Fluorescent nucleobase analogue for cellular visualisation and regulation of immunostimulatory CpG oligodeoxynucleotides

Abstract

In this study, we explored the chemical modification of toll-like receptor 9 (TLR9) agonist DNA using a highly fluorescent thymine analogue, ᵀʰᵉˣT, focusing on its structural and photophysical characteristics. ᵀʰᵉˣT-labelled CpG oligonucleotides effectively demonstrated intracellular localisation within macrophage cell lines. Notably, immunostimulatory activity varied depending on the site of ᵀʰᵉˣT incorporation within the TLR9 agonist sequence. The introduction of fluorescent nucleobases offers a useful approach for visualising immunostimulatory oligonucleotides and for modulating immune responses.