CpG oligodeoxynucleotide
unmethylated sequences of DNA that have immunostimulatory properties
CpG oligodeoxynucleotides (or CpG ODN) are short single-stranded synthetic DNA molecules that contain a cytosine triphosphate deoxynucleotide ("C") followed by a guanine triphosphate deoxynucleotide ("G"). The "p" refers to the phosphodiester link between consecutive nucleotides, although some ODN have a modified phosphorothioate (PS) backbone instead. When these CpG motifs are unmethylated, they act as immunostimulants. CpG motifs are considered pathogen-associated molecular patterns (PAMPs) due to their abundance in microbial genomes but their rarity in vertebrate genomes. The CpG PAMP is recognized by the pattern recognition receptor (PRR) Toll-Like Receptor 9 (TLR9), which is constitutively expressed only in B cells and plasmacytoid dendritic cells (pDCs) in humans and other higher primates.
History
Since 1893, it has been recognized that Coley's toxin, a mixture of bacterial cell lysate, has immunostimulatory properties that could reduce the progression of some carcinomas, but it was not until 1983 that Tokunaga et al. specifically identified bacterial DNA as the underlying component of the lysate that elicited the response. Then, in 1995 Krieg et al. demonstrated that the CpG motif within bacterial DNA was responsible for the immunostimulatory effects and developed synthetic CpG ODN. Since then, synthetic CpG ODN have been the focus of intense research due to the Type I pro-inflammatory response they elicit and their successful use as vaccine adjuvants.
Structural features
Synthetic CpG ODN differ from microbial DNA in that they have a partially or completely phosphorothioated (PS) backbone instead of the typical phosphodiester backbone and a poly G tail at the 3' end, 5' end, or both.
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This entry incorporates text from “CpG oligodeoxynucleotide” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.