Abstract
Myeloid dendritic cells (DCs) play an important role in the immune response; therefore, the search for compounds that can effectively activate DCs is a needful goal. This study was aimed to investigate the effect of synthetic CpG oligodeoxynucleotides (CpG-ODN) on the maturation and allostimulatory activity of myeloid DCs in comparison with other PAMP and DAMP molecules. For the research, we synthesized known CpG-ODN class C (SD-101 and D-SL03) containing thiophosphate internucleotide groups, and their original phosphate-modified analogues (SD-101M and D- SL03M) with mesylphosphoramide internucleotide groups (M = μ-modification). The effects of CpG-ODN and other activators were evaluated on DCs generated from blood monocytes in the presence of GM-CSF and IFN-α (IFN-DC) or IL-4 (IL4-DC). Evaluation of the intracellular TLR-9 expression showed that both types of DCs (IFN-DC and IL4-DC) contained on average 52 and 80 % of TLR-9-positive cells, respectively. The CpG-ODNs studied enhanced the allostimulatory activity of IFN-DCs, and the effect of μ-modified CpG-ODNs was higher than that of CpG-ODNs with thiophosphate groups. The stimulating effect of CpG-ODN at a dose of 1.0 μg/ml was comparable (for D-SL03, D-SL03M, SD-101) with or exceeded (for SD-101M) the effect of LPS at a dose of 10 μg/ml. At the same time, IFN-DCs were characterized by greater sensitivity to the action of CpG-ODNs than IL4-DCs. The enhancement of DC allostimulatory activity in the presence of CpG-ODNs was associated with the induction of final DC maturation, which was confirmed by a significant decrease in the number of CD14+DC, an increase in mature CD83+DC and a trend towards an increase in CD86+DC. Interestingly, the characteristic ability of LPS to enhance the expression of the co-stimulatory molecule OX40L on DCs was revealed only for the μ-analogue SD-101M. In addition, CpG-ODNs (SD-101 and SD-101M) had a stimulatory effect on IFN-γ production comparable to the action of LPS. The data obtained indicate a stimulating effect of CpG-ODN on the maturation and allostimulatory activity of human myeloid DCs, which is more pronounced for μ-modified analogs.
Highlights
Dendritic cells (DC) play an important role in immune responses, justifying their application as cellular targets and potential cellular modality for developing novel anti-cancer immunotherapies
This study aimed to assess the effects of CpG oligodeoxynucleotides (CpG-ODN) on maturation and allostimulatory activity of myeloid DC gene rated from blood monocytes in the presence of GM-CSF and IFN-α (IFN-DC) or IL-4 (IL4-DC) in comparison with other Pathogen-associated molecular patterns (PAMP) (LPS) and da mage-associated molecular patterns (DAMP) activators
The assessment of intracellular TLR-9 expression in freshly isolated blood mo nocytes derived from healthy donors and immature IFN-DC/IL4-DC generated after 3- and 5-days culture, respectively, showed that the proportion of TLR-9-po sitive cells in monocyte precursors and IL4-DC was at about 80 % level (Fig. 1)
Summary
Dendritic cells (DC) play an important role in immune responses, justifying their application as cellular targets and potential cellular modality for developing novel anti-cancer immunotherapies. PAMP-dependent effects are mediated via pattern-recognition receptors, while DAMP molecules are recognised by intracellular sensors and activate DC via secondary messengers, such as tumour-necrosis factor α (TNF-α) (Jounai et al, 2013; Kawasaki, Kawai, 2014). The effects of various compounds on human DC are usually assessed in vitro in monocyte-derived DC cell cultures generated in the presence of GM-CSF/IL4 or GM-CSF/IFN-α (Cehim, Chies, 2019) cytokine combinations. In these settings, a Toll-like receptor 4 (TLR-4)-specific ligand, bacterial lipopolysaccharide (LPS), serves as a standard cell activator.
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