Interferon- inducing complexes and rna duplexes and methods of use

An immunostimulatory complex comprising at least first and second RNA duplexes, each duplex comprising:

• a first strand comprising, from the 5′ terminus, the sequence 5′-C—N19-3′, and
• a second strand comprising, at the 3′ terminus, the sequence 5′-N′19-GGG-3′,
• wherein:
• N and N′ are any of C, A, G, and U;
• N and N′ are complementary;
• the 3′ terminal GG dinucleotide of the second strand forms a 3′ GG dinucleotide overhang;
• the first duplex is complexed with the at least second duplex via Hoogsteen base pairing between the 3′ GG overhang on each duplex;
• and
• the first strand, at the 5′ terminus, does not comprise the sequence 5′-CUGA-3′.

An immunostimulatory RNA duplex having

• a) a first strand having from 5′ to 3′ a GNNN (SEQ ID NO:
• 1) sequence flanked by at least 22 nucleotides on each side;
• and
• b) a second strand having from 5′-3′ a GGGC (SEQ ID NO:
• 2) sequence flanked by at least 22 nucleotides on each side,
• wherein the first and second strands are complementary to each other.

A method of preparing an RNAi molecule to promote degradation of a target RNA, the method comprising:

• a) identifying CCC trinucleotide repeats in the sequence of a target RNA;
• b) selecting a nucleotide sequence from 20 nucleotides to the upper limit for a dsRNA duplex that avoids a double-stranded RNA-activated protein kinase response, and lacks CCC repeats in a target RNA sequence as a candidate RNAi sequence);
• c) synthesizing an RNA molecule complementary to the sequence selected in step (b);
• and
• d) synthesizing an RNA molecule complementary to the RNA molecule synthesized in step (c),
• wherein combination of the RNA molecules synthesized in steps (c) and (d) produces an RNAi molecule that is less immunostimulatory than an RNAi molecule that targets the same target RNA but comprises a CCC trinucleotide repeat.