Suppression of immunostimulatory siRNA-driven innate immune activation by 2'-modified RNAs

Biochem Biophys Res Commun. 2007 Sep 14;361(1):122-6. doi: 10.1016/j.bbrc.2007.06.177. Epub 2007 Jul 16.


Single-stranded (ss) and double-stranded (ds) small interfering RNAs (siRNAs) containing immunostimulatory RNA motifs can activate innate immunity through Toll-like receptor 7/8 (TLR7/8), leading to the production of proinflammatory cytokines and type I interferon. More recently, we have noted that 2'-uridine modified ss or ds siRNAs not only evade immune activation, but can suppress TLR signaling triggered by their unmodified counterparts. Here we compared the inhibitory effects of several 2'-modifications. In contrast to 2'-deoxy uridine modified ss siRNAs, 2'-O-methyl uridine modified ss siRNAs inhibited at nanomolar concentrations the production of TNF-alpha induced by a variety of immunostimulatory RNA sequences. Using oligonucleotide microarrays, we highlight the strong suppressive effect of RNA-containing 2'-O-methyl uridines. Indeed, nearly all of the 270 genes induced by an immunostimulatory ss siRNA were completely inhibited or downregulated by cotreatment with its 2'-O-methyl modified version. Also, 2'-O-methyl modified RNAs inhibited E. coli total RNA or mitochondrial RNA to induce TNF-alpha production in human monocytes. Collectively, these data indicate that 2'-modified RNAs, in particular those containing 2'-O-methyl modification, are recognized with high affinity by TLR7/8, but do not induce downstream signaling. Therefore, this new generation of TLR antagonists can be used as immunosuppressive agents to interfere with TLR signaling.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adjuvants, Immunologic / antagonists & inhibitors
  • Adult
  • Gene Expression / drug effects
  • Humans
  • Immunity, Innate / drug effects*
  • Immunosuppressive Agents / chemistry*
  • Immunosuppressive Agents / pharmacology
  • Monocytes / drug effects
  • Monocytes / immunology
  • Oligoribonucleotides / chemistry*
  • Oligoribonucleotides / pharmacology
  • RNA Interference*
  • RNA, Small Interfering / antagonists & inhibitors*
  • Toll-Like Receptors / antagonists & inhibitors*


  • Adjuvants, Immunologic
  • Immunosuppressive Agents
  • Oligoribonucleotides
  • RNA, Small Interfering
  • Toll-Like Receptors