mRNA-LNPs induce immune activation and cytokine release in human whole blood assays across diverse health conditions.

RNA medicines have become a promising platform for therapeutic use in recent years. Understanding the immunomodulatory effects of novel mRNA-lipid nanoparticles (LNPs) is crucial for future therapeutic development. An in vitro whole blood assay was developed to assess the impact of mRNA-LNPs on immune cell function, cytokine release, and complement activation. mRNA-LNPs significantly increased CD69 expression on T cells and natural killer cells, and CD80/CD86 on myeloid subsets, in a dose-dependent fashion. Furthermore, mRNA-LNPs elicited a robust release of pro-inflammatory cytokines, including tumor necrosis factor-α, interleukin (IL)-1β, monocyte chemoattractant protein-1, IL-6, and IP-10, indicating a potent immune response. Notably, mRNA-LNPs stimulate early cytokine production prior to triggering immune cell activation, suggesting a temporal and biological relationship. Moreover, mRNA-LNPs induce complement activation via the alternative pathway, as evidenced by increased serum sC5b-9, C3a, and Bb, which can amplify the inflammatory response and potentially impact safety. In vitro effects of mRNA-LNPs in whole blood of healthy human donors were compared with those from disease cohorts including systemic lupus erythematosus, type 2 diabetes mellitus, and cancer donors. The differences in mRNA-LNP effects on samples from healthy and diseased populations may impact therapeutic efficacy or toxicity, indicating a need for tailoring LNPs for specific target populations.