Structure and Composition Define Immunorecognition of Nucleic Acid Nanoparticles

Abstract

Nucleic acid nanoparticles (NANPs) have evolved as a new class of therapeutics with the potential to detect and treat diseases. Despite tremendous advancements in NANP development, their immunotoxicity, one of the major impediments in clinical translation of traditional therapeutic nucleic acids (TNAs), has never been fully characterized. Here, we describe the first systematically studied immunological recognition of 25 representative RNA and DNA NANPs selected to have different design principles and physicochemical properties. We discover that, unlike traditional TNAs, NANPs used without a delivery carrier are immunoquiescent. We show that interferons (IFNs) are the key cytokines triggered by NANPs after their internalization by phagocytic cells, which agrees with predictions based on the experiences with TNAs. However, in addition to type I IFNs, type III IFNs also serve as reliable biomarkers of NANPs, which is usually not characteristic of TNAs. We show that overall immunostimulation relies on NANP shapes, connectivities, and compositions. We demonstrate that, like with traditional TNAs, plasmacytoid dendritic cells serve as the primary interferon producers among all peripheral blood mononuclear cells treated with NANPs, and scavenger receptor-mediated uptake and endosomal Toll-like receptor signaling are essential for NANP immunorecognition. The TLR involvement, however, is different from that expected for traditional TNA recognition. Based on these results, we suggest that NANP technology may serve as a prototype of auxiliary molecular language for communication with the immune system and the modulation of immune responses.

Tuning the size, shape and structure of RNA nanoparticles for favorable cancer targeting and immunostimulation

“…Larger nanoparticle sizes show greater sensitivity to phagocytosis than the corresponding smaller ones. A similar finding was reported when using varying sizes of RNA polygons, in which RNA hexagons induced more IFNs than any smaller RNA polygons (Hong et al, ). These findings answered important questions regarding size in the rational design of RNA nanoparticles for favorable cancer accumulation and immune‐interactions.…”

“…A 3D RNA tetrahedron carrying immunostimulatory oligonucleotides exhibited stronger immunostimulatory activity than the planar triangular counterpart, when size and payload stoichiometry were controlled to be equivalent (Guo et al, ). Likewise, globular RNA cubes induced stronger immunostimulation compared to planar hexameric RNA rings, which were more immunostimulatory than RNA fibers (Figure e) (Hong et al, ). These findings suggest a trend of increasing immunostimulatory properties of RNA nanoparticles from linear, to planar, and to 3D structure.…”

“…Copyright 2018 Elsevier Inc). and (Reprinted with permission from Hong et al (). Copyright 2018 American Chemical Society, respectively)…”

“…Interestingly, the intra‐ and intermolecular connectivity appeared to be another factor that affects the immunostimulation of RNA nanoparticles. Afonin Lab reported that RNA rings, assembled from pre‐folded monomers via intermolecular interaction (kissing loops), exhibited less immunostimulatory activity than RNA cubes formed via intramolecular hydrogen bonds (Hong et al, ). This result suggests that RNA connectivity may play a role, but this mechanism needs further investigation.…”

“…Recently, however, more studies have been reported on understanding the broad mechanisms that define the pharmacological and immunological profile of RNA nanoparticles. A variety of their physicochemical properties were recognized to be associated with their in vivo behaviors, including size, shape, stoichiometry/module density, surface chemistry, composition, hydrophobicity, and elasticity (Abdelmawla et al, ; Afonin et al, ; Guo et al, ; Halman et al, ; Hong et al, ; Jasinski, Li, & Guo, ; Jasinski, Yin, et al, ; Johnson et al, ; Ke et al, ; Khisamutdinov, Li, et al, ; Lee, Urban, Xu, Sullenger, & Lee, ; Pi et al, ; Shi et al, ; Shu et al, ). Here, this brief review aims to integrate the recent progress seen in the study of RNA nanoparticle on biodistribution and immunostimulation, while focusing on the defining aspects of their design and physiochemical properties precisely tuned to treat different cancers.…”