Combined use of chemically modified nucleobases and nanostructured DNA for enhanced immunostimulatory activity of CpG oligodeoxynucleotide

Yuki Araie, Shozo Ohtsuki, Soyoung Park, Makoto Nagaoka, Keisuke Umemura, Hiroshi Sugiyama, Kosuke Kusamori, Yuki Takahashi, Yoshinobu Takakura, Makiya Nishikawa

Research output: Contribution to journalArticlepeer-review

Abstract

Oligodeoxynucleotide (ODN) containing a cytosine-phosphate-guanine (CpG) motif, or CpG ODN, is considered suitable for treating immune diseases, including allergies. Although the phosphorothioate modification is used to enhance the stability and immunostimulatory activity of CpG ODNs, it is associated with the risk of adverse effects. Construction of nanostructured DNA assemblies, such as tripod- and hexapod-like structured DNAs, tripodna and hexapodna, respectively, were also found to increase this activity. The chemical modification of nucleobases could be another approach for enhancing CpG ODN activity. Here, we examined whether chemically modified nucleobase substitutions can enhance CpG ODN activity by measuring tumor necrosis factor α (TNF-α) release after addition to murine macrophage-like RAW264.7 cells. First, the guanine at the 18th position of phosphodiester CpG 1668 was substituted with several chemically modified guanines, and then the various guanines were substituted. Among all tested substitutions, 15,18-thdG, in which two guanines outside the CpG motif were substituted with the 2-aminothieno[3,4-d]pyrimidine guanine mimic (thdG), was the most effective. Compared to 32P-CpG 1668, 32P-15,18-thdG was taken up more efficiently by the RAW264.7 cells. Then, 15,18-thdG was incorporated into tripodna and hexapodna. 15,18-thdG/tri- or hexapodna induced higher TNF-α release from the RAW264.7 cells than PO CpG 1668/tri- or hexapodna, respectively. These results indicate that the thdG substitution is a useful effective strategy for enhancing the immunostimulatory activity of CpG DNAs in both single stranded and DNA nanostructure forms.

Original languageEnglish
Article number115864
JournalBioorganic and Medicinal Chemistry
Volume29
DOIs
Publication statusPublished - 1 Jan 2021

Keywords

  • Chemical modification
  • CpG DNA
  • Nucleic acid therapeutics
  • Nucleobases
  • dG

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