Site of chemical modifications in CpG containing phosphorothioate oligodeoxynucleotide modulates its immunostimulatory activity.

Phosphorothioate oligodeoxynucleotides containing CpG motifs have immunostimulatory activity. Appropriate substitution of deoxynucleosides in the flanking region of CpG-containing phosphorothioate oligodeoxynucleotides with 2'-O-methylribonucleosides results in significant decreases or increases in their immunostimulatory activities. The results provide insights in how to chemically modify phosphorothioate oligodeoxynucleotides containing CpG motifs to suppress or enhance their immunostimulatory activity for different therapeutic uses.