CPG DNA promotes the maturation and function of human monocyte-derived dendritic cells (modc) via indirect effects

Bacterial DNA containing unmethylated CpG motifs are excellent immune adjuvants that preferentially induce Thl-responses. In this study, we examined the effect of CpG oligodeoxynucleotides (ODN) on the maturation and function of human CD14 MoDC. CpG ODNs have been shown to stimulate DC, NK cell and B cell activation and the release of proinflammatory cytokines. Adding the CpG ODN, 2006 (5 (Ig/ml), on days 0, 3,5, or 7 to GM-CSF/1L-4 driven MoDC cultures for 2-3 days had modest effects on MoDC generation and maturation. However, in MoDC cultures containing 5-15% NK and B cells, CpG 2006 resulted in a rapid activation and maturation of MoDC. Significant increases of cell surface expression of HLA-ABC, -DR, CD40, CD54, CD80, CD83, and CD86 were detected on the CpG 2006-treated as compared to non-treated MoDC controls. MLR responses induced by CpG 2006-treated MoDC were 1.8- to 3.3-fold greater than non-treated MoDC controls and 56- to 160-fold greater than that induced by peripheral blood mononuclear cells (PBMNC). To determine the potential mechanism of MoDC maturation, the effect of CpG 2006 on purified CD56 NK cells, CD19 B cells, and CD14" monocytes from normal donors (n=5) was analyzed. CpG 2006 induced rapid activation of bulk PBMNC in short-term (48 hrs) cultures with enhanced production of IFNa, IFNy, TNFa, IL-6, and IL-12p40 in culture supernatants. Supernatant from the CpG cultured cells added to day-7 MoDC cultures induced MoDC activation. Treating CD56 NK cells with CpG 2006 upregulated the cell surface expression of CD69, augmented cytolytic activity against human NK-sensitive and NK-resistant leukemia cell lines, and increased IFNy and TNFa production. CpG 2006 treatment of CD 19 B cells induced proliferation and increased IL-6 and TNFa production. In contrast, treating purified CD14 cells with CpG 2006 did not show enhanced cytokine production. Neither IL-18 nor IL-12p70 was detected in CpG-treated groups. Adding purified NK or B cells with CpG 2006 to immature MoDC derived from purified CD 14 cells reproduced the observed CpG-induced maturation effects on MoDC. In summary, the data demonstrate that a CpG ODN can promote the maturation and function of CD 14+ MoDC via indirect effects. The findings support the potential of using CpG ODN as an immune adjuvant for MoDCbased vaccines in immunotherapy trials.