Cpg Oligodeoxynucleotide-Mediated Effects on B-Cell Chronic Lymphocytic Leukemia In Vitro Are Influenced by Cytogenetic Status and the Presence of Serum.

Immunostimulatory CpG-containing oligodeoxynucleotides (CpG ODN) are TLR9 agonists that mediate a number of immunologic effects in normal and malignant B cells including upregulation of immunogenic molecules. They are therefore felt to be attractive as potential components of immunotherapy for B cell chronic lymphocytic leukemia (B-CLL). The cytogenetic status of B-CLL is predictive of clinical prognosis, but little is known about how CpG ODN-mediated effects on B-CLL cells correlate with cytogenetic status. The present study was designed to explore the impact cytogenetic status has on in vitro B-CLL cell survival and immunogenicity. Since most in vitro studies to date have been performed under serum-low conditions, we also evaluated how the presence of autologous serum or plasma impacts on CpG ODN-mediated effects on B-CLL cells. B-CLL cytogenetic status by interphase FISH, as well as immunophenotype and cell survival in the absence or presence of CpG ODN was determined in 23 samples. CpG ODN decreased in vitro survival of B-CLL cells with good prognosis cytogenetics, but had little effect on cells with poor prognosis cytogenetics. In contrast, CpG ODN upregulated costimulatory and antigen-presenting molecules and enhanced allogeneic T cell response in samples with good and poor prognosis cytogenetics. The optimal concentration for CpG ODN-mediated effects in the presence of 100% autologous serum or plasma was higher (10–20 micrograms/ml ODN) than for serum-low conditions (2.5–5 micrograms/ml ODN). The observed inhibition of CpG ODN-mediated effects by serum directly correlated with a lower uptake of ODN into B-CLL cells in the presence of serum. In conclusion, CpG ODN induced changes in B-CLL consistent with enhanced immunogenicity in all samples studied, but induced apoptosis most effectively in the subset of B-CLL cells with good prognosis cytogenetics. Approximately 4-fold more CpG ODN was needed to induce these changes when serum was present as compared to low serum conditions due to decreased ODN uptake by the cells in the presence of serum. These studies suggest CpG ODN may be useful as immunotherapeutic agents for B-CLL irrespective of cytogenetic status because of their potential effects on immunogenicity. Higher systemic doses of CpG ODN than previously thought might be necessary to induce these changes because of the effect of serum proteins on ODN uptake.