Methods and compositions for activation of innate immune responses through RIG-I like receptor signaling

1. An isolated nucleic acid molecule with a non-naturally occurring sequence, the isolated nucleic acid comprising:

a 5′-arm region comprising a terminal triphosphate;

a poly-uracil core comprising at least 8 contiguous uracil residues; and

a 3′-arm region comprising at least 8 nucleic acid residues, wherein the 5′-most nucleic acid residue of the 3′-arm region is an adenine residue, and wherein the 3′-arm region is at least 30% uracil residues,

wherein the 5′-arm region and the poly-uracil core do not naturally occur contiguously together in a Hepatitis C virus.

2. The isolated nucleic acid molecule of claim 1 , wherein the poly-uracil core comprises at least 18 contiguous uracil residues.

3. The isolated nucleic acid molecule of claim 1 , wherein the 3′-arm region is at least 40%, 50%, 60%, or 70% uracil residues.

4. The isolated nucleic acid molecule of claim 1 , wherein the 3′-arm region comprises a plurality of short stretches of between 2 and 15 contiguous uracil residues with one or more cytosine residues interspersed between the plurality of short stretches.

5. The isolated nucleic acid molecule of claim 1 , wherein the 3′-arm region is covalently linked directly to the 3′-end of the poly-uracil core.

6. The isolated nucleic acid molecule of claim 1 , wherein the 5′-arm region further comprises one or more nucleic acid residues disposed between the terminal triphosphate and the poly-uracil core.

7. The isolated nucleic acid molecule of claim 1 , wherein the nucleic acid molecule is capable of inducing retinoic acid-inducible gene I (RIG-I)-like receptor (RLR) activation.

8. The isolated nucleic acid molecule of claim 7 , wherein the RLR is RIG-I.

9. An isolated nucleic acid molecule with a non-naturally occurring sequence, the isolated nucleic acid comprising:

a 5′-arm region comprising a terminal triphosphate;

a poly-uracil core comprising at least 18 contiguous uracil residues; and

a 3′-arm region comprising at least 8 nucleic acid residues, wherein the 5′-most nucleic acid residue of the 3′-arm region is a cytosine residue, and wherein the 3′-arm region is at least 30% uracil residues,

and wherein the 5′-arm region and the poly-uracil core do not naturally occur contiguously together in a Hepatitis C virus.

10. A pharmaceutical composition comprising the isolated nucleic acid molecule of claim 9 and an acceptable carrier.

11. The pharmaceutical composition of claim 10 , further comprising a viral antigen, a bacterial antigen, a protozoal antigen, a fungal antigen, and/or a helminth antigen, or an attenuated, inactivated, or killed virus, bacterium, protozoan, fungus, and/or helminth.

12. The pharmaceutical composition of claim 10 , further comprising an anti-viral therapeutic, an anti-bacterial therapeutic, an anti-protozoal therapeutic, an anti-fungal therapeutic, an anti-helminth therapeutic, and/or an adjuvant.

13. A method of inducing RLR signaling in a subject, the method comprising: administering to the subject an effective amount of a pharmaceutical composition of claim 10 .

14. The method of claim 13 , further comprising administering a viral antigen, a bacterial antigen, a protozoal antigen, a fungal antigen, and/or a helminth antigen, or an attenuated, inactivated, or killed virus, bacterium, protozoan, fungus, and/or helminth.

15. The method of claim 14 , wherein the virus is a member of, or is derived from, the Flaviviridae, Paramyxoviridae, Hepaciviridae, Orthomyxoviridae, Bunyaviridae, Arenaviridae, Reoviridae, Retroviridae, Enteroviruses, Picornaviridae, Coronaviridae, or Noroviridae families, or the viral antigen is derived from a virus of the Flaviviridae, Paramyxoviridae, Hepaciviridae, Orthomyxoviridae, Bunyaviridae, Arenaviridae, Reoviridae, Retroviridae, Enteroviruses, Picornaviridae, Coronaviridae, or Noroviridae families.

16. The method of claim 15 , wherein the virus is a West Nile virus, dengue virus, Japanese encephalitis virus, vesicular stomatitis virus, hepatitis C virus, respiratory syncytial virus, yellow fever virus, influenza A virus, Lassa fever virus, Hantavirus, lymphocytic choriomenengitis virus, polio virus, parainfluenza virus, rotavirus, human immunodeficiency virus (HIV), human T-lymphotropic virus (HTLV), enterovirus 21 and strains thereof, severe acute respiratory syndrome (SARS) virus, Middle East respiratory syndrome (MERS) virus, corona virus, or norovirus, or is derived therefrom.

17. The method of claim 16 , wherein the virus is an attenuated West Nile virus derived from a lineage 2 Madagascar strain of West Nile virus.

18. The method of claim 13 , wherein the administration step does not induce septic shock in the subject.

19. The method of claim 13 , wherein induction of RLR signaling is manifested by an increase in IFN-β levels, an increase in ISG54 levels, or an increase in IRF3 phosphorylation.

20. The method of claim 13 , wherein the RLR is RIG-I.

21. The isolated nucleic acid molecule of claim 9 , wherein the 3′-arm region is at least 40%, 50%, 60%, or 70% uracil residues.

22. The isolated nucleic acid molecule of claim 9 , wherein the 3′-arm region comprises a plurality of short stretches of between 2 and 15 contiguous uracil residues with one or more cytosine residues interspersed between the plurality of short stretches.

23. The isolated nucleic acid molecule of claim 9 , wherein the 3′-arm region is covalently linked directly to the 3′-end of the poly-uracil core.

24. The isolated nucleic acid molecule of claim 9 , wherein the 5′-arm region further comprises one or more nucleic acid residues disposed between the terminal triphosphate and the poly-uracil core.

25. The isolated nucleic acid molecule of claim 9 , wherein the nucleic acid molecule is capable of inducing retinoic acid-inducible gene I (RIG-I)-like receptor (RLR) activation.

26. The isolated nucleic acid molecule of claim 25 , wherein the RLR is RIG-I.