CpG oligodeoxynucleotides (or CpG ODNs) are synthetic oligonucleotides that contain unmethylated CpG motifs. CpG ODN can bind to and activate a Toll-like receptor 9 (TLR9) and leading to strong immunostimulatory effects. So far 3 major classes of CpG ODNs have been identified, based on their structural and biological characteristics, and are designated Type A, Type B, and Type C. Type A ODNs, which feature a central palindromic CpG-containing phosphodiester (PO) structure followed by a phosphorothioate (PS) homopolymeric G-stretch, are robust inducers of interferon-α (IFN-α) production and dendritic cell maturation. Type B ODNs, in contrast, contain a full phosphorothioate backbone with one or more CpG dinucleotides. They strongly activate B cells but stimulate weakly IFN-α secretion. Type C ODNs, combine the properties of both Type A and B, and are characterized by their complete PS backbone and palindromic CpG-containing motifs. Type C ODNs induce strong IFN-α production from pDC and B cell stimulation.
ODN 2137 can be used as a control for ODN 2006.