CpG ODNs are synthetic oligodeoxynucleotides (ODNs) containing unmethylated cytosine guanine dinucleotide (CpG), which can simulate bacterial DNA to stimulate immune cells of many mammals, including human beings. It can directly activate B cells and monocytes (macrophages and dendritic cells), indirectly activate various immune effector cells such as NK cells and T cells, enhance their functions and cytokine secretion, enhance antigen processing and presentation, induce Th1 type immune response, produce strong humoral and cellular immunity, and enhance specific and nonspecific immune responses.


Mammalian innate immune systems recognize pathogenic microorganisms through pattern recognition receptors. Toll-like receptors (TLR9) are one of the main innate immune pattern recognition receptors. The natural ligand of TLR9 is the unmethylated CpG in the genome of viruses and bacterium. TLR9, activated by its ligand, can produce a strong Th1 dominant immune response in the body and has broad applications, including infectious diseases, cancers, etc.
Different types of CpG ODNs have different structural characteristics and immune effects. They are generally divided into three types: Class A, Class B, and Class C. Synbio Technologies can provide these three types of CpG ODNs of various species.
Class A: It has a palindromic sequence containing CpG dinucleotide as its core, poly G tails at both ends, and partial phosphorothioated modifications on the phosphodiester bond skeleton. Through the palindrome sequence and poly G tail to form a high-level structure, it can activate plasmocytoid dendritic cells and induce a large number of type I interferons, which has weak activity against B cells.
Class B: It is a type of linear CpG ODN modified with full phosphorothioates. It has strong immunostimulatory activity on B cells, but cannot activate plasmocytoid dendritic cells.
Class C: It is a type of CpG ODN modified with full phosphorothioates. It can form a dimer through the palindromic sequence, and have the activity of Class A and Class B CpG ODNs. It can activate both plasmocytoid dendritic cells and B cells.

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[1]. Krieg, A.M. et al., 1995. CpG motifs in bacterial DNA trigger direct B-cell activation. Nature, 374(6522):546-9.
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[4]. Marshall JD. et al., 2005. Superior activity of the type C class of ISS in vitro and in vivo across multiple species. DNA Cell Biol. 24(2):63-72.
[5]. Ballas ZK. et al., 2001. Divergent therapeutic and immunologic effects of oligodeoxynucleotides with distinct CpG motifs. J Immunol. 167(9):4878-86.