Synthesis, purification, and characterization of oligoribonucleotides that act as agonists of TLR7 and/or TLR8.

Viral single-stranded (ss) RNA is the natural ligand for TLR7 and TLR8. Synthetic ssRNA has been shown to act as a ligand for TLR7 and TLR8. We have previously reported a novel RNA structure, referred to as stabilized immune modulatory RNA (SIMRA), in which two short phosphorothioate oligoribonucleotides were linked through their 3'-ends via a linker. SIMRA compounds had greater stability in serum than unmodified ssRNA and induced immune responses via TLR7 and/or TLR8. SIMRA compounds were synthesized using phosphoramidite chemistry on controlled-pore glass solid support derivatized with a linker. After cleavage from the solid support and removal of protecting groups, SIMRA compounds were purified on an anion-exchange HPLC followed by desalting/dialysis, and lyophilization. SIMRA compounds were characterized for their purity and sequence integrity by anion-exchange HPLC, capillary gel electrophoresis, polyacrylamide gel electrophoresis, and MALDI-TOF mass spectrophotometric analysis. As SIMRA compounds induce TLR7- and/or TLR8-mediated Th1-type immune responses, they have potential utility as therapeutic agents for a broad range of diseases, including cancer, infectious diseases, asthma, and allergies, and as adjuvants with vaccines.