Suppression of immunostimulatory siRNA-driven innate immune activation by 2'-modified RNAs.
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.
Sioud
Mouldy
M
Department of Immunology, Institute for Cancer Research, Rikshopitalet-Radiumhospitalet Medical Center, Oslo, Norway. mosioud@ulrik.uio.no
Furset
Gro
G
Cekaite
Lina
L
D000276:Adjuvants, Immunologic / Q000037:antagonists & inhibitors; D000328:Adult; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D007113:Immunity, Innate / Q000187:drug effects*; D007166:Immunosuppressive Agents / Q000737:chemistry* / Q000494:pharmacology; D009000:Monocytes / Q000187:drug effects / Q000276:immunology; D009843:Oligoribonucleotides / Q000737:chemistry* / Q000494:pharmacology; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000037:antagonists & inhibitors*; D051193:Toll-Like Receptors / Q000037:antagonists & inhibitors*
D000276:Adjuvants, Immunologic; D007166:Immunosuppressive Agents; D009843:Oligoribonucleotides; D034741:RNA, Small Interfering; D051193:Toll-Like Receptors