Cytokine and Ig‐production by CG‐containing sequences with phosphorodiester backbone and dumbbell‐shape

Background: Immunostimulatory oligodeoxynucleotides (CpG‐ODN) usually contain phosphorothioate (PS) backbones for nucleotide protection, which may result in some nonspecific side‐effects like prolongation of coagulation time. Objective: The aim of the present study was to investigate the immunomodulatory potential of DNA molecules without PS backbones. Thus, we designed phosphorodiester (PO) molecules with a dumbbell‐like covalently‐closed structure (dSLIM‐30L1). Methods: We analyzed their effects on peripheral blood mononuclear cells (PBMC) from spontaneous high and low immunoglobulin (Ig)E producer (allergic and nonallergic donors) in comparison with linear CpG‐ODN (lin‐30L1) with PS backbones, using enzyme‐linked immunosorbent assay and flow cytometry. Results: We observed a decrease of spontaneous IgE levels in PBMC from high IgE producer of approximately 27% with both dSLIM‐30L1 and lin‐30L1. In addition, both molecules enhanced the production of IgA, IgM and IgG1/IgG2, but with a slightly different pattern. Both molecules stimulated the secretion of the TH1‐like cytokines interleukin (IL)‐2, interferon‐γ and IL‐12p40 and the pro‐inflammatory cytokine IL‐6. The immunomodulatory potential of dSLIM‐30L1 and lin‐30L1 was also effective in PBMC from nonallergic donors, as was confirmed for IL‐2, IL‐12p40, IgG1/IgG2 and IgM. Conclusion: Our data show an inhibition of IgE production but also enhancement of the inflammatory cytokine response in PBMC from allergic and nonallergic donors by covalently‐closed PO‐based dSLIM‐30L1 with a pattern similar to that of linear PS‐based lin‐30L1, while avoiding PS‐modifications and thus PS‐mediated side‐effects. Whether such molecules are useful for the treatment of allergic diseases will need further clarification by appropriate in vivo studies.