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Lack of interferon response in animals to naked siRNAs


RNA interference (RNAi) is rapidly becoming the method of choice for the elucidation of gene function and the identification of drug targets. As with other oligonucleotide-based strategies, RNAi is envisioned to ultimately be useful as a human therapeutic. Unlike previous nucleic acid therapeutics, small interfering RNAs have the potential to elicit immune responses via interactions with Toll-like receptor 3 and trigger interferon responses like long, double-stranded RNA and its analogs, such as poly(I:C)1. Recently, the safety of siRNAs has been questioned because they have been shown to trigger an interferon response in cultured cells2,3,4,5. We show here that it is possible to administer naked, synthetic siRNAs to mice and downregulate an endogenous or exogenous target without inducing an interferon response.

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Figure 1: IL-12 induction in RAW-264.7 cells and in mice.
Figure 2: Efficacy of synthetic siRNA in mice.
Figure 3: IFN-α induction in mice.


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The authors would like to thank Jean Lee and Hu Wong for critical blood chemistry and liver panel analyses. We thank Anton McCaffrey and Mark Kay for a donation of the plasmid used in our studies. J.D.H. acknowledges the Whitaker Foundation for a doctoral fellowship. S.H. is supported by an endowment in Molecular Pathology from the Las Madrinas Foundation at CHLA.

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Correspondence to Mark E Davis.

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M.E.D. is a consultant to and has a financial interest in Insert Therapeutics, Inc.

Supplementary information

Supplementary Fig. 1

RNase digestion of poly(I:C) and siRNA. (PDF 151 kb)

Supplementary Fig. 2

Synthetic siRNA does not alter mouse CBC or liver enzyme levels. (PDF 85 kb)

Supplementary Fig. 3

Degradation kinetics of synthetic siRNA in mouse serum. (PDF 193 kb)

Supplementary Fig. 4

Sequence-specific target down-regulation by siRNA in RAW-264.7 cells. (PDF 97 kb)

Supplementary Fig. 5

Synthetic siRNA accomplishes sequence-specific RNAi of an exogenous target in mice. (PDF 74 kb)

Supplementary Fig. 6

Lack of IL-12 and IFN-a induction by siRNA in C57BL/6 mice. (PDF 94 kb)

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Heidel, J., Hu, S., Liu, X. et al. Lack of interferon response in animals to naked siRNAs. Nat Biotechnol 22, 1579–1582 (2004).

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