Improvement of the Nuclease Resistance and Immunostimulatory Activity of CpG Oligodeoxynucleotides by Conjugation to Sugar-Immobilized Gold Nanoparticles

Koki Murata; Kai Harayama; Mayuko Shimoda; Mayumi Niimura; Masahiro Wakao; Yasuo Suda; Toshiro Moroishi; Hiroyuki Shinchi

doi:10.1021/acs.bioconjchem.4c00145

Improvement of the Nuclease Resistance and Immunostimulatory Activity of CpG Oligodeoxynucleotides by Conjugation to Sugar-Immobilized Gold Nanoparticles

Bioconjug Chem. 2024 May 8. doi: 10.1021/acs.bioconjchem.4c00145. Online ahead of print.

Authors

Koki Murata¹, Kai Harayama¹, Mayuko Shimoda², Mayumi Niimura², Masahiro Wakao¹, Yasuo Suda³, Toshiro Moroishi^{2

4}, Hiroyuki Shinchi¹

Affiliations

¹ Department of Engineering, Chemistry and Biotechnology program, Graduate School of Science and Engineering, Kagoshima University, 1-21-40 Korimoto, Kagoshima 890-0065, Japan.
² Department of Molecular and Medical Pharmacology, Faculty of Life Sciences, Kumamoto University, Kumamoto 860-8556, Japan.
³ Collaborative Research Laboratory on Glyco-nanotechnology, Graduate School of Science and Engineering, Kagoshima University, 1-21-40 Korimoto, Kagoshima 890-0065, Japan.
⁴ Center for Metabolic Regulation of Healthy Aging, Faculty of Life Science, Kumamoto University, Kumamoto 860-8556, Japan.

PMID: 38718344
DOI: 10.1021/acs.bioconjchem.4c00145

Abstract

Adjuvants are essential substances for vaccines and immunotherapies that enhance antigen-specific immune responses. Single-stranded oligodeoxynucleotides containing an unmethylated CpG motif (CpG ODNs) are agonistic ligands for toll-like receptor 9 that initiate an innate immune response. They represent promising adjuvants for antiviral and antitumor immunotherapies; however, CpG ODNs have some limitations, such as poor nuclease resistance and low cell membrane permeability. Therefore, an effective formulation is needed to improve the nuclease resistance and immunostimulatory effects of CpG ODNs. Previously, we demonstrated the selective delivery of a small molecule toll-like receptor 7 ligand to immune cells through sugar-binding receptors using sugar-immobilized gold nanoparticles (SGNPs), which significantly enhanced the potency of the ligand. In this study, we examined SGNPs as carriers for partially phosphorothioated A-type CpG ODN (D35) and an entirely phosphorothioated B-type CpG ODN (K3) and evaluated the functionality of the sugar moiety on SGNPs immobilized with CpG ODN. SGNPs immobilized with D35 (D35-SGNPs) exhibited improved nuclease resistance and the in vitro and in vivo potency was significantly higher compared with that of unconjugated D35. Furthermore, the sugar structure on the GNPs was a significant factor in enhancing the cell internalization ability, and enhanced intracellular delivery of D35 resulted in improving the potencies of the A-type CpG ODN, D35. SGNPs immobilized with K3 (K3-SGNPs) exhibited significantly higher induction activities for both humoral and cellular immunity compared with unconjugated K3 and D35-SGNPs. On the other hand, sugar structure on K3-SGNPs did not affect the immunostimulatory effects. These results indicate that the sugar moiety on K3-SGNPs primarily functions as a hydrophilic dispersant for GNPs and the formulation of K3 to SGNPs contributes to improving the immunostimulatory activity of K3. Because our CpG ODN-SGNPs have superior induction activities for antigen-specific T-cell mediated immune responses, they may be effective adjuvants for vaccines and immunotherapies.