Immunostimulatory Effects Triggered by Self-Assembled Microspheres with Tandem Repeats of Polymerized RNA Strands

Self-assembled RNA particles have been exploited widely to maximize the therapeutic potential of RNA. However, the immune response via RNA particles is not fully understood. In addition, the investigation of the immunogenicity from RNA-based particles is required owing to inherent immunostimulatory effects of RNA for clinical translation. To examine the immune stimulating potency, rationally designed microsized RNA particles, called RNA microspheres (RMSs), are generated with single or double strands via rolling circle transcription. The RMSs show an exceptional stability in the presence of serum, while they are selectively degraded under endolysosomal conditions. With precisely controlled size, both RMSs are successfully taken up by macrophages. Unlike the nature of RNA fragments, RMSs induce only basal-level expression of inflammatory cytokines as well as type I interferon from macrophages, suggesting that RMSs are immunocompatible in the therapeutic dose range. Taken together, this study could help accelerate clinical translation and broaden the applicability of the self-assembled RNA-based particles without being limited by their potential immunotoxicity, while a systematic controllability study observing the release of RNA fragments from RMSs would provide self-assembled RNA-based structures with a great potential for immunomodulation.