title: Nuclease-resistant immunostimulatory phosphodiester CpG oligodeoxynucleotides as human Toll-like receptor 9 agonists.
abstract: BACKGROUND
  Unmethylated cytosine-guanine (CpG) motif-containing oligodeoxynucleotides (ODNs) have been well characterized as agonists of Toll-like receptor 9 (TLR9). ODNs with a phosphorothioate (PTO) backbone have been studied as TLR9 agonists since natural ODNs with a phosphodiester (PD) backbone are easily degraded by a serum nuclease, which makes them problematic for therapeutic applications. However, ODNs with a PTO backbone have been shown to have undesirable side effects. Thus, our goal was to develop nuclease-resistant, PD ODNs that are effective as human TLR9 (hTLR9) agonists.
  
  
  RESULTS
  The sequence of ODN2006, a CpG ODN that acts as an hTLR9 agonist, was used as the basic CpG ODN material. The 3'-end modification of ODN2006 with a PD backbone (PD-ODN2006) improved its potential as an hTLR9 agonist because of increased resistance to nucleolytic degradation. Moreover, 3'-end modification with oligonucleotides showed higher induction than modification with biotin, FITC, and amino groups. Further, enhancement of hTLR9 activity was found to be dependent on the number of CpG core motifs (GTCGTT) in the PD ODN containing the 3'-end oligonucleotides. In particular, ODN sequences consisting of two to three linked ODN2006 sequences with a PD backbone (e.g., PD-ODN2006-2006 and PD-ODN2006-2006-2006) acted as effective agonists of hTLR9 even at lower concentrations.
  
  
  CONCLUSIONS
  This study showed that PD-ODN2006-2006 and PD-ODN-2006-2006-2006 can be used as potentially safe agonists for hTLR9 activation instead of CpG ODNs with a PTO backbone. We propose these CpG ODNs consisting of only a PD backbone as a novel class of CpG ODN.
authors.affiliation: Graduate School of Life Science, Hokkaido University, N10W8, Kita-ku, Sapporo 060-0810, Japan.
authors.forename: Wenjun
authors.initials: W
authors.lastname: Meng
authors.forename: Tomohiko
authors.initials: T
authors.lastname: Yamazaki
authors.forename: Yuuki
authors.initials: Y
authors.lastname: Nishida
authors.forename: Nobutaka
authors.initials: N
authors.lastname: Hanagata
mesh_terms: D001483:Base Sequence; D002460:Cell Line; D002478:Cells, Cultured; D003851:Deoxyribonucleases; D004355:Drug Stability; D006801:Humans; D015850:Interleukin-6 / Q000378:metabolism; D007963:Leukocytes, Mononuclear / Q000187:drug effects / Q000378:metabolism; D008969:Molecular Sequence Data; D016328:NF-kappa B / Q000378:metabolism; D059372:Nucleotide Motifs; D009838:Oligodeoxyribonucleotides / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D051217:Toll-Like Receptor 9 / Q000819:agonists* / Q000378:metabolism
chemical_list: C408982:CPG-oligonucleotide; C508600:IL6 protein, human; D015850:Interleukin-6; D016328:NF-kappa B; D009838:Oligodeoxyribonucleotides; C495371:TLR9 protein, human; D051217:Toll-Like Receptor 9; D003851:Deoxyribonucleases