facilitate enhanced anti-leukemic CTL responses

Acute lymphoblastic leukemia (ALL) is the most common pediatric malignancy. Although the majority of patients initially respond to upfront chemotherapy, relapses with poor prognosis occur in approximately 20% of cases. Thus, novel therapeutic strategies are required to improve long-term survival. B-cell precursor (BCP)-ALL cells express low levels of immunogenic molecules and, therefore, are poorly recognized by the immune system. In the present study, we investigated the effect of various combinations of potent B-cell stimulators including CpG, Interleukin (IL)-2 family cytokines and CD40 ligand (CD40L) on the immunogenicity of primary BCP-ALL cells and a series of BCP-ALL cell lines. The combination of CpG, IL-4 and CD40L was identified as most effective to enhance expression of immunogenic molecules on BCP-ALL cells, resulting in an increased capacity to induce both allogeneic and autologous cytotoxic T lymphocytes (CTL). Importantly, such CTL exhibited significant anti-leukemic cytotoxicity not only towards treated, but also towards untreated BCP-ALL cells. Our results demonstrate that the combination of CpG with other B-cell stimulators is more efficient than CpG alone in generating immunogenic BCP-ALL cells and anti-leukemic CTL. Our results may stimulate the development of novel adoptive T cell transfer approaches for the management of BCP-ALL.

CpG oligodeoxynucleotide-based therapy of lymphoid malignancies

Preclinical and early clinical trials indicate synthetic oligodeoxynucleotides containing unmethylated CG dinucleotides (CpG ODN) have potent immunostimulatory effects. CpG ODN are being explored as immune adjuvants in vaccination strategies and as potential treatments for a wide variety of disorders including cancer and asthma. Therapeutic approaches designed to take advantage of this potent class of agents are based largely on the ability of CpG ODN to activate professional antigen presenting cells (APCs) that express the target receptor - Toll-Like Receptor 9 (TLR9). B-cell malignancies are unique in that the malignant cells themselves express TLR9. CpG ODN can have a direct effect on the malignant B cells and lead to activation induced cell death. CpG ODN also alter the phenotype of target malignant B cells as indicated by upregulation of MHC, immunostimulatory molecules, and antigens that serve as targets for other approaches to lymphoma immunotherapy such as CD20. B cell malignancies are also relatively sensitive to the cytokines that are produced by dendritic cells in response to CpG ODN. Thus, B cell malignancies appear to be uniquely sensitive to CpG ODN because of both the direct and indirect effects the CpG ODN on target cells and the sensitivity of B cell malignancies to an immune response. Preclinical studies support further exploration of the potential of CpG ODN as a component of therapy for lymphoid malignancies. Ongoing clinical trials are exploring the potential of CpG ODN, both alone and in combination with other agents.