TLR9 and STING agonists synergistically induce innate and adaptive type-II IFN

Eur J Immunol. 2015 Apr;45(4):1159-69. doi: 10.1002/eji.201445132. Epub 2015 Feb 5.


Agonists for TLR9 and Stimulator of IFN Gene (STING) act as vaccine adjuvants that induce type-1 immune responses. However, currently available CpG oligodeoxynucleotide (ODN) (K-type) induces IFNs only weakly and STING ligands rather induce type-2 immune responses, limiting their potential therapeutic applications. Here, we show a potent synergism between TLR9 and STING agonists. Together, they make an effective type-1 adjuvant and an anticancer agent. The synergistic effect between CpG ODN (K3) and STING-ligand cyclic GMP-AMP (cGAMP), culminating in NK cell IFN-γ (type-II IFN) production, is due to the concurrent effects of IL-12 and type-I IFNs, which are differentially regulated by IRF3/7, STING, and MyD88. The combination of CpG ODN with cGAMP is a potent type-1 adjuvant, capable of inducing strong Th 1-type responses, as demonstrated by enhanced antigen-specific IgG2c and IFN-γ production, as well as cytotoxic CD8(+) T-cell responses. In our murine tumor models, intratumoral injection of CpG ODN and cGAMP together reduced tumor size significantly compared with the singular treatments, acting as an antigen-free anticancer agent. Thus, the combination of CpG ODN and a STING ligand may offer therapeutic application as a potent type-II IFN inducer.

Keywords: Adjuvant; CpG ODN; IFN-γ; STING; TLR; cGAMP.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adjuvants, Immunologic / pharmacology
  • Animals
  • Cell Line, Tumor
  • Drug Synergism
  • Female
  • Immunoglobulin G / biosynthesis
  • Immunoglobulin G / immunology
  • Interferon Regulatory Factor-3 / metabolism
  • Interferon Regulatory Factor-7 / metabolism
  • Interferon Type I / metabolism
  • Interferon-gamma / biosynthesis*
  • Interferon-gamma / immunology
  • Interleukin-12 / metabolism
  • Membrane Proteins / agonists*
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Myeloid Differentiation Factor 88 / metabolism
  • Neoplasms / therapy*
  • Nucleotides, Cyclic / pharmacology*
  • Oligodeoxyribonucleotides / pharmacology*
  • T-Lymphocytes, Cytotoxic / immunology*
  • Toll-Like Receptor 9 / agonists*


  • Adjuvants, Immunologic
  • CPG-oligonucleotide
  • Immunoglobulin G
  • Interferon Regulatory Factor-3
  • Interferon Regulatory Factor-7
  • Interferon Type I
  • Irf3 protein, mouse
  • Irf7 protein, mouse
  • Membrane Proteins
  • Myd88 protein, mouse
  • Myeloid Differentiation Factor 88
  • Nucleotides, Cyclic
  • Oligodeoxyribonucleotides
  • Sting1 protein, mouse
  • Tlr9 protein, mouse
  • Toll-Like Receptor 9
  • cyclic guanosine monophosphate-adenosine monophosphate
  • Interleukin-12
  • Interferon-gamma